ELECTROPLATING APPARATUS AND METHODS UTILIZING INDEPENDENT CONTROL OF IMPINGING ELECTROLYTE
Methods and apparatus for electroplating substrates are described herein. In some cases, an ionically resistive element is positioned near the substrate, creating a cross flow manifold between the ionically resistive element and the substrate. During plating, fluid may enter the cross flow manifold upward through the channels in the ionically resistive element, and (optionally) laterally through a cross flow side inlet. The flow paths combine in the cross flow manifold and exit at the cross flow outlet, which may be positioned opposite the cross flow inlet. In some embodiments, the ionically resistive element may include two or more flow regions, where the flow through each flow region is independently controllable. In these or other embodiments, an electrolyte jet may be included to flow additional electrolyte toward the substrate at a particular radial location or locations during plating. In some embodiments, the ionically resistive element may be omitted.
The disclosed embodiments relate to methods and apparatus for controlling electrolyte hydrodynamics during electroplating. More particularly, methods and apparatus described herein are particularly useful for plating metals onto semiconductor wafer substrates, such as through resist plating of small microbumping features (e.g., copper, nickel, tin and tin alloy solders) having widths less than, e.g., about 50 μm, and copper through silicon via (TSV) features.
Electrochemical deposition processes are well-established in modern integrated circuit fabrication. The transition from aluminum to copper metal line interconnections in the early years of the twenty-first century drove a need for increasingly sophisticated electrodeposition processes and plating tools. Much of the sophistication evolved in response to the need for ever smaller current carrying lines in device metallization layers. These copper lines are formed by electroplating the metal into very thin, high-aspect ratio trenches and vias in a methodology commonly referred to as “damascene” processing (pre-passivation metalization).
Electrochemical deposition is now poised to fill a commercial need for sophisticated packaging and multichip interconnection technologies known generally and colloquially as wafer level packaging (WLP) and through silicon via (TSV) electrical connection technology. These technologies present their own very significant challenges due in part to the generally larger feature sizes (compared to Front End of Line (FEOL) interconnects) and high aspect ratios.
Depending on the type and application of the packaging features (e.g., through chip connecting TSV, interconnection redistribution wiring, or chip to board or chip bonding, such as flip-chip pillars), plated features are usually, in current technology, greater than about 2 micrometers and are typically about 5-100 micrometers in their principal dimension (for example, copper pillars may be about 50 micrometers). For some on-chip structures such as power busses, the feature to be plated may be larger than 100 micrometers. The aspect ratios of the WLP features are typically about 1:1 (height to width) or lower, though they can range as high as perhaps about 2:1 or so, while TSV structures can have very high aspect ratios (e.g., in the neighborhood of about 20:1).
With the shrinking of WLP structure sizes from 100-200 um to less than 50 um comes a unique set of problems because at this scale, the hydrodynamic and mass transfer boundary layers are nearly equivalent. For prior generations with larger features, the transport of fluid and mass into a feature was carried by the general penetration of the flow fields into the features, but with smaller features, the formation of flow eddies and stagnation can inhibit both the rate and uniformity of mass transport within the growing feature. Therefore, new methods of creating uniform mass transfer within smaller “microbump” and TSV features are required.
Further, the time constant τ (the 1D diffusion equilibration time constant) for a purely diffusion process scales with feature depth L and the diffusion constant D as
Assuming an average-reasonable value for the diffusion coefficient of a metal ion (e.g., 5×10−6 cm2/sec), a relatively large FEOL 0.3 um deep damascene feature would have a time constant of only about 0.1 msec, but a 50 um deep TSV of WLP bump would have a time constant of several seconds.
Not only feature size, but also plating speed differentiates WLP and TSV applications from damascene applications. For many WLP applications, depending on the metal being plated (e.g., copper, nickel, gold, silver solders, etc.), there is a balance between the manufacturing and cost requirements on the one hand and the technical requirements and technical difficulty on the other hand (e.g., goals of capital productivity with wafer pattern variability and on wafer requirements like within die and within feature targets). For copper, this balance is usually achieved at a rate of at least about 2 micrometers/minute, and typically at least about 3-4 micrometers/minute or more. For tin plating, a plating rate of greater than about 3 um/min, and for some applications at least about 7 micrometers/minute may be required. For nickel and strike gold (e.g., low concentration gold flash film layers), the plating rates may be between about 0.1 to 1 um/min. At these metal-relative higher plating rate regimes, efficient mass transfer of metal ions in the electrolyte to the plating surface is important.
In certain embodiments, plating must be conducted in a highly uniform manner over the entire face of a wafer to achieve good plating uniformity WIthin a Wafer (WIW), WIthin and among all the features of a particular Die (WID), and also WIthin the individual Features themselves (WIF). The high plating rates of WLP and TSV applications present challenges with respect to uniformity of the electrodeposited layer. For various WLP applications, plating must exhibit at most about 5% half range variation radially along the wafer surface (referred to as WIW non-uniformity, measured on a single feature type in a die at multiple locations across the wafer's diameter). A similar equally challenging requirement is the uniform deposition (thickness and shape) of various features of either different sizes (e.g. feature diameters) or feature density (e.g. an isolated or embedded feature in the middle of an array of the chip die). This performance specification is generally referred to as the WID non-uniformity. WID non-uniformity is measured as the local variability (e.g. <5% half range) of the various features types as described above versus the average feature height or other dimension within a given wafer die at that particular die location on the wafer (e.g. at the mid radius, center or edge).
A final challenging requirement is the general control of the within feature shape. Without proper flow and mass transfer convection control, after plating a line or pillar can end up being sloped in either a convex, flat or concave fashion in two or three dimensions (e.g. a saddle or a domed shape), with a flat profile generally, though not always, preferred. While meeting these challenges, WLP applications must compete with conventional, potentially less expensive pick and place serial routing operations. Still further, electrochemical deposition for WLP applications may involve plating various non-copper metals such as solders like lead, tin, tin-silver, and other underbump metallization materials, such as nickel, gold, palladium, and various alloys of these, some of which include copper. Plating of tin-silver near eutectic alloys is an example of a plating technique for an alloy that is plated as a lead free solder alternative to lead-tin eutectic solder.
SUMMARYCertain embodiments herein relate to methods and apparatus for electroplating one or more materials onto a substrate. In many cases the material is a metal and the substrate is a semiconductor wafer, though the embodiments are no so limited. Typically, the embodiments herein utilize an ionically resistive element (sometimes also referred to as a channeled ionically resistive plate (CIRP), a channeled ionically resistive element, an ionically resistive plate, a high resistance virtual anode, or similar name) positioned near the substrate, creating a cross flow manifold defined on the bottom by the ionically resistive element, and on the top by the substrate. In various embodiments, during plating, fluid enters the cross flow manifold both upward through the channels in the ionically resistive element, and laterally through a cross flow side inlet positioned proximate one side of the substrate. The flow paths combine in the cross flow manifold and exit at the cross flow exit, which is positioned opposite the cross flow inlet.
In a number of embodiments, the ionically resistive element may include a plurality of flow regions, where the channels in each flow region are supplied with electrolyte from separate sources referred to as electrolyte source regions. These electrolyte source regions may be used to independently control delivery of electrolyte through the channels in each of the flow regions of the ionically resistive element. In these or other embodiments, an electrolyte jet may be provided to deliver additional electrolyte toward the substrate at a particular location. The electrolyte jet may be fed from a separate jet manifold in some cases, which may allow the flow through the jets to be independently controlled from other flow rates.
In one aspect of the disclosed embodiments, an electroplating apparatus is provided, the apparatus including: an electroplating chamber configured to contain an electrolyte and an anode while electroplating metal onto a substrate, the substrate being substantially planar; an inlet for introducing electrolyte to the electroplating chamber; an outlet for removing electrolyte from the electroplating chamber; a substrate holder configured to hold the substrate such that a plating face of the substrate is separated from the anode during electroplating; and an electrolyte jet configured to deliver electrolyte toward the plating face of the substrate in a non-uniform manner, where a flow rate through the electrolyte jet and a total flow rate through the electroplating chamber are independently controllable.
In certain embodiments, the electrolyte jet may be an edge jet configured to deliver the electrolyte such that it preferentially impinges upon a peripheral region of the substrate. In other embodiments, the electrolyte jet may be an inner jet configured to deliver electrolyte such that it preferentially impinges upon a non-peripheral region of the substrate. In various cases, the electrolyte jet may include a plurality of individual jets. In some such cases, at least two of the plurality of individual jets of the electrolyte jet may be positioned to deliver electrolyte at different radial locations. For instance, a first individual jet of the plurality of electrolyte jets may be configured to deliver electrolyte at a peripheral region of the substrate, and a second individual jet of the plurality of electrolyte jets may be configured to deliver electrolyte at a non-peripheral region of the substrate. The electrolyte jet may be divided into at least a first region and a second region, each of the first and second regions of the electrolyte jet being supplied electrolyte from a distinct electrolyte source, and each of the first and second regions of the electrolyte jet including at least one of the plurality of individual jets, where a first flow rate through the first region of the electrolyte jet is independently controllable from a second flow rate through the second region of the electrolyte jet. In some cases, the electrolyte jet may be provided at a particular azimuthal location or locations such that as the substrate rotates, an area on the plating face of the substrate is cyclically exposed to (i) regions where the electrolyte jet is present and (ii) regions where the electrolyte jet is absent. Within regions where the electrolyte jet is present, the electrolyte jet may deliver electrolyte at different radial locations, where the flow rate of electrolyte through the electrolyte jet is non-uniform at the different radial locations.
In some implementations, the electrolyte jet may be configured to direct electrolyte toward the substrate at a normal angle with respect to the plating face of the substrate. In these or other cases, the electrolyte jet may be configured to direct electrolyte toward the substrate at a non-normal angle with respect to the plating face of the substrate. In various embodiments, the electrolyte jet may include at least one individual jet that is angled radially inwards. In some cases, the apparatus may further include a jet manifold that supplies electrolyte to the electrolyte jet. In a particular embodiment, the apparatus further includes an ionically resistive element including a substrate-facing surface that is separated from the plating face of the substrate by a gap, the gap forming a cross flow manifold, where the ionically resistive element is at least coextensive with the plating face of the substrate during electroplating, the ionically resistive element adapted to provide electrolyte transport and ionic transport through the ionically resistive element during electroplating; a side outlet to the cross flow manifold for receiving electrolyte flowing in the cross flow manifold; and an ionically resistive element manifold that supplies electrolyte below the ionically resistive element, where the ionically resistive element manifold and the jet manifold are separated from one another. In another embodiment, the apparatus further includes an ionically resistive element including a substrate-facing surface that is separated from the plating face of the substrate by a gap, the gap forming a cross flow manifold, where the ionically resistive element is at least coextensive with the plating face of the substrate during electroplating, the ionically resistive element adapted to provide electrolyte transport and ionic transport through the ionically resistive element during electroplating; a side inlet to the cross flow manifold for introducing electrolyte to the cross flow manifold; a side outlet to the cross flow manifold for receiving electrolyte flowing in the cross flow manifold; and a cross flow injection manifold, where the side inlet and the side outlet are positioned proximate azimuthally opposing perimeter locations on the plating face of the substrate during electroplating, where the cross flow injection manifold supplies electrolyte to the side inlet, and where the jet manifold and the cross flow injection manifold are separated from one another. In these or other embodiments, the apparatus may further include an edge flow element positioned proximate a periphery of the substrate and at least partially radially inside of a corner formed at an interface between the substrate and the substrate holder, where the edge flow element is configured to direct electrolyte into the corner formed at the interface between the substrate and the substrate holder, the edge flow element being ring-shaped or arc-shaped. In another particular embodiment, the apparatus may further include an ionically resistive element including a substrate-facing surface that is separated from the plating face of the substrate by a gap, the gap forming a cross flow manifold, where the ionically resistive element is at least coextensive with the plating face of the substrate during electroplating, the ionically resistive element adapted to provide electrolyte transport and ionic transport through the ionically resistive element during electroplating, where the electrolyte jet includes a channel that extends from a first location to a second location, the first location being positioned below a plane formed by the substrate-facing surface of the ionically resistive element, and the second location being positioned at or above the plane formed by the substrate-facing surface of the ionically resistive element.
In another aspect of the disclosed embodiments, an electroplating apparatus is provided, the apparatus including: (a) an electroplating chamber configured to contain an electrolyte and an anode while electroplating metal onto a substrate, the substrate being substantially planar; (b) a substrate holder configured to hold the substrate such that a plating face of the substrate is separated from the anode during electroplating; (c) an ionically resistive element including: (i) a substrate-facing surface that is separated from the plating face of the substrate by a gap, the gap forming a cross flow manifold, (ii) a first flow region and a second flow region, where each of the first and second flow regions allow for transport of an electrolyte through the ionically resistive element during electroplating, where the ionically resistive element is at least coextensive with the plating face of the substrate during electroplating, the ionically resistive element adapted to provide ionic transport through the ionically resistive element during electroplating; (d) an ionically resistive element manifold positioned below the ionically resistive element, the ionically resistive element manifold including a first electrolyte source region and a second electrolyte source region, the first and second electrolyte source regions being separated from one another, where the first electrolyte source region supplies electrolyte to the first flow region of the ionically resistive element and the second electrolyte source region supplies electrolyte to the second flow region of the ionically resistive element, and where a flow of electrolyte through the first flow region is independently controllable from a flow of electrolyte through the second flow region; and (e) a side outlet to the cross flow manifold for receiving electrolyte flowing in the cross flow manifold.
In some embodiments, the apparatus may further include a controller including executable instructions for flowing electrolyte through the first flow region at a first average linear velocity and for flowing electrolyte through the second flow region at a second average linear velocity, the first and second average linear velocities being different from one another. For instance, in some cases the first flow region may be positioned at a peripheral region of the ionically resistive element, and the second flow region may be positioned at a non-peripheral region of the ionically resistive element, and the first average linear velocity of electrolyte through the first flow region may be higher than the second average linear velocity of electrolyte through the second flow region. In another example, the first flow region may be positioned at a peripheral region of the ionically resistive element, the second flow region may be positioned at a non-peripheral region of the ionically resistive element, and the first average linear velocity of electrolyte through the first flow region may be lower than the second average linear velocity of electrolyte through the second flow region. In various implementations, the ionically resistive element may include a third flow region that allows for transport of electrolyte through the ionically resistive element during electroplating, the ionically resistive element manifold may include a third electrolyte source region that is separated from the first and second electrolyte source regions, and the third electrolyte source region may supply electrolyte to the third flow region of the ionically resistive element.
The first and second flow regions may differ from one another in some respect. In some cases, the first and second flow regions of the ionically resistive element may have different average porosities. In these or other cases, the first and second flow regions of the ionically resistive element may each include channels through the ionically resistive element, where the channels in the first flow region have an average diameter that is different from an average diameter of the channels in the second flow region. In these or other cases, the first and second flow regions of the ionically resistive element may each include channels through the ionically resistive element, where the channels in the first flow region are positioned in a different pattern compared to the channels in the second flow region. In various embodiments, the apparatus may further include an edge flow element positioned proximate a periphery of the substrate and at least partially radially inside of a corner formed at an interface between the substrate and the substrate holder, where the edge flow element is configured to direct electrolyte into the corner formed at the interface between the substrate and the substrate holder, the edge flow element being ring-shaped or arc-shaped. In these or other embodiments, the apparatus may further include an electrolyte jet in fluidic communication with the cross flow manifold, where the electrolyte jet is configured to deliver electrolyte such that it impinges upon the plating face of the substrate, and where a flow of electrolyte through the electrolyte jet is independently controllable from a flow of electrolyte through the ionically resistive element. In some such cases, the apparatus further includes an edge flow element positioned proximate a periphery of the substrate and at least partially radially inside of a corner formed at an interface between the substrate and the substrate holder, where the edge flow element is configured to direct electrolyte into the corner formed at the interface between the substrate and the substrate holder, the edge flow element being ring-shaped or arc-shaped. In various implementations, the first and second flow regions may be azimuthally separated from one another such that as the substrate rotates, a region on the substrate is cyclically exposed to the first and second flow regions.
In a further aspect of the disclosed embodiments, an electrolyte jet assembly for use in an electroplating apparatus is provided, the electrolyte jet assembly including: a frame including a portion that is ring-shaped or arc-shaped, the frame being configured to engage with a substrate holder and/or an ionically resistive element of the electroplating apparatus; and a plurality of jets positioned on the frame, each jet including a channel through which electrolyte flows during electroplating, where the jets are configured to deliver impinging electrolyte on a plating face of a substrate supported in the substrate holder during electroplating.
In some embodiments, at least a portion of the jets may be configured to deliver electrolyte to the substrate at a peripheral region of the substrate. In these or other embodiments, at least a portion of the jets may be configured to deliver electrolyte to the substrate at a non-peripheral region of the substrate. In some implementations, a first set of the plurality of jets may be configured to deliver electrolyte to the substrate at a peripheral region of the substrate, and a second set of the plurality of jets may be configured to deliver electrolyte to the substrate at a non-peripheral region of the substrate. The electrolyte jet may include a first region and a second region, each of the first and second regions including at least one of the plurality of jets, where a flow of electrolyte through the jet(s) in the first region is independently controllable from a flow of electrolyte through the jet(s) in the second region.
In some cases, the frame may be ring-shaped, and the electrolyte jet may a first region, a second region, a third region, and a fourth region, the first and third regions of the electrolyte jet being azimuthally opposite one another, the second and fourth regions of the electrolyte jet being azimuthally opposite one another, where the first and third regions may each include at least one of the plurality of jets, where the second region may not include any jets, and where the fourth region may optionally include at least one of the plurality of jets. The jets may be provided along a particular portion of the frame. For example, in some cases the jets may be provided along one or more arcs spanning a total of at least about 90°. In some such cases, the jets may be provided along one or more arcs spanning a total of at least about 180°. In various implementations, the frame may include an edge flow element configured to passively and preferentially direct electrolyte toward a corner formed by an interface between the substrate and the substrate holder.
In a further aspect of the disclosed embodiments, a method of electroplating material onto a substrate is provided, the method including electroplating the substrate in any of the electroplating apparatus described herein. In a further aspect of the disclosed embodiments, a method of electroplating material onto a substrate is provided, the method including flowing electrolyte through the plurality of jets of any of the electrolyte jet assemblies described herein.
In a further aspect of the disclosed embodiments, a method of electroplating material onto a substrate is provided, the method including: (a) immersing the substrate in electrolyte in an electroplating apparatus; (b) flowing electrolyte through an electrolyte jet onto a plating face of the substrate, where the electrolyte jet preferentially delivers electrolyte to the plating face of the substrate in a radially and/or azimuthally non-uniform manner, where a flow rate of electrolyte through the electrolyte jet is independently controllable from a total flow rate of electrolyte through the electroplating apparatus; and (c) electroplating the material onto the substrate while flowing the electrolyte as in (b).
In some embodiments, the electroplating apparatus may include an ionically resistive element that is separated from a plating face of the substrate by a gap, the gap forming a cross flow manifold, where the ionically resistive element is adapted to provide ionic transport through the ionically resistive element during electroplating, where (b) further includes flowing electrolyte through the ionically resistive element, and where the flow rate of electrolyte through the electrolyte jet is independently controllable from a flow rate of electrolyte through the ionically resistive element. In some such cases, (b) may further include flowing electrolyte from a cross flow injection manifold, into the cross flow manifold, and out a side outlet. The flow rate of electrolyte through the electrolyte jet may be independently controllable from a flow rate of electrolyte through the cross flow injection manifold.
In various embodiments, the electrolyte jet may include a plurality of jets. The electrolyte jet may preferentially deliver electrolyte to a particular region. For example, the electrolyte jet may preferentially deliver electrolyte to a peripheral region of the plating face of the substrate. In other cases, the electrolyte jet may preferentially deliver electrolyte to a non-peripheral region of the plating face of the substrate. In these or other embodiments, the method may further include rotating the substrate, and the electrolyte jet may deliver electrolyte to the plating face of the substrate in an azimuthally non-uniform way such that as the substrate rotates, an area on the plating face of the substrate is cyclically exposed to (i) regions where the electrolyte jet is present and delivers electrolyte to the substrate, and to (ii) regions where the electrolyte jet is not present.
In a further aspect of the disclosed embodiments, a method of electroplating material onto a substrate is provided, the method including: (a) immersing the substrate in electrolyte in an electroplating apparatus, the electroplating apparatus including: a substrate holder, an anode, an ionically resistive element that is separated from a plating face of the substrate by a gap, the gap forming a cross flow manifold, where the ionically resistive element includes a plurality of flow regions, each flow region being adapted to provide ionic transport through the ionically resistive element during electroplating, an ionically resistive element manifold positioned under the ionically resistive element, the ionically resistive element manifold including a plurality of electrolyte source regions that are separated from one another, each electrolyte source region configured to supply electrolyte to one of the plurality of flow regions of the ionically resistive element, and a side outlet configured to receive electrolyte flowing in the cross flow manifold; (b) flowing electrolyte: (i) from a first electrolyte source region of the plurality of electrolyte source regions, through a first flow region of the plurality of flow regions of the ionically resistive element, and into the cross flow manifold, and (ii) from a second electrolyte source region of the plurality of electrolyte source regions, through a second flow region of the plurality of flow regions of the ionically resistive element, and into the cross flow manifold, where a flow of electrolyte in (i) is independently controllable from a flow of electrolyte in (ii); and (c) electroplating the material onto the substrate while flowing electrolyte as in (b).
In some embodiments, the first flow region of the ionically resistive element may be configured to deliver electrolyte to a peripheral region of the substrate, the second flow region of the ionically resistive element may be configured to deliver electrolyte to a non-peripheral region of the substrate, and the flow of electrolyte passing through the first flow region of the ionically resistive element may have a higher linear velocity than the flow of electrolyte passing through the second flow region of the ionically resistive element. In these or other cases, the method may further include rotating the substrate, the first and second electrolyte source regions may be provided at different azimuthal positions, the first and second flow regions of the ionically resistive element may be provided at different azimuthal positions, and as the substrate rotates, an area on the plating face of the substrate may be cyclically positioned proximate the first and second flow regions of the ionically resistive element.
These and other features will be described below with reference to the associated drawings.
In this application, the terms “semiconductor wafer,” “wafer,” “substrate,” “wafer substrate,” and “partially fabricated integrated circuit” are used interchangeably. One of ordinary skill in the art would understand that the term “partially fabricated integrated circuit” can refer to a silicon wafer during any of many stages of integrated circuit fabrication thereon. The following detailed description assumes the disclosed embodiments are implemented on a wafer. Oftentimes, semiconductor wafers have a diameter of 200, 300 or 450 mm. However, the embodiments are not so limited. The work piece may be of various shapes, sizes, and materials. In addition to semiconductor wafers, other work pieces that may take advantage of the disclosed embodiments include various articles such as printed circuit boards and the like.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the presented embodiments. The disclosed embodiments may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail to not unnecessarily obscure the disclosed embodiments. While the disclosed embodiments will be described in conjunction with the specific embodiments, it will be understood that it is not intended to limit the disclosed embodiments.
Described herein are apparatus and methods for electroplating one or more metals onto a substrate. Embodiments are described generally where the substrate is a semiconductor wafer; however the embodiments are not so limited.
Disclosed embodiments include electroplating apparatus configured for, and methods including, control of electrolyte hydrodynamics during plating so that highly uniform plating layers are obtained. In specific implementations, the disclosed embodiments employ methods and apparatus that create combinations of impinging flow (flow directed at or perpendicular to the work piece surface) and shear flow (sometimes referred to as “cross flow” or flow with velocity parallel to the work piece surface).
In various embodiments, an ionically resistive element is positioned below a substrate, creating a cross flow manifold between the ionically resistive element and the substrate. Electrolyte flows upward through channels in the ionically resistive element, and optionally, laterally from a side inlet to a side outlet, the side inlet and side outlet each positioned above the ionically resistive element and azimuthally opposed to one another to accommodate cross flowing electrolyte in the cross flow manifold.
In a number of embodiments, the ionically resistive element may include a plurality of flow regions. In some such embodiments, the flow through each flow region can be independently controlled. Example embodiments of ionically resistive elements having a plurality of flow regions are shown in
One embodiment is an electroplating apparatus including the following features: (a) a plating chamber configured to contain an electrolyte and an anode while electroplating metal onto a substrate, the substrate being substantially planar; (b) a substrate holder configured to hold the substrate such that a plating face of the substrate is separated from the anode during electroplating; (c) an ionically resistive element including (i) a substrate-facing surface that may be substantially parallel to and separated from the plating face of the substrate, (ii) a plurality of flow regions, each flow region including a plurality of channels (which may or may not communicate with one another), where the channels allow for transport of an electrolyte through the ionically resistive element during electroplating; and (d) a plurality of electrolyte source regions, each electrolyte source region positioned at least partially below the ionically resistive element, and each electrolyte source region being configured to deliver electrolyte to one of the plurality of flow regions of the ionically resistive element. In various embodiments, the electrolyte flows through two or more of the flow regions of the ionically resistive element are independently controllable. This independent control permits tailoring the hydrodynamic conditions near the substrate to create uniform electroplated features.
Another embodiment is an electroplating apparatus that includes the following features: (a) a plating chamber configured to contain an electrolyte and an anode while electroplating metal onto a substrate, the substrate being substantially planar; (b) a substrate holder configured to hold the substrate such that a plating face of the substrate is separated from the anode during electroplating; (c) an ionically resistive element including a substrate-facing surface that may be substantially parallel to and separated from the plating face of the substrate, the ionically resistive element including a plurality of channels that allow for transport of an electrolyte through the ionically resistive element during electroplating; (d) an electrolyte jet configured to deliver electrolyte toward the substrate proximate a periphery of the substrate; (e) a jet manifold that delivers electrolyte to the electrolyte jet during electroplating; and (f) an ionically resistive element manifold that delivers electrolyte to the channels in the ionically resistive plate. In various embodiments, the flow through the electrolyte jet is independently controllable with respect to the flow through the ionically resistive element.
Another embodiment is an electroplating apparatus including the following features: (a) a plating chamber configured to contain an electrolyte and an anode while electroplating metal onto a substantially planar substrate; (b) a substrate holder configured to hold the substantially planar substrate such that a plating face of the substrate is separated from the anode during electroplating, where when the substrate is positioned in the substrate holder, a corner forms at the interface between the substrate and substrate holder, the corner defined on top by the plating face of the substrate and on the side by the substrate holder; (c) an ionically resistive element including a substrate-facing surface that is substantially parallel to and separated from a plating face of the substrate during electroplating, the ionically resistive element including a plurality of flow regions, each flow region including a plurality of channels (which may or may not communicate with one another), where the channels allow for transport of the electrolyte through the element during electroplating; (d) a plurality of electrolyte source regions, each electrolyte source region positioned at least partially below the ionically resistive element, and each electrolyte source region being configured to deliver electrolyte to one of the plurality of flow regions of the ionically resistive element; (e) a mechanism for creating and/or applying a shearing force (cross flow) to the electrolyte flowing at the plating face of the substrate; and (f) a mechanism for promoting shear flow near the periphery of the substrate, proximate a substrate/substrate holder interface. Though the wafer is substantially planar, it also typically has one or more microscopic trenches and may have one or more portions of the surface masked from electrolyte exposure. In various embodiments, the apparatus also includes a mechanism for rotating the substrate and/or the ionically resistive element while flowing electrolyte in the electroplating cell in the direction of the substrate plating face.
In certain implementations, the mechanism for applying cross flow is an inlet with, for example, appropriate flow directing and distributing means on or proximate to the periphery of the ionically resistive element. The inlet directs cross flowing catholyte along the substrate-facing surface of the ionically resistive element. The inlet is azimuthally asymmetric, partially following the circumference of the ionically resistive element, and having one or more gaps, and defining a cross flow injection manifold between the ionically resistive element and the substantially planar substrate during electroplating. Other elements are optionally provided for working in concert with the cross flow injection manifold. These may include a cross flow injection flow distribution showerhead and a cross flow confinement ring, which are further described below in conjunction with the figures.
In certain implementations, the mechanism for promoting shear flow near the periphery of the substrate is an edge flow element. The edge flow element may be an integral part of an ionically resistive element or substrate holder in some cases. In other cases, the edge flow element may be a separate piece that interfaces with the ionically resistive element or with the substrate holder. In some cases where the edge flow element is a separate piece, a variety of differently shaped edge flow elements may be separately provided to allow the flow distribution near the edge of a substrate to be tuned for a given application. In various cases the edge flow element may be azimuthally asymmetric. Further details regarding the edge flow element are presented below.
In certain embodiments, the apparatus is configured to enable flow of electrolyte in the direction towards or perpendicular to a substrate plating face to produce an average flow velocity of at least about 3 cm/s (e.g., at least about 5 cm/s or at least about 10 cm/s) exiting the holes of the ionically resistive element during electroplating. In certain embodiments, the apparatus is configured to operate under conditions that produce an average transverse electrolyte velocity of about 3 cm/sec or greater (e.g., about 5 cm/s or greater, about 10 cm/s or greater, about 15 cm/s or greater, or about 20 cm/s or greater) across the center point of the plating face of the substrate. These flow rates (i.e., the flow rate exiting the holes of the ionically resistive element and the flow rate across the plating face of the substrate) are in certain embodiments appropriate in an electroplating cell employing an overall electrolyte flow rate of about 20 L/min and an approximately 12 inch diameter substrate. The embodiments herein may be practiced with various substrate sizes. In some cases, the substrate has a diameter of about 200 mm, about 300 mm, or about 450 mm. Further, the embodiments herein may be practiced at a wide variety of overall flow rates. In certain implementations, the overall electrolyte flow rate is between about 1-60 L/min, between about 6-60 L/min, between about 5-25 L/min, or between about 15-25 L/min. The flow rates achieved during plating may be limited by certain hardware constraints, such as the size and capacity of the pump being used. One of skill in the art would understand that the flow rates cited herein may be higher when the disclosed techniques are practiced with larger pumps.
In some embodiments, the electroplating apparatus contains separated anode and cathode chambers in which there are different electrolyte compositions, electrolyte circulation loops, and/or hydrodynamics in each of two chambers. An ionically permeable membrane may be employed to inhibit direct convective transport (movement of mass by flow) of one or more components between the chambers and maintain a desired separation between the chambers. The membrane may block bulk electrolyte flow and exclude transport of certain species such as organic additives while permitting transport of ions such as cations. In some embodiments, the membrane contains DuPont's NAFION™ or a related ionically selective polymer. In other cases, the membrane does not include an ion exchange material, and instead includes a micro-porous material. Conventionally, the electrolyte in the cathode chamber is referred to as “catholyte” and the electrolyte in the anode chamber is referred to as “anolyte.” Frequently, the anolyte and catholyte have different compositions, with the anolyte containing little or no plating additives (e.g., accelerator, suppressor, and/or leveler) and the catholyte containing significant concentrations of such additives. The concentration of metal ions and acids also often differs between the two chambers. An example of an electroplating apparatus containing a separated anode chamber is described in U.S. Pat. No. 6,527,920, filed Nov. 3, 2000 [attorney docket NOVLP007]; U.S. Pat. No. 6,821,407, filed Aug. 27, 2002 [attorney docket NOVLP048], and U.S. Pat. No. 8,262,871, filed Dec. 17, 2009 [attorney docket NOVLP308] each of which is incorporated herein by reference in its entirety.
In some embodiments, the anode membrane need not include an ion exchange material. In some examples, the membrane is made from a micro-porous material such as polyethersulfone manufactured by Koch Membrane of Wilmington, Mass. This membrane type is most notably applicable for inert anode applications such as tin-silver plating and gold plating, but may also be used for soluble anode applications such as nickel plating.
In certain embodiments, and as described more fully elsewhere herein, catholyte is injected into a manifold region, referred to hereafter as the “ionically resistive element manifold region”, in which electrolyte is fed, accumulates, and then is distributed and passes substantially uniformly through the various non-communication channels of the ionically resistive element directly towards the wafer surface. In some embodiments where the ionically resistive element includes a plurality of flow regions, the ionically resistive element manifold region may be implemented as a plurality of electrolyte source regions instead of a single electrolyte source region. The electrolyte source regions are physically separated from one another. Each of the plurality of electrolyte source regions may deliver electrolyte to one of the plurality of flow regions on the ionically resistive element. Various pumps, valves, controllers, etc. may be used to control the flow of electrolyte through each electrolyte source region and through each flow region. In this way, flow through the different flow regions of the ionically resistive element can be independently controlled. In these or other embodiments, independent control of electrolyte delivery in two or more regions of the apparatus may be achieved by using an electrolyte jet that delivers electrolyte from a jet manifold toward the substrate at a particular location on the substrate. Control over the flow through the electrolyte jet may be independent from control over the flow through other regions or components of the apparatus, e.g., through the channels in the ionically resistive element or through the side inlet to the cross flow manifold. In another similar embodiment, an electrolyte jet is provided, but it is fed from another manifold in the apparatus such as the cross flow injection manifold (as shown in
In the following discussion, when referring to top and bottom features (or similar terms such as upper and lower features, etc.) or elements of the disclosed embodiments, the terms top and bottom are simply used for convenience and represent only a single frame of reference or implementation of the disclosed embodiments. Other configurations are possible, such as those in which the top and bottom components are reversed with respect to gravity and/or the top and bottom components become the left and right or right and left components.
While some aspects described herein may be employed in various types of plating apparatus, for simplicity and clarity, most of the examples will concern wafer-face-down, “fountain” plating apparatus. In such apparatus, the work piece to plated (typically a semiconductor wafer in the examples presented herein) generally has a substantially horizontal orientation (which may in some cases vary by a few degrees from true horizontal for some part of, or during the entire plating process) and may be powered to rotate during plating, yielding a generally vertically upward electrolyte convection pattern. Integration of the impinging flow mass from the center to the edge of the wafer, as well as the inherent higher angular velocity of a rotating wafer at its edge relative to its center, creates a radially increasing sheering (wafer parallel) flow velocity. One example of a member of the fountain plating class of cells/apparatus is the Sabre® Electroplating System produced by and available from Novellus Systems, Inc. of San Jose, Calif. Additionally, fountain electroplating systems are described in, e.g., U.S. Pat. No. 6,800,187, filed Aug. 10, 2001 [attorney docket NOVLP020] and U.S. Pat. No. 8,308,931, filed Nov. 7, 2008 [attorney docket NOVLP299], which are incorporated herein by reference in their entireties.
The substrate to be plated is generally planar or substantially planar. As used herein, a substrate having features such as trenches, vias, photoresist patterns and the like is considered to be substantially planar. Often these features are on the microscopic scale, though this is not necessarily always the case. In many embodiments, one or more portions of the surface of the substrate may be masked from exposure to the electrolyte.
The following description of
Cup 102 is supported by struts 104, which are connected to a top plate 105. This assembly (102-105), collectively assembly 101, is driven by a motor 107, via a spindle 106. Motor 107 is attached to a mounting bracket 109. Spindle 106 transmits torque to a wafer (not shown in this figure) to allow rotation during plating. An air cylinder (not shown) within spindle 106 also provides vertical force between the cup and cone 103 to create a seal between the wafer and a sealing member (lipseal) housed within the cup. For the purposes of this discussion, the assembly including components 102-109 is collectively referred to as a wafer holder 111. Note however, that the concept of a “wafer holder” extends generally to various combinations and sub-combinations of components that engage a wafer and allow its movement and positioning.
A tilting assembly including a first plate 115, that is slidably connected to a second plate 117, is connected to mounting bracket 109. A drive cylinder 113 is connected both to plate 115 and plate 117 at pivot joints 119 and 121, respectively. Thus, drive cylinder 113 provides force for sliding plate 115 (and thus wafer holder 111) across plate 117. The distal end of wafer holder 111 (i.e. mounting bracket 109) is moved along an arced path (not shown) which defines the contact region between plates 115 and 117, and thus the proximal end of wafer holder 111 (i.e. cup and cone assembly) is tilted upon a virtual pivot. This allows for angled entry of a wafer into a plating bath.
The entire apparatus 100 is lifted vertically either up or down to immerse the proximal end of wafer holder 111 into a plating solution via another actuator (not shown). Thus, a two-component positioning mechanism provides both vertical movement along a trajectory perpendicular to an electrolyte and a tilting movement allowing deviation from a horizontal orientation (parallel to electrolyte surface) for the wafer (angled-wafer immersion capability). A more detailed description of the movement capabilities and associated hardware of apparatus 100 is described in U.S. Pat. No. 6,551,487 filed May 31, 2001 and issued Apr. 22, 2003 [attorney docket NOVLP022], which is herein incorporated by reference in its entirety.
Note that apparatus 100 is typically used with a particular plating cell having a plating chamber which houses an anode (e.g., a copper anode or a non-metal inert anode) and electrolyte. The plating cell may also include plumbing or plumbing connections for circulating electrolyte through the plating cell—and against the work piece being plated. It may also include membranes or other separators designed to maintain different electrolyte chemistries in an anode compartment and a cathode compartment. In one embodiment, one membrane is employed to define an anode chamber, which contains electrolyte that is substantially free of suppressors, accelerators, or other organic plating additives, or in another embodiment, where the inorganic plating composition of the anolyte and catholyte are substantially different. Means of transferring anolyte to the catholyte or to the main plating bath by physical means (e.g. direct pumping including values, or an overflow trough) may optionally also be supplied.
The following description provides more detail of the cup and cone assembly of the clamshell.
To load a wafer into 101, cone 103 is lifted from its depicted position via spindle 106 until cone 103 touches top plate 105. From this position, a gap is created between the cup and the cone into which wafer 145 can be inserted, and thus loaded into the cup. Then cone 103 is lowered to engage the wafer against the periphery of cup 102 as depicted, and mate to a set of electrical contacts (not shown in 1B) radially beyond the lip seal 143 along the wafer's outer periphery.
Spindle 106 transmits both vertical force for causing cone 103 to engage a wafer 145 and torque for rotating assembly 101. These transmitted forces are indicated by the arrows in
Cup 102 has a compressible lip seal 143, which forms a fluid-tight seal when cone 103 engages wafer 145. The vertical force from the cone and wafer compresses lip seal 143 to form the fluid tight seal. The lip seal prevents electrolyte from contacting the backside of wafer 145 (where it could introduce contaminating species such as copper or tin ions directly into silicon) and from contacting sensitive components of apparatus 101. There may also be seals located between the interface of the cup and the wafer which form fluid-tight seals to further protect the backside of wafer 145 (not shown).
Cone 103 also includes a seal 149. As shown, seal 149 is located near the edge of cone 103 and an upper region of the cup when engaged. This also protects the backside of wafer 145 from any electrolyte that might enter the clamshell from above the cup. Seal 149 may be affixed to the cone or the cup, and may be a single seal or a multi-component seal.
Upon initiation of plating, cone 103 is raised above cup 102 and wafer 145 is introduced to assembly 102. When the wafer is initially introduced into cup 102—typically by a robot arm—its front side, 142, rests lightly on lip seal 143. During plating the assembly 101 rotates in order to aid in achieving uniform plating. In subsequent figures, assembly 101 is depicted in a more simplistic format and in relation to components for controlling the hydrodynamics of electrolyte at the wafer plating surface 142 during plating. Thus, an overview of mass transfer and fluid shear at the work piece follows.
As depicted in
In some embodiments, electrolyte flow ports are configured to aid transverse flow, alone or in combination with a flow shaping plate and a flow diverter as described herein. Various embodiments are described below in relation to a combination with a flow shaping plate and a flow diverter, but the embodiments are not so limited. Note that in certain embodiments it is believed that the magnitude of the electrolyte flow vectors across the wafer surface are larger proximate the vent or gap and progressively smaller across the wafer surface, being smallest at the interior of the pseudo chamber furthest from the vent or gap. As depicted in
Some embodiments include electrolyte inlet flow ports configured for transverse flow enhancement in conjunction with flow shaping plate and flow diverter assemblies.
In one embodiment, for example as described in relation to
Numerous figures are provided to further illustrate and explain the embodiments disclosed herein. The figures include, among other things, various drawings of the structural elements and flow paths associated with a disclosed electroplating apparatus. These elements are given certain names/reference numbers, which are used consistently in describing
The following embodiments assume, for the most part, that electroplating apparatus includes a separate anode chamber. The described features are contained in a cathode chamber, which includes a membrane frame 274 and membrane 202 that separate the anode chamber from the cathode chamber. Any number of possible anode and anode chamber configurations may be employed. In the following embodiments, the catholyte contained in the cathode chamber is largely located either in a cross flow manifold 226 or in the ionically resistive element manifold 208 or in channels 258 and 262 for delivering catholyte to these two separate manifolds.
While many of the figures herein illustrate the ionically resistive element manifold 208 as a single electrolyte source region, it is understood that in various embodiments the ionically resistive element manifold 208 is implemented as a plurality of electrolyte source regions. In cases where the ionically resistive element includes a plurality of flow regions, each of the electrolyte source regions delivers electrolyte to one of the plurality of flow regions on the ionically resistive element. This configuration allows for independent control of the electrolyte delivery to each flow region, which allows the hydrodynamic conditions within the plating cell to be closely tailored for a particular application. Embodiments where a plurality of flow regions and electrolyte source regions are used are further discussed below, for example in relation to
Much of the focus in the following description is on controlling the catholyte in the cross flow manifold 226. The catholyte enters the cross flow manifold 226 through two separate entry points: (1) the channels in the ionically resistive element 206 and (2) cross flow initiating structure 250. The catholyte arriving in the cross flow manifold 226 via the channels in the ionically resistive element 206 is directed toward the face of the work piece, typically in a substantially perpendicular direction. Such channel delivered catholyte may form small jets that impinge on the face of the work piece, which is typically rotating slowly (e.g., between about 1 to 30 rpm) with respect to the ionically resistive element. In cases where the ionically resistive element 206 includes a plurality of flow regions fed by a plurality of electrolyte source regions below the ionically resistive element 206, the impinging flow from the jets can be controlled in a non-uniform manner, as described below. The non-uniformity may be radial and/or azimuthal. Where the flow is delivered in a radially non-uniform manner, different flow rates are established through the ionically resistive element at different radial positions. In such cases, the average flow conditions at the edge of the substrate can be different from the average flow conditions near the center of the substrate, for instance. Various examples are described in relation to
In cases where an edge jet is included, an additional impinging flow (or at least partially impinging flow) can be provided to establish jets near the periphery of the substrate, as described below. Similarly, in cases where an inner jet is included, an additional impinging flow (or at least partially impinging flow) can be provided to establish jets at a non-peripheral region of the substrate, as described below. The catholyte arriving in the cross flow manifold 226 via the cross flow initiating structure 250 is, in contrast, directed substantially parallel to the face of the work piece.
As indicated in the discussion above, an “ionically resistive element” 206 (also referred to as a “channeled ionically resistive element” or “CIRP” or similar name) is positioned between the working electrode (the wafer or substrate) and the counter electrode (the anode) during plating, in order to shape the electric field and control electrolyte flow characteristics. Various figures herein show the relative position of the ionically resistive element 206 with respect to other structural features of the disclosed apparatus. One example of such an ionically resistive element 206 is described in U.S. Pat. No. 8,308,931, filed Nov. 7, 2008 [attorney docket NOVLP299], which was previously incorporated by reference herein in its entirety. The ionically resistive element described therein is suitable to improve radial plating uniformity on wafer surfaces such as those containing relatively low conductivity or those containing very thin resistive seed layers. Further aspects of certain embodiments of the channeled element are described below.
A “membrane frame” 274 (sometimes referred to as an anode membrane frame in other documents) is a structural element employed in some embodiments to support a membrane 202 that separates an anode chamber from a cathode chamber. It may have other features relevant to certain embodiments disclosed herein. Particularly, with reference to the embodiments of the figures, it may include flow channels 258 and 262 for delivering catholyte toward a cross flow manifold 226 and showerhead 242 configured to deliver cross flowing catholyte to the cross flow manifold 226. The membrane frame 274 may also contain a cell weir wall 282, which is useful in determining and regulating the uppermost level of the catholyte. Various figures herein depict the membrane frame 274 in the context of other structural features associated with the disclosed cross flow apparatus.
Turning to
In certain cases where the ionically resistive element includes a plurality of flow regions (not shown), the membrane frame may be used to define, at least partially, the plurality of electrolyte source regions that feed the different flow regions. For instance, the membrane frame may include walls that project upward (e.g., toward the substrate) to separate adjacent electrolyte source regions from one another. In these or other cases, the ionically resistive element itself may include walls that project downward (e.g., away from the substrate) to define, at least partially, the various electrolyte source regions that feed the different flow regions. In some cases, a separate element (not shown, but separate from ionically resistive element 206 and membrane frame 274) may be provided directly below the ionically resistive element to separate adjacent electrolyte source regions. Generally, any elements that are upstream of the substrate may be used to separate the catholyte flow into separate flows that feed the individual electrolyte source regions.
Returning to
Located generally between the work piece and the membrane frame 274 is the ionically resistive element 206, as well as a cross flow ring gasket 238 and wafer cross flow confinement ring 210, which may each be affixed to the ionically resistive element 206. More specifically, the cross flow ring gasket 238 may be positioned directly atop the ionically resistive element 206, and the wafer cross flow confinement ring 210 may be positioned over the cross flow ring gasket 238 and affixed to a top surface of the ionically resistive element 206, effectively sandwiching the gasket 238. Various figures herein show the cross flow confinement ring 210 arranged with respect to the ionically resistive element 206.
The upper most relevant structural feature of the present disclosure, as shown in
In various embodiments, an edge flow element (not shown in
In certain embodiments, an electrolyte jet (not shown in
Region (2) above, between the top of the ionically resistive element 206 and the bottom of the workpiece when installed in the workpiece holder 254 contains catholyte and is referred to as the “cross flow manifold” 226. In some embodiments, catholyte enters the cathode chamber via a single inlet port. In other embodiments, catholyte enters the cathode chamber through one or more ports located elsewhere in the plating cell. In some cases, there is a single inlet for the bath of the cell, peripheral to the anode chamber and cut out of the anode chamber cell walls. This inlet connects to a central catholyte inlet manifold at the base of the cell and anode chamber. In certain disclosed embodiments, that main catholyte manifold chamber feeds a plurality of catholyte chamber inlet holes (e.g., 12 catholyte chamber inlet holes). In various cases, these catholyte chamber inlet holes are divided into two groups: one group which feeds catholyte to a cross flow injection manifold 222, and a second group which feeds catholyte to the ionically resistive element manifold 208.
The separation of catholyte into two or more different flow paths or streams occurs at the base of the cell in the central catholyte inlet manifold (not shown). That manifold may be fed by a single pipe connected to the base of the cell. In one example. from the main catholyte manifold, the flow of catholyte separates into two streams: 6 of the 12 feeder holes, located on one side of the cell, lead to source the ionically resistive element manifold 208 and eventually supply the impinging catholyte flow through the ionically resistive element's various microchannels. The other 6 holes also feed from the central catholyte inlet manifold, but then lead to the cross flow injection manifold 222, which then feeds the cross flow shower head's 242 distribution holes 246 (which may number more than 100). In cases where (a) the ionically resistive element includes a plurality of flow regions and the ionically resistive element manifold is implemented as a plurality of electrolyte source regions, and/or (b) an electrolyte jet is provided, the main catholyte manifold may be separated into more than two streams. For instance, a first stream may lead to a first electrolyte source region under the ionically resistive element, a second stream may lead to a second electrolyte source region under the ionically resistive element, and a third stream may lead to the cross flow injection manifold. In another example, a first stream leads to the ionically resistive element manifold, a second stream leads to the cross flow manifold, and a third stream leads to a jet manifold. In another example, two or more main catholyte manifolds may be provided, for example where it is desired to provide catholytes having different temperatures and/or compositions at different regions of the apparatus (e.g., (1) catholyte of a first temperature and/or first composition being provided to the cross flow manifold and catholyte of a second temperature and/or second composition being provided to the ionically resistive element manifold, or (2) catholyte of a first temperature and/or first composition being provided to a first electrolyte source region below the ionically resistive element and catholyte of a second temperature and/or second composition being provided to a second electrolyte source region below the ionically resistive element, or (3) catholyte of a first temperature and/or first composition provided to the cross flow manifold/ionically resistive element manifold and catholyte of a second temperature and/or second composition provided to a jet manifold, etc.). In a similar example, a single main catholyte manifold may be provided, but a dosing system, heater, or cooler may be provided to alter the composition and/or temperature of one or more of the electrolyte streams after the streams leave the main catholyte manifold.
After leaving the cross flow shower head holes 246, the catholyte's flow direction changes from (a) normal to the wafer to (b) parallel to the wafer. This change in flow occurs as the flow impinges upon and is confined by a surface in the inlet cavity 250 formed (at least partially) by the cross flow confinement ring 210. Finally, upon entering the cross flow manifold region 226, the two catholyte flows, initially separated at the base of the cell in the central catholyte inlet manifold, are rejoined.
In various embodiments shown in the figures, a fraction of the catholyte entering the cathode chamber is provided directly to the ionically resistive element manifold 208 (which may be implemented as a plurality of electrolyte source regions, the flow through which may be independently controllable) and a portion is provided directly to the cross flow injection manifold 222. At least some, and often but not always all of the catholyte delivered to the ionically resistive element manifold 208 and then to the ionically resistive element lower surface passes through the various microchannels in the plate 206 and reaches the cross flow manifold 226. The catholyte entering the cross flow manifold 226 through the channels in the ionically resistive element 206 enters the cross flow manifold as substantially vertically directed jets (in some embodiments the channels are made at an angle, so they are not perfectly normal to the surface of the wafer, e.g., the angle of the jet may be up to about 45 degrees with respect to the wafer surface normal).
In cases where the ionically resistive element includes a plurality of flow regions that are fed by a plurality of electrolyte source regions (e.g., as described in relation to
The portion of the catholyte that enters the cross flow injection manifold 222 is delivered directly to the cross flow manifold 226 where it enters as a horizontally oriented cross flow below the wafer. On its way to the cross flow manifold 226, the cross flowing catholyte passes through the cross flow injection manifold 222 and the cross flow shower head plate 242 (which, e.g., contains about 139 distributed holes 246 having a diameter of about 0.048″), and is then redirected from a vertically upwards flow to a flow parallel to the wafer surface by the actions/geometry of the cross-flow-confinement-ring's 210 entrance cavity 250.
The absolute angles of the cross flow and the channels/jets need not be exactly horizontal or exactly vertical or even oriented at exactly 90° with one another. In general, however, the cross flow of catholyte in the cross flow manifold 226 is generally along the direction of the work piece surface and the direction of the jets of catholyte emanating from the top surface of the ionically resistive element 206 generally flow towards/perpendicular to the surface of the work piece. In one embodiment where the ionically resistive element includes a plurality of flow regions that are fed by a plurality of electrolyte source regions (e.g., as described in relation to
In some embodiments, the angle, diameter, and/or intensity of flow through a channel in a given flow region of the ionically resistive element may be non-uniform. For instance, as shown in
As mentioned, the catholyte entering the cathode chamber is divided between (i) catholyte that flows from the ionically resistive element manifold 208 (which may be implemented as a plurality of separated electrolyte source regions), through the channels in the ionically resistive element 206 and then into the cross flow manifold 226 and (ii) catholyte that flows into the cross flow injection manifold 222, through the holes 246 in the showerhead 242, and then into the cross flow manifold 226. In addition, in certain implementations additional catholyte is provided to the substrate via an electrolyte jet (e.g., an edge jet and/or inner jet) that delivers catholyte toward the substrate at a particular location on the substrate. The flow directly entering from the cross flow injection manifold region 222 may enter via the cross flow confinement ring entrance ports, sometimes referred to as cross flow side inlets 250, and emanate parallel to the wafer and from one side of the cell. In contrast, the jets of fluid entering the cross flow manifold region 226 via the microchannels of the ionically resistive element 206 enter from below the wafer and below the cross flow manifold 226, and the jetting fluid is diverted (redirected) within the cross flow manifold 226 to flow parallel to the wafer and towards the cross flow confinement ring exit port 234, sometimes also referred to as the cross flow outlet or outlet.
In some embodiments, the fluid entering the cathode chamber is directed into multiple channels 258 and 262 distributed around the periphery of the cathode chamber portion of the electroplating cell chamber (often a peripheral wall). In a specific embodiment, there are 12 such channels contained in the wall of the cathode chamber.
The channels in the cathode chamber walls may connect to corresponding “cross flow feed channels” and/or “jet feed channels” in the membrane frame. Some of these feed channels 262 deliver catholyte directly to the ionically resistive element manifold 208 (or to a specific electrolyte source region therein when the ionically resistive element manifold is implemented as a plurality of electrolyte source regions) or to a manifold that feeds an electrolyte jet. As mentioned, the catholyte provided to the ionically resistive element manifold subsequently passes through the small vertically oriented channels of the ionically resistive element 206 and enters the cross flow manifold 226 as jets of catholyte. In cases where the ionically resistive element manifold is implemented as a plurality of electrolyte source regions, each electrolyte source region delivers catholyte to a particular flow region of the ionically resistive element.
As mentioned, in an embodiment depicted in the figures, catholyte feeds the ionically resistive element manifold 208 through 6 of the 12 catholyte feeder lines/tubes. Those 6 main tubes or lines 262 feeding the ionically resistive element manifold 208 reside below the cross flow confinement ring's exit cavity 234 (where the fluid passes out of the cross flow manifold region 226 below the wafer), and opposite all the cross flow manifold components (cross flow injection manifold 222, showerhead 242, and confinement ring entrance cavity 250).
As depicted in various figures, some cross flow feed channels 258 in the membrane frame lead directly to the cross flow injection manifold 222 (e.g., 6 of 12). These cross flow feed channels 258 start at the base of the anode chamber of the cell and then pass through matching channels of the membrane frame 274 and then connect with corresponding cross flow feed channels 258 on the lower portion of the ionically resistive element 206. See
In a specific embodiment, there are six separate feed channels 258 for delivering catholyte directly to the cross flow injection manifold 222 and then to the cross flow manifold 226. In order to effect cross flow in the cross flow manifold 226, these channels 258 exit into the cross flow manifold 226 in an azimuthally non-uniform manner. Specifically, they enter the cross flow manifold 226 at a particular side or azimuthal region of the cross flow manifold 226. In a specific embodiment depicted in
As mentioned, the portions of the flow paths passing through the membrane frame 274 and feeding the cross flow injection manifold 222 are referred to as cross flow feed channels 258 in the membrane frame. The portions of the flow paths passing through the microchannels in the ionically resistive element 206 and feeding the ionically resistive element manifold are referred to as cross flow feed channels 262 feeding the ionically resistive element manifold 208, or ionically resistive element manifold feed channels 262. In other words, the term “cross flow feed channel” includes both the catholyte feed channels 258 feeding the cross flow injection manifold 222, the catholyte feed channels 262 feeding the ionically resistive element manifold 208, and the catholyte feed channels (not shown) feeding a jet manifold (if any). One difference between the flows 258 and 262 was noted above: the direction of the flow through the ionically resistive element 206 is initially directed at the wafer and is then turned parallel to the wafer due to the presence of the wafer and the cross flow confinement ring 210, whereas the cross flow portion coming from the cross flow injection manifold 222 and out through the cross flow confinement ring entrance ports 250 starts substantially parallel to the wafer. The flow from the electrolyte jets, if present, can be in any direction but is often at least partially impinging on the substrate. While not wishing to be held to any particular model or theory, this combination and mixing of impinging and parallel flow is believed to facilitate substantially improved flow penetration within a recessed/embedded feature and thereby improve the mass transfer.
The flow path within the ionically resistive element 206 that does not pass through the plate's microchannels (instead entering the cross flow manifold 226 as flow parallel to the face of the wafer) begins in a vertically upward direction as it passes through the cross flow feed channel 258 in the plate 206, and then enters a cross flow injection manifold 222 formed within the body of the ionically resistive element 206. The cross flow injection manifold 222 is an azimuthal cavity which may be a dug out channel within the plate 206 that can distribute the fluid from the various individual feed channels 258 (e.g., from each of the individual 6 cross flow feed channels) to the various multiple flow distribution holes 246 of the cross flow shower head plate 242. This cross flow injection manifold 222 is located along an angular section of the peripheral or edge region of the ionically resistive element 206. See for example
In some embodiments, the cross flow in the injection manifold 222 forms a continuous fluidically coupled cavity within the ionically resistive element 206. In this case all of the cross flow feed channels 258 feeding the cross flow injection manifold (e.g., all 6) exit into one continuous and connected cross flow injection manifold chamber. In other embodiments, the cross flow injection manifold 222 and/or the cross flow showerhead 242 are divided into two or more angularly distinct and completely or partially separated segments, as shown in
In many cases, catholyte exits the cross flow injection manifold 222 and passes through a cross flow showerhead plate 242 having many angularly separated catholyte outlet ports (holes) 246. See for example
In a specific embodiment, the cross flow showerhead 242 has 139 angularly separated catholyte outlet holes 246. More generally, any number of holes that reasonably establish uniform cross flow within the cross flow manifold 226 may be employed. In certain embodiments, there are between about 50 and about 300 such catholyte outlet holes 246 in the cross flow showerhead 242. In certain embodiments, there are between about 100 and 200 such holes. In certain embodiments, there are between about 120 and 160 such holes. Generally, the size of the individual ports or holes 246 can range from about 0.020″ to 0.10″, more specifically from about 0.03″ to 0.06″ in diameter.
In certain embodiments, these holes 246 are disposed along the entire angular extent of the cross flow showerhead 242 in an angularly uniform manner (i.e. the spacing between the holes 246 is determined by a fixed angle between the cell center and two adjacent holes). See for example
In certain embodiments, the direction of the catholyte exiting the cross flow showerhead 242 is further controlled by a wafer cross flow confinement ring 210. In certain embodiments, this ring 210 extends over the full circumference of the ionically resistive element 206. In certain embodiments, a cross section of the cross flow confinement ring 210 has an L-shape, as shown in
In some implementations, two or more of the apparatus elements listed herein may be modified and/or combined into a single element. For example, in some implementations the cross flow confinement ring 210, the cross flow inlet 250, the cross flow showerhead 242, the outlet holes 246, an edge jet, an inner jet, and an edge flow element (or some subset of these elements) are provided together in a single unit that may be referred to as a topside insert. The topside insert may be positioned at least partially peripherally outside of the ionically resistive element 206, at about the same horizontal location as the ionically resistive element 206 (though the topside insert may extend below and/or above the ionically resistive element). The topside insert may also define, at least partially, the cross flow injection manifold 222. Examples having a topside insert as described in this section are shown in
Returning to the embodiment in
In some embodiments, the geometry of the cross flow confinement ring outlet 234 may be tuned in order to further optimize the cross flow pattern. For example, a case in which the cross flow pattern diverges to the edge of the confinement ring 210 may be corrected by reducing the open area in the outer regions of the cross flow confinement ring outlet 234. In certain embodiments, the outlet manifold 234 may include separated sections or ports, much like the cross flow injection manifold 222. In some embodiments, the number of outlet sections is between about 1-12, or between about 4-6. The ports are azimuthally separated, occupying different (usually adjacent) positions along the outlet manifold 234. The relative flow rates through each of the ports may be independently controlled in some cases. This control may be achieved, for example, by using control rods 270 similar to the control rods described in relation to the inlet flow. In another embodiment, the flow through the different sections of the outlet can be controlled by the geometry of the outlet manifold. For example, an outlet manifold that has less open area near each side edge and more open area near the center would result in a solution flow pattern where more flow exits near the center of the outlet and less flow exits near the edges of the outlet. Other methods of controlling the relative flow rates through the ports in the outlet manifold 234 may be used as well (e.g., pumps, etc.). In many embodiments, the outlet manifold 234 is positioned such that it is centered at a position azimuthally opposite the position of the inlet 250. In some other cases, one or more outlet manifolds may be positioned at a location that is not azimuthally opposite the position of the inlet. Such outlet(s) may be provided alternatively or in addition to an outlet positioned azimuthally opposite the inlet. The outlet(s) may be configured to produce a particular desired flow pattern over the surface of the substrate, for example.
As mentioned, bulk catholyte entering the catholyte chamber is directed separately into the cross flow injection manifold 222 and the ionically resistive element manifold 208 (which may be implemented as a plurality of electrolyte source regions in certain cases) through multiple channels 258 and 262, e.g., 12 separate channels. In certain embodiments, the flows through these individual channels 258 and 262 are independently controlled from one another by an appropriate mechanism. In some embodiments, this mechanism involves separate pumps for delivering fluid into the individual channels. In other embodiments, a single pump is used to feed a main catholyte manifold, and various flow restriction elements that are adjustable may be provided in one or more of the channels feeding the flow path provided so as to modulate the relative flows between the various channels 258 and 262, and between the cross flow injection manifold 222 and the ionically resistive element manifold 208 (and/or to the electrolyte source region(s) in the ionically resistive element manifold 208) and/or along the angular periphery of the cell. In various embodiments depicted in the figures, one or more fluidic adjustment rods 270 (sometimes also referred to as flow control elements) are deployed in the channels where independent control is provided. In the depicted embodiments, the fluidic adjustment rod 270 provides an annular space in which catholyte is constricted during its flow toward the cross flow injection manifold 222 or the ionically resistive element manifold 208. In a fully retracted state, the fluidic adjustment rod 270 provides essentially no resistance to flow. In a fully engaged state, the fluidic adjustment rod 270 provides maximal resistance to flow, and in some implementations stops all flow through the channel. In intermediate states or positions, the rod 270 allows intermediate levels of constriction of the flow as fluid flows through a restricted annular space between the channel's inner diameter and the fluid adjustment rod's outer diameter.
In some embodiments, the adjustment of the fluidic adjustment rods 270 allows the operator or controller of the electroplating cell to favor flow to either the cross flow injection manifold 222 or to the ionically resistive element manifold 208. In cases where the ionically resistive element manifold 208 is implemented as a plurality of electrolyte source regions, the fluidic adjustment rods (or other flow control elements such as pumps, valves, etc.) may be used to independently control the flow of electrolyte to the individual electrolyte source regions. The flow to each electrolyte source region of the ionically resistive element manifold 208 can be independent from the flow to other electrolyte source regions and from the flow to other regions of the electroplating apparatus (e.g., independent of the flow to the cross flow injection manifold, and independent of the flow to the anode chamber). In certain embodiments, independent adjustment of the fluidics adjustment rods 270 in the channels 258 that deliver catholyte directly to the cross flow injection manifold 222 allows the operator or controller to control the azimuthal component of fluid flow into the cross flow manifold 226. The effect of these adjustments are discussed further in the Experimental section below.
Another element that may be included near the periphery of the substrate is an edge jet. The number of individual jets can be adapted for a particular application. Each jet may be formed as a cavity through which electrolyte flows. In some cases these cavities are relatively small such that the electrolyte passing through the jets can be delivered at a high linear velocity toward the plating face of the substrate. In some embodiments, the cavities are provided as long thin slits, for example as described in relation to
Because the edge jet preferentially delivers electrolyte at the periphery of the substrate, the mass transfer conditions in this region are preferentially enhanced. As such, edge jets may be particularly useful in cases where the features proximate the edge of the substrate do not fill as completely as features proximate the center of the substrate. This phenomenon is common in electroplating semiconductor substrates, and may be a result of edge-thick photoresist that makes plating near the edges of the substrate relatively more challenging than plating near the center of the substrate. This issue is further described in relation to
In a similar embodiment, a different type of electrolyte jet may be provided. Instead of an edge jet that delivers fluid at a peripheral region of the substrate, an inner jet may be provided to deliver fluid at a non-peripheral region of the substrate. Details described in relation to an edge jet may similarly apply to an inner jet (except for the location where each element delivers electrolyte). In some cases, an electrolyte jet may deliver electrolyte near the substrate at both peripheral and non-peripheral locations. Details described in relation to an edge jet may similarly apply to an electrolyte jet that delivers electrolyte at both peripheral and non-peripheral locations.
The electrolyte jet may be supplied with electrolyte from various sources such as a cross flow injection manifold, an ionically resistive element manifold, a jet manifold, or a combination of individual manifolds. In one embodiment, the electrolyte jet receives electrolyte from the cross flow injection manifold, as shown in
In similar embodiments to those shown in
In another similar embodiment, the edge jets may be supplied with fluid from the ionically resistive element manifold (e.g., under the ionically resistive element 3206), with appropriate plumbing being provided to direct fluid as needed. In other embodiments, an inner jet or other electrolyte jet may be used in place of, or in addition to, the edge jet. The inner jet may receive fluid from an inner jet manifold (also referred to more generally as a jet manifold), or from another of the listed manifolds.
The disclosed apparatus may be configured to perform the methods described herein. A suitable apparatus includes hardware as described and shown herein and one or more controllers having instructions for controlling process operations in accordance with the disclosed embodiments. The apparatus will include one or more controllers for controlling, inter alia, the positioning of the wafer in the cup 254 and cone, the positioning of the wafer with respect to the ionically resistive element 206, the rotation of the wafer, the delivery of catholyte into the cross flow manifold 226, delivery of catholyte into the ionically resistive element manifold 208 (and in some cases, to the individual electrolyte source regions therein), delivery of catholyte into the cross flow injection manifold 222, delivery of catholyte through an edge jet, delivery of catholyte through an inner jet, the resistance/position of the fluidic adjustment rods 270, the delivery of current to the anode and wafer and any other electrodes, the mixing of electrolyte components, the timing of electrolyte delivery, inlet pressure, plating cell pressure, plating cell temperature, wafer temperature, position of an edge flow element, and other parameters of a particular process performed by a process tool.
A system controller will typically include one or more memory devices and one or more processors configured to execute the instructions so that the apparatus will perform a method in accordance with the disclosed embodiments. The processor may include a central processing unit (CPU) or computer, analog and/or digital input/output connections, stepper motor controller boards, and other like components. Machine-readable media containing instructions for controlling process operations in accordance with the disclosed embodiments may be coupled to the system controller. Instructions for implementing appropriate control operations are executed on the processor. These instructions may be stored on the memory devices associated with the controller or they may be provided over a network. In certain embodiments, the system controller executes system control software . . . .
System control software may be configured in any suitable way. For example, various process tool component subroutines or control objects may be written to control operation of the process tool components necessary to carry out various process tool processes. System control software may be coded in any suitable computer readable programming language.
In some embodiments, system control software includes input/output control (IOC) sequencing instructions for controlling the various parameters described above. For example, each phase of an electroplating process may include one or more instructions for execution by the system controller. The instructions for setting process conditions for an immersion process phase may be included in a corresponding immersion recipe phase. In some embodiments, the electroplating recipe phases may be sequentially arranged, so that all instructions for an electroplating process phase are executed concurrently with that process phase.
Other computer software and/or programs may be employed in some embodiments. Examples of programs or sections of programs for this purpose include a substrate positioning program, an electrolyte composition control program, a pressure control program, a heater control program, and a potential/current power supply control program.
In some cases, the controllers control one or more of the following functions: wafer immersion (translation, tilt, rotation), fluid transfer between tanks, etc. The wafer immersion may be controlled by, for example, directing the wafer lift assembly, wafer tilt assembly and wafer rotation assembly to move as desired. The controller may control the fluid transfer between tanks by, for example, directing certain valves to be opened or closed and certain pumps to turn on and off. The controllers may control these aspects based on sensor output (e.g., when current, current density, potential, pressure, etc. reach a certain threshold), the timing of an operation (e.g., opening valves at certain times in a process) or based on received instructions from a user.
The apparatus/process described hereinabove may be used in conjunction with lithographic patterning tools or processes, for example, for the fabrication or manufacture of semiconductor devices, displays, LEDs, photovoltaic panels and the like. Typically, though not necessarily, such tools/processes will be used or conducted together in a common fabrication facility. Lithographic patterning of a film typically comprises some or all of the following steps, each step enabled with a number of possible tools: (1) application of photoresist on a workpiece, i.e., substrate, using a spin-on or spray-on tool; (2) curing of photoresist using a hot plate or furnace or UV curing tool; (3) exposing the photoresist to visible or UV or x-ray light with a tool such as a wafer stepper; (4) developing the resist so as to selectively remove resist and thereby pattern it using a tool such as a wet bench; (5) transferring the resist pattern into an underlying film or workpiece by using a dry or plasma-assisted etching tool; and (6) removing the resist using a tool such as an RF or microwave plasma resist stripper.
Features of an Ionically Resistive Element Electrical FunctionIn certain embodiments, the ionically resistive element 206 approximates a nearly constant and uniform current source in the proximity of the substrate (cathode) and, as such, may be referred to as a high resistance virtual anode (HRVA) in some contexts. As noted above, this element may also be referred to as a channeled ionically resistive element or a channeled ionically resistive plate (CIRP). Normally, the ionically resistive element 206 is placed in close proximity with respect to the wafer. In contrast, an anode in the same close-proximity to the substrate would be significantly less apt to supply a nearly constant current to the wafer, but would merely support a constant potential plane at the anode metal surface, thereby allowing the current to be greatest where the net resistance from the anode plane to the terminus (e.g., to peripheral contact points on the wafer) is smaller. So while the ionically resistive element 206 has been referred to as a high-resistance virtual anode (HRVA), this does not imply that electrochemically the two are interchangeable. Under certain operational conditions, the ionically resistive element 206 would more closely approximate and perhaps be better described as a virtual uniform current source, with nearly constant current being sourced from across the upper plane of the ionically resistive element 206. While the ionically resistive element is certainly viewable as a “virtual current source”, i.e. it is a plane from which the current is emanating, and therefore can be considered a “virtual anode” because it can be viewed as a location or source from which anodic current emanates, it is the relatively high-ionic-resistance of the ionically resistive element 206 (with respect to the electrolyte) that leads the nearly uniform current across its face and to further advantageous, generally superior wafer uniformity when compared to having a metallic anode located at the same physical location. The plate's resistance to ionic current flow increases with increasing specific resistance of electrolyte contained within the various channels of the plate 206 (often but not always having the same or nearly similar resistance of the catholyte), increased plate thickness, and reduced porosity (less fractional cross sectional area for current passage, for example, by having fewer holes of the same diameter, or the same number of holes with smaller diameters, etc.).
Structure
The ionically resistive element 206 contains micro size (typically less than 0.04″) through-holes that are spatially and ionically isolated from each other and do not form interconnecting channels within the body of ionically resistive element, in many but not all implementations. Such through-holes are often referred to as non-communicating through-holes. They typically extend in one dimension, often, but not necessarily, normal to the plated surface of the wafer (in some embodiments the non-communicating holes are at an angle with respect to the wafer which is generally parallel to the ionically resistive element front surface). Often the through-holes are parallel to one another. Often the holes are arranged in a square array. Other times the layout is in an offset spiral pattern. These through-holes are distinct from 3-D porous networks, where the channels extend in three dimensions and form interconnecting pore structures, because the through-holes restructure both ionic current flow and fluid flow parallel to the surface therein, and straighten the path of both current and fluid flow towards the wafer surface. However, in certain embodiments, such a porous plate, having an interconnected network of pores, may be used in place of the 1-D channeled element (ionically resistive element). When the distance from the plate's top surface to the wafer is small (e.g., a gap of about 1/10 the size of the wafer radius, for example less than about 5 mm), divergence of both current flow and fluid flow is locally restricted, imparted and aligned with the ionically resistive element channels.
One example ionically resistive element 206 is a disc made of a solid, non-porous dielectric material that is ionically and electrically resistive. The material is also chemically stable in the plating solution of use. In certain cases the ionically resistive element 206 is made of a ceramic material (e.g., aluminum oxide, stannic oxide, titanium oxide, or mixtures of metal oxides) or a plastic material (e.g., polyethylene, polypropylene, polyvinylidene difluoride (PVDF), polytetrafluoroethylene, polysulphone, polyvinyl chloride (PVC), polycarbonate, and the like), having between about 6,000-12,000 non-communicating through-holes. The ionically resistive element 206, in many embodiments, is substantially coextensive with the wafer (e.g., the ionically resistive element 206 has a diameter of about 300 mm when used with a 300 mm wafer) and resides in close proximity to the wafer, e.g., just below the wafer in a wafer-facing-down electroplating apparatus. Preferably, the plated surface of the wafer resides within about 10 mm, more preferably within about 5 mm of the closest ionically resistive element surface. To this end, the top surface of the ionically resistive element 206 may be flat or substantially flat. Often, both the top and bottom surfaces of the ionically resistive element 206 are flat or substantially flat.
Another feature of the ionically resistive element 206 is the diameter or principal dimension of the through-holes and its relation to the distance between the ionically resistive element 206 and the substrate. In certain embodiments, the diameter of each through-hole (or of a majority of through-holes, or the average diameter of the through-holes) is no more than about the distance from the plated wafer surface to the closest surface of the ionically resistive element 206. Thus, in such embodiments, the diameter or principal dimension of the through holes should not exceed about 5 mm, when the ionically resistive element 206 is placed within about 5 mm of the plated wafer surface.
As above, the overall ionic and flow resistance of the plate 206 is dependent on the thickness of the plate and both the overall porosity (fraction of area available for flow through the plate) and the size/diameter of the holes. Plates of lower porosities will have higher impinging flow velocities and ionic resistances. Comparing plates of the same porosity, one having smaller diameter 1-D holes (and therefore a larger number of 1-D holes) will have a more micro-uniform distribution of current on the wafer because there are more individual current sources, which act more as point sources that can spread over the same gap, and will also have a higher total pressure drop (high viscous flow resistance).
In certain cases, however, the ionically resistive plate 206 is porous, as mentioned above. The pores in the plate 206 may not form independent 1-D channels, but may instead form a mesh of through holes which may or may not interconnect. It should be understood that as used herein, the term ionically resistive element (and its synonyms) are intended to include this embodiment, unless otherwise noted.
In a number of embodiments, the ionically resistive element 206 may be modified to include (or accommodate) an edge flow element. The edge flow element may be an integral part of the ionically resistive element 206 (e.g., the ionically resistive element and edge flow element together form a monolithic structure), or it may be a replaceable part installed on or near the ionically resistive element 206. The edge flow element promotes a higher degree of cross-flow, and hence shear on the substrate surface, near the edge of the substrate (e.g., near an interface between the substrate and the substrate holder). Without an edge flow element, an area of relatively low cross-flow may develop near the interface of the substrate and substrate holder, for example due to the geometry of substrate and substrate holder, and the direction of electrolyte flow. The edge flow element may act to increase cross-flow in this area, thereby promoting more uniform plating results across the substrate. Further details related to the edge flow element are presented below.
In these or other embodiments, the ionically resistive element 206 may include a plurality of flow regions. In various cases, the flow through each flow region can be controlled independently of the flow through other flow regions. Each flow region may receive electrolyte from a particular electrolyte source region of the ionically resistive element manifold 208. Examples of ionically resistive elements having a plurality of flow regions are shown in
In a simple embodiment shown in
Various characteristics described in relation to
The presence of an ionically resistive but ionically permeable element (ionically resistive element) 206 close to the wafer substantially reduces the terminal effect and improves radial plating uniformity in certain applications where terminal effects are operative/relevant, such as when the resistance of electrical current in the wafer seed layer is large relative to that in the catholyte of the cell. The ionically resistive element 206 also simultaneously provides the ability, in some embodiments, to have a substantially spatially-uniform impinging flow of electrolyte directed upwards at the wafer surface by acting as a flow diffusing manifold plate. In other embodiments, the ionically resistive element 206 includes a plurality of flow regions that, in operation, permit independent control over the flow through each flow region. In such cases, the impinging flow of electrolyte is purposefully spatially non-uniform (e.g., radially and/or azimuthally non-uniform), for example to compensate for on-substrate non-uniformities that are present before electroplating takes place. Importantly, if the same element 206 is placed farther from the wafer, the uniformity of ionic current and flow improvements become significantly less pronounced or non-existent.
Further, because non-communicating through-holes do not allow for lateral movement of ionic current or fluid motion within the ionically resistive element, the center-to-edge current and flow movements are blocked within the ionically resistive element 206, leading to further improvement in radial plating uniformity. In the embodiment shown in
It is noted that in some embodiments, the ionically resistive element 206 can be used primarily or exclusively as an intra-cell electrolyte flow resistive, flow controlling and thereby flow shaping element, sometimes referred to as a turboplate. This designation may be used regardless of whether or not the plate 206 tailors radial deposition uniformity by, for example, balancing terminal effects and/or modulating the electric field or kinetic resistances of plating additives coupled with the flow within the cell. Thus, for example, in TSV and WLP electroplating, where the seed metal thickness is generally large (e.g. >1000 Å thick) and metal is being deposited at very high rates, uniform distribution of electrolyte flow is very important, while radial non-uniformity control arising from ohmic voltage drop within the wafer seed may be less necessary to compensate for (at least in part because the center-to-edge non-uniformities are less severe where thicker seed layers are used). Therefore the ionically resistive element 206 can be referred to as both an ionically resistive ionically permeable element, and as a flow shaping element, and can serve a deposition-rate corrective function by either altering the flow of ionic current, altering the convective flow of material, or both.
In some cases, flow through the different flow regions of the ionically resistive element may be tailored to provide additional flow of electrolyte toward areas of the substrate where relatively greater mass transfer conditions are desired. For instance, enhanced mass transfer may be desirable in areas where the features are relatively deeper, which may be a result of relatively taller/thicker photoresist (or a purposeful design of the substrate).
Thicker photoresist corresponds with deeper features, making it difficult to plate uniformly between the different feature shapes. This difficulty may arise due to the different diffusion boundary layer thicknesses for the different feature shapes. The diffusion boundary layer thickness refers in this case to the distance between the bottom of a recessed feature and the depth at which the electroplating conditions become diffusion-controlled. The diffusion boundary layer is thicker for deeper features and thinner for shallower features. To compensate for this difference, additional electrolyte flow can be directed at areas of the substrate where the photoresist is thicker, increasing the mass transfer in these areas and making the diffusion boundary layer thickness more uniform between the different feature shapes.
Distance Between Wafer and Channeled PlateIn certain embodiments, a wafer holder 254 and associated positioning mechanism hold a rotating wafer very close to the parallel upper surface of the ionically resistive element 206. During plating, the substrate is generally positioned such that it is parallel or substantially parallel to the ionically resistive element (e.g., within about 10°). Though the substrate may have certain features thereon, only the generally planar shape of the substrate is considered in determining whether the substrate and ionically resistive element are substantially parallel.
In typical cases, the separation distance is about 0.5-10 millimeters, or about 2-8 millimeters. In some cases, the separation distance is about 2 mm or less, for example about 1 mm or less. This small plate to wafer distance can create a plating pattern on the wafer associated with proximity “imaging” of individual holes of the pattern, particularly near the center of wafer rotation. In such circumstances, a pattern of plating rings (in thickness or plated texture) may result near the wafer center. To avoid this phenomenon, in some embodiments, the individual holes in the ionically resistive element 206 (particularly at and near the wafer center) can be constructed to have a particularly small size, for example less than about ⅕th the plate to wafer gap. When coupled with wafer rotation, the small pore size allows for time averaging of the flow velocity of impinging fluid coming up as a jet from the plate 206 and reduces or avoids small scale non-uniformities (e.g., those on the order of micrometers). Despite the above precaution, and depending on the properties of the plating bath used (e.g. particular metal deposited, conductivities, and bath additives employed), in some cases deposition may be prone to occur in a micro-non-uniform pattern (e.g., forming center rings) as the time average exposure and proximity-imaging-pattern of varying thickness (for example, in the shape of a “bulls eye” around the wafer center) and corresponding to the individual hole pattern used. This can occur if the finite hole pattern creates an impinging flow pattern that is non-uniform and influences the deposition. In this case, introducing lateral flow across the wafer center, and/or modifying the regular pattern of holes right at and/or near the center, have both been found to largely eliminate any sign of micro-non-uniformities otherwise found there.
Porosity of Channeled PlateIn various embodiments, the ionically resistive element 206 has a sufficiently low porosity and pore size to provide a viscous flow resistance backpressure and high vertical impinging flow rates at normal operating volumetric flow rates. In some cases, about 1-10% of the ionically resistive element 206 is open area allowing fluid to reach the wafer surface. In particular embodiments, about 2-5% the plate 206 is open area. In a specific example, the open area of the plate 206 is about 3.2% and the effective total open cross sectional area is about 23 cm2.
In some embodiments, the porosity in the ionically resistive element 206 is uniform across the area of the ionically resistive element. In other embodiments, the porosity may be different at different regions of the ionically resistive element. In a particular embodiment where the ionically resistive element includes a plurality of flow regions, the average porosity in one flow region may be higher than the average porosity in another flow region. In a particular example, one flow region of the plate may have an average porosity that is greater than the average porosity of another flow region by a factor of at least about 1.2, for example at least about 1.5 or at least about 2. For instance, a first flow region may have a porosity that is about 2% and a second flow region may have a porosity that is about 2.4% (1.2*2%=2.4%). Such differences in channel porosity may be used (alone or in combination with other factors such as pump speed, valve position, and/or differences in channel size) to tune the velocity of the impinging flow on the substrate at different areas.
Hole Size of Channeled PlateThe porosity of the ionically resistive element 206 can be implemented in many different ways. In various embodiments, it is implemented with many vertical holes of small diameter. In some cases the plate 206 does not consist of individual “drilled” holes, but is created by a sintered plate of continuously porous material. Examples of such sintered plates are described in U.S. Pat. No. 6,964,792, [attorney docket NOVLP023] which is herein incorporated by reference in its entirety. In some embodiments, drilled non-communicating holes have a diameter of about 0.01 to 0.08 inches. In some cases, the holes have a diameter of about 0.02 to 0.03 inches, or between about 0.03-0.06 inches. As mentioned above, in various embodiments the holes have a diameter that is at most about 0.2 times the gap distance between the ionically resistive element 206 and the wafer. The holes are generally circular in cross section, but need not be. Further, to ease construction, all holes in the plate 206 may have the same diameter. However this need not be the case, and both the individual size and local density of holes may vary over the plate surface as specific requirements may dictate.
As an example, a solid plate 206 made of a suitable ceramic or plastic material (generally a dielectric insulating and mechanically robust material), having a large number of small holes provided therein, e.g. at least about 1000 or at least about 3000 or at least about 5000 or at least about 6000 (9465 holes of 0.026 inches diameter has been found useful). As mentioned, some designs have about 9000 holes. The porosity of the plate 206 is typically less than about 5 percent so that the total flow rate necessary to create a high impinging velocity is not too great. Using smaller holes helps to create a large pressure drop across the plate as compared to larger holes, aiding in creating a more uniform upward velocity through the plate.
In another example, channels of different sizes are provided on a single ionically resistive element 206. In a particular embodiment where the ionically resistive element includes a plurality of flow regions, the channels in one flow region may be smaller in average diameter than the channels in another flow region. In some cases, one flow region of the ionically resistive element may have an average channel diameter that is larger than the average channel diameter of another flow region by a factor of at least about 1.2, for example at least about 1.5 or at least about 2. In a particular example, a first flow region of the ionically resistive element has an average channel diameter of about 0.020 inches, and a second flow region of the ionically resistive element has an average channel diameter of about 0.024 inches (1.2*0.020 inches=0.024 inches). Such differences in channel diameter may be used (alone or in combination with other factors such as pump speed, valve position, and differences in porosity) to tune the velocity of the impinging flow on the substrate at different areas.
Generally, the distribution of holes over the ionically resistive element 206 may be of uniform density and non-random. In some cases, however, the density of holes may vary, particularly in the radial direction or corresponding with different flow regions of an ionically resistive element. In a specific embodiment, as described more fully below, there is a greater density and/or diameter of holes in the region of the plate that directs flow toward the center of the rotating substrate. Further, in some embodiments, the holes directing electrolyte at or near the center of the rotating wafer may induce flow at a non-right angle with respect to the wafer surface. Further, the hole patterns in this region may have a random or partially random distribution of non-uniform plating “rings” to address possible interaction between a limited number of holes and the wafer rotation. In some embodiments, the hole density proximate an open segment of a flow diverter or confinement ring 210 is lower than on regions of the ionically resistive element 206 that are farther from the open segment of the attached flow diverter or confinement ring 210.
Flow RegionsAs mentioned, in certain embodiments the ionically resistive element may include a plurality of flow regions. Each flow region may be supplied with electrolyte from a particular electrolyte source region of the ionically resistive element manifold. This configuration allows the flow through each flow region of the ionically resistive element to be controlled independently from the flow through other flow regions and independently from the flow through the cross flow injection manifold. The different electrolyte source regions are separated from one another to permit individual control over the flow through the different electrolyte source regions/flow regions. The separated electrolyte source regions may be in physical contact with one another (e.g., sharing a wall between them), and may be in fluidic communication with one another at some point in the apparatus (e.g., after passing through the ionically resistive element). The relevant consideration that “separates” the electrolyte source regions from one another is the ability to independently control the flow rates through each manifold.
Examples of ionically resistive elements having a plurality of flow regions are shown in
As used herein, the concept of independent control of flow rates does not necessarily mean that a first flow rate through one portion of the apparatus has no effect on a second flow rate through another portion of the apparatus. Rather, independent control of flow rates means that the relevant flow rates can be simultaneously controlled as desired (e.g., controlling one flow rate does not preclude simultaneously controlling another flow rate).
Ionically Resistive Element JetsIn some embodiments, the ionically resistive element may be adapted to include one or more ionically resistive element jets. Such jets may be similar to the electrolyte jets described herein. However, the ionically resistive element jets differ from the electrolyte jets in that the ionically resistive element jets are formed in/on the ionically resistive element itself. Typically, the openings of the jets are raised compared to the opening of the channels in the main body of the ionically resistive element.
As mentioned below,
In many implementations, electroplating results may be improved through the use of an edge flow element and/or a flow insert. Generally speaking, an edge flow element affects the flow distribution near the periphery of the substrate, proximate the interface between the substrate and substrate holder. The edge flow element differs from an electrolyte jet in that an electrolyte jet includes channels through which electrolyte is actively delivered, whereas edge flow elements do not actively deliver electrolyte, but rather, passively affect the flow of electrolyte in the vicinity of the edge flow element (although in some cases the edge flow elements may be dynamic/adjustable, as mentioned below). In some embodiments, the edge flow element may be integral with an ionically resistive element. In some other embodiments, the edge flow element may be integral with a substrate holder. In yet other embodiments, the edge flow element may be a separate piece that can be installed on an ionically resistive element or substrate holder. The edge flow element may be used to tune the flow distribution near the edge of the substrate, as is desired for a particular application. Advantageously, the flow element promotes a high degree of cross-flow near the periphery of the substrate, thereby promoting more uniform (from center to edge of the substrate), high quality electroplating results. An edge flow element is typically positioned, at least partially, radially inside of the inner edge of the substrate holder/the periphery of the substrate. In some cases, an edge flow element may be at least partially positioned at other locations, for example under the substrate holder and/or radially outside of the substrate holder, as described further below. In a number of drawings herein, the edge flow element is referred to as the “flow element.”
The edge flow element may be made of various materials. In some cases, the edge flow element may be made of the same material as the ionically resistive element and/or the substrate holder. Generally speaking, it is desirable for the material of the edge flow element to be electrically insulating.
Another method for improving cross-flow near the periphery of the substrate is to use a high rate of substrate rotation. However, fast substrate rotation presents its own set of disadvantages, and in various embodiments may be avoided. For example, where the substrate is rotated too quickly, it can prevent formation of an adequate cross-flow across the substrate surface. In certain embodiments, therefore, the substrate may be rotated at a rate between about 50-300 RPM, for example between about 100-200 RPM. Similarly, cross-flow near the periphery of the substrate can be promoted by using a relatively smaller gap between the ionically resistive element and the substrate. However, smaller ionically resistive element-substrate gaps result in electroplating processes that are more sensitive and have tighter tolerance ranges for process variables.
The modeling results show the predicted shear velocity at a location 0.25 mm from the surface of the substrate. Notably, the shear flow decreases dramatically near the edge of the substrate.
As shown in
In certain embodiments, the edge flow element 1710 may be shaped such that the cross flow in the cross flow manifold 1702 is directed more favorably into the corner formed by the substrate 1700 and substrate holder 1706. A variety of shapes may be used to achieve this purpose.
In one example, shims may be used to adjust the position (and to some degree shape) of an edge flow element. For instance, a series of shims may be provided, with shims of various heights for different applications and desired flow patterns/characteristics. The shims may be installed between the ionically resistive element and the edge flow element to raise the height of the edge flow element, thereby reducing the distance between the edge flow element and the substrate/substrate holder. In some cases, the shims may be used in an azimuthally asymmetric way, thereby achieving a different edge flow element height at different azimuthal locations. The same result can be achieved using screws (as shown by element 1912 in
In some implementations, the position and/or shape of the edge flow element 1910 may be dynamically adjusted during a plating process, for example using electric or pneumatic actuators.
Returning to
In similar embodiments, any combination of cross-sectional shapes may be used. Generally speaking, the cross-sectional shapes may be any shapes including, but not limited to, triangular, square, rectangular, circular, ellipsoidal, rounded, curved, pointed, trapezoidal, corrugated, hour-glass shaped, etc. Flow through passages may or may not be provided through the edge flow element 2010 itself. In another similar embodiment, the cross-sectional shapes may be similar, but of varying sizes around the periphery, thus introducing the azimuthal asymmetry. Likewise, the cross-sectional shapes may be the same or similar, but positioned at different vertical and/or horizontal locations with respect to the substrate/substrate holder and/or ionically resistive element 2004. The transition to different cross-sectional shapes may be abrupt or gradual. In
With respect to
In some embodiments, the vertical distance between the uppermost part of an edge flow element and the uppermost portion of an ionically resistive element may be between about 0-5 mm, for example between about 0-1 mm. In these or other cases, this distance may be at least about 0.1 mm, or at least about 0.25 mm, at one or more locations on the edge flow element. The vertical distance between the uppermost part of an edge flow element and the substrate may be between about 0.5-5 mm, in some cases between about 1-2 mm. In various embodiments, the distance between the uppermost part of an edge flow element and the uppermost portion of the ionically resistive element is between about 10-90% of the distance between the raised portion of the ionically resistive element and the substrate surface, in some cases between about 25-50%. The “uppermost portion of the ionically resistive element” referenced in this paragraph excludes the edge flow element itself (e.g., in cases where the edge flow element is integral with the ionically resistive element). Typically, the uppermost portion of the ionically resistive element is an upper surface of the ionically resistive element, positioned opposite the substrate in the cross-flow manifold. In various embodiments, as shown in
Returning to the embodiment of
Notably, the flow in the corner formed between the substrate 2200 and the substrate holder 2206 is somewhat low, but is improved compared to the case where no edge flow element 2210 is provided.
In certain embodiments, the edge flow element has a width (measured as the difference between the outer radius and the inner radius) between about 0.1-50 mm. In some such cases, this width is at least about 0.01 mm or at least about 0.25 mm. Typically, at least a portion of this width is positioned radially interior of the inner edge of the substrate holder. The height of the edge flow element depends in large part upon the geometry of the remaining parts of the electroplating apparatus, for example the height of the cross-flow manifold. Further, the height of the edge flow element depends on how this element is installed in an electroplating apparatus, and the accommodations made in other pieces of equipment (e.g., grooves machined into the ionically resistive element). In certain implementations, an edge flow element may have a height that is between about 0.1-5 mm, or between about 1-2 mm. Where shims are used, they can be provided at a variety of thicknesses. These thicknesses are also dependent upon the geometry of the plating apparatus and the accommodations made in the ionically resistive element or other portion of the apparatus for securing the edge flow element therein. For example, if the edge flow element fits into a groove in the ionically resistive element, as shown in
In terms of position, the edge flow element is typically positioned such that at least a portion of the edge flow element is radially interior of the inner edge of the substrate support. In many cases this means that the edge flow element is positioned such that at least a portion of the edge flow element is radially interior of the edge of the substrate itself. The horizontal distance by which the edge flow element extends inward from the inner edge of the substrate support may in certain embodiments be at least about 1 mm, or at least about 5 mm, or at least about 10 mm, or at least about 20 mm. In some embodiments, this distance is about 30 mm or less, for example about 20 mm or less, about 10 mm or less, or about 2 mm or less. In these or other embodiments, the horizontal distance by which the edge flow element extends radially outward from the inner edge of the substrate support may be at least about 1 mm, or at least about 10 mm. Generally, there is no upper limit for the distance by which the edge flow element extends radially outward from the inner edge of the substrate support, so long as the edge flow element can fit in the electroplating apparatus.
Another way in which the edge flow element may be azimuthally asymmetric is by providing flow bypass passages of different dimensions at different locations on the edge flow element. For example, the flow bypass passages near the inlet and/or outlet may be wider or narrower, or taller or shorter, than flow bypass passages farther away from the inlet and/or outlet. Similarly, the flow bypass passages near the inlet may be wider or narrower, or taller or shorter, than flow bypass passages near the outlet. In these or other cases, the space between adjacent flow bypass passages may be non-uniform. In some embodiments, the flow bypass passages may be closer together (or farther apart) near the inlet and/or outlet regions, compared to regions that are farther away from the inlet and/or outlet. Similarly, the flow bypass passages may be closer together (or farther apart) near the inlet area compared to the outlet area. The shape of the flow bypass passages may also be azimuthally asymmetric, for example to promote cross-flow. One way to accomplish this in certain implementations may be to use flow bypass passages that are, to some degree, aligned with the direction of cross-flow. In some embodiments, the height of the edge flow element is azimuthally asymmetric. The relatively higher portions may be aligned with an inlet and/or outlet side of the electroplating apparatus in some embodiments. This same result can be accomplished using an edge flow element having an azimuthally symmetric height, installed onto an ionically resistive element using shims of varying heights.
While it is understood that electrolyte may exit the electroplating cell at many positions, the “outlet area” of the electroplating cell is understood to be the area opposite the inlet (where the cross-flowing electrolyte originates, not considering electrolyte which enters the cross-flow manifold through holes in the ionically resistive element). In other words, the inlet corresponds to the upstream area, where the cross-flow substantially originates, and the outlet corresponds to the downstream area that is opposite the upstream area.
The table in
In various embodiments, an electrolyte jet may be included to provide additional impinging electrolyte flow toward the substrate at a particular location on the substrate. This flow is in addition to the impinging electrolyte that passes through an ionically resistive element. The term electrolyte jet includes both edge jets (which preferentially deliver electrolyte near the periphery of the substrate compared to other regions of the substrate) and inner jets (which preferentially deliver electrolyte at non-peripheral regions of the substrate compared to peripheral regions of the substrate), as described herein. The term also includes electrolyte jets that deliver electrolyte at both peripheral and non-peripheral regions of the substrate. The term electrolyte jet is not intended to cover any jets that are formed by channels in an ionically resistive element. However, in some cases the ionically resistive element may be adapted to include both channels and jets. In such embodiments, the jets formed in the ionically resistive element are referred to as ionically resistive element jets, which are further described above. As used herein, the terms “electrolyte jet,” “edge jet,” and “inner jet” are understood to include a plurality of individual jets unless otherwise stated.
In some cases, as shown in
The electrolyte jets may be implemented in a uniform or non-uniform manner. The non-uniformities may be radial and/or azimuthal. Although
The electrolyte jets may be positioned in a particular way with respect to the channels in the ionically resistive element. Generally speaking, the electrolyte jets in many cases are not closely electrically connected to the anode, and therefore do not play a strong role in the distribution of current toward the substrate (though they do play a strong role in the distribution of flow toward the substrate). By contrast, the channels in the ionically resistive element are often provided specifically to control the distribution of current toward the substrate (and to some extent, the flow distribution toward the substrate). In some cases, some or all of the electrolyte jets and the channels in the ionically resistive element may be aligned with one another azimuthally. This results in a relatively high delivery of impinging electrolyte on the substrate, as well as high local voltage at the same time. This may be particularly useful in areas of the substrate where relatively greater plating is desired, e.g., where photoresist is relatively thick and/or where features are otherwise relatively large. In these or other cases, some or all of the electrolyte jets may alternate with the channels in the ionically resistive element (e.g., such that the electrolyte jets and the ionically resistive element channels are provided at different azimuthal locations). In some such embodiments, the electrolyte jets may be provided proximate the radius and/or diameter of the of the substrate, so that as the substrate rotates, a relevant portion of the substrate experiences: (i) relatively high convection conditions paired with relatively low current/voltage conditions in regions where the flow from the electrolyte jet(s) impinge upon the substrate, and (ii) relatively low convection conditions paired with relatively high current/voltage conditions in regions where the flow from the channels in the ionically resistive element impinges upon the substrate. By alternating between high convection/low voltage and low convection/high voltage conditions, the time constant for electroplating is increased, which may result in more uniform plaint results between different feature sizes/shapes. Each electrolyte jet acts to flush the features in a particular region with new plating solution when that region of the substrate is proximate the electrolyte jet, and then current is applied to the region with relatively low convection when the relevant portion of the substrate is proximate the channels in the ionically resistive element.
In various embodiments, an electrolyte jet may be implemented to preferentially deliver electrolyte toward the substrate at a peripheral region of the substrate (in which case the electrolyte jet may be referred to as an edge jet) or at a non-peripheral region of the substrate (in which case the electrolyte jet may be referred to as an inner jet).
Edge JetsIn certain implementations, the electroplating apparatus may include an edge jet. The edge jet may include a single jet, or a plurality of jets. The edge jet may be positioned proximate the periphery of the substrate when the substrate is being electroplated, and acts to preferentially provide additional electrolyte to the plating face of the substrate near the periphery of the substrate as opposed to near the center of the substrate. This additional fluid flow may preferentially enhance the hydrodynamic conditions near the edge of the substrate compared to the center. This preferential enhancement may combat pre-existing non-uniformities on a substrate, for example photoresist that is thicker near the edge of the substrate and thinner near the center of the substrate, as described in relation to
It may be beneficial to ensure that the electrolyte delivered to and through the edge jets is relatively isolated electrically from the electrolyte that is present in or below the ionically resistive element manifold. The electrolyte that passes through the jets may have a nominally high electrical path to the anode. This electrical isolation establishes/maintains uniform delivery of current to the substrate. However, in some cases, the jets may be configured to provide a short electrical path between the anode and the jets. In this way, the jets can be used to inject additional current at a desired location.
The edge jets may be oriented to deliver electrolyte at a normal or non-normal angle toward the substrate, as shown in
A topside insert 3360 extends around the entire periphery of the cross flow manifold, as shown in
In another embodiment, an area where no edge jets are provided may correspond with an inlet to the cross flow manifold. In another embodiment shown in
The edge jets may be formed in a variety of manners. In some embodiments, the edge jets are formed by a topside insert as described in relation to
The channels forming the jets may end at a vertical location that is above, at, or below the substrate-facing surface of the ionically resistive element. Similarly, the channels forming the jets may end at a vertical location that is above, at, or below the location at which the horizontally cross flowing electrolyte enters the cross flow manifold. In some cases, the jets may be implemented as flutes that may or may not extend above the substrate-facing surface of the ionically resistive element, for example as shown in
The diameter of the jets may be between about 0.01-0.25 inches, for example between about 0.020-0.125 inches. The diameter of the jets may be uniform or non-uniform among the different jets. In some cases, the jets have a substantially circular cross section. In other cases, the jets may be implemented as slits/slots to thereby distribute the electrolyte in a more fan-like manner, for example as shown in
In some embodiments, one or more inner jets may be provided. These inner jets are similar to the edge jets described above, but extend further inward toward the center of the substrate. In this way, the inner jets can preferentially promote enhanced mass transfer at any desired location. The inner jets may generally have any of the characteristics described in relation to the edge jets, except that they deliver electrolyte at non-peripheral locations on the substrate. Edge Jets and inner jets may collectively be referred to as electrolyte jets.
In some embodiments, the inner jets may be used to preferentially promote enhanced hydrodynamic conditions at a particular location that is radially inward from the periphery of the substrate. In other words, the inner jets may deliver fluid at a non-peripheral location that is within a certain distance of the center of the substrate. In some such cases, the inner jets may extend radially inward to provide fluid at a location that is radially outward from the center of the substrate by no more than about 25%, or 50%, or 75%, or 85%, as compared to the radius of the substrate. In one example where the substrate has a diameter of about 300 mm and a radius of about 150 mm, the inner jets deliver fluid to the substrate at a radius of about 37.5 mm (0.25*150 mm=37.5 mm).
In a particular embodiment, both edge jets and inner jets may be provided. In another particular embodiment, edge jets, inner jets, and an edge flow element may be provided. In another embodiment, any combination of the following features may be present: edge jets, inner jets, an edge flow element, an ionically resistive element with plurality of flow regions, and an ionically resistive element manifold having a plurality of electrolyte source regions.
It is to be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated may be performed in the sequence illustrated, in other sequences, in parallel, or in some cases omitted. Likewise, the order of the above described processes may be changed.
The subject matter of the present disclosure includes all novel and nonobvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.
Modulation of Cross Flow Manifold and CurrentIn certain implementations, the height of the cross flow manifold may be modulated during electroplating. In some such embodiments, the cross flow manifold may be modulated between a sealed state and an unsealed state. The substrate may be selectively rotated while the cross flow manifold is in the unsealed state. Such techniques are further described in U.S. patent application Ser. No. 15/225,716, filed Aug. 1, 2016, and titled “DYNAMIC MODULATION OF CROSS FLOW MANIFOLD DURING ELECTROPLATING,” which is herein incorporated by reference. In these or other embodiments, the current applied to the substrate may be modulated during electroplating. The timing of the current modulation may correspond to the timing of the cross flow manifold height modulation. Such current modulation techniques are further described in U.S. patent application Ser. No. 15/413,252, filed Jan. 23, 2017, and titled “MODULATION OF APPLIED CURRENT DURING SEALED ROTATIONAL ELECTROPLATING,” which is herein incorporated by reference in its entirety.
A few observations that suggest that improved cross flow through the cross flow manifold 226 is desirable are presented in this section. Throughout this section, two basic plating cell designs are tested. Both designs contain a confinement ring 210, sometimes referred to as a flow diverter, defining a cross flow manifold 226 on top of the ionically resistive element 206. Neither design includes an edge flow element, though such an element may be added to either setup, as desired. The first design, sometimes referred to as the control design and/or the TC1 design, does not include a side inlet to this cross flow manifold 226. Instead, in the control design, all flow into the cross flow manifold 226 originates below the ionically resistive element 206 and travels up through the holes in the ionically resistive element 206 before impinging on the wafer and flowing across the face of the substrate. The second design, sometimes referred to as the second design and/or the TC2 design, includes a cross flow injection manifold 222 and all associated hardware for injecting fluid directly into the cross flow manifold 226 without passing through the channels or pores in the ionically resistive element 206 (note that in some cases, however, the flow delivered to the cross flow injection manifold passes through dedicated channels near the periphery of the ionically resistive element 206, such channels being distinct/separate from the channels used to direct fluid from the ionically resistive element manifold 208 to the cross flow manifold 226).
While the above is a full description of the specific embodiments, various modifications, alternative constructions and equivalents may be used. Therefore, the above description and illustrations should not be taken as limiting the scope of the disclosed embodiments.
For example, various elements described herein may be combined as desired for a particular application. Similarly, various elements described herein may be omitted as desired for a particular application. One element that may be omitted in certain embodiments is the side inlet to the cross flow manifold for introducing cross-flowing electrolyte. In such embodiments, the cross flow injection manifold may be similarly omitted, and all of the electrolyte flowing in the cross flow manifold may originate from (a) the ionically resistive element manifold (which may be implemented as a plurality of electrolyte source regions), and/or (b) the edge jets, if present. Example apparatus are further described in U.S. Pat. No. 8,795,480, which is herein incorporated by reference in its entirety. While having additional electrolyte flow originating from the cross flow injection manifold/side inlet may be beneficial in a number of implementations, it is not necessary for practicing the disclosed embodiments.
Claims
1. An electroplating apparatus comprising:
- an electroplating chamber configured to contain an electrolyte and an anode while electroplating metal onto a substrate, the substrate being substantially planar;
- an inlet for introducing electrolyte to the electroplating chamber;
- an outlet for removing electrolyte from the electroplating chamber;
- a substrate holder configured to hold the substrate such that a plating face of the substrate is separated from the anode during electroplating; and
- an electrolyte jet configured to deliver electrolyte toward the plating face of the substrate in a non-uniform manner, wherein a flow rate through the electrolyte jet and a total flow rate through the electroplating chamber are independently controllable.
2. The apparatus of claim 1, wherein the electrolyte jet is an edge jet configured to deliver the electrolyte such that it preferentially impinges upon a peripheral region of the substrate.
3. The apparatus of claim 1, wherein the electrolyte jet is an inner jet configured to deliver electrolyte such that it preferentially impinges upon a non-peripheral region of the substrate.
4. The apparatus of claim 1, wherein the electrolyte jet comprises a plurality of individual jets.
5. The apparatus of claim 4, wherein at least two of the plurality of individual jets of the electrolyte jet are positioned to deliver electrolyte at different radial locations.
6. The apparatus of claim 5, wherein a first individual jet of the plurality of electrolyte jets is configured to deliver electrolyte at a peripheral region of the substrate, and wherein a second individual jet of the plurality of electrolyte jets is configured to deliver electrolyte at a non-peripheral region of the substrate.
7. The apparatus of claim 4, wherein the electrolyte jet is divided into at least a first region and a second region, each of the first and second regions of the electrolyte jet being supplied electrolyte from a distinct electrolyte source, and each of the first and second regions of the electrolyte jet comprising at least one of the plurality of individual jets, wherein a first flow rate through the first region of the electrolyte jet is independently controllable from a second flow rate through the second region of the electrolyte jet.
8. The apparatus of claim 4, wherein the electrolyte jet is provided at a particular azimuthal location or locations such that as the substrate rotates, an area on the plating face of the substrate is cyclically exposed to (i) regions where the electrolyte jet is present and (ii) regions where the electrolyte jet is absent.
9. The apparatus of claim 8, wherein within regions where the electrolyte jet is present, the electrolyte jet delivers electrolyte at different radial locations, wherein the flow rate of electrolyte through the electrolyte jet is non-uniform at the different radial locations.
10. The apparatus of claim 1, wherein the electrolyte jet is configured to direct electrolyte toward the substrate at a normal angle with respect to the plating face of the substrate.
11. The apparatus of claim 1, wherein the electrolyte jet is configured to direct electrolyte toward the substrate at a non-normal angle with respect to the plating face of the substrate.
12. The apparatus of claim 11, wherein the electrolyte jet comprises at least one individual jet that is angled radially inwards.
13. The apparatus of claim 1, further comprising a jet manifold that supplies electrolyte to the electrolyte jet.
14. The apparatus of claim 13, further comprising
- an ionically resistive element including a substrate-facing surface that is separated from the plating face of the substrate by a gap, the gap forming a cross flow manifold, wherein the ionically resistive element is at least coextensive with the plating face of the substrate during electroplating, the ionically resistive element adapted to provide electrolyte transport and ionic transport through the ionically resistive element during electroplating;
- a side outlet to the cross flow manifold for receiving electrolyte flowing in the cross flow manifold; and
- an ionically resistive element manifold that supplies electrolyte below the ionically resistive element, wherein the ionically resistive element manifold and the jet manifold are separated from one another.
15. The apparatus of claim 13, further comprising
- an ionically resistive element including a substrate-facing surface that is separated from the plating face of the substrate by a gap, the gap forming a cross flow manifold, wherein the ionically resistive element is at least coextensive with the plating face of the substrate during electroplating, the ionically resistive element adapted to provide electrolyte transport and ionic transport through the ionically resistive element during electroplating;
- a side inlet to the cross flow manifold for introducing electrolyte to the cross flow manifold;
- a side outlet to the cross flow manifold for receiving electrolyte flowing in the cross flow manifold; and
- a cross flow injection manifold, wherein the side inlet and the side outlet are positioned proximate azimuthally opposing perimeter locations on the plating face of the substrate during electroplating, wherein the cross flow injection manifold supplies electrolyte to the side inlet, and wherein the jet manifold and the cross flow injection manifold are separated from one another.
16. The apparatus of claim 1, further comprising an edge flow element positioned proximate a periphery of the substrate and at least partially radially inside of a corner formed at an interface between the substrate and the substrate holder, wherein the edge flow element is configured to direct electrolyte into the corner formed at the interface between the substrate and the substrate holder, the edge flow element being ring-shaped or arc-shaped.
17. The apparatus of claim 1, further comprising wherein the electrolyte jet comprises a channel that extends from a first location to a second location, the first location being positioned below a plane formed by the substrate-facing surface of the ionically resistive element, and the second location being positioned at or above the plane formed by the substrate-facing surface of the ionically resistive element.
- an ionically resistive element including a substrate-facing surface that is separated from the plating face of the substrate by a gap, the gap forming a cross flow manifold, wherein the ionically resistive element is at least coextensive with the plating face of the substrate during electroplating, the ionically resistive element adapted to provide electrolyte transport and ionic transport through the ionically resistive element during electroplating;
18. An electroplating apparatus comprising:
- (a) an electroplating chamber configured to contain an electrolyte and an anode while electroplating metal onto a substrate, the substrate being substantially planar;
- (b) a substrate holder configured to hold the substrate such that a plating face of the substrate is separated from the anode during electroplating;
- (c) an ionically resistive element comprising: (i) a substrate-facing surface that is separated from the plating face of the substrate by a gap, the gap forming a cross flow manifold, (ii) a first flow region and a second flow region, wherein each of the first and second flow regions allow for transport of an electrolyte through the ionically resistive element during electroplating, wherein the ionically resistive element is at least coextensive with the plating face of the substrate during electroplating, the ionically resistive element adapted to provide ionic transport through the ionically resistive element during electroplating;
- (d) an ionically resistive element manifold positioned below the ionically resistive element, the ionically resistive element manifold comprising a first electrolyte source region and a second electrolyte source region, the first and second electrolyte source regions being separated from one another, wherein the first electrolyte source region supplies electrolyte to the first flow region of the ionically resistive element and the second electrolyte source region supplies electrolyte to the second flow region of the ionically resistive element, and wherein a flow of electrolyte through the first flow region is independently controllable from a flow of electrolyte through the second flow region; and
- (e) a side outlet to the cross flow manifold for receiving electrolyte flowing in the cross flow manifold.
19. An electrolyte jet assembly for use in an electroplating apparatus, the electrolyte jet assembly comprising:
- a frame comprising a portion that is ring-shaped or arc-shaped, the frame being configured to engage with a substrate holder and/or an ionically resistive element of the electroplating apparatus; and
- a plurality of jets positioned on the frame, each jet comprising a channel through which electrolyte flows during electroplating, wherein the jets are configured to deliver impinging electrolyte on a plating face of a substrate supported in the substrate holder during electroplating.
Type: Application
Filed: Mar 9, 2017
Publication Date: Sep 13, 2018
Inventors: Gabriel Hay Graham (Portland, OR), Bryan L. Buckalew (Tualatin, OR), Lee Peng Chua (Beaverton, OR), Robert Rash (West Linn, OR), James Isaac Fortner (Newberg, OR), Aaron Berke (Portland, OR)
Application Number: 15/455,011
