US20050202180A1

US20050202180A1 - Electrochemical fabrication methods for producing multilayer structures including the use of diamond machining in the planarization of deposits of material

Info

Publication number: US20050202180A1
Application number: US11/029,165
Authority: US
Inventors: Adam Cohen; Uri Frodis; Michael Lockard; Ananda Kumar; Gang Zhang; Dennis Smalley
Original assignee: Microfabrica Inc
Current assignee: Microfabrica Inc
Priority date: 2003-12-31
Filing date: 2005-01-03
Publication date: 2005-09-15
Also published as: WO2005065430A3; EP1711961A4; US20100038253A1; EP1711961A2; US7271888B2; WO2005065436A2; US20050181316A1; WO2005065436A3; US8702956B2; US9714473B2; US7588674B2; KR101177586B1; US20120181180A1; US20140231263A1; WO2005065430A2; US20050142846A1; KR20060130629A; JP2007516856A

Abstract

Electrochemical fabrication methods for forming single and multilayer mesoscale and microscale structures are disclosed which include the use of diamond machining (e.g. fly cutting or turning) to planarize layers. Some embodiments focus on systems of sacrificial and structural materials which are useful in Electrochemical fabrication and which can be diamond machined with minimal tool wear (e.g. Ni—P and Cu, Au and Cu, Cu and Sn, Au and Cu, Au and Sn, and Au and Sn—Pb), where the first material or materials are the structural materials and the second is the sacrificial material). Some embodiments focus on methods for reducing tool wear when using diamond machining to planarize structures being electrochemically fabricated using difficult-to-machine materials (e.g. by depositing difficult to machine material selectively and potentially with little excess plating thickness, and/or pre-machining depositions to within a small increment of desired surface level (e.g. using lapping or a rough cutting operation) and then using diamond fly cutting to complete he process, and/or forming structures or portions of structures from thin walled regions of hard-to-machine material as opposed to wide solid regions of structural material.

Description

RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent Application Nos. 60/534,159, and 60/534,183, both filed Dec. 31, 2003. Each of these referenced applications is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the field of electrochemical fabrication and the associated formation of three-dimensional structures (e.g. microscale or mesoscale structures). In particular, it relates to electrochemical fabrication processes that utilize diamond machining during the planarization of deposited materials.

BACKGROUND OF THE INVENTION

A technique for forming three-dimensional structures (e.g. parts, components, devices, and the like) from a plurality of adhered layers was invented by Adam L. Cohen and is known as Electrochemical Fabrication. It is being commercially pursued by Microfabrica Inc. (formerly MEMGen® Corporation) of Burbank, Calif. under the name EFAB™. This technique was described in U.S. Pat. No. 6,027,630, issued on Feb. 22, 2000. This electrochemical deposition technique allows the selective deposition of a material using a unique masking technique that involves the use of a mask that includes 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 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. (formerly MEMGen® Corporation) of Burbank, Calif. 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 layers of material or may be used 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:

- (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, p161, 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, p244, 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 (EFABTM)”, Chapter 19 of The MEMS Handbook, edited by Mohamed Gad-EI-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.
The electrochemical deposition process 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:

- 1. Selectively depositing at least one material by electrodeposition upon one or more desired regions of a substrate.
- 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.
- 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 the 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 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. At least one CC mask is needed 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 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 the substrate (or onto a previously formed layer or onto a previously deposited portion of a layer) on which deposition is to occur. The pressing together of the CC mask and 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 FIGS. 1A-1C. FIG. 1A shows a side view of a CC mask 8 consisting of a conformable or deformable (e.g. elastomeric) insulator 10 patterned on an anode 12. The anode has two functions. FIG. 1A also depicts a substrate 6 separated from mask 8. One is as a supporting material for the patterned insulator 10 to maintain its integrity and alignment since the pattern may be topologically complex (e.g., involving isolated “islands” of insulator material). The other function is as an anode for the electroplating operation. CC mask plating selectively deposits material 22 onto a substrate 6 by simply pressing the insulator against the substrate then electrodepositing material through apertures 26 a and 26 b in the insulator as shown in FIG. 1B. After deposition, the CC mask is separated, preferably non-destructively, from the substrate 6 as shown in FIG. 1C. 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. 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 FIGS. 1D-1F. FIG. 1D shows an anode 12′ separated from a mask 8′ that includes a patterned conformable material 10′ and a support structure 20. FIG. 1D also depicts substrate 6 separated from the mask 8′. FIG. 1E illustrates the mask 8′ being brought into contact with the substrate 6. FIG. 1F illustrates the deposit 22′ that results from conducting a current from the anode 12′ to the substrate 6. FIG. 1G illustrates the deposit 22′ on substrate 6 after separation from mask 8′. In this example, an appropriate electrolyte is located between the substrate 6 and the anode 12′ and a current of ions coming from one or both of the solution and the anode are conducted through the opening in the mask to the substrate where material is deposited. This type of mask may be referred to as an anodeless INSTANT MASK™ (AIM) or as an anodeless conformable contact (ACC) mask.
Unlike through-mask plating, CC mask plating allows CC masks to be formed completely separate from the fabrication of 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, a photolithographic process may be used. All masks can be generated simultaneously, 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 FIGS. 2A-2F. These figures show that the process involves deposition of a first material 2 which is a sacrificial material and a second material 4 which is a structural material. The CC mask 8, in this example, includes a patterned conformable material (e.g. an elastomeric dielectric material) 10 and a support 12 which is made from deposition material 2. The conformal portion of the CC mask is pressed against substrate 6 with a plating solution 14 located within the openings 16 in the conformable material 10. An electric current, from power supply 18, is then passed through the plating solution 14 via (a) support 12 which doubles as an anode and (b) substrate 6 which doubles as a cathode. FIG. 2A, illustrates that the passing of current causes material 2 within the plating solution and material 2 from the anode 12 to be selectively transferred to and plated on the cathode 6. After electroplating the first deposition material 2 onto the substrate 6 using CC mask 8, the CC mask 8 is removed as shown in FIG. 2B. FIG. 2C depicts the second deposition material 4 as having been blanket-deposited (i.e. non-selectively deposited) over the previously deposited first deposition material 2 as well as over the other portions of the substrate 6. The blanket deposition occurs by electroplating from an anode (not shown), composed of the second material, through an appropriate plating solution (not shown), and to the cathode/substrate 6. The entire two-material layer is then planarized to achieve precise thickness and flatness as shown in FIG. 2D. After repetition of this process for all layers, the multi-layer structure 20 formed of the second material 4 (i.e. structural material) is embedded in first material 2 (i.e. sacrificial material) as shown in FIG. 2E. The embedded structure is etched to yield the desired device, i.e. structure 20, as shown in FIG. 2F.
Various components of an exemplary manual electrochemical fabrication system 32 are shown in FIGS. 3A-3C. The system 32 consists of several subsystems 34, 36, 38, and 40. The substrate holding subsystem 34 is depicted in the upper portions of each of FIGS. 3A to 3C and includes several components: (1) a carrier 48, (2) a metal substrate 6 onto which the layers are deposited, and (3) a linear slide 42 capable of moving the substrate 6 up and down relative to the carrier 48 in response to drive force from actuator 44. Subsystem 34 also includes an indicator 46 for measuring differences in vertical position of the substrate which may be used in setting or determining layer thicknesses and/or deposition thicknesses. The subsystem 34 further includes feet 68 for carrier 48 which can be precisely mounted on subsystem 36.
The CC mask subsystem 36 shown in the lower portion of FIG. 3A includes several components: (1) a CC mask 8 that is actually made up of a number of CC masks (i.e. submasks) that share a common support/anode 12, (2) precision X-stage 54, (3) precision Y-stage 56, (4) frame 72 on which the feet 68 of subsystem 34 can mount, and (5) a tank 58 for containing the electrolyte 16. Subsystems 34 and 36 also include appropriate electrical connections (not shown) for connecting to an appropriate power source for driving the CC masking process.
The blanket deposition subsystem 38 is shown in the lower portion of FIG. 3B and includes several components: (1) an anode 62, (2) an electrolyte tank 64 for holding plating solution 66, and (3) frame 74 on which the feet 68 of subsystem 34 may sit. Subsystem 38 also includes appropriate electrical connections (not shown) for connecting the anode to an appropriate power supply for driving the blanket deposition process.
The planarization subsystem 40 is shown in the lower portion of FIG. 3C and includes a lapping plate 52 and associated motion and control systems (not shown) for planarizing the depositions.
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 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 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 the both the primary and secondary metals. Formation of a second layer may then begin by applying a photoresist layer over the first layer and then repeating the process used to produce the first layer. The process is then 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 the voids in the photoresist are formed by exposure of the photoresist through a patterned mask via X-rays or UV radiation.
Even though electrochemical fabrication as taught and practiced to date, has greatly enhanced the capabilities of microfabrication, and in particular added greatly to the number of metal layers that can be incorporated into a structure and to the speed and simplicity in which such structures can be made, room for enhancing the state of electrochemical fabrication exists.

SUMMARY OF THE INVENTION

It is an object of some embodiments of the invention to provide electrochemical fabrication processes with enhanced capabilities.
It is an object of some embodiments of the invention to provide more rapid planarization of deposited materials during multi-layer electrochemical fabrication of structures.
It is an object of some embodiments of the invention to provide enhanced and/or more reliable surface finish of planarized materials.
It is an object of some embodiments of the invention to provide enhanced electrochemical fabrication embodiments that can reliably and efficient make use of fly cutting to planarize deposited materials.
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 and aspects 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 embodiment or aspect of the invention even though that may be the case with regard to some embodiments and aspects.
In a first aspect of the invention, a process for forming a multilayer three-dimensional structure, including: (a) forming and adhering a layer of material to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material, wherein one or more contact pads exist on the substrate or on a previously formed layer; (b) subjecting the at least one material to a planarization operation which comprises diamond machining (c) repeating the forming and adhering of operation (a) one or more time to form the three-dimensional structure from a plurality of adhered layers.
In a second aspect of the invention, the process of the preceding aspect wherein the planarization operation includes at least one lapping operation or rough cutting operation that brings height of deposition to a level which is closer to that of the final desired level and after which the diamond machining operation brings the level of the deposited materials to a level that is within a defined tolerance of a desired level.
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 method aspects of the invention. These other aspects of the invention may provide various combinations of the aspects presented above or of embodiments presented hereafter as well as provide other configurations, structures, functional relationships, and processes that have not been specifically set forth above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C schematically depict side views of various stages of a CC mask plating process, while FIGS. 1D-G schematically depict a side views of various stages of a CC mask plating process using a different type of CC mask.
FIGS. 2A-2F schematically depict side views of various stages of an electrochemical fabrication process as applied to the formation of a particular structure where a sacrificial material is selectively deposited while a structural material is blanket deposited.
FIGS. 3A-3C schematically depict side views of various example subassemblies that may be used in manually implementing the electrochemical fabrication method depicted in FIGS. 2A-2F.
FIGS. 4A-4I schematically depict the formation of a first layer of a structure using adhered mask plating where the blanket deposition of a second material overlays both the openings between deposition locations of a first material and the first material itself.
FIG. 5A provides a flowchart of an electrochemical fabrication process that may be used in practicing some embodiments of the invention.
FIGS. 5B-5I provide block diagrams of operations that may be used during the formation of a single layer of a structure or during the formation of each of a plurality of layers of a multi-layer structure according to first through eighth embodiments of the invention where the outlined operations may be used as operations on in the process of FIG. 5A for the formation of some or all layers of the structures.
FIG. 6 provides a block diagram of a ninth embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIGS. 1A-1G, 2A-2F, and 3A-3C illustrate various features of one form of electrochemical fabrication that are known. Other electrochemical fabrication techniques are set forth in the '630 patent referenced above, in the various previously incorporated publications, in various other patents and patent applications incorporated herein by reference, still others may be derived from combinations of various approaches described in these publications, patents, and applications, or are otherwise known or ascertainable by those of skill in the art from the teachings set forth herein. All of these techniques may be combined with those of the various embodiments of various aspects of the invention to yield enhanced embodiments. Still other embodiments may be derived from combinations of the various embodiments explicitly set forth herein.
FIGS. 4A-4I illustrate various stages in the formation of a single layer of a multi-layer fabrication process where a second metal is deposited on a first metal as well as in openings in the first metal where its deposition forms part of the layer. In FIG. 4A, a side view of a substrate 82 is shown, onto which patternable photoresist 84 is cast as shown in FIG. 4B. In FIG. 4C, a pattern of resist is shown that results from the curing, exposing, and developing of the resist. The patterning of the photoresist 84 results in openings or apertures 92(a)-92(c) extending from a surface 86 of the photoresist through the thickness of the photoresist to surface 88 of the substrate 82. In FIG. 4D, a metal 94 (e.g. nickel) is shown as having been electroplated into the openings 92(a)-92(c). In FIG. 4E, the photoresist has been removed (i.e. chemically stripped) from the substrate to expose regions of the substrate 82 which are not covered with the first metal 94. In FIG. 4F, a second metal 96 (e.g., silver) is shown as having been blanket electroplated over the entire exposed portions of the substrate 82 (which is conductive) and over the first metal 94 (which is also conductive). FIG. 4G depicts the completed first layer of the structure which has resulted from the planarization of the first and second metals down to a height that exposes the first metal and sets a thickness for the first layer. In FIG. 4H the result of repeating the process steps shown in FIGS. 4B-4G several times to form a multi-layer structure are shown where each layer consists of two materials. For most applications, one of these materials is removed as shown in FIG. 4I to yield a desired 3-D structure 98 (e.g. component or device).
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, different types of patterning masks and masking techniques may be used or even techniques that perform direct selective depositions without the need for masking. For example, the conformable contact masks may be used on some layers and non-conformable contact masks and masking operations may be used in association with the formation of other layers. 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) may be used, and 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) may be used.
A first group of embodiments of the invention use diamond machining (i.e. diamond fly cutting or turning) to planarize deposits of materials during the electrochemical fabrication of single layer and multi-layer structures. As diamond machining is not appropriate for effectively machining all materials, embodiments of the invention take on a variety of forms with each having the common element that diamond machining will be used during at least a portion of the planarization operations associated with the formation of one or more layers of a structure being formed. Some embodiments focus on building structures using only structural and sacrificial materials that are readily fly cuttable. Some embodiments, focus on reducing tool wear when one or more of the building materials (e.g. sacrificial materials or structural materials) are hard or difficult to machine (i.e. hard to diamond fly cut).
Many embodiments of electrochemical fabrication processes involve the use of both a structural material and a sacrificial material. In these embodiments, it is desired that the structural material and sacrificial materials meet certain criteria. For example, some common criteria for the structural materials include: (1) desirable physical and chemical properties, (2) relatively low stress, (3) excellent inter-layer adhesion, (4) ability to be deposited over and adequately adhere to sacrificial material, (5) low porosity, and (6) ability to be planarized in conjunction with neighboring regions of sacrificial material using a chosen planarization process without adverse effect on the structure, excessive time and expense spent on performing the planarization process, and with adequate accuracy and repeatability of the process. Some common criteria for sacrificial materials include: (1) excellent etch selectivity with respect to structural material, (2) minimal inter-diffusion with structural material prior to removal, (3) a coefficient of thermal expansion similar to that of the structural material, and (4) ability to be planarized in conjunction with neighboring regions of structural material. Of course, depending on the circumstances, in some embodiments, it may not be necessary for each of these criteria, or even most of these criteria, to be met.

Certain combinations of structural and sacrificial materials have the ability to be planarized using diamond machining with (1) good planarity, both across the wafer and locally (i.e., minimal recession of one material vs. another), (2) minimal smearing of one material into another, and (3) acceptable wear of machining tools. Examples of such material combinations are set forth in Table 1:

	TABLE 1


	Structural Material	Sacrificial Material

	Ni—P (P content	Cu
	preferably 11% or higher)
	Au	Cu
	Cu	Sn
	Cu	Sn—Pb
	Au	Sn
	Au	Sn—Pb

The Ni—P may be deposited via electroless deposition or electrolytically. If electroless Ni—P deposition is used, due to possible limitations on compatibility with some masking materials (e.g. photoresist), it may be desirable to blanket plate the Ni—P after pattern plating of Cu. Alternatively blanket deposition of Ni—P may be followed by selective etching of voids and then locating of sacrificial material therein. To reduce material cost, in some embodiments it may be desirable to pattern plate Au and then blanket deposit Cu. In other embodiments, it may be possible to reduce material costs by first selectively plating Cu then treating the Cu with one of the over-plating reduction techniques disclosed in U.S. patent application Ser. No. 10/841,100, filed May 7, 2004 by Cohen, et al., and entitled “Electrochemical Fabrication Methods Including Use of Surface Treatments to Reduce Overplating and/or Planarization During Formation of Multi-layer Three-Dimensional Structures”, which is hereby incorporated herein by reference as if set forth in full.
FIG. 5A provides a flow chart of an electrochemical fabrication process that may be followed in practicing some embodiments of the invention. The process of FIG. 5A begins with block 102 and then moves forward to block 104 which calls for the defining of variables and parameters. A current layer number variable “n” is defined, a final layer number parameter “N” is specified, a current operation number on layer n, o_n, is defined and for each layer n a final operation number O_nis defined.
Next the process moves forward to block 106 which calls for the supplying of a substrate on which the structure will be formed. After which the process moves forward to block 108 which calls for the setting of the current layer number variable n to 1 (n=1) one and then onto block 112 which calls for the setting of the current operation number variable o_nto 1 (o_n=1).
Next the process moves forward to decision block 114 which makes an inquiry as to whether operation on is a planarization operation. If a negative response is obtained, the process moves forward to block 116 which calls for the performance of operation o_nand thereafter the process moves forward to block 140 which will be described herein later. If a positive response to the inquiry of block 114 is received, the process moves forward to block 118 which calls for the performance of the planarization operation or operations associated with the current value of on and thereafter the process moves forward to block 120 which calls for the making of an endpoint detection measurement after which the process moves forward to block 124 which calls for an analysis of the endpoint detection data.
Next, the process moves forward to block 126 which inquires as to whether or not the planarization objective has been achieved. If the answer to this inquiry is “no” the process moves forward to block 128 which inquires as to whether additional planarization will yield the desired objective. If the answer is “yes”, the process loops back to block 118 where additional planarization operations will be performed, potentially using new parameters based on the fact that some amount of planarization has already occurred.
If block 128 produces a negative response, the process moves forward to block 130 which calls for the taking of one of three actions. The first of which is to institute some form of remedial action and then to jump to any appropriate point in the process to continue structure formation. Such remedial action may include the complete removal of the current layer, resetting of the operation number variable and moving back to block 114 to continue the process. Other remedial actions may involve re-depositing one or more materials and then continuing the process while other remedial actions may involve the recalibration or reworking of planarization fixtures, endpoint detection fixtures, or the like. Still other remedial actions may involve redeposition of some material and then use of a different planarization technique, such as multi-stage lapping, to replace the failed planarization technique.
A second action that may be taken may simply be to ignore the failure and continue the process as it may be determined that the failure on the given layer is not critical to the overall performance of the structure that is being formed.
A third action that may be taken may involve the aborting of the process and restarting it form the beginning or redesigning the structure and then starting the process over.
If block 126 produces a positive response, the process moves forward to block 140 which calls for incrementing the current operation number variable by one and then the process moves forward to block 142 which inquires as to whether the current operation number variable has exceeded the final operation variable number, O_n, for layer n. If the answer to this inquiry is “no”, the process loops back to block 114 for the performance of further operations on the present layer. If on the other hand this block produces a positive response, the process moves forward to block 144 which calls for the incrementing of the layer number variable, n, by one (n=n+1) after which the process moves forward to block 146 which inquires as to whether the current layer number variable, n, has exceeded the final layer number, N (n>N?). If this inquiry produces a positive response, the process moves forward to block 148 and ends. If on the other hand this inquiry produces a negative response, the process loops back to block 112 where the current operation number is reset to one so that operations may begin for creation of a next layer of the structure.
When block 148 is reached and the layer formation process ends, the formation of the structure may not yet be complete as various post processing operations may still need to occur. Such post processing operations may include, for example: (1) heat treating of the structures to improve interlayer adhesion, (2) release of the structure from any sacrificial material used during the layer formation process, (3) dicing of individual die regions on the substrate, (4) separation of the multiple simultaneously formed structures from the substrate on which they were formed, and/or (5) combining structures with other structures functionally or physically to build up desired systems or devices.
FIGS. 5B and 5C provide examples of process operations that may be performed in association with layers formed from the above noted combinations of structural and sacrificial materials. It should be understood that various other process operations are possible and that those set forth in FIGS. 5B and 5C are just examples of two simple versions of such processes.
The embodiment of FIG. 5B uses five operations to form a layer and in some embodiments the operations may be repeated to form additional layers. These operations may be used in producing a desired structure where these operations may be plugged into the process of FIG. 5A or be used in conjunction with a different processing scheme. Block 202 sets forth the first operation which calls for the locating of a mask on a surface of the substrate or previously formed layer where the mask is patterned so as to have openings which correspond to locations where a sacrificial material is to be located. Block 204 sets forth the second operation which calls for the selective depositing of a diamond machinable sacrificial material. Block 206 sets forth the third operation which calls for the removal of the masking material. Block 208 sets forth the fourth operation which calls for the blanket deposition of a diamond machinable structural material. Block 210 sets forth a fifth operation which calls for the diamond machining of the deposited materials to achieve a desired planarization level (i.e. a desired net height).
FIG. 5C sets forth operations similar to those of FIG. 5B with the exception that the structural material will be deposited first and the sacrificial material second. As a result of this change, block 222 sets forth the first operation which calls for a masking material to be located on the surface of the substrate or previously formed layer where openings in the masking material correspond to locations where structural material is to be located. Block 224 calls for the selective deposition of a diamond machinable structural material. Block 226 sets forth the third operation which calls for the removal of the masking material while block 228 sets forth the fourth operation which calls for the blanket deposition of a diamond machinable sacrificial material. Block 230, as did block 210 of FIG. 5B, calls for the diamond machining of the deposited materials.
Some materials and material combinations are inherently unsuited for general use with diamond machining but some embodiments of the invention incorporate operations and or restrictions that minimize the incompatibilities and thus allow diamond machining to be effectively used in conjunction with otherwise unusable materials and material combinations. Materials that are typically considered incompatible with diamond machining are Ni and Ni alloys (with the exception of Ni—P with a high percentage of P). For example, Ni and Ni—Co are difficult to diamond machine due to chemical wear of the single-point diamond tool. In the context of EFAB, several methods can be used to minimize tool wear when using difficult to machine materials, and particular when using them as the structural material. Operations associated with some examples of such processes are set forth in the block diagrams of FIGS. 5D-5I. Operations such as those set forth in the examples of FIGS. 5D-5I may be implemented via a process such as that depicted in FIG. 5A or they may be implemented using different processes. It should also be understood that features of the various example processes may be combined with one another and/or with other processes to derive further embodiments. It should also be understood that the process set forth herein to deal with difficult to machine materials may also be used in conjunction with easier to machine materials without negative effect.
Operations for a first example process where planarization of a difficult to machine material is to occur are set forth in FIG. 5D. The first operation of FIG. 5D is set forth in block 242 which calls for the masking of the substrate or previously formed layer with a patterned mask having openings that correspond to locations where a first of a sacrificial material or a structural material is to be located. The second operation of the process is set forth in block 244 and involves the selective deposition of a first of the sacrificial material or the structural material wherein at least one of the materials is hard to diamond machine. The third operation of the process is set forth in block 246 which calls for the removal of the masking material. The fourth operation of the process is set forth in block 248 which calls for the blanket deposition of a second of the sacrificial material or structural material. The fifth, and final, operation of the process is set forth in block 250 which calls for the vibration assisted diamond machining of the deposited materials to achieve a desired planarization level (i.e. net deposition height).
Use of tool vibration has been described in the literature as a means of reducing tool wear and as a means for extending diamond machining to materials normally considered incapable of being diamond machined. An example of such a publication is “Vibration Assisted Diamond Turning using Elliptical Tool Motion,” by Dow, T A; Cerniway, M; Sohn, A; and Negishi, N, Proceedings of the ASPE, Vol 25, November 2001, pg 92-97. A copy of this article is set forth as Appendix A in U.S. patent application Ser. No. 60/534,159 which has been previously incorporated herein by reference. In alternative embodiments, as opposed to or in addition to using tool vibration to extend tool life, tool life may be extended by machining in an inert gas, machining in an atmosphere containing carbon, and/or machining at cryogenic temperatures. These methods may be applied to planarization operations during electrochemical fabrication.
Instead of trying to machine large, continuous expanses of difficult-to-machine (DM) material, tool wear may be decreased by machining only small amounts of DM material (e.g. structural material) which are embedded within an easily-machined material (e.g., a sacrificial material such as Cu or Sn). This result is partly due to simply having less DM material to machine, but may also be partly due to an effect similar to that produced using tool vibration: the tool no longer contacts DM material continuously but moves in and out of DM material. The amount of time spent machining embedded DM material is determined by the length of the DM feature along the tool path and the tangential speed of the tool relative to the workpiece surface. The time spent can be reduced by changing either of these factors; adjusting the length of the DM feature may impose a change on EFAB design rules. The ‘duty cycle’ (the % of time the tool spends in DM vs. easily-machined material) can also be adjusted by imposing design rules on the EFAB design and/or on the layout of die on a substrate or wafer.
The amount of time that the tool spends machining the difficult-to-machine material may be reduced by: (1) pattern-plating the DM material and blanket plating the more easily-machined material; (2) pattern deposit both materials by either masking over the first deposited material or b inhibiting the deposition of the second material onto the surface of the first deposited material by treating the surface of the first deposited material; (3) plating the DM material with as uniform of a thickness as possible which is not significantly greater than the layer thickness; (4) lapping surface of the depositions down to a level which is slightly above final desired planed level (e.g. 0.5-2 microns above the target level) before diamond machining is used to cut the remaining material down to the final desired level; (5) rough cutting (e.g., using cubic boron nitride, polycrystalline diamond, tungsten carbide) the deposited materials down to a level which is slightly above the final desired planed level before diamond machining occurs; (6) avoiding the existence of as much of the DM material at and above the planarization level as possible during the time that planarization occurs, and/or (7) treat the surface of the hard to machine material to make it more readily machinable, e.g. treat or dope the surface of the hard to machine material with a second material (e.g. dope Ni with P) that changes the material properties of the first material to a depth sufficient to allow machining and, if necessary, remove any residual treatment or dopant after the machining is completed.
In either of techniques (4) or (5), enough material should be left above the final desired planarization level so that any subsurface damage caused by lapping or rough-cutting (it is believed that such surface/subsurface damage can contribute to curling of layers (i.e. distortion form flatness) once the structural material is released from the sacrificial material. The subsurface damage caused by the initial planarization operations may be removed by the diamond machining (which can produce less subsurface damage than some other methods).
An example of a process that implements the 1st technique (of reducing the amount of time that the tool spends cutting difficult to machine material) is set forth in the operations of FIG. 5E. Operation 1 of FIG. 5E is set forth in block 250 and calls for the masking of the surface of the substrate or previously formed layer with a patterned mask that has openings which correspond to locations where a first of a sacrificial material or a structural material is to be located. Operation 2 is set forth in block 264 and calls for the selective deposition of a hard to machine selected one of the sacrificial material or structural material. Operation 3 is set forth in block 266 and calls for the removal of the masking material. Operation 4 is set forth in block 268 and calls for the blanket deposition of the non-selected one of the structural material or sacrificial material which is not hard or difficult to machine. The 5th, and final, operation of the example process is set forth in block 270 and calls for the diamond machining of the deposited materials to achieve a desired level of planarized material.
Numerous variations of these operations are possible and will be apparent to those of skill in the art upon reviewing the teachings set forth herein. For example, the blanket deposition of Operation 4 may be replaced by a selective deposition operation. As another example, in some implementations the selected deposition of Operation 2 may be replaced by a blanket deposition and a subsequent selective etching operation. As a third example the two depositions of Operations 2 and 4may be implemented, for example, via electroplating operations, electroless plating operations, or a combination thereof. As a fourth example, if one of the materials is a dielectric material, appropriate application of one or more seed layer materials may be utilized if necessary.
An example of a process that implements the 4th technique (for reducing the amount of time that the tool spends cutting difficult to machine material) is set forth in the operations of FIG. 5F. FIG. 5F sets forth six operations that may be used in forming one or more layers of a structure. The 1 st operation is set forth in block 282 which calls for the masking of the surface of the substrate or previously formed layer with a patterned mask that has openings which correspond to locations where a selected one of a sacrificial material or structural material is to be located. Operation 2 is set forth in block 284 which calls for the selective deposition of a hard to machine selected one of the sacrificial or structural materials. The 3rd operation is set forth in block 286 which calls for the removal of the masking material. The 4th operation is set forth in block 282 and calls for the blanket deposition of the non-selected one of the structural and sacrificial materials. In this embodiment, it is assumed that the non-selected one of the materials is not hard or difficult to machine.
The 5th operation is set forth in block 290 which calls for using one or more lapping or rough cutting operations to trim the thickness of the deposits to within a small increment of a desired planarization level. The rough cutting operations, if used, may be based on using machine tool tips of cubic boron nitride, polysilicon diamond, or tungsten carbide, for example. The 6th operation is set forth in block 292 which calls for the diamond machining of the thinned down deposited materials such that a desired height of deposition (i.e. surface level) is achieved. As with the other sets of operations set forth herein, numerous variations of the operations described in this example are possible.
An example of a process that implements a variation of the 4th technique (of reducing the amount of time that the tool spends cutting difficult to machine material) is an embodiment that includes the formation of a structure from three-materials as set forth in the operations of FIG. 5G. The layer formation operations of FIG. 5G include ten separate operations. The 1 st of which is set forth in block 322 which calls for the masking of the surface of the substrate or previously formed layer with a patterned mask having openings which correspond to locations where a hard to machine structural material is to be located. The 2nd operation of the process is set forth in block 324 which calls for the selective deposition of the structural material onto the substrate or previously formed layer via the openings in the mask. The 3rd operation of the process is set forth in block 326 which calls for the removal of the masking material. The fourth operation of the process is set forth in block 328 which calls for the blanket deposition of a sacrificial material. The 5th operation of the process is set forth in block 330 which calls for the lapping or rough cutting of the deposited materials to a level which is above, or short of, the ultimate planarization level for the layer. The planarization done in Operation 5 serves two purposes, one of which is the minimization of the thickness of the hard to machine material that will eventually be planarized using diamond machining and the other of which is the obtainment of a uniform working surface on which subsequent operations may be performed.
The 6th operation is set forth in block 332 which calls for the masking of the surface of one or both of the deposited materials with a patterned mask that has openings which correspond to locations where a 3rd material is to be located. In some variations of this process the openings may be made to occur over regions which previously received structural material only while in other variations the openings may be located over some regions that received structural material and other regions that received sacrificial material, while in still further variations the openings may be located over regions occupied by previously deposited sacrificial material only. In the present example it is assumed that the openings in the mask are located only above regions where sacrificial material was deposited.
The 7th operation of the process is set forth in block 334 which calls for the etching of openings into the sacrificial material to a depth which is the sum of the layer thickness plus an incremental tolerance based amount, δ, and an amount which is based on the difference between the rough cut planarization level and the final desired planarization level. The amount δ is set large enough to ensure that the bottom of the layer is reached but not so large that a void is inadvertently formed that extends an undesirable amount into a previous layer.
The 8th operation of this example is set forth in block 336 which calls for the selective deposition of a third material into the openings that have been etched into the sacrificial material. In the present example, it is assumed that the 3rd material is a material that is not difficult to machine. The 9th operation of the process is set forth in block 338 which calls for the removal of the masking material. The 10th operation of this example is set forth in block 340 which calls for the diamond machining of the deposited materials to achieve a desired net height of deposition (i.e. a desired planarization level).
An example of a process that implements a variation of the 4th technique (of reducing the amount of time that the tool spends cutting difficult to machine material) is an embodiment that includes the formation of a structure from three-materials (one of which is a dielectric material) as set forth in the operations of FIG. 5H. The example of FIG. 5H sets forth a twelve operation layer formation process which includes a rough cutting planarization operation and a diamond machining operation and which also includes the deposition of three materials, one of which is a sacrificial material.
The 1 st operation of this example is depicted in block 362 which calls for the masking of the substrate or previously formed layer with a patterned mask having openings which correspond to locations where a conductive, hard to machine structural material is to be located.
The 2nd operation of this example is set forth in block 364 which calls for making a determination as to whether the substrate or previously formed layer is adequately conductive to allow deposition of the structural material. If it is determined that the substrate or previously formed layer is not adequately conductive a seed layer of a selected material and if necessary an adhesion layer of a selected material may be applied. If it is determined that the structural layer is adequately conductive the process proceeds to the 3rd operation.
The 3rd operation of the process is set forth in block 366 which calls for the selective deposition of a conductive structural material. The 4th operation of the process is set forth in block 368 which calls for the removal of the masking material.
The 5th operation of the process is set forth in block 370 which is similar to the second operation of the process as it calls for a determination of whether the exposed portions of the substrate or previously formed layer are adequately conductive to receive a deposit of a conductive sacrificial material. If it is determined that the substrate or previously formed layer is not adequately conductive then a seed layer of a selected material and if necessary an adhesion layer of a selected material may be applied. If it is determined that the structural layer is adequately conductive the process proceed to the 6th operation.
The 6th operation of the process is set forth in block 372 which calls for the blanket deposition of the conductive sacrificial material. The 7th operation of the process calls for the lapping or rough cutting of the deposited materials to a level that is above the desired level for the completed layer by a desired amount z.
The 8th operation of this example is set forth in block 384 which calls for the masking of the surface of the deposited materials with a patterned mask having openings that correspond to locations where a dielectric 3rd material is to be located. As with Operation 6 of FIG. 5G as set forth in block 332 the masking of this operation (Operation 8) and variations of this example may locate openings above the sacrificial material, the structural material, or a combination of both. In the present example it is assumed that the openings are located only over regions of sacrificial material. It is worth noting that in the present example, as well as in the example of FIG. 5F, as a selective etching operation is to be performed in the operation which is subsequent to the masking operation it may not be necessary that the openings in the masking material identically correspond to regions to be etched if such regions are in whole or in part bounded by material that will not be attacked by the particular etchant utilized. As such, in some variations of these examples it may be possible to use masks that deviate from exact etching patterns in certain ways.
Operation 9 of the present example is set forth in block 386 which calls for the etching of openings into the sacrificial material where the openings are etched to a depth equal to the layer thickness plus the amount z plus an incremental amount δ (LT+z+δ). The incremental amount may be associated with a tolerance, or uncertainty, in the exact separation between the upper surface being etched and the location of the bottom of the layer.
Operation 10 is set forth in block 388 which calls for the selective deposition of a 3rd material into the openings that were etched into the sacrificial material.
The 11th operation of this example is set forth in block 390 which calls for the removal of the masking material which was applied in Operation 8.
The 12th, and final, operation of this example calls for diamond machining of the deposited materials to achieve a desired planarization level (i.e. a bounding level for the present layer).
As with the other examples set forth herein numerous variations are possible and will be understood by those of skill in the art after studying the teachings set forth herein. Two such variations may be based on the use of either the 1st masking material applied in Operation 1 or the 2nd masking material applied in Operation 8 as one of the building materials from which layers are to be built up.
The avoidance approach of the 6th technique may be implemented in a variety of different ways, for example, a first implementation might involve depositing the DM material (i.e. difficult to machine material) in all desired locations to an approximately uniform depth and then selectively etching into selected regions (e.g. regions which will be overlaid by the DM material deposited in association with the formation of the next layer). The depth of etching preferably extends at least an incremental amount below the final desired planarization level such that DM material in that portion of the cross-section never undergoes planarization. During continued formation of the layer, if desired, the etched openings may be filled in with an easy to planarize material. Then during formation of a next layer the opening may be etched free of the easy to planarize material and the difficult-to-planarize material may be deposited to fill the voids while it is being deposited to desired locations associated with the next layer. In another alternative, it may not be necessary to back fill the voids prior to planarization as any surface oddities that result near the edge of an unfilled void may simply be hidden by the deposition associated with formation of the next layer. Alternatively to avoid undesired over filling of some areas, the filling of the opening and the depositing of the DM for the next layer may be performed in separate selective filling operations. In still other alternatives, the openings filled with the more easily machinable material may remain filled with the easily machinable material which may simply become trapped therein as a result of depositing the DM material in association with the next layer.
An example of a process that provides an implementation of the 6th technique is set forth in the operations of FIG. 5I. This example also implements a two step planarization process of the 4th technique. The example of FIG. 5I reduces tool wear by (1) using a lapping operation or initial rough cutting operation to trim a thickness of deposited material to a level which is closer to a final desired planarization level and (2) using an etching operation to remove portions of the difficult to machine material from regions where planarization will occur. The layer formation process of FIG. 5I includes nine operations.
The first operation is set forth in block 302. This first operation is a conditional operation which indicates that if regions of hard to machine material on the previous layer are temporarily occupied by a not hard to machine material then the surface of the previous layer should be masked such that some regions of the layer are shielded and such that openings exist in the masking material which leave those regions exposed where the temporarily located, not hard to machine material is to be removed. The operation also calls for the etching away of the not hard to machine material from those temporary locations.
The second operation of the process is set forth in block 304 and calls for the masking of the substrate or previously formed layer with a patterned mask that has openings which correspond to locations where a selected one of a sacrificial material or structural material is to be located.
The third operation is set forth in block 306 which calls for the selective deposition of a hard to machine selected one of the sacrificial material or structural material (i.e. the material for which openings were made in the mask of Operation 2).
The fourth operation is set forth in block 308 which calls for the removal of the masking material.
The fifth operation of the process is set forth in block 310 which calls for the application of a second mask which includes openings that expose selected regions of the hard to machine material that will exist on the next layer. The regions that are to be etched are those which represent the bulk of the intersection regions between locations of hard to machine material on the present layer and hard to machine material on the next layer. Though in some implementations it may be acceptable to etch boundary portions of the intersecting regions, in other implementations it is preferred that boundary portions of the intersecting regions not be subjected to etching.
The sixth operation of the process is set forth in block 312 which calls for the etching of the exposed regions of the hard to machine material so as to reduce them to a height which locates their upper surfaces below the planarization level that is to be achieved.
The seventh operation is set forth in block 314 which calls for the blanket deposition of the non-selected one of the structural material and sacrificial material. In this process it is assumed that this non-selected material is not hard or difficult to machine.
The eighth operation of the process is set forth in block 316 while the ninth operation is set forth in block 318. Blocks 316 and 318, respectively, call for the lapping or rough cutting of the deposited materials and then the diamond machining of the remaining material to trim the deposit height to the desired planarization level. The operations of blocks 316 and 318 are analogous to those set forth in block 290 and 292 respectively of FIG. 5F. As a result of the etching operations of this embodiment there was less of the difficult to machine material present during diamond machining operations and thus less tool wear. Furthermore, due to the fact the etched regions represented intersections between regions on the present layer with those on the next layer, the etched regions will be filled in with the common material during formation of the next layer without any loss of structural accuracy but possibly with an enhancement in structural integrity.
A second implementation may involve the dispensing of the hard to machine material in a two step process, e.g. deposit all desired locations to a first height (which extends to a level below that of the final desired planarization level), and then in a second deposit build up the height of deposition in selected locations. Alternatively, deposit selected locations to a final desired height and then deposit other selected locations to a different final desired height, where one of the heights locates material at or above the desired layer level and the other locates material below the height of the layer level.
A third implementation may involve modifying the data representing the three-dimensional structure so as to define it as a shell or envelop of difficult-to-machine structural material that encapsulates an easy-to-machine material. Alternatively, the structure may be defined as an envelope of structural material that surrounds an internal grid of structural material with intermediate regions of sacrificial material. FIG. 6 sets forth a block diagram of this third implementation of the ₆th approach.
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. Some embodiments may not use any blanket deposition processes. 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 selective deposition processes or blanket deposition processes on some layers, or on all layers, that are not electrodeposition processes. Some embodiments may use nickel as a structural material while other embodiments may use different 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 include use of a sacrificial material but instead use two, three, or more structural materials in forming each layer. For example, in some embodiments, two materials may be deposited per layer and both may be structural materials (e.g. one may be a dielectric of the polymeric, oxide, or ceramic type while the other is a conductive material). In some alternative embodiments, diamond fly cutting planarization operations may be replaced with fly cutting operations based on other tool materials. In some embodiments, selective depositions of conductive and or dielectric materials may occur without using masks but instead using direct writing techniques.
As noted previously, in some of the implementations set forth above, the electrochemical fabrication methods set forth herein may involve the use of selective etching operations to minimize the amount of difficult-to-machine material that is encountered by diamond machining operations. As noted above some embodiments may form structures on a layer-by-layer basis but deviate from a strict planar layer on planar layer build up process in favor of a process that interlacing material between the layers. Such alternating build processes are more fully disclosed in U.S. application Ser. No.10/434,519, filed on May 7, 2003, entitled “Methods of and Apparatus for Electrochemically Fabricating Structures Via Interlaced Layers or Via Selective Etching and Filling of Voids” which is herein incorporated by reference as if set forth in full.
The techniques disclosed herein may be combined with the techniques disclosed in the following patent applications which are focused on the formation of structures on dielectric substrates and/or the formation of structures that incorporate dielectric materials during the formation process and possibility into the final structures as formed. The first of these applications is U.S. patent application Ser. No. 60/534,184, which is entitled “Electrochemical Fabrication Methods Incorporating Dielectric Materials and/or Using Dielectric Substrates”. The second of these applications is U.S. patent application Ser. No. 60/533,932, which is entitled “Electrochemical Fabrication Methods Using Dielectric Substrates”. The third of these applications is U.S. patent application Ser. No. 60/534,157 which is entitled “Electrochemical Fabrication Methods Incorporating Dielectric Materials”. The fourth of these applications is U.S. patent application Ser. No. 10/841,300, which is entitled “Methods for Electrochemically Fabricating Structures Using Adhered Masks, Incorporating Dielectric Sheets, and/or Seed layers That Are Partially Removed Via Planarization”. The fifth of these applications is U.S. patent application Ser. No.10/841,378, which is entitled “Electrochemical Fabrication Method for Producing Multi-layer Three-Dimensional Structures on a Porous Dielectric”. These patent applications are each hereby incorporated herein by reference as if set forth in full herein.
The planarization techniques disclosed herein may be combined with planarization end point detection and parallelism maintenance techniques disclosed in U.S. patent application Ser. No. XX/XXX,XXX (corresponding to Microfabrica Docket No. P-US132-A-MF) which is being filed concurrently herewith 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”. This referenced application is incorporated herein as if set forth in full herein.
Due to the reduction in smearing that may result from use of diamond machining as opposed to lapping, electrochemical fabrication processes that form structures from materials with greatly differing hardness may benefit from the use of diamond lapping in the performance of at least some planarization operations. Some such variations in hardness may exist in embodiments where dielectric materials will be used along with metals.
Microprobe arrays (i.e. arrays of compliant electronic contact elements) may represent a viable application for the use of diamond machining. HM materials may be incorporated into the probe arrays as individual probe elements that, in many cases, have relatively small regions of HM structural material surrounded by relatively large regions of sacrificial materials. Further teaching about microprobes and electrochemical fabrication techniques are set forth in a number of US Patent Applications. These applications include: (1) U.S. patent application Ser. No. XX/XXX,XXX (corresponding to Microfabrica Docket No. P-US129-A-MF) by Chen, et al., filed concurrently herewith, and entitled “Vertical Microprobes for Contacting Electronic Components and Method for Making Such Probes”; (2) U.S. patent application Ser. No. 60/533,975, filed Dec. 31, 2003, by Kim et al. and which is entitled “Microprobe Tips and Methods for Making”; (3) U.S. patent application Ser. No. 60/533,947, by Kumar et al., filed Dec. 31, 2003, and which is entitled “Probe Arrays and Method for Making”; (4) U.S. patent application Ser. No. 60/533,948 by Cohen et al., filed Dec. 31, 2003 and which is entitled “Electrochemical Fabrication Method for Co-Fabricating Probes and Space Transformers”; and (5) U.S. patent application Ser. No. 60/533,897, filed Dec. 31, 2004, by Cohen et al. and which is entitled “Electrochemical Fabrication Process for Forming Multilayer Multimaterial Microprobe structures”. These patent filings are each hereby incorporated herein by reference as if set forth in full herein.
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. A fabrication process for forming a multi-layer three-dimensional structure, comprising:

(a) forming and adhering a layer of material to a previously formed layer and/or to a substrate, wherein the layer comprises a desired pattern of at least one material, wherein one or more contact pads exist on the substrate or on a previously formed layer;

(b) subjecting the at least one material to a planarization operation which comprises diamond machining (c) repeating the forming and adhering of operation (a) one or more time to form the three-dimensional structure from a plurality of adhered layers.

2. The process of claim 1 wherein forming and adhering of the layer of material involves the deposition of a first material and followed by deposition of a second material wherein at least one of the first or second materials is deposited via an electroplating operation.

3. The process of claim 2 wherein the first and second materials comprise Ni—P and Cu.

4. The process of claim 2 wherein the first and second materials comprise Au and Cu.

5. The process of claim 2 wherein the first and second materials comprise Cu and Sn.

6. The process of claim 2 wherein the first material is more difficult to machine than the second material.

7. The process of claim 2 wherein the first material is a structural material and wherein the second material is a sacrificial material.

8. The process of claim 2 wherein the structure comprises an envelope of structural material surrounding an entrapped quantity of sacrificial material, wherein the structural material is more difficult to machine using diamond machining than the sacrificial material.

9. The process of claim 2 wherein the structure comprises an envelope of structural material surrounding an entrapped quantity of sacrificial material, wherein the structural material is more difficult to machine using diamond machining than the sacrificial material.

10. The process of claim 9 wherein the envelope of structural material also surrounds a grid of structural material.

11. The process of claim 2 wherein the planarization operation additionally comprises vibration assisted machining.

12. The process of claim 2 wherein prior to subjecting the deposited material to the planarization operation, the first deposited material is subjected to a selective etching operations that removes a portion of the first material to a level below a final desired planarization level in regions where the etched first material will be overlaid by first material deposited in association with the next layer.

13. The process of claim 1 wherein forming and adhering of the layer of material involves the deposition of a first material, followed by deposition of a second material, and followed by deposition of at least a third material wherein at least one of the first, second, or third materials is deposited via an electroplating operation.

14. The process of any of the preceding claims wherein the planarization operation includes at least one lapping operation or rough cutting operation that brings height of deposition to a level which is closer to that of the final desired level and after which the diamond machining operation brings the level of the deposited materials to a level that is within a defined tolerance of a desired level.

15. The process of claim 14 wherein the lapping or rough cutting substantially planarizes the surfaces and where a difference between the material surface subjected to the lapping or rough cutting is spaced from the final desired planarization level by an amount which is equal to or greater than a depth to which the lapping or rough cutting causes subsurface damage.