FINFET DEVICE WITH AN ETCH STOP LAYER POSITIONED BETWEEN A GATE STRUCTURE AND A LOCAL ISOLATION MATERIAL
One illustrative method disclosed herein includes forming a sacrificial gate structure above a fin, wherein the sacrificial gate structure is comprised of a sacrificial gate insulation layer, a layer of insulating material, a sacrificial gate electrode layer and a gate cap layer, forming a sidewall spacer adjacent opposite sides of the sacrificial gate structure, removing the sacrificial gate structure to thereby define a gate cavity that exposes a portion of the fin, and forming a replacement gate structure in the gate cavity. One illustrative device disclosed herein includes a plurality of fin structures that are separated by a trench formed in a substrate, a local isolation material positioned within the trench, a gate structure positioned around portions of the fin structures and above the local isolation material and an etch stop layer positioned between the gate structure and the local isolation material within the trench.
1. Field of the Invention
Generally, the present disclosure relates to the manufacture of sophisticated semiconductor devices, and, more specifically, to various methods of forming 3-D semiconductor devices, such as FinFET devices, using a replacement gate technique, and a novel 3-D device.
2. Description of the Related Art
The fabrication of advanced integrated circuits, such as CPU's, storage devices, ASIC's (application specific integrated circuits) and the like, requires the formation of a large number of circuit elements in a given chip area according to a specified circuit layout, wherein so-called metal oxide field effect transistors (MOSFETs or FETs) represent one important type of circuit element that substantially determines performance of the integrated circuits. A FET is a planar device that typically includes a source region, a drain region, a channel region that is positioned between the source region and the drain region, and a gate electrode positioned above the channel region. Current flow through the FET is controlled by controlling the voltage applied to the gate electrode. If there is no voltage applied to the gate electrode, then there is no current flow through the device (ignoring undesirable leakage currents, which are relatively small). However, when an appropriate voltage is applied to the gate electrode, the channel region becomes conductive, and electrical current is permitted to flow between the source region and the drain region through the conductive channel region.
To improve the operating speed of FETs, and to increase the density of FETs on an integrated circuit device, device designers have greatly reduced the physical size of FETs over the years. More specifically, the channel length of FETs has been significantly decreased, which has resulted in improving the switching speed of FETs. However, decreasing the channel length of a FET also decreases the distance between the source region and the drain region. In some cases, this decrease in the separation between the source and the drain makes it difficult to efficiently inhibit the electrical potential of the source region and the channel from being adversely affected by the electrical potential of the drain. This is sometimes referred to as a so-called short channel effect, wherein the characteristic of the FET as an active switch is degraded.
In contrast to a FET, which has a planar structure, a so-called FinFET device has a three-dimensional (3-D) structure. More specifically, in a FinFET, a generally vertically positioned fin-shaped active area is formed and a gate electrode encloses both sides and an upper surface of the fin-shaped active area to form a tri-gate structure so as to use a channel having a three-dimensional structure instead of a planar structure. In some cases, an insulating cap layer, e.g., silicon nitride, is positioned at the top of the fin and the FinFET device only has a dual-gate structure. Unlike a planar FET, in a FinFET device, a channel is formed perpendicular to a surface of the semiconducting substrate so as to reduce the physical size of the semiconductor device. Also, in a FinFET, the junction capacitance at the drain region of the device is greatly reduced, which tends to reduce at least some short channel effects.
Device manufacturers are under constant pressure to produce integrated circuit products with increased performance and lower production costs relative to previous device generations. Thus, device designers spend a great amount of time and effort to maximize device performance, while seeking ways to reduce manufacturing costs and improve manufacturing reliability. As it relates to 3D devices, device designers have spent many years and employed a variety of techniques in an effort to improve the performance capability and reliability of such devices.
For many early device technology generations, the gate structures of most transistor elements have been comprised of a plurality of silicon-based materials, such as a silicon dioxide and/or silicon oxynitride gate insulation layer, in combination with a polysilicon gate electrode. However, as the channel length of aggressively scaled transistor elements has become increasingly smaller, many newer generation devices employ gate structures that contain alternative materials in an effort to avoid the short channel effects which may be associated with the use of traditional silicon-based materials in reduced channel length transistors. For example, in some aggressively scaled transistor elements, which may have channel lengths on the order of approximately 10-20 nm or less, gate structures that include a so-called high-k dielectric gate insulation layer and one or more metal layers that function as the gate electrode (HK/MG) have been implemented. Such alternative gate structures have been shown to provide significantly enhanced operational characteristics over the heretofore more traditional silicon dioxide/polysilicon gate structure configurations.
Depending on the specific overall device requirements, several different high-k materials—i.e., materials having a dielectric constant, or k-value, of approximately 10 or greater—have been used with varying degrees of success for the gate insulation layer in an HK/MG gate electrode structure. For example, in some transistor element designs, a high-k gate insulation layer may include tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), titanium oxide (TiO2), aluminum oxide (Al2O3), hafnium silicates (HfSiOx) and the like. Furthermore, one or more non-polysilicon metal gate electrode materials—i.e., a metal gate stack—may be used in HK/MG configurations so as to control the work function of the transistor. These metal gate electrode materials may include, for example, one or more layers of titanium (Ti), titanium nitride (TiN), titanium-aluminum (TiAl), aluminum (Al), aluminum nitride (AlN), tantalum (Ta), tantalum nitride (TaN), tantalum carbide (TaC), tantalum carbonitride (TaCN), tantalum silicon nitride (TaSiN), tantalum silicide (TaSi) and the like.
One well-known processing method that has been used for forming a FinFET device with a high-k/metal gate structure is the so-called “gate last” or “replacement gate” technique. As it relates to the formation of the sacrificial and replacement gate structures, one typical replacement gate technique generally involves the following steps: 1) performing an etching process through a patterned mask layer to define a plurality of trenches in a semiconducting substrate which thereby defines a plurality of fin structures; 2) over-filling the trenches with an insulating material, such as silicon dioxide; 3) performing a chemical mechanical polishing (CMP) process using the hard mask layer as a polish-stop to remove excess amounts of the insulating material; 4) performing an etch-back etching process to remove a desired amount of the insulating material from within the trenches until such time as only the desired amount of the insulating material remains positioned in the bottom of the trenches (hereinafter referred to as the “CMP/etch-back” process); 5) forming a) a layer of material for a sacrificial gate insulation layer, b) depositing a layer of material for a sacrificial gate electrode and c) depositing a layer of material for a gate cap layer; 6) patterning the layers referenced in steps 5a-c to define a sacrificial gate structure; 7) forming a silicon nitride sidewall spacer adjacent the sacrificial gate structure; 8) depositing a layer of insulating material on the device and performing a CMP process that stops on the gate cap layer; 9) performing a plurality of etching processes to remove the gate cap layer, the sacrificial gate electrode and the sacrificial gate insulation layer to thereby define a gate cavity that is laterally defined by the inner walls of the spacers; 10) depositing a final gate insulation layer and one or more metal layers in the gate cavity; and 11) performing a CMP process to remove excess portions of the final gate insulation layer and the various metal layers to thereby define the final gate structure for the FinFET device.
The above-described replacement gate technique, while effective, is not without its problems. First, the above-described process sequence is not readily transferrable to FinFET devices when there is a desire to make another FinFET device to change the fin height, e.g., to change the fin height from 5 nm to 15 or 20 nm. That is, the etching processes that are performed to pattern the sacrificial gate insulation layer, the sacrificial gate electrode layer and the gate cap layer are, more or less, based upon the final desired fin height of the fins in the device. Thus, when exploring potential changes to product designs or actually implementing a change in the fin height on a production device, the patterning process performed on previously manufactured devices may not simply be used on the new devices, i.e., a new gate patterning process sequence may need to be tested and qualified for making the newly designed product, all at great time and expense. As another example, using the above-described process flow, the fins are more susceptible to damage because the patterning of the dummy gate polysilicon material is non-selective relative to the silicon fins and may result in damage to the fins if the hard mask used during the poly etching process is compromised.
The present disclosure is directed to various methods of forming 3-D semiconductor devices, such as FinFET devices, using a replacement gate technique, and to novel 3-D devices that may solve or reduce one or more of the problems identified above.
SUMMARY OF THE INVENTIONThe following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.
Generally, the present disclosure is directed to various methods of forming 3-D semiconductor devices, such as FinFET devices, using a replacement gate technique, and to novel 3-D devices. In one example, the method disclosed herein includes forming a fin in a semiconducting substrate, forming a sacrificial gate structure above the fin, wherein the sacrificial gate structure is comprised of a sacrificial gate insulation layer, a layer of insulating material positioned above the sacrificial gate insulation layer, a sacrificial gate electrode layer positioned above the layer of insulating material and a gate cap layer positioned above the sacrificial gate electrode layer, forming a sidewall spacer adjacent opposite sides of the sacrificial gate structure, removing the sacrificial gate structure to thereby define a gate cavity that exposes a portion of the fin and forming a replacement gate structure in the gate cavity.
Another illustrative method disclosed herein includes forming a plurality of trenches in a semiconducting substrate to thereby define a fin, forming a local isolation region in the trenches, forming an etch stop layer on the isolation regions, forming a sacrificial gate insulation layer above the fin, forming a layer of insulating material above the sacrificial gate insulation layer, forming a sacrificial gate electrode layer above the layer of insulating material and forming a gate cap layer above the sacrificial gate electrode layer. In this embodiment, the method further includes performing at least one first etching process on the gate cap layer and the sacrificial gate electrode layer to define a patterned gate structure comprised of a portion of the gate cap layer and a portion of the sacrificial gate electrode layer, wherein the first etching process stops on the layer of insulating material and exposes portions of the layer of insulating material, performing at least one second etching process to remove the exposed portions of the layer of insulating material, wherein the second etching process stops on and exposes portions of the sacrificial gate insulation, performing at least one third etching process to remove the exposed portions of the gate insulation layer to thereby define a sacrificial gate structure comprised of a portion of the sacrificial gate insulation layer, a portion of the layer of insulating material, a portion of the sacrificial gate electrode layer and a portion of the gate cap layer, wherein the third etching process stops on the etch stop layer, forming a sidewall spacer adjacent opposite sides of the sacrificial gate structure, removing the sacrificial gate structure to thereby define a gate cavity that exposes a portion of the fin and forming a replacement gate structure in the gate cavity.
One illustrative device disclosed herein includes a semiconducting substrate comprising a plurality of fin structures that are separated by a trench formed in the substrate, a local isolation material positioned within the trench, a gate structure positioned around portions of the fin structures and above the local isolation material and an etch stop layer positioned between the gate structure and the local isolation material within the trench.
The disclosure may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:
While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTIONVarious illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present subject matter will now be described with reference to the attached figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the present disclosure with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.
In general, the present disclosure is directed to various methods of forming 3-D semiconductor devices, such as FinFET devices, using a replacement gate technique, and to various novel 3-D devices. In the example described herein, the 3-D device is an illustrative FinFET device. However, after a complete reading of the present application, those skilled in the art will appreciate that the method disclosed herein may be employed on any type of 3-D device. Thus, the inventions disclosed herein should not be considered as being limited to any particular type of 3-D device. Moreover, as will be readily apparent to those skilled in the art upon a complete reading of the present application, the present method is applicable to a variety of devices, including, but not limited to, logic devices, memory devices, etc.
The illustrative device 10 includes a plurality of fins 14 that are defined in the substrate 12, a gate electrode 13, sidewall spacers 17 and a gate cap layer 15.
At the point of fabrication depicted in
The overall size, shape, number and configuration of the trenches 14 and fins 16 may vary depending on the particular application. The depth and width of the trenches 14 may vary depending upon the particular application. In one illustrative embodiment, based on current day technology, the depth of the trenches 14 may range from approximately 50-300 nm and the width of the trenches 14 may range from about 10-50 nm. In some embodiments, the fins 16 may have a width within the range of about 5-30 nm. In the illustrative example depicted in the attached drawings, the trenches 14 and fins 16 are all of a uniform size and shape. However, as discussed more fully below, such uniformity in the size and shape of the trenches 14 and the fins 16 is not required to practice at least some aspects of the inventions disclosed herein. In the example depicted herein, the trenches 14 are formed by performing an anisotropic etching process that results in the trenches 14 having a schematically depicted, generally rectangular configuration. In an actual real-world device, the sidewalls of the trenches 14 may be somewhat inwardly tapered, although that configuration is not depicted in the drawings. In some cases, the trenches 14 may have a reentrant profile near the bottom of the trenches 14. To the extent the trenches 14 are formed by performing a wet etching process, the trenches 14 may tend to have a more rounded configuration or non-linear configuration as compared to the generally rectangular configuration of the trenches 14 that are formed by performing an anisotropic etching process. Thus, the size and configuration of the trenches 14 and the fins 16, and the manner in which they are made, should not be considered a limitation of the present invention. For ease of disclosure, only the substantially rectangular trenches 14 and fins 16 will be depicted in subsequent drawings.
The patterned mask layer 18 is intended to be representative in nature as it may be comprised of a variety of materials, such as, for example, silicon nitride, silicon oxynitride, silicon dioxide, etc. Moreover, the patterned mask layer 18 may be comprised of multiple layers of material, such as, for example, a silicon nitride layer and a layer of silicon dioxide. The patterned mask layer 18 may be formed by forming or depositing the layer(s) of material that comprise the mask layer 18 and thereafter directly patterning the mask layer 18 using known photolithography and etching techniques. Alternatively, the patterned mask layer 18 may be formed by using known sidewall image transfer techniques. Thus, the particular form and composition of the patterned mask layer 18 and the manner in which it is made should not be considered a limitation of the present invention. In the case where the patterned mask layer 18 is comprised of one or more hard mask layers, such layers may be formed by performing a variety of known processing techniques, such as a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, an epitaxial deposition process (EPI), or plasma enhanced versions of such processes, and the thickness of such a layer(s) may vary depending upon the particular application.
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The exposed portions of the sacrificial gate insulation layer 26 depicted in
The etching process(es) 37 may be performed using wet or dry etching processes that use the same etch chemistry or by using a different etch chemistry than that employed in the etching process(es) 35. In one embodiment, the etching processes 35, 37 may be one single etching sequence in which etch chemistries may or may not be changed.
Irrespective of how the exposed portions of the sacrificial gate insulation layer 26 are removed, the methods disclosed herein result in the formation of a novel sacrificial gate structure 39 comprised of the sacrificial gate insulation layer 26, the layer of insulating material 28, the sacrificial gate electrode 30 and the gate cap layer 32.
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The methods disclosed herein result in the formation of a device 10 with various novel features. With reference to
The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
Claims
1-16. (canceled)
17. A device, comprising:
- a semiconducting substrate comprising a plurality of fin structures that are separated by a trench formed in said substrate;
- a local isolation material positioned within said trench;
- a gate structure positioned around portions of said fin structures and above said local isolation material; and
- an etch stop layer positioned between said gate structure and said local isolation material within said trench.
18. The device of claim 17, further comprising source/drain regions positioned above said local isolation material, wherein said etch stop layer is positioned between said source/drain regions and said local isolation material within said trench.
19. The device of claim 17, wherein said gate structure comprises a high-k gate insulation material and at least one metal layer positioned above said high-k gate insulation layer.
20. The device of claim 17, wherein said etch stop layer is positioned on and in contact with said local isolation material within said trench and wherein said gate structure comprises a gate insulation layer that is positioned and in contact with said etch stop layer within said trench.
21. The device of claim 17, wherein said local isolation material is comprised of silicon dioxide and said etch stop layer is comprised of silicon nitride.
22. The device of claim 18, wherein said source/drain regions are merged source/drain regions.
23. The device of claim 17, wherein said gate structure is a replacement gate structure.
24. A device, comprising:
- a semiconducting substrate comprising a plurality of fin structures that are separated by a trench formed in said substrate;
- a local isolation material positioned within said trench;
- an etch stop layer positioned and in contact with said local isolation material within said trench;
- a gate structure positioned around portions of said fin structures, wherein said gate structure comprises a gate insulation layer that is positioned and in contact with said etch stop layer within said trench; and
- source/drain regions positioned above said etch stop layer within said trench.
25. The device of claim 24, wherein said gate insulation layer is comprised of a high-k insulating material.
26. The device of claim 24, wherein said gate structure further comprises at least one metal layer positioned above said gate insulation layer.
27. The device of claim 24, wherein said local isolation material is comprised of silicon dioxide and said etch stop layer is comprised of silicon nitride.
28. The device of claim 24, wherein said source/drain regions are merged source/drain regions.
29. The device of claim 24, wherein said gate structure is a replacement gate structure.
30. The device of claim 24, wherein the source/drain regions aredpositioned and in contact with said etch stop layer within said trench.
31. A device, comprising:
- a semiconducting substrate comprising a plurality of fin structures that are separated by a trench formed in said substrate;
- a local isolation material made of silicon dioxide positioned within said trench;
- an etch stop layer made of silicon nitride positioned and in contact with said local isolation material within said trench;
- a gate structure positioned around portions of said fin structures, wherein said gate structure comprises a high-k gate insulation layer that is positioned and in contact with said etch stop layer within said trench; and
- source/drain regions positioned and in contact with said etch stop layer within said trench.
32. The device of claim 31, wherein said gate structure further comprises at least one metal layer positioned above said high-k gate insulation layer.
Type: Application
Filed: Jul 17, 2014
Publication Date: Nov 6, 2014
Inventors: Xiuyu Cai (Niskayuna, NY), Ruilong Xie (Niskayuna, NY)
Application Number: 14/334,269
International Classification: H01L 29/06 (20060101); H01L 29/78 (20060101);