Methods of Forming Three-Dimensional Structures Having Reduced Stress and/or Curvature
Electrochemical fabrication processes and apparatus for producing single layer or multi-layer structures where each layer includes the deposition of at least two materials and wherein the formation of at least some layers includes operations for reducing stress and/or curvature distortion when the structure is released from a sacrificial material which surrounded it during formation and possibly when released from a substrate on which it was formed. Six primary groups of embodiments are presented which are divide into eleven primary embodiments. Some embodiments attempt to remove stress to minimize distortion while others attempt to balance stress to minimize distortion.
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This application is a continuation of U.S. patent application Ser. No. 11/733,195, filed Apr. 9, 2007. The '195 application claims benefit to U.S. Provisional Patent Application No. 60/790,327, filed Apr. 7, 2006 and the '195 application is a continuation-in-part of U.S. patent application Ser. No. 10/434,519, filed May 7, 2003; and Ser. No. 11/029,220, filed Jan. 3, 2005. The '519 application claims benefit of U.S. Provisional Patent Application No. 60/379,130, filed May 7, 2002. The '220 application claims benefit of U.S. Provisional Patent Application Nos. 60/534,159 and 60/534,183, both filed Dec. 31, 2003. These referenced applications are incorporated herein by reference as if set forth in full herein
FIELD OF THE INVENTIONEmbodiments of this invention relate to the field of electrochemical fabrication and the associated formation of micro-scale or meso-scale single layer or multi-layer three-dimensional structures and more specifically to the use of electrochemical fabrication processes that produce three-dimensional single layer or multi-layer structures having reduced stress, curvature, and/or other stress induced distortions.
BACKGROUND OF THE INVENTIONAn electrochemical fabrication technique for forming three-dimensional structures from a plurality of adhered layers is being commercially pursued by Microfabrica Inc. (formerly MEMGen® Corporation) of Van Nuys, Calif. under the name EFAB™.
Various electrochemical fabrication techniques were described in U.S. Pat. No. 6,027,630, issued on Feb. 22, 2000 to Adam Cohen. Some embodiments of this electrochemical fabrication technique allows the selective deposition of a material using a mask that includes a patterned conformable material on a support structure that is independent of the substrate onto which plating will occur. When desiring to perform an electrodeposition using the mask, the conformable portion of the mask is brought into contact with a substrate, but not adhered or bonded to the substrate, while in the presence of a plating solution such that the contact of the conformable portion of the mask to the substrate inhibits deposition at selected locations. For convenience, these masks might be generically called conformable contact masks; the masking technique may be generically called a conformable contact mask plating process. More specifically, in the terminology of Microfabrica Inc. such masks have come to be known as INSTANT MASKS™ and the process known as INSTANT MASKING™ or INSTANT MASK™ plating. Selective depositions using conformable contact mask plating may be used to form single selective deposits of material or may be used in a process to form multi-layer structures. The teachings of the '630 patent are hereby incorporated herein by reference as if set forth in full herein. Since the filing of the patent application that led to the above noted patent, various papers about conformable contact mask plating (i.e. INSTANT MASKING) and electrochemical fabrication have been published:
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- (1) A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P. Will, “EFAB: Batch production of functional, fully-dense metal parts with micro-scale features”, Proc. 9th Solid Freeform Fabrication, The University of Texas at Austin, p 161, August 1998.
- (2) A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P. Will, “EFAB: Rapid, Low-Cost Desktop Micromachining of High Aspect Ratio True 3-D MEMS”, Proc. 12th IEEE Micro Electro Mechanical Systems Workshop, IEEE, p 244, January 1999.
- (3) A. Cohen, “3-D Micromachining by Electrochemical Fabrication”, Micromachine Devices, March 1999.
- (4) G. Zhang, A. Cohen, U. Frodis, F. Tseng, F. Mansfeld, and P. Will, “EFAB: Rapid Desktop Manufacturing of True 3-D Microstructures”, Proc. 2nd International Conference on Integrated MicroNanotechnology for Space Applications, The Aerospace Co., April 1999.
- (5) F. Tseng, U. Frodis, G. Zhang, A. Cohen, F. Mansfeld, and P. Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal Microstructures using a Low-Cost Automated Batch Process”, 3rd International Workshop on High Aspect Ratio MicroStructure Technology (HARMST'99), June 1999.
- (6) A. Cohen, U. Frodis, F. Tseng, G. Zhang, F. Mansfeld, and P. Will, “EFAB: Low-Cost, Automated Electrochemical Batch Fabrication of Arbitrary 3-D Microstructures”, Micromachining and Microfabrication Process Technology, SPIE 1999 Symposium on Micromachining and Microfabrication, September 1999.
- (7) F. Tseng, G. Zhang, U. Frodis, A. Cohen, F. Mansfeld, and P. Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal Microstructures using a Low-Cost Automated Batch Process”, MEMS Symposium, ASME 1999 International Mechanical Engineering Congress and Exposition, November, 1999.
- (8) A. Cohen, “Electrochemical Fabrication (EFAB™)”, Chapter 19 of The MEMS Handbook, edited by Mohamed Gad-El-Hak, CRC Press, 2002.
- (9) Microfabrication—Rapid Prototyping's Killer Application”, pages 1-5 of the Rapid Prototyping Report, CAD/CAM Publishing, Inc., June 1999.
The disclosures of these nine publications are hereby incorporated herein by reference as if set forth in full herein.
An electrochemical deposition for forming multilayer structures may be carried out in a number of different ways as set forth in the above patent and publications. In one form, this process involves the execution of three separate operations during the formation of each layer of the structure that is to be formed:
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- 1. Selectively depositing at least one material by electrodeposition upon one or more desired regions of a substrate. Typically this material is either a structural material or a sacrificial material.
- 2. Then, blanket depositing at least one additional material by electrodeposition so that the additional deposit covers both the regions that were previously selectively deposited onto, and the regions of the substrate that did not receive any previously applied selective depositions. Typically this material is the other of a structural material or a sacrificial material.
- 3. Finally, planarizing the materials deposited during the first and second operations to produce a smoothed surface of a first layer of desired thickness having at least one region containing the at least one material and at least one region containing at least the one additional material.
After formation of the first layer, one or more additional layers may be formed adjacent to an immediately preceding layer and adhered to the smoothed surface of that preceding layer. These additional layers are formed by repeating the first through third operations one or more times wherein the formation of each subsequent layer treats the previously formed layers and the initial substrate as a new and thickening substrate.
Once the formation of all layers has been completed, at least a portion of at least one of the materials deposited is generally removed by an etching process to expose or release the three-dimensional structure that was intended to be formed. The removed material is a sacrificial material while the material that forms part of the desired structure is a structural material.
The preferred method of performing the selective electrodeposition involved in the first operation is by conformable contact mask plating. In this type of plating, one or more conformable contact (CC) masks are first formed. The CC masks include a support structure onto which a patterned conformable dielectric material is adhered or formed. The conformable material for each mask is shaped in accordance with a particular cross-section of material to be plated (the pattern of conformable material is complementary to the pattern of material to be deposited). At least one CC mask is used for each unique cross-sectional pattern that is to be plated.
The support for a CC mask is typically a plate-like structure formed of a metal that is to be selectively electroplated and from which material to be plated will be dissolved. In this typical approach, the support will act as an anode in an electroplating process. In an alternative approach, the support may instead be a porous or otherwise perforated material through which deposition material will pass during an electroplating operation on its way from a distal anode to a deposition surface. In either approach, it is possible for multiple CC masks to share a common support, i.e. the patterns of conformable dielectric material for plating multiple layers of material may be located in different areas of a single support structure. When a single support structure contains multiple plating patterns, the entire structure is referred to as the CC mask while the individual plating masks may be referred to as “submasks”. In the present application such a distinction will be made only when relevant to a specific point being made.
In preparation for performing the selective deposition of the first operation, the conformable portion of the CC mask is placed in registration with and pressed against a selected portion of (1) the substrate, (2) a previously formed layer, or (3) a previously deposited portion of a layer on which deposition is to occur. The pressing together of the CC mask and relevant substrate occur in such a way that all openings, in the conformable portions of the CC mask contain plating solution. The conformable material of the CC mask that contacts the substrate acts as a barrier to electrodeposition while the openings in the CC mask that are filled with electroplating solution act as pathways for transferring material from an anode (e.g. the CC mask support) to the non-contacted portions of the substrate (which act as a cathode during the plating operation) when an appropriate potential and/or current are supplied.
An example of a CC mask and CC mask plating are shown in
The CC mask plating process is distinct from a “through-mask” plating process in that in a through-mask plating process the separation of the masking material from the substrate would occur destructively. Furthermore in a through mask plating process, opening in the masking material are typically formed while the masking material is in contact with and adhered to the substrate. As with through-mask plating, CC mask plating deposits material selectively and simultaneously over the entire layer. The plated region may consist of one or more isolated plating regions where these isolated plating regions may belong to a single structure that is being formed or may belong to multiple structures that are being formed simultaneously. In CC mask plating as individual masks are not intentionally destroyed in the removal process, they may be usable in multiple plating operations.
Another example of a CC mask and CC mask plating is shown in
Unlike through-mask plating, CC mask plating allows CC masks to be formed completely separate from the substrate on which plating is to occur (e.g. separate from a three-dimensional (3D) structure that is being formed). CC masks may be formed in a variety of ways, for example, using a photolithographic process. All masks can be generated simultaneously, e.g. prior to structure fabrication rather than during it. This separation makes possible a simple, low-cost, automated, self-contained, and internally-clean “desktop factory” that can be installed almost anywhere to fabricate 3D structures, leaving any required clean room processes, such as photolithography to be performed by service bureaus or the like.
An example of the electrochemical fabrication process discussed above is illustrated in
Various components of an exemplary manual electrochemical fabrication system 32 are shown in
The CC mask subsystem 36 shown in the lower portion of
The blanket deposition subsystem 38 is shown in the lower portion of
The planarization subsystem 40 is shown in the lower portion of
In addition to teaching the use of CC masks for electrodeposition purposes, the '630 patent also teaches that the CC masks may be placed against a substrate with the polarity of the voltage reversed and material may thereby be selectively removed from the substrate. It indicates that such removal processes can be used to selectively etch, engrave, and polish a substrate, e.g., a plaque.
The '630 patent further indicates that the electroplating methods and articles disclosed therein allow fabrication of devices from thin layers of materials such as, e.g., metals, polymers, ceramics, and semiconductor materials. It further indicates that although the electroplating embodiments described therein have been described with respect to the use of two metals, a variety of materials, e.g., polymers, ceramics and semiconductor materials, and any number of metals can be deposited either by the electroplating methods therein, or in separate processes that occur throughout the electroplating method. It indicates that a thin plating base can be deposited, e.g., by sputtering, over a deposit that is insufficiently conductive (e.g., an insulating layer) so as to enable subsequent electroplating. It also indicates that multiple support materials (i.e. sacrificial materials) can be included in the electroplated element allowing selective removal of the support materials.
The '630 patent additionally teaches that the electroplating methods disclosed therein can be used to manufacture elements having complex microstructure and close tolerances between parts. An example is given with the aid of
Another method for forming microstructures from electroplated metals (i.e. using electrochemical fabrication techniques) is taught in U.S. Pat. No. 5,190,637 to Henry Guckel, entitled “Formation of Microstructures by Multiple Level Deep X-ray Lithography with Sacrificial Metal layers”. This patent teaches the formation of metal structure utilizing through mask exposures. A first layer of a primary metal is electroplated onto an exposed plating base to fill a void in a photoresist (the photoresist forming a through mask having a desired pattern of openings), the photoresist is then removed and a secondary metal is electroplated over the first layer and over the plating base. The exposed surface of the secondary metal is then machined down to a height which exposes the first metal to produce a flat uniform surface extending across both the primary and secondary metals. Formation of a second layer may then begin by applying a photoresist over the first layer and patterning it (i.e. to form a second through mask) and then repeating the process that was used to produce the first layer to produce a second layer of desired configuration. The process is repeated until the entire structure is formed and the secondary metal is removed by etching. The photoresist is formed over the plating base or previous layer by casting and patterning of the photoresist (i.e. voids formed in the photoresist) are formed by exposure of the photoresist through a patterned mask via X-rays or UV radiation and development of the exposed or unexposed areas.
The '637 patent teaches the locating of a plating base onto a substrate in preparation for electroplating materials onto the substrate. The plating base is indicated as typically involving the use of a sputtered film of an adhesive metal, such as chromium or titanium, and then a sputtered film of the metal that is to be plated. It is also taught that the plating base may be applied over an initial layer of sacrificial material (i.e. a layer or coating of a single material) on the substrate so that the structure and substrate may be detached if desired. In such cases after formation of the structure the sacrificial material forming part of each layer of the structure may be removed along the initial sacrificial layer to free the structure. Substrate materials mentioned in the '637 patent include silicon, glass, metals, and silicon with protected semiconductor devices. A specific example of a plating base includes about 150 angstroms of titanium and about 300 angstroms of nickel, both of which are sputtered at a temperature of 160° C. In another example it is indicated that the plating base may consist of 150 angstroms of titanium and 150 angstroms of nickel where both are applied by sputtering.
Electrochemical Fabrication provides the ability to form prototypes and commercial quantities of miniature objects, parts, structures, devices, and the like at reasonable costs and in reasonable times. In fact, Electrochemical Fabrication is an enabler for the formation of many structures that were hitherto impossible to produce. Electrochemical Fabrication opens the spectrum for new designs and products in many industrial fields. Even though Electrochemical Fabrication offers this new capability and it is understood that Electrochemical Fabrication techniques can be combined with designs and structures known within various fields to produce new structures, certain uses for Electrochemical Fabrication provide designs, structures, capabilities and/or features not known or obvious in view of the state of the art.
A need exists in various fields for miniature devices having improved characteristics, reduced fabrication times, reduced fabrication costs, simplified fabrication processes, greater versatility in device design, improved selection of materials, improved material properties, more cost effective and less risky production of such devices, and/or more independence between geometric configuration and the selected fabrication process.
SUMMARY OF THE INVENTIONIt is an object of some embodiments of the invention to provide an enhanced electrochemical fabrication process capable of forming structures with reduced internal stress.
It is an object of some embodiments of the invention to provide an enhanced electrochemical fabrication process capable of forming structures exhibiting reduced curvature distortion.
Other objects and advantages of various embodiments of the invention will be apparent to those of skill in the art upon review of the teachings herein. The various embodiments of the invention, set forth explicitly herein or otherwise ascertained from the teachings herein, may address one or more of the above objects alone or in combination, or alternatively may address some other object of the invention ascertained from the teachings herein. It is not necessarily intended that all objects be addressed by any single aspect of the invention even though that may be the case with regard to some aspects.
Each of the first through fourteenth aspects of the invention provide a method of forming a multi-layer three-dimensional structure, including: (A) forming a plurality of successive layers of the structure with each successive layer, except for a first layer, adhered to a previously formed layer and with each successive layer comprising at least two materials, one of which is a structural material and the other of which is a sacrificial material, and wherein each successive layer defines a successive cross-section of the three-dimensional structure, and wherein the forming of each of the plurality of successive layers includes: (i) depositing a first of the at least two materials; (ii) depositing a second of the at least two materials; and (B) after the forming of the plurality of successive layers, separating at least a portion of the sacrificial material from the structural material to reveal the three-dimensional structure.
The first aspect of the invention additionally includes, in association with the formation of at least one of the successive layers, dividing the layer into a first thin sublayer and a second thicker sublayer and depositing a primary structural material in a lateral region of the first sublayer to form at least a portion of the sublayer, and thereafter planarizing the primary structural material to a height that bounds the first sublayer, where the thickness of the first sublayer is similar to a known or estimated effective work hardened thickness (e.g. preferably having a thickness between 1/3 and 3 times that of the estimated or known effective work hardened thickness, more preferably between 1/2 and 2 times that of the estimated or known effective work hardened thickness, even more preferably within 2/3 and 3/2 times that of the estimated or known effective work hardened thickness, even more preferably between 4/5 and 5/4 times that of the estimated or known effective work hardened thickness, and most preferably between 9/10 and 10/9 times that of the estimated or known effective work hardened thickness) or less than a known or estimated effective work hardened thickness induced by the planarization operation, and thereafter depositing the primary structural material in a lateral region of the second sublayer, and thereafter planarizing the primary structural material of the second sublayer.
The second aspect of the invention additionally includes, in association with the formation of at least one of the successive layers, dividing the layer into a first thin sublayer and a second thicker sublayer, where the thickness of the first sublayer is substantially less than that of the second sublayer thickness (e.g. it is preferably less than 30%, more preferably less than 20%, and most preferably less than 10% of the second sublayer thickness) and depositing a primary structural material in a lateral region of the first sublayer to form at least a portion of the sublayer, and thereafter planarizing the primary structural material to a height that bounds the first sublayer, and thereafter depositing the primary structural material in a lateral region of the second sublayer, and thereafter planarizing the primary structural material of the second sublayer.
The third aspect of the invention additionally includes, in association with the formation of a first layer to which each successive layer will be adhered, depositing a primary structural material in a lateral region of the first layer to form at least a portion of the first layer, thereafter planarizing the upper surface of the first layer, prior to or after forming one or more successive layers, planarizing the bottom surface of the first layer.
The fourth aspect of the invention additionally includes, forming one or more successive layers on one or more previously formed layers such that the one or more layers are formed on the upper surfaces of the one or more previously formed layers and then reversing a build orientation such that one or more additional layers are formed on the bottom surface of a first formed layer of the previously formed layer or layers.
The fifth aspect of the invention additionally includes, in association with the formation of at least one of the successive layers, depositing a primary structural material in a lateral region of the layer to form at least a majority of the one successive layer in the lateral region, and thereafter planarizing the primary structural material to a height that bounds or exceeds the desired height of the at least one successive layer and such that at least a portion of the primary structural material is work hardened, etching into the primary structural material to form one or more openings that extend into the one successive layer in a least a portion of the lateral region to remove at least a portion of the work hardened primary structural material.
The sixth aspect of the invention additionally includes, in association with the formation of at least one of the successive layers, depositing a primary structural material in a lateral region of the layer to form at least a majority of the one successive layer in the lateral region, and thereafter planarizing the primary structural material to form a surface of the one successive layer, and thereafter sequentially exposing portions of the surface to selected radiation that provides the exposed portions with an elevated temperature and results in less distortion of the lateral region after the separating than would exist in absence of the exposing.
The seventh aspect of the invention additionally includes, in association with the formation of at least one of the successive layers, depositing a primary structural material in a lateral region of the layer to form at least a majority of the one successive layer in the lateral region, and thereafter planarizing the primary structural material to form a surface of the one successive layer, and thereafter sequentially exposing portions of the surface to selected laser radiation which results in less distortion of the lateral region after the separating than would exist in absence of the exposing.
The eighth aspect of the invention additionally includes, in association with the formation of at least one of the successive layers, depositing a primary structural material in a lateral region of the layer to form at least a majority of the one successive layer in the lateral region, and thereafter planarizing the primary structural material to form a surface of the one successive layer, and thereafter exposing at least a portion of the surface to selected radiation which results in less distortion of the lateral region after the separating than would exist in absence of the exposing.
The ninth aspect of the invention additionally includes, in association with the formation of at least one of the successive layers, depositing a primary structural material in a lateral region of the layer to form at least a majority of the one successive layer in the lateral region, and thereafter planarizing the primary structural material to form a surface of the one successive layer, and thereafter applying heat to selected portions of the surface or to the surface as a whole which results in less distortion of the lateral region after the separating than would exist in absence of the heating
The tenth aspect of the invention additionally includes forming at least one layer such that a primary structural material on the layer is provided with an upper surface configuration that is not planar but instead is made to include a plurality of alternating surface recessions and elevations (e.g. where the recessions are relatively narrow. e.g. preferably narrower than 10 um, more preferably narrower than 5 um, even more preferably thinner than 2 um, and most preferably thinner than 1 um) and where the height difference between the recessions and elevations is preferably larger than a depth of work hardening that the surface of the layer may experience during a planarization operations) which provide decoupling of stress found within the elevations
The eleventh aspect of the invention additionally includes, forming at least one layer such that a primary structural material on the layer is provided with an upper surface configuration, planarizing the upper surface, and thereafter forming notches in the planarized surface in a desired pattern where the notches provide decoupling of stress located in separated regions of structural material.
The twelfth aspect of the invention additionally includes, in association with the formation of at least one of the successive layers, depositing a primary structural material in a lateral region of the layer to form the majority of the one successive layer in the lateral region, wherein the primary structural material is a material that cannot be planarized reasonably and effectively by diamond fly cutting and thereafter depositing a secondary structural material in the lateral region of the one successive layer over the primary structural material, wherein the secondary structural material can be planarized reasonably and effectively by diamond fly cutting, and then planarizing the secondary structural material using diamond fly cutting.
The thirteenth aspect of the invention additionally includes, in association with the formation of at least one of the successive layers, depositing a primary structural material in a lateral region of the layer to form the majority of the one successive layer in the lateral region, and thereafter depositing a secondary structural material in the lateral region of the one successive layer over the primary structural material, wherein the secondary structural material has a higher tensile stress than the primary structural material, and then planarizing the secondary structural material without planarizing the primary structural material.
The fourteenth aspect of the invention additionally includes in association with the formation of at least one of the successive layers, depositing a primary structural material in a lateral region of the layer to form at least a majority of the one successive layer in the lateral region, and thereafter planarizing the primary structural material to a height that is less than a desired height of the layer and thereafter depositing at least one secondary structural material to the lateral region to bring the height of the deposited primary and secondary structural materials to a height at least as great as the desired height of the layer, wherein the secondary structural material has a tensile stress greater than a tensile stress of the primary structural material prior to the planarization of the primary structural material.
Additional aspects of the invention provide the additions of the above noted aspects to the formation of the single layers structures as opposed to multiple layer structures.
Additional aspects of the invention provide products produced by the above noted method aspects of the invention.
Further aspects of the invention will be understood by those of skill in the art upon reviewing the teachings herein. Other aspects of the invention may involve apparatus that can be used in implementing one or more of the above process aspects of the invention or devices formed using one of the above process aspects of the invention. These other aspects of the invention may provide various combinations of the aspects, embodiments, and associated alternatives explicitly set forth herein as well as provide other configurations, structures, functional relationships, and processes that have not been specifically set forth above.
Electrochemical Fabrication in General
Various embodiments of various aspects of the invention are directed to formation of three-dimensional structures from materials some of which may be electrodeposited or electroless deposited. Some of these structures may be formed form a single build level formed from one or more deposited materials while others are formed from a plurality of build layers each including at least two materials (e.g. two or more layers, more preferably five or more layers, and most preferably ten or more layers). In some embodiments, layer thicknesses may be as small as one micron or as large as fifty microns. In other embodiments, thinner layers may be used while in other embodiments, thicker layers may be used. In some embodiments structures having features positioned with micron level precision and minimum features size on the order of tens of microns are to be formed. In other embodiments structures with less precise feature placement and/or larger minimum features may be formed. In still other embodiments, higher precision and smaller minimum feature sizes may be desirable.
The various embodiments, alternatives, and techniques disclosed herein may form multi-layer structures using a single patterning technique on all layers or using different patterning techniques on different layers. For example, Various embodiments of the invention may perform selective patterning operations using conformable contact masks and masking operations (i.e. operations that use masks which are contacted to but not adhered to a substrate), proximity masks and masking operations (i.e. operations that use masks that at least partially selectively shield a substrate by their proximity to the substrate even if contact is not made), non-conformable masks and masking operations (i.e. masks and operations based on masks whose contact surfaces are not significantly conformable), and/or adhered masks and masking operations (masks and operations that use masks that are adhered to a substrate onto which selective deposition or etching is to occur as opposed to only being contacted to it). Conformable contact masks, proximity masks, and non-conformable contact masks share the property that they are preformed and brought to, or in proximity to, a surface which is to be treated (i.e. the exposed portions of the surface are to be treated). These masks can generally be removed without damaging the mask or the surface that received treatment to which they were contacted, or located in proximity to. Adhered masks are generally formed on the surface to be treated (i.e. the portion of that surface that is to be masked) and bonded to that surface such that they cannot be separated from that surface without being completely destroyed damaged beyond any point of reuse. Adhered masks may be formed in a number of ways including (1) by application of a photoresist, selective exposure of the photoresist, and then development of the photoresist, (2) selective transfer of pre-patterned masking material, and/or (3) direct formation of masks from computer controlled depositions of material.
Patterning operations may be used in selectively depositing material and/or may be used in the selective etching of material. Selectively etched regions may be selectively filled in or filled in via blanket deposition, or the like, with a different desired material. In some embodiments, the layer-by-layer build up may involve the simultaneous formation of portions of multiple layers. In some embodiments, depositions made in association with some layer levels may result in depositions to regions associated with other layer levels (i.e. regions that lie within the top and bottom boundary levels that define a different layer's geometric configuration). Such use of selective etching and interlaced material deposition in association with multiple layers is described in U.S. patent application Ser. No. 10/434,519, by Smalley, and entitled “Methods of and Apparatus for Electrochemically Fabricating Structures Via Interlaced Layers or Via Selective Etching and Filling of Voids layer elements” which is hereby incorporated herein by reference as if set forth in full.
Temporary substrates on which structures may be formed may be of the sacrificial-type (i.e. destroyed or damaged during separation of deposited materials to the extent they can not be reused), non-sacrificial-type (i.e. not destroyed or excessively damaged, i.e. not damaged to the extent they may not be reused, e.g. with a sacrificial or release layer located between the substrate and the initial layers of a structure that is formed). Non-sacrificial substrates may be considered reusable, with little or no rework (e.g. replanarizing one or more selected surfaces or applying a release layer, and the like) though they may or may not be reused for a variety of reasons.
Definitions
This section of the specification is intended to set forth definitions for a number of specific terms that may be useful in describing the subject matter of the various embodiments of the invention. It is believed that the meanings of most if not all of these terms is clear from their general use in the specification but they are set forth hereinafter to remove any ambiguity that may exist. It is intended that these definitions be used in understanding the scope and limits of any claims that use these specific terms. As far as interpretation of the claims of this patent disclosure are concerned, it is intended that these definitions take presence over any contradictory definitions or allusions found in any materials which are incorporated herein by reference.
“Build” as used herein refers, as a verb, to the process of building a desired structure or plurality of structures from a plurality of applied or deposited materials which are stacked and adhered upon application or deposition or, as a noun, to the physical structure or structures formed from such a process. Depending on the context in which the term is used, such physical structures may include a desired structure embedded within a sacrificial material or may include only desired physical structures which may be separated from one another or may require dicing and/or slicing to cause separation.
“Build axis” or “build orientation” is the axis or orientation that is substantially perpendicular to substantially planar levels of deposited or applied materials that are used in building up a structure. The planar levels of deposited or applied materials may be or may not be completely planar but are substantially so in that the overall extent of their cross-sectional dimensions are significantly greater than the height of any individual deposit or application of material (e.g. 100, 500, 1000, 5000, or more times greater). The planar nature of the deposited or applied materials may come about from use of a process that leads to planar deposits or it may result from a planarization process (e.g. a process that includes mechanical abrasion, e.g. lapping, fly cutting, grinding, or the like) that is used to remove material regions of excess height. Unless explicitly noted otherwise, “vertical” as used herein refers to the build axis or nominal build axis (if the layers are not stacking with perfect registration) while “horizontal” refers to a direction within the plane of the layers (i.e. the plane that is substantially perpendicular to the build axis).
“Build layer” or “layer of structure” as used herein does not refer to a deposit of a specific material but instead refers to a region of a build located between a lower boundary level and an upper boundary level which generally defines a single cross-section of a structure being formed or structures which are being formed in parallel. Depending on the details of the actual process used to form the structure, build layers are generally formed on and adhered to previously formed build layers. In some processes the boundaries between build layers are defined by planarization operations which result in successive build layers being formed on substantially planar upper surfaces of previously formed build layers. In some embodiments, the substantially planar upper surface of the preceding build layer may be textured to improve adhesion between the layers. In other build processes, openings may exist in or be formed in the upper surface of a previous but only partially formed build layers such that the openings in the previous build layers are filled with materials deposited in association with current build layers which will cause interlacing of build layers and material deposits. Such interlacing is described in U.S. patent application Ser. No. 10/434,519. This referenced application is incorporated herein by reference as if set forth in full. In most embodiments, a build layer includes at least one primary structural material and at least one primary sacrificial material. However, in some embodiments, two or more primary structural materials may used without a primary sacrificial material (e.g. when one primary structural material is a dielectric and the other is a conductive material). In some embodiments, build layers are distinguishable from each other by the source of the data that is used to yield patterns of the deposits, applications, and/or etchings of material that form the respective build layers. For example, data descriptive of a structure to be formed which is derived from data extracted from different vertical levels of a data representation of the structure define different build layers of the structure. The vertical separation of successive pairs of such descriptive data may define the thickness of build layers associated with the data. As used herein, at times, “build layer” may be loosely referred simply as “layer”. In many embodiments, deposition thickness of primary structural or sacrificial materials (i.e. the thickness of any particular material after it is deposited) is generally greater than the layer thickness and a net deposit thickness is set via one or more planarization processes which may include, for example, mechanical abrasion (e.g. lapping, fly cutting, polishing, and the like) and/or chemical etching (e.g. using selective or non-selective etchants). The lower boundary and upper boundary for a build layer may be set and defined in different ways. From a design point of view they may be set based on a desired vertical resolution of the structure (which may vary with height). From a data manipulation point of view, the vertical layer boundaries may be defined as the vertical levels at which data descriptive of the structure is processed or the layer thickness may be defined as the height separating successive levels of cross-sectional data that dictate how the structure will be formed. From a fabrication point of view, depending on the exact fabrication process used, the upper and lower layer boundaries may be defined in a variety of different ways. For example by planarization levels or effective planarization levels (e.g. lapping levels, fly cutting levels, chemical mechanical polishing levels, mechanical polishing levels, vertical positions of structural and/or sacrificial materials after relatively uniform etch back following a mechanical or chemical mechanical planarization process). For example, by levels at which process steps or operations are repeated. At levels at which, at least theoretically, lateral extends of structural material can be changed to define new cross-sectional features of a structure.
“Layer thickness” is the height along the build axis between a lower boundary of a build layer and an upper boundary of that build layer.
“Planarization” is a process that tends to remove materials, above a desired plane, in a substantially non-selective manner such that all deposited materials are brought to a substantially common height or desired level (e.g. within 20%, 10%, 5%, or even 1% of a desired layer boundary level). For example, lapping removes material in a substantially non-selective manner though some amount of recession one material or another may occur (e.g. copper may recess relative to nickel). Planarization may occur primarily via mechanical means, e.g. lapping, grinding, fly cutting, milling, sanding, abrasive polishing, frictionally induced melting, other machining operations, or the like (i.e. mechanical planarization). Mechanical planarization maybe followed or proceeded by thermally induced planarization (.e.g. melting) or chemically induced planarization (e.g. etching). Planarization may occur primarily via a chemical and/or electrical means (e.g. chemical etching, electrochemical etching, or the like). Planarization may occur via a simultaneous combination of mechanical and chemical etching (e.g. chemical mechanical polishing (CMP)).
“Structural material” as used herein refers to a material that remains part of the structure when put into use.
“Supplemental structural material” as used herein refers to a material that forms part of the structure when the structure is put to use but is not added as part of the build layers but instead is added to a plurality of layers simultaneously (e.g. via one or more coating operations that applies the material, selectively or in a blanket fashion, to a one or more surfaces of a desired build structure that has been released from a sacrificial material.
“Primary structural material” as used herein is a structural material that forms part of a given build layer and which is typically deposited or applied during the formation of that build layer and which makes up more than 20% of the structural material volume of the given build layer. In some embodiments, the primary structural material may be the same on each of a plurality of build layers or it may be different on different build layers. In some embodiments, a given primary structural material may be formed from two or more materials by the alloying or diffusion of two or more materials to form a single material.
“Secondary structural material” as used herein is a structural material that forms part of a given build layer and is typically deposited or applied during the formation of the given build layer but is not a primary structural material as it individually accounts for only a small volume of the structural material associated with the given layer. A secondary structural material will account for less than 20% of the volume of the structural material associated with the given layer. In some preferred embodiments, each secondary structural material may account for less than 10%, 5%, or even 2% of the volume of the structural material associated with the given layer. Examples of secondary structural materials may include seed layer materials, adhesion layer materials, barrier layer materials (e.g. diffusion barrier material), and the like. These secondary structural materials are typically applied to form coatings having thicknesses less than 2 microns, 1 micron, 0.5 microns, or even 0.2 microns). The coatings may be applied in a conformal or directional manner (e.g. via CVD, PVD, electroless deposition, or the like). Such coatings may be applied in a blanket manner or in a selective manner. Such coatings may be applied in a planar manner (e.g. over previously planarized layers of material) as taught in U.S. patent application Ser. No. 10/607,931. In other embodiments, such coatings may be applied in a non-planar manner, for example, in openings in and over a patterned masking material that has been applied to previously planarized layers of material as taught in U.S. patent application Ser. No. 10/841,383. These referenced applications are incorporated herein by reference as if set forth in full herein.
“Functional structural material” as used herein is a structural material that would have been removed as a sacrificial material but for its actual or effective encapsulation by other structural materials. Effective encapsulation refers, for example, to the inability of an etchant to attack the functional structural material due to inaccessibility that results from a very small area of exposure and/or due to an elongated or tortuous exposure path. For example, large (10,000 μm2) but thin (e.g. less than 0.5 microns) regions of sacrificial copper sandwiched between deposits of nickel may define regions of functional structural material depending on ability of a release etchant to remove the sandwiched copper.
“Sacrificial material” is material that forms part of a build layer but is not a structural material. Sacrificial material on a given build layer is separated from structural material on that build layer after formation of that build layer is completed and more generally is removed from a plurality of layers after completion of the formation of the plurality of layers during a “release” process that removes the bulk of the sacrificial material or materials. In general sacrificial material is located on a build layer during the formation of one, two, or more subsequent build layers and is thereafter removed in a manner that does not lead to a planarized surface. Materials that are applied primarily for masking purposes, i.e. to allow subsequent selective deposition or etching of a material, e.g. photoresist that is used in forming a build layer but does not form part of the build layer) or that exist as part of a build for less than one or two complete build layer formation cycles are not considered sacrificial materials as the term is used herein but instead shall be referred as masking materials or as temporary materials. These separation processes are sometimes referred to as a release process and may or may not involve the separation of structural material from a build substrate. In many embodiments, sacrificial material within a given build layer is not removed until all build layers making up the three-dimensional structure have been formed. Of course sacrificial material may be, and typically is, removed from above the upper level of a current build layer during planarization operations during the formation of the current build layer. Sacrificial material is typically removed via a chemical etching operation but in some embodiments may be removed via a melting operation or electrochemical etching operation. In typical structures, the removal of the sacrificial material (i.e. release of the structural material from the sacrificial material) does not result in planarized surfaces but instead results in surfaces that are dictated by the boundaries of structural materials located on each build layer. Sacrificial materials are typically distinct from structural materials by having different properties therefrom (e.g. chemical etchability, hardness, melting point, etc.) but in some cases, as noted previously, what would have been a sacrificial material may become a structural material by its actual or effective encapsulation by other structural materials. Similarly, structural materials may be used to form sacrificial structures that are separated from a desired structure during a release process via the sacrificial structures being only attached to sacrificial material or potentially by dissolution of the sacrificial structures themselves using a process that is insufficient to reach structural material that is intended to form part of a desired structure. It should be understood that in some embodiments, small amounts of structural material may be removed, after or during release of sacrificial material. Such small amounts of structural material may have been inadvertently formed due to imperfections in the fabrication process or may result from the proper application of the process but may result in features that are less than optimal (e.g. layers with stairs steps in regions where smooth sloped surfaces are desired. In such cases the volume of structural material removed is typically minuscule compared to the amount that is retained and thus such removal is ignored when labeling materials as sacrificial or structural. Sacrificial materials are typically removed by a dissolution process, or the like, that destroys the geometric configuration of the sacrificial material as it existed on the build layers. In many embodiments, the sacrificial material is a conductive material such as a metal. As will be discussed hereafter, masking materials though typically sacrificial in nature are not termed sacrificial materials herein unless they meet the required definition of sacrificial material.
“Supplemental sacrificial material” as used herein refers to a material that does not form part of the structure when the structure is put to use and is not added as part of the build layers but instead is added to a plurality of layers simultaneously (e.g. via one or more coating operations that applies the material, selectively or in a blanket fashion, to a one or more surfaces of a desired build structure that has been released from an initial sacrificial material. This supplemental sacrificial material will remain in place for a period of time and/or during the performance of certain post layer formation operations, e.g. to protect the structure that was released from a primary sacrificial material, but will be removed prior to putting the structure to use.
“Primary sacrificial material” as used herein is a sacrificial material that is located on a given build layer and which is typically deposited or applied during the formation of that build layer and which makes up more than 20% of the sacrificial material volume of the given build layer. In some embodiments, the primary sacrificial material may be the same on each of a plurality of build layers or may be different on different build layers. In some embodiments, a given primary sacrificial material may be formed from two or more materials by the alloying or diffusion of two or more materials to form a single material.
“Secondary sacrificial material” as used herein is a sacrificial material that is located on a given build layer and is typically deposited or applied during the formation of the build layer but is not a primary sacrificial materials as it individually accounts for only a small volume of the sacrificial material associated with the given layer. A secondary sacrificial material will account for less than 20% of the volume of the sacrificial material associated with the given layer. In some preferred embodiments, each secondary sacrificial material may account for less than 10%, 5%, or even 2% of the volume of the sacrificial material associated with the given layer. Examples of secondary structural materials may include seed layer materials, adhesion layer materials, barrier layer materials (e.g. diffusion barrier material), and the like. These secondary sacrificial materials are typically applied to form coatings having thicknesses less than 2 microns, 1 micron, 0.5 microns, or even 0.2 microns). The coatings may be applied in a conformal or directional manner (e.g. via CVD, PVD, electroless deposition, or the like). Such coatings may be applied in a blanket manner or in a selective manner. Such coatings may be applied in a planar manner (e.g. over previously planarized layers of material) as taught in U.S. patent application Ser. No. 10/607,931. In other embodiments, such coatings may be applied in a non-planar manner, for example, in openings in and over a patterned masking material that has been applied to previously planarized layers of material as taught in U.S. patent application Ser. No. 10/841,383. These referenced applications are incorporated herein by reference as if set forth in full herein.
“Adhesion layer”, “seed layer”, “barrier layer”, and the like refer to coatings of material that are thin in comparison to the layer thickness and thus generally form secondary structural material portions or sacrificial material portions of some layers. Such coatings may be applied uniformly over a previously formed build layer, they may be applied over a portion of a previously formed build layer and over patterned structural or sacrificial material existing on a current (i.e. partially formed) build layer so that a non-planar seed layer results, or they may be selectively applied to only certain locations on a previously formed build layer. In the event such coatings are non-selectively applied, selected portions may be removed (1) prior to depositing either a sacrificial material or structural material as part of a current layer or (2) prior to beginning formation of the next layer or they may remain in place through the layer build up process and then etched away after formation of a plurality of build layers.
“Masking material” is a material that may be used as a tool in the process of forming a build layer but does not form part of that build layer. Masking material is typically a photopolymer or photoresist material or other material that may be readily patterned. Masking material is typically a dielectric. Masking material, though typically sacrificial in nature, is not a sacrificial material as the term is used herein. Masking material is typically applied to a surface during the formation of a build layer for the purpose of allowing selective deposition, etching, or other treatment and is removed either during the process of forming that build layer or immediately after the formation of that build layer.
“Multilayer structures” are structures formed from multiple build layers of deposited or applied materials.
“Multilayer three-dimensional (or 3D or 3-D) structures” are Multilayer Structures that meet at least one of two criteria: (1) the structural material portion of at least two layers of which one has structural material portions that do not overlap structural material portions of the other.
“Complex multilayer three-dimensional (or 3D or 3-D) structures” are multilayer three-dimensional structures formed from at least three layers where a line may be defined that hypothetically extends vertically through at least some portion of the build layers of the structure will extend from structural material through sacrificial material and back through structural material or will extend from sacrificial material through structural material and back through sacrificial material (these might be termed vertically complex multilayer three-dimensional structures). Alternatively, complex multilayer three-dimensional structures may be defined as multilayer three-dimensional structures formed from at least two layers where a line may be defined that hypothetically extends horizontally through at least some portion of a build layer of the structure that will extend from structural material through sacrificial material and back through structural material or will extend from sacrificial material through structural material and back through sacrificial material (these might be termed horizontally complex multilayer three-dimensional structures). Worded another way, in complex multilayer three-dimensional structures, a vertically or horizontally extending hypothetical line will extend from one or structural material or void (when the sacrificial material is removed) to the other of void or structural material and then back to structural material or void as the line is traversed along at least a portion of the line.
“Moderately complex multilayer three-dimensional (or 3D or 3-D) structures are complex multilayer 3D structures for which the alternating of void and structure or structure and void not only exists along one of a vertically or horizontally extending line but along lines extending both vertically and horizontally.
“Highly complex multilayer (or 3D or 3-D) structures are complex multilayer 3D structures for which the structure-to-void-to-structure or void-to-structure-to-void alternating occurs once along the line but occurs a plurality of times along a definable horizontally or vertically extending line.
“Up-facing feature” is an element dictated by the cross-sectional data for a given build layer “n” and a next build layer “n+1” that is to be formed from a given material that exists on the build layer “n” but does not exist on the immediately succeeding build layer “n+1”. For convenience the term “up-facing feature” will apply to such features regardless of the build orientation.
“Down-facing feature” is an element dictated by the cross-sectional data for a given build layer “n” and a preceding build layer “n−1” that is to be formed from a given material that exists on build layer “n” but does not exist on the immediately preceding build layer “n−1”. As with up-facing features, the term “down-facing feature” shall apply to such features regardless of the actual build orientation.
“Continuing region” is the portion of a given build layer “n” that is dictated by the cross-sectional data for the given build layer “n”, a next build layer “n+1” and a preceding build layer “n−1” that is neither up-facing nor down-facing for the build layer “n”.
“Minimum feature size” refers to a necessary or desirable spacing between structural material elements on a given layer that are to remain distinct in the final device configuration. If the minimum feature size is not maintained on a given layer, the fabrication process may result in structural material inadvertently bridging the two structural elements due to masking material failure or failure to appropriately fill voids with sacrificial material during formation of the given layer such that during formation of a subsequent layer structural material inadvertently fills the void. More care during fabrication can lead to a reduction in minimum feature size or a willingness to accept greater losses in productivity can result in a decrease in the minimum feature size. However, during fabrication for a given set of process parameters, inspection diligence, and yield (successful level of production) a minimum design feature size is set in one way or another. The above described minimum feature size may more appropriately be termed minimum feature size of sacrificial material regions. Conversely a minimum feature size for structure material regions (minimum width or length of structural material elements) may be specified. Depending on the fabrication method and order of deposition of structural material and sacrificial material, the two types of minimum feature sizes may be different. In practice, for example, using electrochemical fabrication methods and described herein, the minimum features size on a given layer may be roughly set to a value that approximates the layer thickness used to form the layer and it may be considered the same for both structural and sacrificial material widths and lengths. In some more rigorously implemented processes, examination regiments, and rework requirements, it may be set to an amount that is 80%, 50%, or even 30% of the layer thickness. Other values or methods of setting minimum feature sizes may be set.
“Sublayer” as used herein refers to a portion of a build layer that typically includes the full lateral extents of that build layer but only a portion of its height. A sublayer is usually a vertical portion of build layer that undergoes independent processing compared to another sublayer of that build layer.
Stress, Curvature, and Regions of Structures
When forming structures using the electrochemical fabrication methods discussed above, structures or portions of structures may be formed with unintended curvature. This curvature appears to be more prevalence when the thickness between down-facing and overlying up-facing regions is relatively thin (e.g. under 30-60 microns). It appears as the thickness of the structural elements increase the tendency to curve decreases as the overall structure becomes more rigid and less capable of distorting under the load of any unbalanced stresses that were built into the structure. The unintended curvature in the structures themselves cannot be seen prior to the release of the structures (i.e. structural material) from the surrounding sacrificial materials and possibly from the substrate itself. However, at times, unintended curvature can be seen in the build layers themselves particularly when the total thickness of deposited layers becomes relatively thick (e.g. in excess of 700 to 1500 microns) and the lateral (i.e. horizontal extents when the build axis is considered to extend vertically) of the build layers increase (e.g. beyond 100 mm). The build layer curvature may or may not translate into curvature of the build structures themselves depending on the horizontal dimensions of the build structures themselves, the thickness of the structures, whether or not they remained adhered to the substrate, their overall configurations, and the like. Though this application is primarily focused on reducing stress and/or unintended curvature in structures themselves, curvature of build layers is something that can lead to formational difficulties and illustrates the inherent stress, or at least unbalanced stress, that can exist in build layers.
Various techniques exist for minimizing build layer curvature. One such technique includes the use of a thick and very rigid substrate particularly when it is intended that a relatively large thickness of build layers be deposited thereon. Another technique involves the attachment of the substrate to a carrier that tends to stiffen it. Another technique involves the deposition and planarization of material onto the back side of the substrate during the build process to balance the stresses that are induced by the build up of layers on the front side of the substrate. The net amount of material deposited on the back side of the substrate need not be identical to that deposited on the front side and it need not even be the same material. The material deposited onto the back side of the substrate is typically a sacrificial material though it can be structural material or even a mixture of structural and sacrificial material. In fact, in some cases it may be possible to build structures on both sides of the substrate wherein after formation, the structures on both sides of the substrate are released from the sacrificial material and even from the substrate. If the structures are to remain on the substrate they can remain joined with their counterparts on the opposite side of the substrate or they can be separated from their counterparts by slicing the substrate in half (i.e. along a horizontal plane through the substrate.
The identification schemes of
The disclosure of the present invention provides six groups of embodiments which are further broken into a total of eleven primary embodiments for reducing stress or curvature distortion. Though the embodiments present herein are focused on forming multi-layer three-dimensional structures, some of them have application to forming single layer structures with less stress and/or less curvature.
The primary embodiments 99 of the present invention form multi-layer structures with reduced curvature distortion by modifying a process that is used to form at least one layer of the structure or by modifying the design of the structure or of at least one layer of the structure. The first group of embodiments 100 (i.e. Group 1) involves the balancing of stress via creative use of planarization. This group of embodiments includes: (1) a first embodiment 101 that includes formation of at least one layer of the structure that includes a very thin, planarized sub-layer and a thicker planarized sublayer; (2) a second embodiment 102 that includes planarization of the bottom surface of the first layer, and (3) a third embodiment 103 that starts formation of the multi-layer structure by stacking layers using a building axis with a first orientation and then continuing the formation with the orientation of the building axis reversed.
The first embodiment 101 involves the following operations or steps: (1) Determining the critical layers of a structure (e.g. the bottom of the structure, layers including extended down-facing regions, etc.) and (2) forming each critical layer as two sublayers. The first sublayer for each layer has a thickness approximating that of the work hardening depth of the planarization operation so that it becomes substantially compressively stressed. The second sublayer is thicker so that only its upper portion is compressively stressed via planarization. The use of these two sublayers results in a build layer, as a whole, having more balanced stress and thus preferably having less distortion or curvature.
The second embodiment 102 involves the formation of a structure by stacking layers one above one another and planarizing the top of each layer including the potential of inducing stress in each layer. For example, some planarization operations may include the lapping of both sacrificial and structural materials that form the layer. After formation of one or more layers, (e.g. via lapping) and after formation of one or more layers, planarizing the bottom of the first layer using an appropriate technique to induce a balancing stress therein (e.g. via lapping).
The third embodiment 103 involves forming a structure by stacking successive layers one above one another. Starting with the first layer, the top of each of plurality of layers is planarized with stress being induced into each. Planarizing, for example, may occur via lapping. After formation of one or more layers, the orientation of the build axis is reversed and the formation of the structure is continued by adding one or more additional layers to the bottom side of the first layer. During the formation of these additional layers, the top side of one or more of the additional layers is planarized. With respect to the original orientation, the bottom side of the additional layers is planarized.
The second group of embodiments 200 includes the reduction of stress in one or more layers of a structure by removal of worked hardened material. This group of embodiments includes a fourth embodiment 201 that involves etching away at least a portion of any work hardened material and possibly depositing additional material to partially or completely fill any void crated by the etching.
The fourth embodiment 201 includes forming structures by depositing materials, planarizing the materials, and etching back at least one of the materials. The etching back may, for example, be performed with either wet etching or dry etching. Wet etching may be performed chemically or in some circumstances electrochemically. Dry etching may be isotropic or anisotropic. If anisotropic, dry etching may be performed without a mask assuming both structural and sacrificial materials are etched at a reasonably uniform rate. The etching may be performed in a variety of alternative manners, for example: (1) masks may be used if structural material is being etched and if sacrificial material will be damaged by etchant, (2) masks may use “smaller” openings for etching if edge placement is critical and if etchant attacks the sacrificial material, (3) etching may be applied to only those portions of structural material that are non-up-facing surfaces of the structure, (4) etching may be applied to regions that are non-up-facing and that are inset from sidewalls and up-facing regions by an “offset” amount, and/or 5) etching may be applied only to regions whose net thickness (i.e. thickness between up-facing and down-facing regions) is less than a cut off amount which may be a fixed amount or a variable amount based on length of the region, whether the regions is supported from only one side or opposite sides, the thickness of the region etc. Additional operations or steps may be optionally performed, for example: (1) material may be re-deposited to non-up-facing regions during formation of the next layer, (2) material may be re-deposited to up-facing regions if etching was uniform enough and if re-deposition can occur in a uniform enough manner, (3) it may be possible to use a combination of alternating etching and plating to remove the stressed material and re-deposit a material having less stressed.
The third group of embodiments 300 involves the removal of stress without the removal of the work hardened material. This group of embodiments includes: (1) a fifth embodiment 301 involving the use of focused heating to anneal work hardened material and a (2) sixth embodiment 302 involving the use of blanket or selective heating to anneal work hardened material.
The fifth embodiment 301 includes the use of focused heating (e.g. from a laser beam) to anneal one or more small lateral regions of the surface of the layer preferably to a shallow depth (e.g.˜the depth of work hardening) and then scanning or jumping the focused heating in a desired pattern over the surface to be annealed. In this embodiment the annealing is preferably, though not necessarily performed prior to release from any sacrificial material. In this embodiment, the annealing may occur over only a selected portion of the structural material of the layer (e.g. the portion that is part of a thin, e.g. less than 50-100 um, structural thickness), over all of the structural material of the layer, or even over both structural and sacrificial material regions. The annealing of this embodiment preferably occurs after planarization of the layer is completed. However, if sufficient heat is applied annealing of work hardened material on the previously formed layer may occur.
The sixth embodiment 302 includes the use of blanket or selectively applied heating to anneal the surface of a layer preferably to a shallow depth (e.g.˜the depth of work hardening) potentially using one or more flash exposures of heat energy. In this embodiment annealing is preferably, though not necessarily, performed prior to release from any sacrificial material. Selective application may include heating of desired structural material regions, heating of all structural material regions, or heating of selected structural and sacrificial material regions. The annealing of this embodiment preferably occurs after planarization of the layer is completed. However, if sufficient heat is applied annealing of work hardened material on the previously formed layer may occur.
The fourth group of embodiments 400 involves the reduction of stress via the isolation of stress. This group of embodiments includes (1) a seventh embodiment 401 involving modifying the structure by inserting breaks into what would otherwise be contiguous regions of work hardened structural material and (2) an eighth embodiment 402 involves modifying the structure by removing selected regions of work hardened material.
The seventh embodiment 401 includes forming a desired structure with at least one surface (which would be preferentially formed of structural material in the absence of undesired stress and/or curvature distortion) being formed from alternating regions of structural material with either no material or with sacrificial material, wherein the regions of no material or sacrificial material are preferably narrower than the regions of structural material and wherein after planarization the sacrificial material, if present, is removed.
The eighth embodiment 402 includes forming a desired structure with at least one surface (which would be preferentially formed of continuous structural material in the absence of undesired stress and/or curvature distortion) being formed from structural material and after planarization etching, dicing, laser ablation, or otherwise forming notches in the structural material that are preferably though not necessarily thin relative to the width of the structural material islands being formed and wherein the depth of notching is preferably, though not necessarily, thin (e.g.˜the depth of work hardening)
The fifth group of embodiments 500 involves reducing the stress by planarizing using a non-stress inducing technique or a technique. This group includes a ninth embodiment 501 involving formation of a layer from two structural materials one of which is subject to planarization and may be planarized without inducing work hardening.
The ninth embodiment 501 includes formation of a layer of a structure where first structural material deposited is low stress (compressive or tensile) and where second structural material deposited is low stress and is planarizable by a low or non-stress inducing method (e.g. diamond turning or fly cutting) and where low or non-stress inducing planarization of the second material occurs leaving a layer having reduced stress.
The sixth group of embodiments 600 involves reducing stress in a build layer which is formed using different materials having different stress levels after deposition and planarizing one of them. This group of embodiments includes: (1) a tenth embodiment 601 involving forming a build layer using a low stress material and a tensile stress material (TSM), & planarizing the TSM and (2) an eleventh embodiment 602 involving forming a build layer that deposition of a low stress material, planarization of the low stress material followed by deposition of a relatively thin TSM.
The tenth embodiment 601 includes formation of a build layer of a structure where a first structural material deposited is low stress (compressive or tensile) and where second structural material deposited is higher tensile stress and where the layer is planarized through the higher tensile stress material such that compressive stresses induced by planarization are at least partially balanced so that stress and/or curvature is reduced.
The eleventh embodiment 602 includes formation of a build layer of a structure where a first structural material deposited is low stress (compressive or tensile) and where the planarization sets the height of the material at somewhat less than the desired layer thickness or layer level and where compressive stress induced by planarization occurs and thereafter a thin high tensile stress material is deposited to at least partially balance the compressive stress and bring the thickness to the layer thickness or the upper surface of the layer to the desired layer level.
The process start with block 109 and proceeds to block 110 which calls for defining the layers n=1 to N which are required to fabricate a desired structure or structures and which calls for defining which layers of the structure will receive modified processing for curvature of stress reduction (i.e. which layers will be processed using curvature reduction processing or CRP). Block 111 set the value of the layer number variable “n” equal to one. Block 112 enquires as to whether or not the current layer “n” will be formed using CRP. If response is “no”, the process moves to block 113 which calls for the formation of layer “n” using a desired formation process (i.e. one that may not be tailored to reduce curvature or stress). After formation of layer “n” the process moves forward to block 114 which increments the layer number variable “n” by one (i.e. n=n+1). After block 114 the process moves to the enquiry of block 115 which enquires as to whether n>N, where N is the number of the final layer to be formed. If the answer is “yes” the process moves to block 116 and ends otherwise it loops back to block 112.
If the answer to the enquiry of block 112, for the current layer is “yes” the process moves forward to blocks 117, 118, and 119 to implement the curvature reduction technique of this embodiment. Block 117, calls for the division of layer “n” into sublayers “na” and “nb” where “na” defines the lower portion of layer “n” and represents a thin layer that can be made to undergo work hardening (e.g. via planarization) through the majority, if not all, of its thickness while sublayer “nb” defines the majority of the thickness of layer “n”. In alternative embodiments, the data manipulations of block 117 may be performed prior to the initiation of any physical formation of the structure. From block 117 the process moves forward to block 118 which calls for the formation of sublayer “na” according to its build instructions where deposited materials will be planarized to set the height of sublayer “na” equal to the desired height and where the planarization will cause stress and/or work hardening of the sub layer “na” through most if not all of its thickness.
After completion of sublayer “na”, the process moves forward to block 119 which calls for the formation of sublayer “nb” where the planarization process used only work hardens a portion of the thickness of sublayer “nb”. In effect, this process results in the work hardening or stressing of both the bottom and top of layer “n” which should help balance the stress induced in the layer and help reduce an net stress that would lead to curvature of the layer. From step 119 the process loops back to block 114. The process is then continued until all layers 1 to N of the structure are formed.
Step 113-A calls for the selectively depositing a first material according to a desired pattern of layer “n”, step 113-B calls for depositing a second material to fill voids in the 1st material on layer “n”, while step calls for planarizing the deposited first and second materials. In the present embodiment, these steps complete the formation of layer “n”. Typically one of the first material or the second material is a sacrificial material while the other is a structural material. In other embodiments, different operations/steps may be used in forming layers.
Step 118-A calls for forming selectively depositing a first material according to a desired pattern of layer “n” with a height appropriate for yielding a desired thickness of sublayer “na”, step 118-B calls for depositing a second material to fill voids in the first material on sublayer “na”, and step 118-C calls for planarizing the deposited first and second materials such that stress/work hardening is introduced into “na”. In the present embodiment, these steps complete the formation of sublayer “na”. Typically one of the first material or the second material is a sacrificial material while the other is a structural material. In other embodiments, different operations/steps may be used in forming sublayer “na”.
Step 119-A calls for selectively depositing a first material according to a desired pattern of layer “n” with a height appropriate for yielding a desired thickness of sublayer “nb”, step 119-B calls for depositing a second material to fill voids in the first material on sublayer “nb”, and Step 119-C calls for planarizing the deposited first and second materials with work hardening introduced into only a minority of the thickness of “nb”. In the present embodiment, these steps complete the formation of sublayer “nb”. Typically one of the first material or the second material is a sacrificial material while the other is a structural material. In other embodiments, different operations/steps may be used in forming sublayer “nb”.
Block 123 calls for forming a sublayer region “na” according to its build instructions while filling non-CRP structural regions using sacrificial material, e.g. by selectively depositing a first material, blanket depositing a second material, and planarizing the materials where the planarization induces work hardening.
From Block 123 the process moves forward to either block 124-1A or 124-2A depending on whether a first option is chosen or a second option. Block 124-1A calls for etching away sacrificial material deposited to the non-CRP structural material region(s). This etching may be formed selective after masking has occurred. After block 124-1A, the process moves to block 124-B which calls for forming sublayer “nb” according to its build instructions while depositing structural material to fill the non-CRP structural material region(s) that were initially filled with sacrificial material, e.g. by selectively depositing a first material, blanket depositing 2nd material, and then planarizing. As noted above the second option takes the process to block 124-2A which calls for forming sublayer “nb” according to its build instructions while depositing sacrificial material to the non-CRP structural material region(s) and thereafter moving to block 124-2B which calls for the etching away of sacrificial material deposited to the non-CRP structural material region(s) from both the “na” and “nb” portions of layer “n” after which the process moves forward to block 124-2C which calls for depositing structural material to the etched region(s) and then planarizing.
The process of
An example of the third embodiment of the invention may be implemented by inserting additional steps into the process of
As with the other embodiments, presented herein, the sixth embodiment may be implemented in a number of different ways. The heating that induces annealing may (1) expose the entire upper surface of the layer, (2) a mask may be formed on the upper surface of the layer to shield portions of the layer, (3) be supplied via an array of sources so with only selected sources powered. Various other alternatives are also possible and will be understood by those of skill in the art.
An Implementation of the Seventh Embodiment of the Invention and Some AlternativesAs with the other embodiments, presented herein, this embodiment may be implemented in a number of different ways including use of the CRP on a plurality of layers (instead of just the one illustrate). The stress relief gaps may filled in with a material that does not reintroduce stress, reintroduces less stress or even introduces stress that is opposite to that induced by the work hardening.
An Implementation of the Ninth Embodiment of the Invention and Some AlternativesFIGS. 28A-28G-2 depict the state of an example process as applied to a single layer cantilever structure, which is formed along with a post, where the layer of the cantilever structure is divided into two sublayers implementing the an example of the ninth embodiment where the structural portion of the layers is formed from two vertically stacked materials where planarization of the upper structural material occurs and where the upper material is planarizable by a non-stress inducing process (e.g. diamond fly cutting).
As with the other embodiments, presented herein, this embodiment may be implemented in a number of different ways including use of the CRP on a plurality of layers (instead of just the one illustrated). In some embodiments it may be acceptable if some portion of the material 914-A reaches the planarization level so long as it doesn't represent a large area that could negatively impact the effectiveness of the planarization process.
An Implementation of the Tenth Embodiment of the Invention and Some AlternativesAs with the other embodiments, presented herein, this embodiment may be implemented in a number of different ways including use of the CRP on a plurality of layers (instead of just the one illustrated).
An Implementation of the Eleventh Embodiment of the Invention and Some AlternativesAs with the other embodiments, presented herein, this embodiment may be implemented in a number of different ways including use of the CRP on a plurality of layers (instead of just the one illustrated).
Further Alternatives and Conclusions:
The various embodiments explicitly set forth in this application may take on a variety of alternative forms. For example, the orders of depositing structural and sacrificial material may be varied, different numbers of sacrificial and structural materials may be used, different mechanical, chemical, and electrochemical etching and planarization processes may be used. Depositions may be made using electrochemical techniques, electroless deposition techniques, sputtering, spraying, spreading, as well as via other processes. Electrochemical deposition may take the form of electroplating of fixed current density, pulsed electroplating, reverse pulse plating.
Curvature reduction processes may involve or additionally include techniques to change grain structure within layers, such as for example, reverse pulse plating, formation of grain nucleation sites within a layer. Curvature reduction processes may involve theoretical or empirically determined process parameters that are optimized for a given situation. Though a portion of this application has been written based on the assumption that work hardening occurs near the surface of some materials (e.g. nickel, nickel-cobalt, other nickel alloys, and the like) when subjected to some planarization processes (e.g. lapping), the effectiveness of any stress reduction process or curvature reduction process should dictate the appropriateness of the process and not whether the assumed work hardening theory is determined to be accurate, inaccurate, or simply incomplete.
The curvature reduction techniques may be implemented on a critical or selected region basis, critical of selected layer basis, based on locations or layers containing up-facing regions, locations or layers containing non-up-facing regions, regions that are thin relative to a predefined value, regions have length to thickness aspect ratio that meet or do not meet certain criteria. Rework of layers that are determined to be, or are suspected of being faulty may be performed.
It will be understood by those of skill in the art or will be readily ascertainable by them that various additional operations may be added to the processes set forth herein. For example, between performances of the various deposition operations, the various etching operations, and the various planarization operations cleaning operations, activation operations, and the like may be desirable.
Some embodiments may employ diffusion bonding or the like to enhance adhesion between successive layers of material. Various teachings concerning the use of diffusion bonding in electrochemical fabrication processes are set forth in U.S. patent application Ser. No. 10/841,384 which was filed May 7, 2004 by Cohen et al. which is entitled “Method of Electrochemically Fabricating Multilayer Structures Having Improved Interlayer Adhesion” and which is hereby incorporated herein by reference as if set forth in full. This application is hereby incorporated herein by reference as if set forth in full.
Further teachings about planarizing layers and setting layers thicknesses and the like are set forth in the following US Patent Applications which were filed Dec. 31, 2003: (1) U.S. Patent Application No. 60/534,159 by Cohen et al. and which is entitled “Electrochemical Fabrication Methods for Producing Multilayer Structures Including the use of Diamond Machining in the Planarization of Deposits of Material” and (2) U.S. Patent Application No. 60/534,183 by Cohen et al. and which is entitled “Method and Apparatus for Maintaining Parallelism of Layers and/or Achieving Desired Thicknesses of Layers During the Electrochemical Fabrication of Structures”. The techniques disclosed explicitly herein may benefit by combining them with the techniques disclosed in U.S. patent application Ser. No. 11/029,220, filed Jan. 3, 2005 by Frodis, et al., and which is entitled “Method and Apparatus for Maintaining Parallelism of Layers and/or Achieving Desired Thicknesses of Layers During the Electrochemical Fabrication of Structures”. These patent filings are each hereby incorporated herein by reference as if set forth in full herein.
Additional teachings concerning the formation of structures on dielectric substrates and/or the formation of structures that incorporate dielectric materials into the formation process and possibility into the final structures as formed are set forth in a number of patent applications: (1) U.S. Patent Application No. 60/534,184, by Cohen, which as filed on Dec. 31, 2003, and which is entitled “Electrochemical Fabrication Methods Incorporating Dielectric Materials and/or Using Dielectric Substrates”; (2) U.S. Patent Application No. 60/533,932, by Cohen, which was filed on Dec. 31, 2003, and which is entitled “Electrochemical Fabrication Methods Using Dielectric Substrates”; (3) U.S. Patent Application No. 60/534,157, by Lockard et al., which was filed on Dec. 31, 2004, and which is entitled “Electrochemical Fabrication Methods Incorporating Dielectric Materials”; (4) U.S. Patent Application No. 60/574,733, by Lockard et al., which was filed on May 26, 2004, and which is entitled “Methods for Electrochemically Fabricating Structures Using Adhered Masks, Incorporating Dielectric Sheets, and/or Seed Layers that are Partially Removed Via Planarization”; and U.S. Patent Application No. 60/533,895, by Lembrikov et al., which was filed on Dec. 31, 2003, and which is entitled “Electrochemical Fabrication Method for Producing Multi-layer Three-Dimensional Structures on a Porous Dielectric”. The techniques disclosed explicitly herein may benefit by combining them with the techniques disclosed in U.S. patent application Ser. No. 11/029,216 filed Jan. 3, 2005 by Cohen et al. and entitled “Electrochemical Fabrication Methods Incorporating Dielectric Materials and/or Using Dielectric Substrates”. These patent filings are each hereby incorporated herein by reference as if set forth in full herein.
Some embodiments may not use any blanket deposition process. Some embodiments may involve the selective deposition of a plurality of different materials on a single layer or on different layers. Some embodiments may use blanket or selective depositions processes that are not electrodeposition processes. Some embodiments may form structures from two or more materials where one or more of the materials are coated with thin deposits of dielectric material and one or more materials are treated as a sacrificial material and removed after the formation of a plurality of layers. Some embodiments may use nickel or a nickel alloy as a structural material while other embodiments may use different materials such as gold, silver, or any other electrodepositable or electroless depositable materials. Some embodiments may use copper as the structural material with or without a sacrificial material. Some embodiments may remove a sacrificial material while other embodiments may not.
Though various portions of this specification have been provided with headers, it is not intended that the headers be used to limit the application of teachings found in one portion of the specification from applying to other portions of the specification. For example, it should be understood that alternatives acknowledged in association with one embodiment, are intended to apply to all embodiments to the extent that the features of the different embodiments make such application functional and do not otherwise contradict or remove all benefits of the adopted embodiment. Various other embodiments of the present invention exist. Some of these embodiments may be based on a combination of the teachings herein with various teachings incorporated herein by reference.
As noted above, embodiments of the invention may take a variety of forms some of which have been set forth herein in detail while others are described or summarized in a more cursory manner, while still others will be apparent to those of skill in the art upon review of the teachings herein though they are not explicitly set forth herein. Further embodiments may be formed from a combination of the various teachings explicitly set forth in the body of this application. Even further embodiments may be formed by combining the teachings set forth explicitly herein with teachings set forth in the various applications and patents referenced herein, each of which is incorporated herein by reference. In view of the teachings herein, many further embodiments, alternatives in design and uses of the instant invention will be apparent to those of skill in the art. As such, it is not intended that the invention be limited to the particular illustrative embodiments, alternatives, and uses described above but instead that it be solely limited by the claims presented hereafter.
Claims
1. In a method of forming a multi-layer three-dimensional structure, including: (A) forming a plurality of successive layers of the structure with each successive layer, except for a first layer, adhered to a previously formed layer and with each successive layer comprising at least two materials, one of which is a structural material and the other of which is a sacrificial material, and wherein each successive layer defines a successive cross-section of the three-dimensional structure, and wherein the forming of each of the plurality of successive layers includes: (i) depositing a first of the at least two materials; (ii) depositing a second of the at least two materials; and (B) after the forming of the plurality of successive layers, separating at least a portion of the sacrificial material from the structural material to reveal the three-dimensional structure, wherein the improvement comprises:
- in association with the formation of at least one of the successive layers, dividing the layer into a first thin sublayer and a second thicker sublayer and depositing a primary structural material in a lateral region of the first sublayer to form at least a portion of the sublayer, and thereafter planarizing the primary structural material to a height that bounds the first sublayer, where the thickness of the first sublayer is similar to a known or estimated effective work hardened thickness (e.g. preferably having a thickness between 1/3 and 3 times that of the estimated or known effective work hardened thickness, more preferably between 1/2 and 2 times that of the estimated or known effective work hardened thickness, even more preferably within 2/3 and 3/2 times that of the estimated or known effective work hardened thickness, even more preferably between 4/5 and 5/4 times that of the estimated or known effective work hardened thickness, and most preferably between 9/10 and 10/9 times that of the estimated or known effective work hardened thickness) or less than a known or estimated effective work hardened thickness induced by the planarization operation, and thereafter depositing the primary structural material in a lateral region of the second sublayer, and thereafter planarizing the primary structural material of the second sublayer.
2. In a method of forming a multi-layer three-dimensional structure, including: (A) forming a plurality of successive layers of the structure with each successive layer, except for a first layer, adhered to a previously formed layer and with each successive layer comprising at least two materials, one of which is a structural material and the other of which is a sacrificial material, and wherein each successive layer defines a successive cross-section of the three-dimensional structure, and wherein the forming of each of the plurality of successive layers includes: (i) depositing a first of the at least two materials; (ii) depositing a second of the at least two materials; and (B) after the forming of the plurality of successive layers, separating at least a portion of the sacrificial material from the structural material to reveal the three-dimensional structure, wherein the improvement comprises:
- in association with the formation of at least one of the successive layers, depositing a primary structural material in a lateral region of the layer to form at least a majority of the one successive layer in the lateral region, and thereafter planarizing the primary structural material to a height that bounds or exceeds the desired height of the at least one successive layer and such that at least a portion of the primary structural material is work hardened, etching into the primary structural material to form one or more openings that extend into the one successive layer in a least a portion of the lateral region to remove at least a portion of the work hardened primary structural material.
3. The method of claim 2 further comprising depositing structural material into the one or more openings after etching.
4. The method of claim 3 wherein the depositing of structural material into the one or more openings occurs during deposition associated with formation of a subsequent successive layer.
5. The method of claim 3 wherein the depositing of structural material into the one or more openings occurs prior to being a deposition associated with formation of a subsequent successive layer.
6. The method of claim 1 where curvature during formation of the structure is reduced by forming the structure on a thick rigid substrate.
7. The method of claim 1 where curvature during formation of the structure is reduced by plating material periodically on the back side of the substrate as a thickness of deposited material on the front side of increase.
8. The method of claim 7 wherein the material plated on the back side of the substrate is planarized after it is deposited.
9. In a method of forming a multi-layer three-dimensional structure, including: (A) forming a plurality of successive layers of the structure with each successive layer, except for a first layer, adhered to a previously formed layer and with each successive layer comprising at least two materials, one of which is a structural material and the other of which is a sacrificial material, and wherein each successive layer defines a successive cross-section of the three-dimensional structure, and wherein the forming of each of the plurality of successive layers includes: (i) depositing a first of the at least two materials; (ii) depositing a second of the at least two materials; and (B) after the forming of the plurality of successive layers, separating at least a portion of the sacrificial material from the structural material to reveal the three-dimensional structure, wherein the improvement comprises:
- forming at least one layer such that a primary structural material on the layer is provided with an upper surface configuration, planarizing the upper surface, and thereafter forming notches in the planarized surface in a desired pattern where the notches provide decoupling of stress located in separated regions of structural material.
Type: Application
Filed: Jan 14, 2011
Publication Date: Jun 23, 2011
Applicant:
Inventors: Ananda H. Kumar , Jorge Sotelo Alberran , Adam L. Cohen , Kieun Kim , Michael S. Lockard , Uri Frodis , Dennis R. Smalley
Application Number: 13/006,814
International Classification: C25D 5/48 (20060101); C25D 5/10 (20060101);
