US20040065551A1

US20040065551A1 - Electrochemical deposition with enhanced uniform deposition capabilities and/or enhanced longevity of contact masks

Info

Publication number: US20040065551A1
Application number: US10/434,317
Authority: US
Inventors: Gang Zhang
Original assignee: University of Southern California USC
Current assignee: University of Southern California USC
Priority date: 2002-05-07
Filing date: 2003-09-02
Publication date: 2004-04-08

Abstract

An electrochemical fabrication process for producing multi-layer three-dimensional structures includes selectively electrodepositing one or more building materials using contact masks. In some embodiments, a copper pyrophosphate plating solution is used and is formulated to allow simultaneous deposition to a large area (>=about 1.44 mm²) and to a small area (<=about 0.05 mm²) wherein the thickness of deposition to the smaller area is no less than ½ that to the large area when the deposition to the large area <=about 10 μm in thickness and where the solution contains >=about 30 g/L of copper. In other embodiments contact masks include a support structure that is treated with a corrosion inhibitor (e.g. BTA) prior to attaching or forming a patterned material on it and/or plating baths are operated at low temperature either of which may be useful in extending the life of the masks.

Description

RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent Application Nos. 60/379,136 and 60/379,131 both of which were filed on May 7, 2002 and which are both incorporated herein by reference as if set forth in full.[0001]

GOVERNMENT SUPPORT

[0002] This invention was made with Government support under Grant Number DABT63-97-C-0051 awarded by DARPA. The Government has certain rights.

FIELD OF THE INVENTION

This invention relates to the field of electrochemical deposition and more particularly to the field of electrochemical deposition using conformable contact masks that are formed separate from a substrate (e.g. INSTANT MASKS™)to control deposition, such as for example in Electrochemical Fabrication (e.g. EFAB™) where such masks are used to control the selective electrochemical deposition of one or more materials according to desired cross-sectional configurations so as to build up three-dimensional structures from a plurality of at least partially adhered layers of deposited material.

BACKGROUND

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 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 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 (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.

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. 1(a)-1(c). FIG. 1(a) 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. 1(a) 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. 1(b). After deposition, the CC mask is separated, preferably non-destructively, from the substrate 6 as shown in FIG. 1(c). 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. 1(d)-1(f). FIG. 1(d) shows an anode 12′ separated from a mask 8′ that comprises a patterned conformable material 10′ and a support structure 20. FIG. 1(d) also depicts substrate 6 separated from the mask 8′. FIG. 1(e) illustrates the mask 8′ being brought into contact with the substrate 6. FIG. 1(f) illustrates the deposit 22′ that results from conducting a current from the anode 12′ to the substrate 6. FIG. 1(g) 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. 2(a)-2(f). 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. 2(a), 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. 2(b). FIG. 2(c) 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. 2(d). 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. 2(e). The embedded structure is etched to yield the desired device, i.e. structure 20, as shown in FIG. 2(f).

Various components of an exemplary manual

electrochemical fabrication system

32 are shown in FIGS. 3(a)-3(c). 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. 3(a) to 3(c) 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. 3(a) 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. 3(b) 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. 3(c) and includes a lapping plate 52 and associated motion and control systems (not shown) for planarizing the depositions.

When desiring to electroplate copper, various types of plating baths are known in the electrodeposition arts. One such standard bath type involves use of pyrophosphate copper. Atotech USA, Inc. of Somerset, N.J. supplies materials and recommendations for pyrophosphate copper plating baths under the name UNICHROME®. The UNICHROME pyrophosphate copper plating process is taught by Atotech in their technical information sheet revision 4/93. A range of components and optimum values of the UNICHROME plating bath are supplied in those teachings and are set forth in the following table (TABLE 1).

TABLE 1


UNICHROME ® Plating Solution Table

Component or
Condition	Range	Optimum

Copper as metal	18.8 to 30.0 g/L	22.5 g/L (3 oz/gal)
	(2.5 to 4.0 oz/gal
P₂O₇: Cu ratio	7.4 to 8.0:1	7.7:1
Ammonia as NH₃ or	0.375 to 2.25 g/L	1.20 g/L (0.16
	(0.05 to 0.3 oz/gal)	oz/gal)
Ammonia as HH₄OH	1.41 to 8.67 mL/L	5 mL/L
	(0.18 to 1.11 fl. oz/gal)
pH (electrometric)	8.0-8.5	8.3
Temperature	46° C. to 57° C.	52° C. (125° F.)
	(115° F.-135° C.)
Cathode Current	2.2 to 3.2 A/dm²	2.7 A/dm² (25 A/ft²)
Density	(20-30 A/ft²)
Anode Current	2.7 to 5.4 A/dm²	3.8 A/dm² (35 A/ft²)
Density	(25-50 A/ft²)

The primary components for Atotech's “optimum” bath are Atotech components C-11-Xb (35 mL/L) and C-10-Xb (333 mL/L). C-10-Xb supplies copper pyrophosphate while the C-11-Xb provides some form of pyrophosphate without copper. The “optimum” solution additionally includes 5 mL/L of NH ₄OH with the remainder being water. The solution also probably contains additives (included within the C-11-Xb and/or the C-10-Xb components) which are proprietary to Atotech and which are unknown to the present inventor.

General recommendations for pyrophosphate baths can be found in various sources. From the article “Copper Plating” in the ASM Handbook Vol. 5 (Surface Engineering, Ed. C. M. Cotell et al, ASM International, 1994), by L. M. Weisenberger and B. J. Durkin, and from “Electroplating: Fundamentals of Surface Finishing”, McGraw-Hill Book Co., 1978, by F. A. Lowenheim, generalized copper pyrophosphate plating solution components and operating conditions are believed to be those set forth in the following table (TABLE 2):

	TABLE 2


	Typical

	Components or Conditions
	Copper metal (comes from copper	19-30 g/L
	pyrophosphate)
	Potassium pyrophosphate	235-405 g/L
	Copper pyrophosphate	52-84 g/L
	Ammonium hydroxide	3.75-11.0 mL/L
	Potassium nitrate	3.0-12.0 g/L
	Weight ratio (pyrophosphate:copper)	7:1-8:1
	Additives	As recommended
	Operating conditions
	Temperature, ° C.	43-60° C.
	Current density, mA/cm²	10-70
	Anode and cathode efficiency, %	≈100
	pH	8.0-8.7
	Anode	OFHC copper
	Anode/cathode area ratio	1:1-2:1
	Agitation	Air

From “Modern Electroplating”, 4 ^thEdition, edited by Mordechay Schlesinger and Milan Paunovic, John Wiley & Sons, Inc., 2000, Part D, pages 122-133, the optimum range of constituents for a copper pyrophosphate plating solution are given in the following table (TABLE 3):

	TABLE 3


	Typical

	Components
	Copper, Cu²⁺	22-38 g/L
	Pyrophosphate, (P₂O₇)⁴⁻	150-250 g/L
	Nitrate, NO₃ ⁻	5-10 g/L
	Ammonia, NH₃	1-3 g/L
	Orthophosphate, (HPO₄)²⁻	<113 g/L
	Additives	As required
	Operating conditions
	Weight ratio (pyrophosphate:copper)	7.0:1 to 8.0:1
	pH	8.0-8.8
	Temperature	50-60° C.
	Cathode current density	1-8 A/dm²
	Anode and cathode efficiency, %	≈100
	Anode/cathode area ratio	1:1-2:1
	Agitation - m³(min)⁻¹ (m⁻² of surface)	1-1.5

From these three tables it can be seen that there isn't a single “optimal” bath formulation and set of operating conditions for all plating situations and further there is even some variability in the range of formulation parameters and use parameters for what may be considered “standard-type” plating situations. The references from which these tables have been extracted are hereby incorporated herein by reference as if set forth in full herein.

The '630 patent as well as the other CC masking (e.g. INSTANT MASKING) and electrochemical fabrication (e.g. EFAB) publications noted above describe copper as a preferred material for selective deposition during the selective deposition process.

The '630 patent indicates that uniformity of deposits can be obtained by using a cyclic plating process to deposit layers. In the cyclic plating process the applied current is interrupted in synchronization with removing the mask from the substrate, which simultaneously replenishes the electrolyte additives, vents any gases, and discharges particulates and broken-down additives from the microvolume defined by the support portion of the mask, the substrate, and the conformable portion of the mask. Current is then re-applied in synchronization with remating the mask with the substrate. The '630 patent indicates that this method can be repeated until the desired thickness of metal has been deposited.

The '630 patent also indicates that electroplating methods can be performed at low temperatures, thereby allowing integrated circuits and silicon wafers to be used as plating substrates. The '630 patent further indicates that an electrolyte filtration system can be incorporated into a heating and pumping system to continuously circulate and warm the electrolyte to maintain homogeneous concentration and constant temperature. It further indicates that hydrogen bubble formation can also be minimized by, among other things, decreasing temperature of the electrolyte and that copper deposition rate can be improved by, among other things, increasing temperature of the electrolyte. Another teaching of the '630 patent is an indication that the masks are preferably chemically non-reactive with respect to the plating electrolytes at the temperatures at which the plating operations are conducted.

The '630 patent also indicates that it is preferable to prepare the anode surface prior to receiving the mask so as to maximize adhesion to the mask and examples of such preparation methods include chemical microetching, lapping, sandblasting, and sintering a thin layer of powder onto the surface. It is further indicated that a chemical adhesion promoter (e.g., Sylgard Prime Coat) can also be used.

The first publication listed above indicates that commercially-available electrolytes (i.e. plating baths) such as acid copper, cyanide copper, pyrophosphate copper, Watts bath, and nickel sulfamate have been employed in EFAB experiments. The second publication indicates that commercially available plating baths for both Ni and Cu, with bath chemistry and deposition parameters adjusted to yield deposition with minimal stress have been employed in the EFAB process. The fifth publication also indicates that commercially available plating baths were used.

The fourth and sixth publications listed above indicate that the bath chemistry and deposition parameters of commercially-available plating baths for both Ni and Cu were modified to meet the requirements of the micro plating process and that both baths provide minimal residual stress. The fourth publication further indicates that by using INSTANT MASKING and the modified Cu plating bath with optimized operating parameters, flash-free patterned Cu deposits with adequate thickness were produced and the publication additionally provides a figure depicting a deposit having a thickness of about 13 μm. The sixth reference indicates that a copper deposit of approximately 13 μm thickness was formed and it provides a figure of a portion of a mask used in obtaining the deposition as well as a figure of a portion of the resulting deposition itself. The figure of this sixth publication showing the deposition is similar to FIG. 5 of the instant application.

The eighth publication teaches that INSTANT MASKING involves conditions that are very different from those in standard electroplating baths, in which a large volume of bath is available, and that a solid understanding of the electrochemical phenomena under these conditions is not yet available. It additionally indicates that one immediate concern may involve deposit thickness since there is a very small volume (as little as tens of picoliters) of deposition material during INSTANT MASK plating within the electrochemical cell formed by the anode, cathode, and patterned elastomers. However, it also indicates that this problem can be solved by making the INSTANT MASK anode from the material that is intended to be electrodeposited and that can be dissolved during the deposition to provide “feedstock”. This publication provides the same two figures as found in the sixth publication concerning a deposition mask and the deposition made therefrom.

In addition to the teachings noted above, references (2) and (4)-(7) indicate that the electrodeposition processes can be performed at temperatures lower than 60° C.

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 pyrophosphate copper is used in normal plating operations and its use in CC mask plating and in electrochemical fabrication has been briefly described in the above references, it optimization for CC mask plating processes and electrochemical fabrication processes and particularly for micro-CC mask plating processes or micro-electrochemical fabrication processes have not been taught.

Similarly, though some suggestions have been given on how to improve adhesion between a CC mask support and the conformable material and even the though the desire for non-reactiveness between the mask and the electrolyte has been presented, no further teachings or suggestions have been given on the need to extend the useful life of CC masks or methods for doing such.

Each of the above noted publications that is explicitly directed to the CC mask plating and electrochemical fabrication processes, whether taken alone or in combination, are silent concerning deposition problems that can arise when attempting to simultaneously plate areas or volumes of different sizes (particularly different sized micro-volumes) and are silent concerning particular modifications to the CC mask plating and electrochemical fabrication processes that can be made to address such problems. As one of the theoretical advantages of CC mask plating processes and the electrochemical fabrication processes involve their capability to build structures (one or more layers) of arbitrary geometry in as short of a time as possible, it is important to be able to electrodeposit relatively similar thicknesses of material regardless of variations in sizes of individual independent plating regions.

A need remains in the field of electroplating with CC masks and in electrochemical fabrication for improved processes that can allow more versatile structural formation, more rapid formation, more reliable formation, enhanced process latitude associated with successful formation of structures, and/or more cost effective formation regardless of whether such characteristics will be explicitly required or experienced during any particular formation process.

A need remains in the field for improving the reliability of the CC mask plating and electrochemical fabrication processes, for lowering the cost of structure production, and for improving the structure formation time. Unrecognized CC mask failure prior to selective deposition or CC mask failure during selective deposition can lead to the production of unacceptable structures. Time and cost may be wasted in rebuilding structures or at minimum in stripping away and redepositing the problematic depositions. A cost and time savings can result from enhancing the reliability or longevity of CC masks and if CC masks are to be reused for multiple depositions a cost savings can result from needing to produce fewer CC masks. As such a need exists in the field of CC mask plating and electrochemical fabrication for improved CC masks and processes for using and making them.

SUMMARY OF THE INVENTION

It is an object of certain aspects of the invention to provide a contact mask (e.g. CC mask) plating or electrochemical fabrication process that allows for improved versatility when using copper as a selective deposition material.

It is an object of certain aspects of the invention to provide a contact mask (e.g. CC mask) plating or electrochemical fabrication process that allows for improved speed when using copper as a selective deposition material.

It is an object of certain aspects of the invention to provide a contact mask (e.g. CC mask) plating or electrochemical fabrication process that allows for enhanced reliability of structure formation when using copper as a selective deposition material.

It is an object of certain aspects of the invention to provide a contact mask (e.g. CC mask) plating or electrochemical fabrication process that has enhanced process latitude associated with the successful formation of structures when using copper as a selective deposition material.

It is an object of certain aspects of the invention to provide a contact mask (e.g. CC mask) plating or electrochemical fabrication process that is capable of being more cost effective when using copper as a selective deposition material.

It is an object of certain aspects of the invention to provide a contact mask (e.g. CC mask) with improved longevity.

It is an object of certain aspects of the invention to provide a contact mask (e.g. CC mask) plating process or electrochemical fabrication process with improved reliability.

It is an object of certain aspects of the invention to provide a shortening of effective production time for structures formed using contact masks (e.g. CC masks).

It is an object of certain aspects of the invention to provide a reduction in cost associated with producing structures using contact masks (e.g. CC masks).

It is an object of certain aspects of the invention to provide a process for forming contact masks (e.g. CC masks) having enhanced useful lifetimes.

Other objects and advantages of various aspects of the invention will be apparent to those of skill in the art upon review of the teachings herein. The various aspects of the invention, set forth explicitly herein or otherwise ascertained from the teachings herein, may address any one of the above objects alone or in combination, or alternatively may not address any of the objects set forth above but instead address some other object ascertained from the teachings herein. It is not intended that all of these objects be addressed by any single aspect of the invention even though that may be the case with regard to some aspects.

In a first aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers includes: (A) supplying a plurality of preformed masks, wherein each mask includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask includes a support structure that supports the patterned conformable dielectric material; (B) selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may include previously deposited material; and (C) forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said forming includes repeating operation (B) a plurality of times; wherein at least a plurality of the selective depositing operations include (1) contacting the substrate and the conformable material of a selected preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; wherein the selected deposition material is copper; and wherein the plating solution includes a pyrophosphate copper solution that contains more than 30.0 grams of copper per liter.

In a specific variation of the first aspect of the invention the pyrophosphate copper solution contains no less than about 35 grams of copper per liter. In a further specific variation the pyrophosphate copper solution contains no less than about 40 grams of copper per liter.

In a second aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers includes: (A) supplying a plurality of preformed masks, wherein each mask includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask includes a support structure that supports the patterned conformable dielectric material; (B) selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may include previously deposited material; and (C) forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said forming includes repeating operation (B) a plurality of times; wherein at least a plurality of the selective depositing operations include (1) contacting the substrate and the conformable material of a selected preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; wherein the selected deposition material is copper; and wherein the plating solution includes a pyrophosphate copper solution that contains more than 240 grams of pyrophosphate.

In a specific variation of the second aspect of the invention the pyrophosphate copper solution contains no less than about 280 grams of pyrophosphate per liter. In a further specific variation the pyrophosphate copper solution contains no less than about 320 grams of pyrophosphate per liter.

In a third aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers includes: (A) supplying a plurality of preformed masks, wherein each mask includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask includes a support structure that supports the patterned conformable dielectric material; (B) selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may include previously deposited material; and (C) forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said forming includes repeating operation (B) a plurality of times; wherein at least a plurality of the selective depositing operations include (1) contacting the substrate and the conformable material of a selected preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; wherein the selected deposition material is copper; and wherein the plating solution includes a pyrophosphate copper solution that includes effective amounts of copper and pyrophosphate such that the solution is capable of simultaneously depositing metallic copper to a smaller area (i.e. an area no larger than about 0.05 mm ²) and a larger area (i.e. an area no smaller than about 1.4 mm²) such that the height of deposition of the smaller area is no less than one-half the height of deposition of the larger area when the height of deposition of the larger area is greater than 10 μm.

In a specific variation of the third aspect of the invention the height of deposition of the smaller area is no less than 65% of the height of deposition of the larger area. In a further specific variation the height of deposition of the smaller area is no less than 80% of the height of deposition of the larger area.

In a fourth aspect of the invention a CC masking process for producing a structure includes: (A) supplying at least one preformed mask that includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein the at least one mask includes a support structure that supports the patterned conformable dielectric material; and (B) selectively depositing at least a portion of a layer onto the substrate, including (1) contacting the substrate and the conformable material of the preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; wherein the selected deposition material is copper; and wherein the plating solution includes a pyrophosphate copper solution that contains more than 30.0 grams of copper per liter.

In a specific variation of the fourth aspect of the invention the pyrophosphate copper solution contains no less than about 35 grams of copper per liter. In a further specific variation the pyrophosphate copper solution contains no less than about 40 grams of copper per liter.

In a fifth aspect of the invention provides a CC masking process for producing a structure includes: (A) supplying at least one preformed mask that includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein the at least one mask includes a support structure that supports the patterned conformable dielectric material; and (B) selectively depositing at least a portion of a layer onto the substrate by (1) contacting the substrate and the conformable material of the preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; wherein the selected deposition material is copper; and wherein the plating solution includes a pyrophosphate copper solution that contains more than 240 grams of pyrophosphate.

In a specific variation of the fifth aspect of the invention the pyrophosphate copper solution contains no less than about 280 grams of pyrophosphate per liter. In a further specific variation the pyrophosphate copper solution contains no less than about 320 grams of pyrophosphate per liter.

In a sixth aspect of the invention a CC masking process for producing a three-dimensional structure, includes: (A) supplying at least one preformed mask that includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein the at least one mask includes a support structure that supports the patterned conformable dielectric material; (B) selectively depositing at least a portion of a layer onto the substrate by (1) contacting the substrate and the conformable material of the preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; wherein the selected deposition material is copper; and wherein the plating solution includes a pyrophosphate copper solution that includes effective amounts of copper and pyrophosphate such that the solution is capable of simultaneously depositing metallic copper to a smaller area (i.e. an area no larger than about 0.05 mm ²) and a larger area (i.e. an area no smaller than about 1.4 mm²) such that the height of deposition of the smaller area is no less than one-half the height of deposition of the larger area when the height of deposition of the larger area is greater than 10 μm.

In a specific variation of the sixth aspect of the invention the height of deposition of the smaller area is no less than 65% of the height of deposition of the larger area. In a further specific variation the height of deposition of the smaller area is no less than 80% of the height of deposition of the larger area.

In a seventh aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers includes: (A) supplying a plurality of preformed masks, wherein each mask includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask includes a support structure that supports the patterned conformable dielectric material; (B) selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may include previously deposited material; and (C) forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said forming includes repeating operation (B) a plurality of times; wherein at least a plurality of the selective depositing operations include (1) contacting the substrate and the conformable material of a selected preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; and wherein the patterned conformable material is bonded to the support structure, which support structure includes the anode for current flow through the plating solution during selective deposition, and wherein prior to the conformable material and support structure being joined together, the support structure undergoes a treatment with a corrosion inhibitor.

In an eighth aspect of the invention a CC mask plating process for producing a structure, includes: (A) supplying at least one preformed mask that includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein the at least one mask includes a support structure that supports the patterned conformable dielectric material; and (B) selectively depositing at least a portion of a layer onto the substrate, including (1) contacting the substrate and the conformable material of the preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; wherein the patterned conformable material is bonded to the support structure, which support structure includes the anode for current flow through the plating solution during selective deposition, and wherein prior to the conformable material and support structure being joined together, the support structure undergoes a treatment with a corrosion inhibitor.

In a ninth aspect of the invention a process of forming a mask for use in an electrodeposition process includes: (A) supplying a support structure; (B) applying a corrosion inhibitor to the support structure; (C) supplying a flowable material that can become an conformable dielectric material upon solidification; (D) after application of the corrosion inhibitor, applying the flowable material to the support structure, patterning the flowable material, and solidifying the flowable material such that (1) bonding between the support structure and the solidified material is achieved, (2) the material becomes an conformable dielectric material, and (3) the conformable material has a pattern including at least one negative region wherein the conformable material does not overlay the support structure and a positive region where the conformable material does overlay the support structure.

In a tenth aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers includes: (A) supplying a plurality of preformed masks, wherein each mask includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask includes a support structure that supports the patterned conformable dielectric material; (B) selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may include previously deposited material; and (C) forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said forming includes repeating operation (B) a plurality of times; wherein at least a plurality of the selective depositing operations include (1) contacting the substrate and the conformable material of a selected preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; and wherein the plating solution is a copper solution that is at a temperature of less than about 43° C.

In an eleventh aspect of the invention a CC mask plating process for producing a structure includes: (A) supplying at least one preformed mask that includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein the at least one mask includes a support structure that supports the patterned conformable dielectric material; and (B) selectively depositing at least a portion of a layer onto the substrate, including (1) contacting the substrate and the conformable material of the preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; wherein the plating solution is a copper solution that is at a temperature of less than about 43° C.

In a twelfth aspect of the invention an electrochemical fabrication apparatus for producing a three-dimensional structure from a plurality of adhered layers includes: (A) a plurality of preformed masks, wherein each mask includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask includes a support structure that supports the patterned conformable dielectric material; (B) means for selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may include previously deposited material; and (C) means for forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said means for forming includes means for repeating the use of (B) a plurality of times; wherein the means for selectively depositing includes: (1) means for contacting the substrate and the conformable material of a selected preformed mask; (2) means for conducting an electric current, in presence of a plating solution, through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) means for separating the selected preformed mask from the substrate; and wherein the patterned conformable material is bonded to the support structure, which support structure includes the anode for current flow through the plating solution during selective deposition, and wherein a surface of the support structure that is bonded to the conformable material includes a modified chemical structure that enhances the corrosion resistance of a plurality of the preformed masks.

In a thirteenth aspect of the invention a CC mask plating apparatus for producing a structure includes: (A) a preformed mask that includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein the at least one mask includes a support structure that supports the patterned conformable dielectric material; and (B) means for selectively depositing at least a portion of a layer onto the substrate, including (1) means for contacting the substrate and the conformable material of the preformed mask; (2) means for conducting an electric current, in presence of a plating solution, through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) means for separating the selected preformed mask from the substrate; wherein the patterned conformable material is bonded to the support structure, which support structure includes the anode for current flow through the plating solution during selective deposition, and wherein a surface of the support structure that is bonded to the conformable material includes a modified chemical structure that enhances the corrosion resistance of the preformed mask.

In a fourteenth aspect of the invention a CC mask for use in electroplating operations, includes: a preformed mask that includes a patterned conformable dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein the at least one mask includes a support structure that supports the patterned conformable dielectric material; and wherein the patterned conformable material is bonded to the support structure, which support structure includes the anode for current flow through the plating solution during selective deposition, and wherein a surface of the support structure that is bonded to the conformable material includes a modified chemical structure that enhances the corrosion resistance of the preformed mask.

In a fifteenth aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers includes: (A) supplying a plurality of preformed masks, wherein each mask includes a patterned dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask includes a support structure that supports the patterned dielectric material; (B) selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may include previously deposited material; and (C) forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said forming includes repeating operation (B) a plurality of times; wherein at least a plurality of the selective depositing operations include (1) contacting the substrate and the dielectric material of a selected preformed mask or proximately locating the substrate and dielectric material of a selected preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; and wherein the selected deposition material is copper; and wherein the plating solution includes a pyrophosphate copper solution that contains more than about 30.0 grams of copper per liter; or wherein the plating solution includes a pyrophosphate copper solution that contains more than about 240 grams of pyrophosphate; or wherein the selected deposition material is copper; and wherein the plating solution includes a pyrophosphate copper solution that includes effective amounts of copper and pyrophosphate such that the solution is capable of (1) simultaneously depositing metallic copper to a smaller area (i.e. an area no larger than about 0.05 mm ²) and a larger area (i.e. an area no smaller than about 1.4 mm²) such that the height of deposition of the smaller area is no less than one-half the height of deposition of the larger area when the height of deposition of the larger area is greater than 10 μm.

In a sixteenth aspect of the invention an electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers includes: (A) supplying a plurality of preformed masks, wherein each mask includes a patterned dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask includes a support structure that supports the patterned dielectric material; (B) selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may include previously deposited material; and (C) forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said forming includes repeating operation (B) a plurality of times; wherein at least a plurality of the selective depositing operations include: (1) contacting the substrate and the dielectric material of a selected preformed mask; (2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode includes a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and (3) separating the selected preformed mask from the substrate; wherein prior to the dielectric material and support structure being joined together, the support structure undergoes a treatment with a corrosion inhibitor, or wherein the plating solution is a copper solution that is at a temperature of less than about 43° C.

In a seventeenth aspect of the invention a contact mask for use in electroplating operations includes: a preformed mask that includes a patterned dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein the at least one mask includes a support structure that supports the patterned dielectric material; and wherein the patterned dielectric material is bonded to the support structure, which support structure includes the anode for current flow through the plating solution during selective deposition, and wherein a surface of the support structure that is bonded to the dielectric material includes a modified chemical structure that enhances the corrosion resistance of the preformed mask.

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 combinations of the above noted aspects of the invention and/or addition of various features of one or more embodiments. Other aspects of the invention may involve apparatus that can be used in implementing one or more of the above method aspects of the invention. These other aspects of the invention may provide various combinations of the aspects presented above as well as provide other configurations, structures, functional relationships, and processes that have not been specifically set forth above.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIGS. [0086] 1(a)-1(c) schematically depict side views of various stages of a CC mask plating process, while FIGS. 1(d)-(g) schematically depict a side views of various stages of a CC mask plating process using a different type of CC mask.
FIGS. [0087] 2(a)-2(f) 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. [0088] 3(a)-3(c) schematically depict side views of various example subassemblies that may be used in manually implementing the electrochemical fabrication method depicted in FIGS. 2(a)-2(f).
FIGS. [0089] 4(a)-4(i) 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. 4([0090] a) depicts an example of a CC mask having one large deposition area and seven smaller deposition areas.
FIGS. [0091] 4(b)-4(d) provide SEM photographs, at various magnifications, of depositions that occurred when using the CC mask of FIG. 4(a) in combination with a UNICHROME® pyrophosphate copper plating solution that was optimized according to the vendor's recommendations.
FIG. 5 provides an SEM image of a portion of the depositions made from a mask similar to that shown in FIG. 4([0092] a) while using a first modified plating solution.
FIGS. [0093] 6(a) and 6(b) provide SEM images of depositions, at two different magnifications, made from a mask similar to that shown in FIG. 4(a) while using a second modified plating solution at two different magnifications.
FIGS. [0094] 7(a) and 7(b) provide SEM images of depositions, at two different magnifications, made from a mask similar to that shown in FIG. 4(a) while using a third modified plating solution.
FIG. 8 provides an SEM image of depositions made from a mask similar to that shown in FIG. 4([0095] a) while using a fourth modified plating solution.
FIG. 9 provides an SEM image of depositions made from a mask similar to that shown in FIG. 4([0096] a) while using a fifth modified plating solution.
FIGS. [0097] 4(a)-4(e) illustrate a micromolding method for forming CC masks.
FIG. 5 provides a schematic illustration of an interface structure between a CC mask support and the conformable material when using a silane coupling agent. [0098]
FIG. 6([0099] a) provides a picture of a sample CC mask prior to use.
FIG. 6([0100] b) provides a picture of an untreated CC mask after a 440 minute real use test.
FIG. 6([0101] c) provides a picture of a BTA treated CC mask after a 516 minute real use test.
FIGS. [0102] 7(a) and 7(b) provide contrasting pictures of a BTA treated mask and an untreated mask after using the masks to electroplating operations for 30 minutes and 16 minutes respectively.

DETAILED DESCRIPTION

FIGS. [0103] 1(a)-1(g), 2(a)-2(f), and 3(a)-3(c) 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. [0104] 4(a)-4(i) 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. 4(a), a side view of a substrate 82 is shown, onto which patternable photoresist 84 is cast as shown in FIG. 4(b). In FIG. 4(c), 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. 4(d), a metal 94 (e.g. nickel) is shown as having been electroplated into the openings 92(a)-92(c). In FIG. 4(e), 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. 4(f), 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. 4(g) 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. 4(h) the result of repeating the process steps shown in FIGS. 4(b)-4(g) 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. 4(i) to yield a desired 3-D structure 98 (e.g. component or device).
In the description to follow, headers on the text are intended to aid in the reading of this document but are not intended to limit the scope of the teachings herein. Embodiments, alternatives, and techniques described under one heading may be combined with the embodiments, alternatives, and techniques described under a different heading. Though the embodiments discussed herein are primarily focused on conformable contact masks and masking operations, the various embodiments, alternatives, and techniques disclosed herein may have application to 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 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). [0105]
A basic standard plating configuration (i.e. non-CC mask plating configuration) includes an anode and a cathode which are immersed in a plating bath. The distance between the anode and cathode is at least 1 mm. A power source provides a pre-set current passing through the plating cell so that the anode metal usually dissolves into the plating bath and the metal ions in the plating bath are reduced at the cathode to become a metallic deposit. Depending on various parameters, including the composition of the plating bath, the plating bath is usually operated at a constant temperature some wherein the range of between 20-60° C. The plating bath is agitated mechanically or by compressed air to ensure that fresh plating solution is delivered to the cathode and that the products of the electrochemical reactions are removed from the electrodes into the bulk solution. [0106]
Through-mask plating is a selective plating process since the substrate (cathode) is patterned by a thin non-conductive material (e.g. a patterned photoresist). Otherwise, its plating configuration is the same as that of standard plating process as outlined above. As such, through-mask plating, for the purposes herein, may be considered a selective form of standard plating. [0107]
CC mask plating is different from normal and through-mask plating in several aspects. In one form of CC mask plating, the plating bath is trapped in a closed volume defined by the substrate, the side walls of the conformable material, and the anode. Examples of such [0108] closed volumes 26 a and 26 b are depicted in FIG. 1(b). Another form of CC mask plating may involve the use of a porous support and a distal anode. In this alternative form of CC mask plating, the barrier presented by the support portion of the CC mask, though allowing at least some ion exchange, may present a sufficient hindrance to the exchange of some components of the plating solution that the solution in the deposition region may still be considered to be substantially isolated from the bulk solution. This trapping results in little or no mass exchange between the volume of solution in the plating region and the bulk solution and as such no or little fresh solution with proper additives can be supplied into the microspace and no or little reaction products can be removed.
A preferred form of CC mask plating involves closed volumes where at least one of the dimensions of at least one of the plating volumes is on the order of tens of microns (e.g. 20 to 100 μm) or less. As such, this form of CC mask plating may be considered to be a microbath plating process (i.e. micro-CC mask plating). [0109]
In micro-CC mask plating, the preferred separation between the anode and cathode is presently between about 20 μm and about 100 μm, and more preferably between about 40 and 80 μm. As such, regardless of the size of the area being deposited, these preferred embodiments may be considered to be micro-CC mask plating processes. Of course thinner separation distances (e.g. 10 μm or less) and thicker separation distances (300 μm or more) are possible. Due to this close spacing between anode and cathode, deposition processes at the cathode and dissolution processes at the anode, unlike standard plating, are highly interacting. [0110]
Agitating the plating bath, as is common with standard plating processes, though possible, is not necessarily desirable in electrochemical fabrication due potentially to the high interaction between anode and cathode processes and due to the believed enhanced risk of shorting when agitation is used. Shorting refers to a portion of the deposition height bridging the space between the cathode and the anode prior to the lapse of the desired deposition time, in which case the current is directed almost solely through deposited conductive material as opposed to flowing primarily through the plating bath as intended such that the continuing of deposition is inhibited. [0111]
Using a pyrophosphate bath at high temperature (i.e. above around 43° C. to 45° C.), though recommended in the standard plating processes, is not desirable in the current form of micro-CC mask plating due to the higher rate of attack at the interface between the CC mask support and the conformable material and the associated shortening of CC mask life. [0112]

CC mask plating has its own characteristics and the conventional wisdom associated with standard plating processes may be more of a hindrance than a help in developing commercially viable CC mask plating processes and systems. The following Table (TABLE 4) provides a detailed comparison of various aspects of the two forms of standard plating (i.e. non-selective and through-mask plating) and micro-CC mask plating.

TABLE 4


	Standard Plating

		Through-mask	Micro-CC mask
Characteristic	Normal plating	plating	plating

Patterned cathode	No	Yes	Yes
Separation between	Macroscale	Macroscale	Microscale,
anode and cathode			<˜80 μm
Closed microbath	No	No	Yes
plating
Bath agitation	Useful & Easy	Useful & Easy	Possible but
			problematic
Bath heating	Useful & Easy	Useful & Easy	Possible but
			problematic
Fresh bath supplied	Yes	Yes	No
to electrodes
Products removed	Yes	Yes	No
from electrodes
Cathode:anode area	Variable	Variable	1:1
ratio
Plating time	Not limited	Not limited	Limited
Interaction between	Insignificant	Insignificant	Significant
cathode and anode

Some experiments were performed to test the effectiveness of copper pyrophosphate plating solutions for use in CC mask plating in electrochemical fabrication. Some tests were performed to test corrosion resistance of copper when immersed in a commercially available bath called Cu—P which was purchased from Technic Inc. of Cranston, R.I. Another bath was mixed in-house using components and recommendations from Atotech. The formulation of this second solution followed Atotech's “optimum” recommendations for the UNICHROME Pyrophosphate Copper Plating Process. The bath was formulated using (1) 35 mL/L of C-11-Xb, (2) 333 mL/L of C-10-Xb, and (3) 5 mL/L of NH[0114] ₄OH, with the remainder of the solution being H₂O. It is believed that the Atotech supplied components contained various additives but it is not known precisely what these additives might be. It is possible that one of the additives is a nitrate salt such as potassium nitrate as it is generally considered a standard component in these pyrophosphate baths. To minimize contamination risk, the solution was prepurified by being pumped through a 1.0 μm filter device (POLYCAP™ HD from Whatman) before being used for CC mask plating. The resulting solution matched Atotech's “optimum” formulation recommendations set forth previously.
The function of each of the primary components of the pyrophosphate copper plating bath may be briefly summarized as follows. Copper pyrophosphate, Cu[0115] ₂P₂O₇, dissolves in a potassium pyrophosphate (K₄P₂O₇) solution forming the complex ion Cu(P₂O₇)₂ ⁶⁻ which is the source of copper ions in the plating bath. The bath pH is important since at pH values above 11, Cu(OH)₂precipitates, while either CuH₂P₂O₇or Cu₂P₂O₇precipitate at a pH below 7. Between pH values of 7 and 11, the bath is relatively stable, but undergoes slow hydrolysis as defined by:
P₂O₇ ⁴⁻+H₂O→2PO₄ ³⁻+2H⁺ (or 2HPO₄ ²⁻)
The concentration limit of orthophosphate (PO[0116] ₄ ³⁻) is about 100 g/L. Above this limit, the conductivity and bright-plating range suffer. Improper operation such as low pH, high P₂O₇:Cu ratio, or temperature above 60° C. will also build up orthophosphate. Since there is no way to remove orthophosphate from the bath, the bath will eventually need to be discarded. Nitrate ions in the bath can permit a higher limiting current density since they act as hydrogen acceptors to reduce cathode polarization. A small amount of ammonia in the bath produces more uniform and lustrous deposits and improves anode dissolution. Organic additives within controlled, limited concentrations refine the grain structure, impart leveling characteristics to the plating bath, and act as brighteners. Although some baths are operated without additives, most commercial pyrophosphate baths employ proprietary materials.
The electrochemical deposition reactions at the cathode and the dissolution reaction at the anode can be described as follows: [0117]
At the cathode: [0118]
Cu(P₂O₇)₂ ⁶⁻+e⁻→Cu(P₂O₇)₂ ⁷⁻
Cu(P₂O₇)₂ ⁷⁻+e⁻→Cu+2P₂O₇ ⁴⁻
At the anode: [0119]
Cu−2e⁻→Cu²⁺ (via a multistep mechanism)
Cu²⁺+2P₂O₇ ⁴⁻→Cu(P₂O₇)₂ ⁶⁻

Enhancing Uniformity of Depositions

When the above noted “optimum” plating solution was used in the CC mask plating process, an unexpected result occurred. It was observed that non-uniform amounts of deposition occurred when individual masks included micro-volumes having different dimensions. FIG. 4([0120] a) depicts a CC mask that was used in a plating operation that led to the unexpected result. The mask consists of a combined anode and support structure 102 made of OFHC (oxygen free high conductivity) copper onto which a silicone pattern (SYLGARD® 184 silicone elastomer from Dow Corning Corp) has been molded. The molded pattern has open regions through which plating can occur and regions occupied by the conformable silicone which will mate against the substrate to inhibit deposition in the mated areas. The pattern includes a large deposition region 110 whose outer perimeter is bounded by silicone 104 and which is internally bounded by silicone regions 106, 108, and 112. The large deposition region has an outer perimeter of about 1700 μm while the regions 106, 108, and 112 have outer surfaces that are substantially rectangular in shape (about 500 μm by 240 μm) with cut off corners. Silicone regions 106 and 112 act as outer boundaries for numerous smaller regions 116 and 122 that are to be plated. Smallest plating region 116 consists of a large square region (about 170 μm by 170 μm) with a smaller square adjacent thereto (about 70 μm by 70 μm) with the larger square having a center region filled by a square of silicone (about 80 μm by 80 μm). The somewhat larger plating regions 122 are rectangular regions (about 380 μm by 120 μm) that each contain two square blocks of silicone (each block being about 90 μm by 90 μm).
When this mask was used for plating, the patterned deposit of FIG. 4([0121] b) resulted. Examination of the depositions of FIG. 4(b) indicate that the smaller regions 116′ and 122′ have much thinner deposits than does larger region 110′. The difference in deposition height between region 116′ and those portions of the large region 122′ that fall within rectangular region 124 as seen in FIG. 4(b) are more clearly seen in FIG. 4(c). The CC mask used in forming these deposits may be considered to include eight independent micro-molds (one big one and seven small ones) which isolate the plating bath into eight independent volumes. Theoretically, the applied current should be uniformly distributed over the entire copper area and a uniform deposit thickness should be obtained. In this experiment, the plating time was 30 minutes with an applied current of 315 μA. The 315 μA was intended to yield a current density of 20 mA/cm²over the total plating area (about 1.6 mm²) of the mask. The experiment was performed with the plating bath at room temperature. The theoretical deposition thickness should have been about 13.4 μm and should have been uniform over all deposition areas. The deposits from all small micro-molds were much thinner (approximately 4.5 μm) than that from the big micro-mold (approximately 13 μm). The large deposition region 110′ had an area of about 1.4 mm². The smallest deposition region 116′ had an area of about 26,000 μm²(i.e. about 0.03 mm²) while the somewhat larger regions 122′ each had areas of about 48,000 μm²(i.e. about 0.05 mm²).
In addition, the deposit texture also showed differences between the smaller deposition regions and the larger deposition region. The difference in deposit texture can be seen in FIG. 4([0122] d) which depicts portions of regions 116′ and 110′ under higher magnification. While the texture in the large micro-mold region looked normal, the texture in the small micro-mold region looked softer and more powdery. In embodiments where the copper is being deposited as a sacrificial material the quality of deposit in the small micro-mold region may still result in a functional deposit but even in those circumstances the lack of build up in thickness remains a problem.
The mechanism of this phenomenon is not fully understood, but two additional facts were ascertained: (1) the situation does not occur for submasks without multiple independent micro-molds, and (2) the quality and thickness from all eight micro-molds was not noticeably different after plating for about 4 minutes (i.e., deposition thicknesses of about 1.8 μm) even for this specific submask. These two facts suggest that this problem is related to the multiple isolated micro-molds in one mask. The differences of quality and thickness gradually appear with plating time. As the bigger micro-mold has a thicker deposit than the smaller micro-mold, it suggests that the cathode in the smaller micro-mold attracts less plating current density than that in the big micro-mold. [0123]
From what is known, it is clear that when plating operations simultaneously involve depositions into an area at least as large as [0124] region 110′ (i.e. greater than or equal to about 1.4 mm²) and one or more regions that have an area equal to or smaller than regions 122′ (i.e. less than or equal to about 0.05 mm²) an unacceptable deposition results when using a pyrophosphate copper bath according to one manufacturer's optimum solution recommendations. The need to modify the conformable contact masking process (e.g. the electrochemical fabrication process) is apparent. As such, if one wants to maximize the ability of conformable contact mask plating to form structures of arbitrary shape in the shortest time (for a desired amount of build up in a deposition direction (i.e. a direction perpendicular to the plane of deposition)), then ability to deposit uniform thicknesses regardless of deposition area patterns is critical. Such uniform deposition patterns minimize time spent not only in deposition but also in planarizing away any differences in height.
In solving this problem, many experiments were carried out. The experimental results indicated that the situation was greatly improved when the concentration of the major copper and pyrophosphate component (i.e. C-10-Xb and whatever other unknown components are hidden in therein) of the plating solution are increased over that in the manufacturer's “optimal” bath. [0125]
FIG. 5 shows the results of deposition for a portion of [0126] regions 110′ and 122′ and for all of region 116′ when a first modified plating solution was used. This first modified solution contained double the amount of C-10-Xb as found in the “optimal” solution. As such this modified solution contained double the copper of the first solution and almost double the pyrophosphate. The modified plating bath was formulated to contain (1) 35 mL of C-11-Xb, (2) 666 mL of C-10-Xb, (3) 5 mL of (29%) NH₄OH, and (4) 294 mL of H₂O. As can be seen from the results in FIG. 5, the deposition height of the smaller region is no less than about 80% to 90% of the height of deposition of the larger region. This first modified solution not only produced a more uniform deposition but it also reduced formation of isolated spikes. These spikes can be seen in FIGS. 4(b)-4(d) but most clearly in FIG. 4(d). In the experiment that resulted in the deposition of FIG. 5, the same plating time (i.e. 30 minutes) and current (i.e. a current intending to result in a current density of 20 mA/cm²) and temperature (i.e. room temperature) were used as with the original (i.e. the manufacture's optimum) plating bath used in producing the results in FIGS. 4(b)-4(d).
This first modified formulation was not only modified to yield a desired result it was also modified to such an extent its formulation no longer fell within the scope of the Manufacturer's recommendations for total copper (i.e. it was modified to contain more than about 30 g/L) and for total pyrophosphate (i.e. it was modified to contain more than about 240 g/L). These modifications also placed this first modified solution outside the generalized upper limit for copper. That is the amount used was above the 30 g/L upper limit as taught by Atotech but also as set forth in the combined teachings of the ASM Handbook Vol. 5, 1994 and in “Electroplating: Fundamentals of Surface Finishing”, 1978. Furthermore, the amount used exceeded the 38 g/L upper limit set forth in “Modern Electroplating”, 2000. [0127]

Other formations were also tested that yielded acceptable results in that they caused more uniform depositions to occur. These other formations are set forth in the following table (TABLE 5) with examples of resulting depositions shown in the FIGS. 6(a)-6(b), 7(a)-7(b), 8, and 9.

TABLE 5


	Modified	Modified	Modified	Modified
Component	Formula #	2	Formula #3	Formula #4	Formula #5

C-10-Xb	905 mL/L	666 mL/L	666 mL/L	666 mL
C-11-Xb	95 mL/L	70 mL/L	35 mL/L	35 mL/L
NH₄OH (29%)	0 mL/L	0 mL/L	0 mL/L	10 mL/L
H₂O	0 mL/L	264 mL/L	299 mL/L	289 mL/L
Approximate	˜90-100%	˜80-90%	˜80-90%	˜80-90%
Small to Large
Area
Deposition
Thickness
Other Features				Many Spikes
Figures	6(a)-6(b)	7(a)-7(b)	8	9

In some experiments an additive called P-1 from Technic Inc. of Cranston, R.I. was added (up to 0.5 mL/L). This additive was used to help reduce stress in the deposited material and no significant impact on deposition thickness or uniformity was noted. [0129]
In some preferred embodiments of the invention the copper concentration is greater than about 30 g/L, more preferably greater than about 35 g/L and most preferably greater than about 40 g/L. In some preferred embodiments of the invention the pyrophosphate concentration is greater than about 240 g/L, more preferably no less than about 280 g/L and most preferably no less than about 320 g/L. [0130]
In some preferred embodiments a pyrophosphate copper solution is used that includes effective amounts of copper and pyrophosphate such that the solution is capable of (1) simultaneously depositing metallic copper to a smaller area (i.e. an area no larger than about 0.05 mm[0131] ²) and a larger area (i.e. an area no smaller than about 1.4 mm²) such that the height of deposition of the smaller area is no less than one-half the height of deposition of the larger area when the height of deposition of the larger area is greater than about 10 μm. In more preferred embodiments the height of deposition of the smaller area is no less than 65% of the height of deposition of the larger area and in most preferred embodiments it is no less than 80% of the height of the deposition of the larger area. In other embodiments not only are effective amounts of copper and pyrophosphate concentrations utilized but also the amount of copper used is set at above 30 g/L, more preferably no less than about 35 g/l, and most preferably no less than about 40 g/L.

Enhancing Longevity of Contact Masks

Some preferred embodiments of the present invention use plating temperatures that are lower than the minimum (i.e. 45° C.) of the recommended operating temperature range (i.e. 45° C. -60° C.) that is taught by the vendor (Atotech) from whom the plating bath components (UNICHROME Pyrophosphate Copper Plating Solution components) were purchased. Furthermore, the pyrophosphate copper plating bath temperatures utilized are lower than the minimum of the temperature range (˜43° C.) as recommended for pyrophosphate solutions in general. Though operating the plating baths at lower temperatures have several disadvantages (for example related to a potential lowering of the maximum deposition rate or the potential increase in deposit stress), it has been observed that the useful life of CC masks may be increased by such low temperature operation. [0132]
Some preferred embodiments of the present invention treat the support/anode structure of a CC mask with a corrosion inhibitor prior to bringing the support/anode into contact with the conformable (e.g. elastomeric) material. Experiments have shown that the use of a corrosion inhibitor can extend the useful life of CC masks. [0133]
In electrochemical fabrication, prior to beginning the layer-by-layer deposition of a structure, one or more CC masks must be formed. Various methods for forming CC masks were taught in the '630 patent referenced above. CC mask fabrication refers to the formation of a layer of patterned conformable material on a supporting material. One method of forming CC masks is presented in FIGS. [0134] 4(a)-4(e). FIG. 4 shows how patterns are transferred by a micro-molding technique. First a micro-mold 102 having a base 104 and a relief pattern 106 is manufactured (e.g. by a standard photolithography process). Then a conformable, curable material 108 (e.g. a silicone, such as Sylgard 184 from Dow Corning Corp) is applied on the micro-mold 102 as shown in FIG. 4(a). A material 112 (e.g. a copper plate) that will become a support for the CC mask is pressed against the conformable material and the micro-mold as shown in FIG. 4(b). The conformable material is cured so as to attain a relief pattern 106′ that is substantially the complement of the micro-mold relief pattern 106. The supporting material with the patterned conformable material is demolded from the micro-mold 102 after the conformable material has cured as shown in FIG. 4(c). A pre-CC mask 114 is then obtained as shown in FIGS. 4(c) and 4(d). The pre-CC mask may include a silicone residue 116 in valleys of the relief pattern. Finally, the residue 116 of the conformable material is removed, e.g. using Reactive Ion Etching (RIE) as schematically illustrated with impinging lines 118 as shown in FIG. 4(d) yielding the CC mask 120 as shown in FIG. 4(e).
The micro-mold may be fabricated employing IC-based techniques, e.g. photolithography of a layer of photoresist over a silicon wafer to produce small features on the micro scale. An example of a useful class of photoresists is epoxy based SU-8 whose different variations can be used to yield thicknesses as great as 500 μm or more in a single coating. Micro-molds were made using SU-8 5 (one version of SU-8) and SU-8 developer (from Microlithography Chemical Corp of Newton, Mass.). [0135]
In CC mask plating, a preferred conformable material is a silicone rubber. Silicone can be patterned while in a liquid state and then it can be cured to take a desired form. Silicones refer to a whole family of organo-silicon compounds based on a backbone or molecular chain of alternating silicon and oxygen atoms. Desirable characteristics of silicone rubbers include, for example, excellent resistance to non-elastic compression setting, excellent electrical insulation, good chemical resistance, and lack of toxicity. A preferred supporting material for the silicone rubber is metallic copper which can double as an anode during CC mask plating. An example of a silicone that has been found useful for CC mask plating is SYLGARD® 184 silicone elastomer from Dow Corning Corporation of MIDLAND, Mich. It is a two part liquid product, including a base and a curing agent. An example of a useful copper is oxygen free high conductivity (OFHC) copper (from Goodfellow of Huntingdon, England) having a purity of 99.95+% and that is supplied in disk form. The original disks were planarized using a 2 μm diamond slurry and then polished. [0136]
As an example, a more detailed process for molding the conformable material than that presented in FIG. 4 may include the following activities: [0137]
1. Passivate the micro-mold. For example, an SU-8 5 mold may be passivated in a vacuum desiccator along with a release agent. A few drops of silane (Tridecafluoro-1,1,2,2-tetrahydrooctyl)-1-trichlorosilane) can function as the release agent and may be placed beside the micro-mold in an open container. The desiccator is pumped down to 710 mm Hg and is held in that state for two hours. [0138]
2. Clean the copper disk. This may be done using toluene, acetone, DI water, immersion in 5% H[0139] ₂SO₄, and another DI water rinse. Dry the disk. This may be done, for example, by using compressed nitrogen. Apply an adhesion promoter to the copper disk. This may involve, use of a silane based material such as, for example, SYLGARD® Prime Coat adhesion promoter (from Dow Corning). This material may be applied to the copper disk and then spun at 1000 rpm for 30 seconds and then exposed to air for about 1-2 hours.
3. Prepare the liquid conformable material for molding. For example, mix the base and curing agent of SYLGARD® 184. Degas the liquid by application of a slight vacuum, for example, by placing the liquid silicone in the vacuum desiccator at 710 mm Hg until no bubbles are seen. Pour the liquid over the mold and degas again. Place the copper disk face-down on the mold and press it down and hold it (e.g. using a custom fixture) while exposing it to air for 1 hour and then putting it in the oven at 65° C. for 6 hours. [0140]
4. Demold the combined copper support and patterned elastomer from the mold. [0141]
5. Etch away any silicone residue (from the recesses of the relief pattern), for example using RIE, so that the copper (i.e. anode) surface becomes exposed. [0142]
A single micro-mold may be used to make multiple masks. [0143]
An ideal CC mask preferably has several attributes: (1) It can perfectly mask desirable areas without flash deposit and has minimum deformation during CC mask plating; (2) It possesses good adhesion between the silicone rubber and the support; (3) It shows good chemical resistance to electroplating baths; (4) It is robust and can be exposed to plating solution for a sufficiently long time and can be used in plating operations one or more times to make desired deposits. [0144]
It is generally desirable for CC masks to share a common support. Because of this, each individual CC mask is exposed to plating bath under potentially three different conditions: (1) during plating using the specific mask, (2) during plating using different masks, and (3) during non-plating periods of time while still immersed. As such, the effective life of a specific CC mask is not necessarily determined solely by a mask's ability to withstand the effects directly associated with its use during plating but also on its ability to withstand the effects of immersion while other masks are being used for plating and while no plating is occurring. Since the time spent in the bath during periods when a particular mask is not being directly used for plating may be many times, or even tens of times, longer than the time it will be used for plating, the determination of effective mask longevity preferably takes into consideration of all of these issues. [0145]
Using a UNICHORME plating bath as described above, experiments have shown that the treatment of the copper support with a corrosion inhibitor such as Benzotriazole (BTA, C[0146] ₆H₄N₃H) can extend the useful life of a CC mask considerably.
Generally, it has been observed that CC mask failure occurs due to delamination of the conformable material from the support. This delamination in electrochemical fabrication appears to be primarily an interface failure process in which the adhesion of silicone to copper gradually decreases and finally the features of the patterned conformable material leave the copper anode. This interface failure typically determines the life of a CC mask. This failure, in a real service environment, may result from different effects, including electrochemical effects (CC mask plating), chemical effects (chemical attack by the plating bath) and mechanical effects (the mating and unmating processes). The electrochemical effects may not only include those impacting a given mask that is associated with plating but also other masks that share a common support. The sharing of the support may result in all masks being raised to an elevated electrical potential while in contact with the plating solution even when they are not involved in plating operations. The raising of electrical potential (even without current flow may result in a change in the electrochemical interaction between the mask and the plating solution. [0147]
The interface of the silicone rubber and the copper in a CC mask is easily attacked by the plating baths. A schematic illustration of an interface structure using a silane coupling agent is shown in FIG. 5. A [0148] copper support 112 generally includes an oxide coating 122 to which one end of the silane molecules 124 attach. The other end of the silane molecules adhere to the silicone elastomeric material 106′ via organic groups, represented by “X”s, of any of a variety of types that can react with silicone. Interface failure occurs at the silane coupling agent (e.g. Sylgard Prime Coat), the Cu₂O film, or both. Gradual damage to the interface occurs as the silane is hydrolyzed by water diffusion. This alone could eventually cause silicone delamination.
Although the corrosion inhibition mechanism of BTA is not fully known, it is believed that the basic action of BTA involves the formation of a polymeric complex with Cu[0149] ⁺ ions, (Cu⁺BTA⁻)_n. The complex is believed to be a thin (<50 Å) film with a highly polymerized network. The protection provided by this film is believed to be proportional to its degree of polymerization. Though some believe that the Cu₂O layer is a necessary substrate for the BTA adsorption onto the Copper anode and is necessary as a source of Cu⁺ ions for the formation of the Cu⁺BTA⁻ complex, it is possible that the film can also be formed on an oxide free copper substrate. The film is believed to grow by reaction of Cu⁺ diffusing through the film of Cu⁺BTA⁻ or Cu₂O.
The corrosion behavior of bulk copper foils treated in 1% BTA at 50° C. for 30 minutes was investigated in a Cu—P bath (Technic Inc.). The copper foils were dipped in 5% H[0150] ₂SO₄for 10 seconds, then rinsed with DI water and then immediately put into the BTA solution. The corrosion potentials of the untreated and BTA treated copper foils were measured with an EG&G 273A Potentiostat/Galvanostat (from Ametek, Inc. of Paoli, Pa. under the tradename of Princeton Applied Research). The reference electrode was a saturated calomel electrode (SCE). Because of the apparent formation of polymeric film on the copper, the potential moved more positive from −260 mV to +220 mV (FIG. 3.14). A dipping test in the Cu—P bath at room temperature indicated that an untreated copper foil lost its original luster in less than 18 hours, while a BTA treated foil kept its luster for at least 66 hours. The corrosion rate and corrosion rating of BTA treated copper foils in the UNICHROME bath at 50° C. were also measured. The corrosion rate of the BTA treated foils was greatly decreased from 55 μm/yr down to 4 μm/yr.
For the treated copper to function as an anode, the non-masked (i.e. non-silicone covered) regions must be free of the BTA polymeric film during CC mask plating. In other words, prior to the occurrence of any plating operations it is desired that the BTA polymeric film be limited to those CC mask regions covered by silicone. Tests confirmed that the RIE treatment used to remove residual silicone could also be used to remove the BTA polymeric films. The BTA treatment step can be integrated into the mask fabrication process before the application of the primer. This may be done for example by immersing a copper disk in 1% BTA bath at 50° C. for 15-30 minutes. It is believed that a BTA treatment step, or other corrosion inhibitor treatment step could be applied to other mask formation processes. [0151]
BTA treated CC masks were also evaluated for their delamination behavior in real service environments. One immersion test in the Unichrome bath indicated that delamination was about 6-8 μm at some features after a combination of 15 hours immersion at 50° C. followed by 16 hours of immersion at room temperature. Even after an additional 8 hours at 50° C., the mask still showed acceptable adhesion (i.e. delamination had not proceeded to an unacceptable level). BTA increased the corrosion resistance significantly. [0152]
Observation of unused CC masks (i.e. submasks) on a BTA treated support after a real use immersion test (i.e. an immersion test involving multiple cycles of periods oscillating between immersion without electrical potential and immersion at potential) involving the formation of a multilayer structure showed that a uniform delamination of about 8-10 μm from each side in the Unichrome bath at 20° C. occurred after a total of about 516 minutes. Of the 516 minutes of immersion, the support was held at anodic potential for about 321 minutes (i.e. about 62% of the time). This corresponds to an average delamination rate of 1.0 μm/hr. In similar circumstances an untreated mask showed a delamination rate of 2.7 μm/hr after about 440 minutes of immersion. BTA treatment enhanced the corrosion resistance of the mask and extended the mask life in the plating bath. FIG. 6([0153] a) depicts an unused mask including a copper support 132, a surrounding silicone region 134 and a number of internal silicone regions 136 a-136 h. In FIG. 6(a) the width of elements 136 a-136 g is about 90 μm. FIG. 6(c) shows the mask that was used in the 516 minute real-use test mentioned above while FIG. 6(b) depicts the mask used in the 440 minute real-use test mentioned above. As can be seen from comparing FIGS. 6(b) and 6(c) the BTA treated mask has a cleaner and better appearance even though it remained in the solution for about 76 minutes longer.
Even with the BTA treatment, it can be seen that there is a significant difference between the delamination rates for unused masks (e.g. masks which have not been associated with deposition) in the static immersion test versus the real-use immersion test. [0154]
Electrochemical delamination was also tested for a BTA treated mask. A uniform average delamination of 20 μm formed during a 30 min plating in the UNICHROME bath at 20° C. at a current density of 20 mA/cm[0155] ². This corresponds to a delamination rate was 0.67 μm/min. The treated mask used in this test is shown in FIG. 7(a). For an untreated mask, experimentation showed a delamination of about 16-18 μm after about 16 minutes of CC mask plating, which corresponds to a rate of about 1-1.1 μm/min. As such, the delamination rate during plating for the treated BTA is about 40% less than that for the untreated masks. The untreated mask used in this test is shown in FIG. 7(b) where severe delamination can be seen. A comparison of FIGS. 7(a) to 7(b) shows that the BTA treated surfaces, FIG. 7(a), that are overlaid with silicone (i.e. the bars and the material outside the circle) have a uniform appearance and thus good adhesion (i.e. little delamination) while the untreated surfaces, FIG. 7(b), that are overlaid with silicone show an irregular appearance and thus varying extends of delamination.
The lifetime of a silicone-on-copper CC mask in a real service environment is greatly restricted by chemical, electrochemical and mechanical effects but treatment of the support with a corrosion inhibitor can significantly increase the life of the mask, particularly when the mask may be exposed to plating solution for periods of time that are many times the periods that will be used for plating. [0156]
Though the preferred inhibitor for use in the present invention is BTA, it is believed that other copper corrosion inhibitors might be useful as well. For example materials that might be useful in alternative embodiments include MBT (Mercaptobenzothiazole) and TTA (tolyltriazole) and other compositions derived from, within the same class as, or of similar structure to BTA, MBT, or TTA. It is believed that TTA is a better corrosion inhibitor in an oxidizing environment than either MBT or BTA and as contact or proximity mask support elements may be maintained in an oxidizing state during electrodeposition operations, use of TTA may prove to provide better protection. In other alternative embodiments, it may be possible to treat the support with more than one corrosion inhibitor to achieve even further improvements in CC mask effective life. In other alternative embodiments, if selective depositions will occur via CC mask plating where materials other than copper will be used, it is believed that the treatment of the support material by one or more known corrosion inhibitors may be useful for extending the life of CC masks that will used with these other deposition materials. [0157]
CC mask longevity may be enhanced by operating the selective deposition bath at temperatures below those normally recommended for use with pyrophosphate plating baths. For example, in the “optimum” Unichrome plating bath, the corrosion rate in a static immersion test was determined to be more than 3 times higher at 50° C. than at 20° C. [0158]
U.S. patent application Ser. No. ______ (Corresponding to MEMGen Docket No. P-US063-A-MG), filed on May 7, 2003, and entitled “Selective Electrochemical Deposition Methods Using Pyrophosphate Copper Plating Baths Containing Ammonium Salts, Citrate Salts and/or Selenium Oxide” is generally directed to a electrochemical fabrication process and apparatus that can form three dimensional multi-layer structures using pyrophosphate copper plating solutions that contain citrate salts, selenium oxide, and/or excess ammonium salts. In some embodiments the citrate salts are provided in concentrations that yield improved anode dissolution, reduced formation of pinholes on the surface of deposits, reduced likelihood of shorting between anode and cathode during deposition processes, and reduced plating voltage throughout the period of deposition. A preferred citrate salt is ammonium citrate in concentrations ranging from somewhat more that about 10 g/L for 10 mA/cm[0159] ²current density to as high as 200 g/L or more for a current density as high as 40 mA/cm. In some embodiments deposits having enhanced ductility and/or reduced tendency to crack are provided.
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 process and/or they may not use a planarization 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 depositions processes that are not electrodeposition processes. Some embodiments may use selective deposition processes on some layers that are not conformable contact masking processes and are not even electrodeposition processes. Some embodiments may use nickel as a structural material while other embodiments may use different materials such as gold, silver, or any other electrodepositable materials that can be separated from the copper and/or some other sacrificial material. 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. In some embodiments the anode may be different from the conformable contact mask support and the support may be a porous structure or other perforated structure. Some embodiments may use multiple conformable contact masks with different patterns so as to deposit different selective patterns of material on different layers and/or on different portions of a single layer. In some embodiments, the depth of deposition will be enhanced by pulling the conformable contact mask away from the substrate as deposition is occurring in a manner that allows the seal between the conformable portion of the CC mask and the substrate to shift from the face of the conformal material to the inside edges of the conformable material. [0160]
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. [0161]

Claims

I claim:

1. An electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers, the process comprising:

(A) supplying a plurality of preformed masks, wherein each mask comprises a patterned dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein each mask comprises a support structure that supports the patterned dielectric material;

(B) selectively depositing at least a portion of a layer onto the substrate, wherein the substrate may comprise previously deposited material; and

(C) forming a plurality of layers such that each successive layer is formed adjacent to and adhered to a previously deposited layer, wherein said forming comprises repeating operation (B) a plurality of times;

wherein at least a plurality of the selective depositing operations comprise

(1) contacting the substrate and the dielectric material of a selected preformed mask or proximately locating the substrate and dielectric material of a selected preformed mask;

(2) in presence of a plating solution, conducting an electric current through the at least one opening in the selected mask between an anode and the substrate, wherein the anode comprises a selected deposition material, and wherein the substrate functions as a cathode, such that the selected deposition material is deposited onto the substrate to form at least a portion of a layer; and

(3) separating the selected preformed mask and the substrate; and

wherein the selected deposition material is copper; and wherein the plating solution comprises a pyrophosphate copper solution that contains more than about 30.0 grams of copper per liter; or

wherein the plating solution comprises a pyrophosphate copper solution that contains more than about 240 grams of pyrophosphate; or

wherein the selected deposition material is copper; and wherein the plating solution comprises a pyrophosphate copper solution that comprises effective amounts of copper and pyrophosphate such that the solution is capable of (1) simultaneously depositing metallic copper to a smaller area (i.e. an area no larger than about 0.05 mm²) and a larger area (i.e. an area no smaller than about 1.4 mm²) such that the height of deposition of the smaller area is no less than one-half the height of deposition of the larger area when the height of deposition of the larger area is greater than 10 μm.

2. The process of claim 1 wherein the plating solution comprises a pyrophosphate solution that comprises (1) effective amounts of copper and pyrophosphate such that the solution is capable of simultaneously depositing metallic copper to a smaller area (i.e. an area no larger than about 0.05 mm²) and a larger area (i.e. an area no smaller than about 1.4 mm²) such that the height of deposition of the smaller area is no less than one-half the height of deposition of the larger area when the height of deposition of the larger area is greater than 10 μm, (2) more than 30.0 grams of copper per liter, and (3) more than 240 grams of pyrophosphate per liter.

3. The process of claim 1 wherein the solution comprises no less about than 35 grams of copper per liter.

4. The process of claim 1 wherein the solution comprises no less about than 40 grams of copper per liter.

5. The process of claim 1 wherein the solution comprises no less than about 280 grams of pyrophosphate per liter.

6. The process of claim 1 wherein the solution comprises no less than about 320 grams of pyrophosphate per liter.

7. The process of claim 1 wherein the plating solution comprises a pyrophosphate solution that comprises (1) effective amounts of copper and pyrophosphate such that the solution is capable of simultaneously depositing metallic copper to a smaller area (i.e. an area no larger than about 0.05 mm²) and a larger area (i.e. an area no smaller than about 1.4 mm²) such that the height of deposition of the smaller area is no less than 65% the height of deposition of the larger area when the height of deposition of the larger area is greater than 10 μm.

8. The process of claim 1 wherein the plating solution comprises a pyrophosphate solution that comprises (1) effective amounts of copper and pyrophosphate such that the solution is capable of simultaneously depositing metallic copper to a smaller area (i.e. an area no larger than about 0.05 mm2) and a larger area (i.e. an area no smaller than about 1.4 mm2) such that the height of deposition of the smaller area is no less than 80% the height of deposition of the larger area when the height of deposition of the larger area is greater than 10 μm.

9. The process of claim 1 wherein the plating bath is at a temperature below about 43° C. when conduction of the electric current begins.

10. The process of claim 1 wherein the plating bath is at a temperature below about 38° C. when conduction of the electric current begins.

11. The process of claim 1 wherein the plating solution is not agitated during selective deposition.

12. The process of claim 1 wherein the formation of each of a number of layers comprise at least one blanket deposition as well as the selective deposition wherein for a given layer the selectively deposited material is different from a material deposited by blanket deposition.

13. The process of claim 1 wherein the plurality of selective depositions comprise the deposition of a plurality of different materials.

14. The process of claim 1 wherein at least a portion of one layer is formed by a non-electroplating deposition process.

15. The process of claim 1 wherein a plurality of depositions occur during the formation of each of a number of layers wherein at least one of the depositions on each of the number of layers deposits copper and at least one of the other depositions on the number of layers deposits nickel.

16. The process of claim 1 wherein a number of the plurality of layers are each formed by depositing at least one structural material using at least one deposition and by depositing at least one sacrificial material by using at least one other deposition.

17. The process of claim 16 wherein at least a portion of the at least one sacrificial material is removed after formation of a plurality of layers to reveal a three-dimensional structure comprised of at least one structural material.

18. The process of claim 1 wherein the dielectric comprises a conformable material and a thickness of the conformable material of at least one selected mask is less than 100 μm and is more preferably less than 50 μm.

19. The process of claim 1 wherein the formation of at least a plurality of layers additionally comprises removing a portion of the deposited material such that a desired surface level is obtained.

20. An electrochemical fabrication process for producing a three-dimensional structure from a plurality of adhered layers, the process comprising:

wherein at least a plurality of the selective depositing operations comprise

(1) contacting the substrate and the dielectric material of a selected preformed mask;

(3) separating the selected preformed mask from the substrate; and

wherein prior to the dielectric material and support structure being joined together, the support structure undergoes a treatment with a corrosion inhibitor, or

wherein the plating solution is a copper solution that is at a temperature of less than about 43° C.

21. The process of claim 20 wherein the support structure comprises copper and wherein the corrosion treatment comprises exposing a surface of the support structure to BTA.

22. A contact mask for use in electroplating operations, comprising:

a preformed mask that comprises a patterned dielectric material that includes at least one opening through which deposition can take place during the formation of at least a portion of a layer, and wherein the at least one mask comprises a support structure that supports the patterned dielectric material; and

wherein the patterned dielectric material is bonded to the support structure, which support structure comprises the anode for current flow through the plating solution during selective deposition, and

wherein a surface of the support structure that is bonded to the dielectric material comprises a modified chemical structure that enhances the corrosion resistance of the preformed mask.

23. The apparatus of claim 22 wherein the modified chemical structure comprises a polymerized structure.

24. The apparatus of claim 23 wherein the modified chemical structure comprises BTA.