U.S. patent application number 10/841347 was filed with the patent office on 2005-04-07 for multi-step release method for electrochemically fabricated structures.
This patent application is currently assigned to Microfabrica Inc.. Invention is credited to Cohen, Adam L., Lockard, Michael S., McPherson, Dale S..
Application Number | 20050072681 10/841347 |
Document ID | / |
Family ID | 34397332 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050072681 |
Kind Code |
A1 |
Cohen, Adam L. ; et
al. |
April 7, 2005 |
Multi-step release method for electrochemically fabricated
structures
Abstract
Multi-layer structures are electrochemically fabricated from at
least one structural material (e.g. nickel), that is configured to
define a desired structure and which may be attached to a
substrate, and from at least one sacrificial material (e.g. copper)
that surrounds the desired structure. After structure formation,
the sacrificial material is removed by a multi-stage etching
operation. In some embodiments sacrificial material to be removed
may be located within passages or the like on a substrate or within
an add-on component. The multi-stage etching operations may be
separated by intermediate post processing activities, they may be
separated by cleaning operations, or barrier material removal
operations, or the like. Barriers may be fixed in position by
contact with structural material or with a substrate or they may be
solely fixed in position by sacrificial material and are thus free
to be removed after all retaining sacrificial material is
etched.
Inventors: |
Cohen, Adam L.; (Los
Angeles, CA) ; Lockard, Michael S.; (Lake Elizabeth,
CA) ; McPherson, Dale S.; (Burbank, CA) |
Correspondence
Address: |
MICROFABRICA INC.
DENNIS R. SMALLEY
1103 W. ISABEL ST.
BURBANK
CA
91506
US
|
Assignee: |
Microfabrica Inc.
Burbank
CA
|
Family ID: |
34397332 |
Appl. No.: |
10/841347 |
Filed: |
May 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10841347 |
May 7, 2004 |
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10434497 |
May 7, 2003 |
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10841347 |
May 7, 2004 |
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10607931 |
Jun 27, 2003 |
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10841347 |
May 7, 2004 |
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10309521 |
Dec 3, 2002 |
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10841347 |
May 7, 2004 |
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10434497 |
May 7, 2003 |
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10841347 |
May 7, 2004 |
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10434103 |
May 7, 2003 |
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10841347 |
May 7, 2004 |
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10434295 |
May 7, 2003 |
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10841347 |
May 7, 2004 |
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10434519 |
May 7, 2003 |
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60379184 |
May 7, 2002 |
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60392531 |
Jun 27, 2002 |
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60392531 |
Jun 27, 2002 |
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60415374 |
Oct 1, 2002 |
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60464504 |
Apr 21, 2003 |
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60476554 |
Jun 6, 2003 |
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60338638 |
Dec 3, 2001 |
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60340372 |
Dec 6, 2001 |
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60379133 |
May 7, 2002 |
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60379182 |
May 7, 2002 |
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60379184 |
May 7, 2002 |
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60415374 |
Oct 1, 2002 |
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60379130 |
May 7, 2002 |
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60392531 |
Jun 27, 2002 |
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60379184 |
May 7, 2002 |
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60392531 |
Jun 27, 2002 |
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60379182 |
May 7, 2002 |
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60430809 |
Dec 3, 2002 |
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60379133 |
May 7, 2002 |
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60379130 |
May 7, 2002 |
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Current U.S.
Class: |
205/170 ;
205/223 |
Current CPC
Class: |
B81C 1/00126 20130101;
H01P 11/00 20130101; H05K 3/4647 20130101; B81C 2201/0109 20130101;
H01P 1/202 20130101; G01P 15/0802 20130101; H01P 11/007 20130101;
G01P 15/125 20130101; C23C 18/1651 20130101; H01P 3/06 20130101;
H01P 5/183 20130101; B81C 2201/0197 20130101; C23C 18/1605
20130101; B81B 2201/042 20130101; H01P 11/005 20130101; C25D 1/003
20130101 |
Class at
Publication: |
205/170 ;
205/223 |
International
Class: |
C25D 005/10 |
Claims
We claim:
1. An electrochemical fabrication process for producing a
multi-layer three-dimensional structure from a plurality of adhered
layers, the process comprising: (A) forming a layer by depositing
at least one sacrificial material and at least one structural
material onto a substrate, wherein the substrate may comprise
previously deposited layers, and wherein the depositing of at least
one of the materials comprises an electrodeposition or electroless
deposition operation; (B) repeating (A) one or more times such that
a plurality of layers are formed and such that successive layers
are formed adjacent to and adhered to previously formed layers; (C)
performing a first etching operation to remove at least a first
portion of at least one material from the plurality of layers or
from the substrate; and (D) performing a second etching operation,
which is distinct from the first etching operation, to remove at
least a portion of at least one material from the plurality of
layers or from the substrate.
2. An electrochemical fabrication process for producing a
multi-layer three-dimensional structure from a plurality of adhered
layers, the process comprising: (A) forming a layer by depositing
at least one sacrificial material and at least one structural
material onto a substrate, wherein the substrate may comprise
previously deposited layers, and wherein at least one of the
materials comprises a metal or electroless deposition operation;
(B) repeating (A) one or more times such that a plurality of layers
are formed and such that successive layers are formed adjacent to
and adhered to previously formed layers; (C) performing a first
etching operation to remove at least a first portion of at least
one material from the plurality of layers or from the substrate;
and (D) performing a second etching operation, which is distinct
from the first etching operation, to remove at least a portion of
at least one material from the plurality of layers or from the
substrate.
3. The process of claim 1 additionally comprising: (D) 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;
wherein at least a plurality of the selective depositing operations
comprise: (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,
whereby a 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.
4. The process of claim 1 wherein a plurality of selective
depositing operations comprise: (1) providing an adhered patterned
mask on a surface of the substrate, wherein the mask includes at
least one opening; (2) in presence of a plating solution,
conducting an electric current through the at least one opening in
the adhered mask between an anode and the substrate, whereby a
selected deposition material is deposited onto the substrate to
form at least a portion of a layer; and (3) removing the mask from
the substrate.
5. The process of claim 1 wherein a plurality of selective
depositing operations comprise: (1) providing an adhered patterned
mask on a surface of the substrate, wherein the mask includes at
least one opening; (2) while the patterned mask is adhered to the
substrate, depositing a selected deposition material through the at
least one opening in the adhered mask onto the substrate, and (3)
removing the mask from the substrate.
6. The process of claim 1 wherein the first etching operation
comprises use of at least a first etchant and a first set of
etching parameters and wherein the second etching operation
comprises use of at least a second etchant and a second set of
etching parameters.
7. The process of claim 6 wherein the first and second etchants are
different from one another.
8. The process of claim 7 wherein the first etchant selectively
attacks one of the materials of the layers while substantially
non-reactive with regard to another material of the layers.
9. The process of claim 6 wherein the first set of etching
parameters are different from the second set of etching
parameters.
10. The process of claim 6 wherein the first and second etching
operations are separated by an intervening operation.
11. The process of claim 1 where the first etching operation
removes a first material and the second operation removes a second
material which is different from the first material.
12. The process of claim 1 wherein the first etching operation ends
at a hard stop.
13. The process of claim 1 where the three-dimensional structure is
protected from the first etchant and etching operation by a
material that substantially surrounds the structure and, which is
not attacked significantly by the first etchant.
14. The process of claim 1 where the three-dimensional structure is
protected from the first etchant and etching operation by a barrier
material and by a substrate on which the structure is formed which
are resistant to the first etching operation.
15. The process of claim 1 where the three dimensional structures
is protected from the first etchant and etching operation by a
barrier material which has a surface which is at least partially
conformal with end spaced from a surface of the structure.
16. An electrochemical fabrication process for producing a
three-dimensional structure from a plurality of adhered layers, the
process comprising: (A) forming a layer by depositing at least one
sacrificial material and at least one structural material onto a
substrate, wherein the substrate may comprise previously deposited
layers, and wherein the depositing of at least one of the materials
comprises an electrodeposition operation or electroless deposition;
(B) repeating (A) one or more times such that a plurality of layers
are formed and such that successive layers are formed adjacent to
and adhered to previously formed layers; (C) performing a first
etching operation to remove at least a first portion of at least
one material from the plurality of layers or from the substrate;
(D) performing an intervening operation, after performing the first
etching operation; (E) performing a second etching operation, after
the intervening operation, to remove at least a portion of at least
one material from the plurality of layers or from the
substrate.
17. The process of claim 16 additionally comprising: (F) 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;
wherein at least a plurality of selective depositing operations
comprise: (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,
whereby a 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.
18. The process of claim 16 wherein a plurality of selective
depositing operations comprise: (1) providing an adhered patterned
mask on a surface of the substrate, wherein the mask includes at
least one opening; (2) in presence of a plating solution,
conducting an electric current through the at least one opening in
the adhered mask between an anode and the substrate, whereby a
selected deposition material is deposited onto the substrate to
form at least a portion of a layer; and (3) removing the mask from
the substrate.
19. The process of claim 12 additionally comprising: (D) 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;
wherein at least a plurality of the selective depositing operations
comprise: (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,
whereby a 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.
20. The process of claim 18 wherein the first etching operation
comprises use of at least a first etchant and a first set of
etching parameters and wherein the second etching operation
comprises use of at least a second etchant and a second set of
etching parameters.
21. The process of claim 20 wherein the first and second etchants
are different from one another.
22. The process of claim 21 wherein the first etchant selectively
attacks one of the materials of the layers while substantially
non-reactive with regard to another material of the layers.
23. The process of claim 22 wherein the at least one structural
material comprises nickel, the at least one sacrificial material
comprises copper, and wherein the first etchant is substantially
selective to copper while substantially non-reactive with
nickel.
24. The process of claim 16 wherein the intervening operation is an
operation that removes etchant from at least one surface that was
being etched by the first etching operation.
25. The process of claim 24 wherein the second etching operation
uses the same etchant as did the first operation and wherein the
second etching operation continues to operate on at least a portion
of the at least one surface being etched by the first etching
operation.
26. The process of claim 25 wherein the process additionally
comprises: at least a second intervening operation which is
performed after the second etching operation; and at least a third
etching operation that is performed after the second intervening
operation.
27. The process of claim 16 wherein the intervening operation
removes an etching barrier that was protecting at least a portion
of the multi-layer structure or substrate during the first etching
operation.
28. The process of claim 27 wherein the second etching operation
operates to remove material located around a previously protected
surface.
29. The process of claim 27 wherein removal of the etching barrier
occurs at least in part by use of a planarization operation.
30. The process of claim 28 wherein the first etching operation
removes at least portion of a sacrificial material located in a
passage or indentation on or within the substrate while the etching
barrier protects at least a portion of the multi-layer
structure.
31. The process of claim 30 wherein the second etching operation
attacks sacrificial material forming part of the plurality of
layers.
32. The process of claim 16 wherein the formation of the plurality
of layers comprises formation of a desired structure and at least
one temporary etching barrier that is adhered to the substrate or
to structural material on at least one layer.
33. The process of claim 16 wherein the formation of the plurality
of layers comprises formation of a desired structure and at least
one temporary etching barrier that is adhered only to sacrificial
material.
34. The process of claim 33 wherein the temporary barrier falls
away from the desired structure after a surrounding quantity of
sacrificial material has been removed.
35. The process of claim 16 wherein the intervening operation
includes reorienting the structure with respect to a direction of
application of an etchant or with respect to a gravitational force.
Description
RELATED APPLICATIONS
[0001] This application is a Continuation-in-Part of both U.S.
patent application No. 10/434,497 filed May 7, 2003 and U.S. patent
application No. 10/607,931 filed Jun. 27, 2003; U.S. patent
application No. 10/434,497 claims benefit of U.S. Provisional
Patent Application No. 60/379,184, filed May 7, 2002, and No.
60/392,531, filed Jun. 27, 2002. U.S. patent application Ser. No.
10/607,931 claims benefit of U.S. Provisional Patent Application
No. 60/392,531, filed Jun. 27, 2002, No. 60/415,374, filed Oct. 1,
2002, No. 60/464,504, filed Apr. 21, 2003, and 60/476,554, filed on
Jun. 6, 2003; U.S. patent application Ser. No. 10/607,931 is also a
continuation-part of U.S. patent application Ser. No. 10/309,521,
filed on Dec. 3, 2002 and Ser. Nos. 10/434,497, 10/434,103,
10/434,295, and 10/434,519 each filed on May 7, 2003; U.S. patent
application Ser. No. 10/309,521 claims benefit of U.S. Provisional
Patent Application No. 60/338,638, filed on Dec. 3, 2001, No.
60/340,372, filed on Dec. 6, 2001, No. 60/379,133, filed on May 7,
2002, No. 60/379,182, filed on May 7, 2002, No. 60/379,184, filed
on May 7, 2002, No. 60/415,374 filed on Oct. 1, 2002, No.
60/379,130, filed on May 7, 2002, and No. 60/392,531, filed on Jun.
27, 2002; U.S. patent application Ser. No. 10/434,497 in turn
claims benefit of U.S. Provisional Patent Application No.
60/379,184, filed May 7, 2002, and No. 60/392,531, filed Jun. 27,
2002; U.S. patent application Ser. No. 10/434,103 in turn claims
benefit of U.S. Provisional Patent Application No. 60/379,182,
filed May 7, 2002, and No. 60/430,809, filed Dec. 2, 2002; U.S.
patent application Ser. No. 10/434,295 in turn claims benefit of
U.S. Provisional Patent Application No. 60/379,133, filed May 7,
2002; and U.S. patent application Ser. No. 10/434,519 in turn
claims benefit of U.S. Provisional Patent Application No.
60/379,130, filed May 7, 2002. Each of these priority applications
is incorporated herein by reference as if set forth in full.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the field of
electrochemical fabrication and the associated formation of
three-dimensional structures via a layer-by-layer build up of
deposited materials. In particular, it relates to the formation of
microstructures embedded in sacrificial material and the release of
those microstructures from the sacrificial materials via two or
more distinct etching operations.
BACKGROUND OF THE INVENTION
[0003] A technique for forming three-dimensional structures (e.g.
parts, components, devices, and the like) from a plurality of
adhered layers was invented by Adam L. Cohen and is known as
Electrochemical Fabrication. It is being commercially pursued by
Microfabrica.TM. Inc. (formerly MEMGen.RTM. Corporation) of
Burbank, Calif. under the name EFAB.RTM.. This technique was
described in U.S. Pat. No. 6,027,630, issued on Feb. 22, 2000. This
electrochemical deposition technique allows the selective
deposition of a material using a unique masking technique that
involves the use of a mask that includes patterned conformable
material on a support structure that is independent of the
substrate onto which plating will occur. When desiring to perform
an electrodeposition using the mask, the conformable portion of the
mask is brought into contact with a substrate while in the presence
of a plating solution such that the contact of the conformable
portion of the mask to the substrate inhibits deposition at
selected locations. For convenience, these masks might be
generically called conformable contact masks; the masking technique
may be generically called a conformable contact mask plating
process. More specifically, in the terminology of Microfabrica.TM.
Inc. (formerly MEMGen.RTM. Corporation) of Burbank, Calif. such
masks have come to be known as INSTANT MASKS.TM. and the process
known as INSTANT MASKING or INSTANT MASK.TM. 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:
[0004] (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.
[0005] (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.
[0006] (3) A. Cohen, "3-D Micromachining by Electrochemical
Fabrication", Micromachine Devices, March 1999.
[0007] (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.
[0008] (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.
[0009] (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.
[0010] (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.
[0011] (8) A. Cohen, "Electrochemical Fabrication (EFABTM)",
Chapter 19 of The MEMS Handbook, edited by Mohamed Gad-EI-Hak, CRC
Press, 2002.
[0012] (9) "Microfabrication--Rapid Prototyping's Killer
Application", pages 1-5 of the Rapid Prototyping Report, CAD/CAM
Publishing, Inc., June 1999.
[0013] The disclosures of these nine publications are hereby
incorporated herein by reference as if set forth in full
herein.
[0014] 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:
[0015] 1. Selectively depositing at least one material by
electrodeposition upon one or more desired regions of a
substrate.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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 26a and 26b 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.
[0024] 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 includes 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.TM. (AIM) or as an
anodeless conformable contact (ACC) mask.
[0025] 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.
[0026] 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).
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] In addition to the above teachings, the '630 patent
indicates that electroplating methods can be used in combination
with insulating materials. In particular it indicates that though
the electroplating methods have been described with respect to two
metals, a variety of materials, e.g., polymers, ceramics and
semiconductor materials, and any number of metals can be deposited
either by the electroplating methods described, or in separate
processes that occur throughout the electroplating method. It
further indicates that a thin plating base can be deposited, e.g.,
by sputtering, over a deposit that is insufficiently conductive
(e.g., an insulating layer) so as to enable continued
electroplating. It even further indicates that multiple support
materials can be included in the electroplated element allowing
selective removal of the support materials.
[0032] 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.
[0033] Even in view of these teaching, a need remains in the
electrochemical fabrication arts for techniques that can improve
production reliability, enhance control of post-layer fabrication
process operations, ease post layer fabrication handling, and even
overcome process defects that might otherwise result in production
failures.
SUMMARY OF THE INVENTION
[0034] An object of some embodiments of various aspects of the
invention is to improve electrochemical fabrication production
reliability.
[0035] An object of some embodiments of various aspects of the
invention is to enhance control of post-layer fabrication process
control, overcome process defects that would otherwise result in
production failures.
[0036] An object of some embodiments of various aspects of the
invention is to ease post-layer fabrication handling.
[0037] An object of some embodiments of various aspects of the
invention is to overcome process defects that might otherwise
result in production failures.
[0038] 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 it may not address any of the objects
set forth above but instead address some other object of the
invention which may be 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.
[0039] A first aspect of the invention provides an electrochemical
fabrication process for producing a multi-layer three-dimensional
structure from a plurality of adhered layers, the process
including: (A) forming a layer by depositing at least one
sacrificial material and at least one structural material onto a
substrate, wherein the substrate may include previously deposited
layers, and wherein the depositing of at least one of the materials
includes an electrodeposition operation; (B) repeating (A) one or
more times such that a plurality of layers are formed and such that
successive layers are formed adjacent to and adhered to previously
formed layers; (C)performing a first etching operation to remove at
least a first portion of at least one material from the plurality
of layers or from the substrate; and (D) performing a second
etching operation, which is distinct from the first etching
operation, to remove at least a portion of at least one material
from the plurality of layer or from the substrate.
[0040] A second aspect of the invention provides an electrochemical
fabrication process for producing a three-dimensional structure
from a plurality of adhered layers, the process including: (A)
forming a layer by depositing at least one sacrificial material and
at least one structural material onto a substrate, wherein the
substrate may include previously deposited layers, and wherein the
depositing of at least one of the materials includes an
electrodeposition operation; (B) repeating (A) one or more times
such that a plurality of layers are formed and such that successive
layers are formed adjacent to and adhered to previously formed
layers; (C) performing a first etching operation to remove at least
a first portion of at least one material from the plurality of
layers or from the substrate; (D) performing an intervening
operation, after performing the first etching operation;
(E)performing a second etching operation, after the intervening
operation, to remove at least a portion of at least one material
from the plurality of layer or from the substrate.
[0041] 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 are configured to implement 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 DESCRIPTION OF THE DRAWINGS
[0042] FIGS. 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.
[0043] FIGS. 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.
[0044] FIGS. 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).
[0045] FIGS. 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.
[0046] FIG. 5(a) depicts a block diagram of the basic operations of
a first group of embodiments.
[0047] FIGS. 5(b)-5(d) depict block diagrams expanding on samples
of alternatives for Operation 2 of FIG. 5.
[0048] FIG. 6(a) depicts a block diagram for a second group of
embodiments.
[0049] FIG. 6(b) depicts a block diagram for a third group of
embodiments.
[0050] FIGS. 7(a)-7(d) schematically provide side views
illustrating various stages of an embodiment of FIG. 6(a) as
applied to a specific group of layers.
[0051] FIGS. 8(a)-8(c) schematically provide side views
illustrating various stages of another embodiment of the
invention.
[0052] FIGS. 9(a)-9(c) schematically provide side views
illustrating various stages of another embodiment of the invention
which may be used to correct a fabrication defect.
[0053] FIGS. 10(a) and 10(b) depict block diagrams of a fourth and
fifth group of embodiments.
[0054] FIG. 11 depicts a perspective view of a coaxial RF device
that may be electrochemically fabricated and could benefit from a
post process multi-step, multi-stage, or multi-operation release of
the structural material.
[0055] FIGS. 12(a)-12(e) schematically depict various stages of an
etching and infiltration process as seen on a horizontal plane (a
plane parallel to the plane of the substrate) mid way through a
coaxial transmission line similar to one of the four branches of
the coaxial device of FIG. 11 where a central conductor can be seen
along with etching holes that extend through each side of the outer
conductor.
[0056] FIG. 13 depicts a perspective view of the coaxial device of
FIG. 10 with an additional shielding structure forming a "chimney"
around the central portion of the structure.
[0057] FIGS. 14(a) and 14(b) depict the structure of FIG. 12 with
the addition of a temporary etch stop layer (shown in FIG. 14(a) as
partially transparent and in FIG. 14(b) as opaque) that shields the
distal regions of the arms of the structure which are outside the
"chimney" region.
[0058] FIG. 15 depicts a perspective view of the same coaxial
device of FIGS. 10 and 12-14 but with a different form of an etch
barrier that aids in providing a multi-stage etching effect.
[0059] FIG. 16 depicts a view of the coaxial device of FIG. 15
where the inside portion of an arm is more clearly visible and it
can be seen that the etching barrier doesn't extend completely to
the substrate.
[0060] FIG. 17(a) depicts an end view of one of the coaxial arms of
the device and etching barrier of FIGS. 15 and 16 while FIG. 17(b)
depicts an end view of the same structure but with a double etching
barrier.
[0061] FIGS. 18(a) and 18(b) depict block diagrams of process
operations associated with sixth and seventh groups of
embodiments.
[0062] FIGS. 19(a)-19(e) schematically depict side views of an
implementation of the process of FIG. 18(a).
DETAILED DESCRIPTION
[0063] FIGS. 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
explicitly set forth herein to yield enhanced embodiments. Still
other embodiments may be derived from combinations of the various
embodiments explicitly set forth herein.
[0064] FIGS. 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 operations 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).
[0065] The various embodiments, alternatives, and techniques
disclosed herein may be used in combination with electrochemical
fabrication techniques that use different types of patterning masks
and masking techniques. For example, conformable contact masks and
masking operations may be used, proximity masks and masking
operations (i.e. operations that use masks that at least partially
selectively shield a substrate by their proximity to the substrate
even if contact is not made) may be used, non-conformable masks and
masking operations (i.e. masks and operations based on masks whose
contact surfaces are not significantly conformable) may be used,
and adhered masks and masking operations (masks and operations that
use masks that are adhered to a substrate onto which selective
deposition or etching is to occur as opposed to only being
contacted to it) may be used.
[0066] FIG. 5(a) depicts a block diagram of the basic elements or
operations of a first group of embodiments. Block 102 indicates
that in a first operation (i.e. Operation 1) a plurality of layers
will be formed (e.g. by electrochemical fabrication) and that the
layers will include: (1) a desired structure that is formed from at
least one structural material, and (2) a sacrificial support
structure that is formed from at least one sacrificial material.
Block 104 indicates that a second operation (i.e. Operation 2) will
include the performance of a plurality of etching operations for
the purpose of removing a desired portion of the at least one
sacrificial material wherein each etching operation is performed
with a desired etchant and a desired process. In the present
application, some embodiments involve use of two or more etching
operations with each separated from the other by at least one "hard
stop" (i.e. fixed or substantially fixed end points for results of
the etching operations). Other embodiments will distinguish
successive etching operations without use of hard stops.
[0067] FIG. 5(b)-5(d) depict block diagrams expanding on examples
of various alternative embodiments for Operation 2 of FIG. 5(a). In
FIG. 5(b), it is indicated that Operation 2 includes at least two
elements: (1) a first etch using a first etchant, 112, and (2) a
second etch using a second etchant that is different from the first
etchant, 114. In the embodiment of FIG. 5(b), the two processes may
be the same with the exception of the etchant used. In FIG. 5(c),
it is indicated that Operation 2 includes at least two elements:
(1) a first etch using an etchant and a first process, 122, and (2)
a second etch using an etchant and a second process that is
different from the first process, 124. In the embodiment of FIG.
5(c), the two etchants may be the same. In FIG. 5(d), it is
indicated that Operation 2 includes at least two elements: (1) a
first etch using a first etchant and a first etchant process, 132,
and (2) a second etch using a second etchant and a second process,
134, wherein the second etchant is different from the first etchant
and the first etching process is different from the second process.
For the purposes of the present application varying the time of
etching is not considered to constitute a different etching
process, but varying the temperature, varying the type of or lack
of agitation, or flow used, varying the concentration of etchant
significantly, varying additives included in the etchant, or
varying other parameters would constitute use of a different
process.
[0068] In FIG. 6(a), it is indicated that Operation 2 includes at
least three elements: (1) a first etch, 142, (2) performance of a
post processing operation on at least a portion of the layers
remaining after the first etch, 144, and (3) a second etch. FIG.
6(a) further provides eight examples of what might be involved in
performance of the second task 144: (A) the performance of an
intermediate etch, 144-1, using a different etchant, a different
process, or both operating on the same or a different material than
that operated on by the first etchant (B) the infiltration of at
least a portion of a void left by the first etch with a material,
144-2, (C) dicing of individual components to separate them from
one another, 144-3, (D) deposition of additional material, 144-4;
(E) removal of some material by other than an etching operation,
such as a planarization operation, 144-5; (F) separating the
structure from the substrate on which it was formed, 144-6; (G)
attaching a secondary substrate or component and possibly removing
the substrate on which the structure was formed, 144-7; and/or (H)
performing a heat treatment operation, 144-8. Of course many other
possible intermediate operations will be readily apparent to those
of skill in the art upon review of the teachings herein.
[0069] In FIG. 6(b) it is indicated that Operation 2 includes at
least three elements: (1) a first etch, 142, (2) performance of an
intervening non-post-processing task, 148, and (3) a second etch,
146. FIG. 6(b) further provides three examples of what might be
involved in the performance of the intervening task 148: (A)
replacement of the etchant that is being used, 148-1; (B) cleaning
of the structure to remove saturated etchant from localized
regions, 148-2; and/or (C) repositioning the structure with respect
to the etchant, e.g. by rotating it with respect to gravity to
improve efficiency, by exposing a different portion of the
structure to the etchant or extracting a portion of the structure
from the etchant, and the like, 148-3. The cleaning noted in (B)
may take the form of a rinse in distilled water, or other substance
that may facilitate removal of the saturated etchant. It may
include agitation of the structure or directed streams of a
cleaning solution.
[0070] Examples of various circumstances in which some of the above
embodiments might be practiced are illustrated in FIGS. 7(a)-7(d),
8(a)-8(c), and 9(a)-9(c).
[0071] FIGS. 7(a)-7(d) illustrate an example where a single
structural material is used in combination with a single
sacrificial material. In this embodiment the desired multi-layer
structure 202 is surrounded by three levels of material. The
multi-layer structure 202 is initially surrounded by a first region
of the sacrificial material 204 (with the exception of where the
structure contacts the substrate 210. The first region of
sacrificial material 204 is surrounded by a barrier 206 (e.g. a
thin barrier) of the structural material (with the exception of
where it contacts the substrate 210 ). A barrier 206 is in turn
surrounded by a second region of the sacrificial material 208 (with
the exception of where it contacts the substrate 210 ).
[0072] The first and second regions of sacrificial material 204 and
208, respectively, may be a consequence of the process that was
used to build up the layers (e.g. the lateral build dimensions may
have fixed extents regardless of the lateral dimensions of the
desired structure 202 and as such what is not part of the desired
structure may generally be formed of sacrificial material). In the
present embodiment the barrier 206 was formed to allow a controlled
etch stop to exist when the etching of region 208 occurs.
[0073] Such a stop may be desirable for a variety of reasons. For
example, if the etchant used to remove the sacrificial material
doesn't have high enough selectively for removing the sacrificial
material as compared to the structural material, regions of the
structural material exposed to the structural material etchant for
longer periods of time or with higher levels of agitations and the
like, may suffer unacceptable levels of damage while structural
material regions exposed to the etchant for shorter periods of time
may not suffer such levels of damage. In such cases the barrier 206
may be used to help ensure a smaller etching time and/or a more
uniform etching time which may improve the quality of the
fabricated structure. In some embodiments, the barrier may be a
rectangular box as shown in FIGS. 7(a) and 7(b) while in other
embodiments the barrier may be have a configuration that conforms
to the shape of the structure or at least partially conforms to the
shape of the structure so as to leave a more uniform thickness of
sacrificial material for the final etching operation or operations
to remove. In some embodiments, the barrier may have a
substantially uniform thickness while in others the barrier may
have a varying thickness, for example, if only the inner surface
conforms to the shape of the desired structure.
[0074] In this process, the etching of the sacrificial material is
preferably performed with an etchant that doesn't attack the
structural material though it may be performed with an etchant that
has a much slower rate of attack (e.g. greater than about 10 times
slower and more preferably greater than about 100 times slower) on
the material of barrier 206 than on the material of 208. Once the
barrier 206 is reached, etching is stopped and some other post
layer fabrication activities may occur. The structural material of
206 can then be etched using a selective etchant that doesn't
attack the sacrificial material of 204 (or attacks it at a much
slower rate). Additional post layer fabrication activities can
occur at this point if desired and then when ready a final etch of
the sacrificial material can occur to expose or release the desired
multi-layer structure 202.
[0075] In some embodiments the sacrificial material may be copper
and the structural material may be nickel, and as such the etchants
may be appropriately selected to etch one but not the other. For
example, the nickel etchant may be Rostrip.RTM. nickel stripper M-7
from Atotech of Enthone-OMI while the copper stripper may be
Enthone C-38 from New Haven, Conn. More particularly the
sacrificial material etchant (e.g. copper etchant) may be chosen
such that it does not significantly attack the structural material
(e.g. nickel) while the structural material etchant need not have
the same differential in selectivity as any slight to moderate
damage to the sacrificial material will not be significant so long
as removal of sacrificial material by the structural material
etchant doesn't cause the etchant to inadvertently reach the body
of the desired structure. Various stages in the multioperation
etching process are exemplified in FIGS. 7(b)-7(d). FIG. 7(b)
depicts the stage after the removal of the outer sacrificial
material 208, FIG. 7(c) depicts the stage of processing after
removal of the barrier 206, and FIG. 7(d) depicts the final stage
where the desired structure 202 is released from sacrificial
material 204. In some alternative embodiments, use of multiple
barrier layers is possible.
[0076] In some other embodiments the sacrificial material, for
example, may be nickel while the structural material may be copper.
The M-7 and C-38 strippers may be used. It is noted that the M-7
stripper can attack copper so it may be desirable to ensure that
the stripper does not reach some portions of the desired structure
202 much sooner than it reaches other portions of the structure. In
such embodiments, use of a conformable barrier or at least a
barrier having an inner surface that is at least partially
conformable to the surface of the desired structure may lead to
more uniform etch time and thus a decrease in risk of damaging the
desired structure.
[0077] FIGS. 8(a)-8(c) depict an example where two different
sacrificial materials are used along with a structural material. In
this process a stop point is still achieved during the etching
process and the number of etching operations are reduced to two
instead of three as in the embodiment illustrated in FIG.
7(a)-7(d). It is possible that the outer sacrificial material may
be the same as the structural material. In FIG. 8(a) a desired
multi-layer structure 202 is surrounded completely by a first
sacrificial material 204 (with the exception of the contact area
with the substrate 214 ) which in turn is surrounded completely by
a second sacrificial material 212 (with the exception of the
contact area with the substrate 214 ). A first etch is used to
remove the second sacrificial material 212 and a second etch is
used to remove the first sacrificial material 204. In different
embodiments desired post layer fabrication processes can occur
before the etching operations, between the etching operations, or
after the etching operations.
[0078] In some embodiments, the inner surface of the second
sacrificial material 212 and the outer surface of the first
sacrificial material 204 may be conformable or partially
conformable to the surface of the desired structure 202 so that
etching time to remove the first sacrificial material is made more
uniform. In some embodiments, analysis of the geometry dependence
of etching rates may be used to derive a configuration for the
interface of the first and second sacrificial materials that leads
to a desired level of uniformity in etching rate (i.e. removal of
sacrificial material so that the desired structure is exposed to
etchant along all or most surfaces at about the same time) where
the resulting configuration deviates from a conformable surface at
least in part due to one or more geometry based etching rate
dependencies such as limited etchant access in certain regions,
limited flow of etchant in certain regions, tendency for etchant to
become saturated in certain regions, and the like.
[0079] FIG. 9(a)-9(c) illustrate an example where a desired
multi-layer structure 202 is formed with imperfections 203. These
imperfections are shown as very thin "streamers" formed from the
same material as structure 202. These imperfections may result from
the structural material being plated underneath ill seated CC masks
or adhered masks that have not been adequately attached to the
substrate or previously formed layer (this phenomenon may be termed
"flash"), from the structural material being smeared into the
sacrificial material during planarization processes (this
phenomenon may be termed "smear"), or from the structural material
being plated into cracks within the sacrificial material (this
phenomenon may be termed "ribbons" and typically results in
structures that are vertically elongated and elongated in one
lateral dimension but very thin in the other lateral dimension). A
first etching operation results in the removal of the sacrificial
material 204 as depicted in FIG. 9(b) but leaves behind the
imperfections. Since the imperfection are very thin, a structural
material etchant may be used to remove the imperfections while
doing little damage to the desired portion of structure 202 as
shown in FIG. 9(c). As the etchant being used to attack the
imperfections also attacks the structure 202, it is important that
etching time be controlled. For enhanced control the selected
etchant may be used in a diluted form (i.e. concentrations of the
etchant that are less than those recommended or largely recognized
as appropriate for the given etchant, e.g. 50%, 25%, 10%, or even
less of the recommended concentration range) or at sub-normal
temperatures (i.e. temperatures below those recommended or largely
recognized as appropriate for the given etchant, e.g. temperatures
5.degree. C., 10.degree. C., 20.degree. C. or more degrees under
that recommended temperature range).
[0080] FIG. 10(a) depicts a block diagram of a fourth group of
embodiments. In this group of embodiments, as with the example of
FIGS. 7(a)-7(d), an etching barrier is formed out of a barrier
material which may be the same as one of the structural materials
or it may be different. The barrier material is chosen based on the
fact that the sacrificial material may be etched without etching
through the barrier material even though in some embodiments it
would be acceptable if the barrier material were damaged by the
etchant. In some embodiments of this group, the etching barrier may
form a permanent part of a structural element even though its
configuration was not part of the intended design. In these
embodiments, the configuration of the barrier material does not
adversely affect the usability of the intended structure. In some
of these embodiments the barrier material may include both a
removable element as well as an element that will become a
permanent part of the structure. In some of these embodiments, the
removable part of the barrier may be removable by, for example,
etching operations, planarization operations, or other machining
operations. In some embodiments, unlike the example of FIGS.
7(a)-7(d), the etching barrier may be constructed to allow etching
access to a portion of the structure while inhibiting etchant from
reaching a different portion of the structure.
[0081] The process of FIG. 10(a) begins with Operation 1,
designated with reference number 242. Operation 1 calls for the
formation of a plurality of layers such that three results are
achieved: (1) a desired structure is formed from at least one
structural material; (2) a sacrificial support structure is formed
from at least one sacrificial material; and (3) an etch barrier is
formed out of a barrier material where the etch barrier includes a
removable element and may also include a permanent structural
element.
[0082] After performance of Operation 1 the process moves forward
to Operation 2, element 244, which calls for, optionally, adding on
of any additional desired etching barrier elements. Such barrier
elements may be positioned at desired locations and held in place
in any appropriate manner, for example, by adhesion, pressure,
retention clips, or the like. These additional barrier elements may
be conductive materials or dielectric materials, rigid materials,
or conformable materials.
[0083] After Operation 2 is completed, the process moved forward to
Operation 3, element 246, which calls for the performance of one or
more etching operations which may or may not be intermixed with
various desired intermediate operations. From Operation 3 the
process moves forward to Operation 4, element 248, which calls for
removal of at least one etching barrier.
[0084] After Operation 4 is complete, the process moves forward to
Operation 5, element 250, which calls for the performance of one or
more additional etching operations which may or may not be
intermixed with various other operations. The completion of
Operation 5 may result in the completed release of the desired
structure from the sacrificial material or alternatively release
may not yet be completed and the process may loop back to element
244, Operation 2, or element 248, Operation 4.
[0085] FIG. 10(b) depicts a process block diagram for a fifth group
of embodiments where an etching barrier is again used but where the
etching barrier is either not attached to the structural material
or substrate or is attached to the structural material or substrate
in an easily removable manner. Such attachment would generally be
of a minimal nature and would be intended to inhibit accidental
release of the barrier material until such a time that it could be
safely removed. Alternatively, the minimal attaching structure
could ensure that movement of the etching barrier does not
adversely impact further etching operations. Examples of minimal
attachment structures could be very thin, horizontal or vertical
extending web-like or post-like structures. Detachment of the
barrier material could occur by gripping the material and snapping
the fragile post or web like elements. The thin element could
possibly be destroyed by passing an electric current through them
or they could possibly be removed by a controlled etching operation
which may attack only the barrier material or it may attack both
the desired structure and the attachment elements of the barrier
material which are preferably delicate enough they will be removed
prior to an intolerable damage to the desired structure
occurring.
[0086] The process of FIG. 10(b) begins with Operation 1, element
262. Operation 1 calls for the formation of a plurality of layers
such that: (1) a desired structure is formed which includes at
least one structural material; (2) a sacrificial support structure
is formed and includes at least one sacrificial material; and (3)
the formation of at least one etch barrier out of a barrier
material where the etch barrier is either not attached to the
desired structure or is attached to the desired structure in an
easily removable manner.
[0087] From Operation 1 the process moves forward to Operation 2
and then to Operation 3 which are the same operations called for in
the process of FIG. 10(a) and are given like reference
numerals.
[0088] The process then moves forward to Operation 4, element 264,
which calls for removing at least one etching barrier with or
without the stopping of the etching of Operation 3. The removal of
the etching barrier will allow a significant enhancement to the
etching process in the region that was previously protected by the
barrier. The completion of Operation 4 may represent the completed
release of the desired structure from the sacrificial material or
alternatively it may represent the reaching of an interim state
from which the process may loop back to Operation 2 or otherwise
continue in a different manner. In some embodiments Operation 3
would be stopped, a different operation performed (e.g. filing the
etched region with a dielectric.
[0089] The embodiments of the processes of FIGS. 10(a) and 10(b)
may be used in a variety of circumstances. Some such circumstances
may involve the desire to locate dielectric materials or other
infiltrated materials at select locations while still retaining at
least some sacrificial material in place so as to keep different
portions of a structure from moving relative to one another prior
to their being locked in position by an infiltrated material.
[0090] Certain devices and structures that are electrochemically
fabricated require or would benefit from dielectric or other
material used as part of the structure, or require that their
elements remain in a particular geometrical relationship with one
another (e.g., as designed), rather than be distorted by stresses,
inertial forces, thermal effects, and so forth. The use of another
structural material to constrain the movement of elements composed
of a primary structural material may be desirable in some cases.
Despite these benefits, in some embodiments, it may not be
desirable to incorporate such a secondary or tertiary structural
material on a layer-by-layer basis during fabrication.
[0091] RF coaxial components made using electrochemical fabrication
as disclosed in U.S. patent application Ser. No. 10/309,521, filed
Dec. 3, 2002, by Brown et al., entitled "Miniature RF and Microwave
Components and Methods for Fabricating Such Components" and
published as US 2003-0222738 A1 and U.S. patent application Ser.
No. 10/607,931, filed Jun. 27, 2003, by Brown et al, entitled
"Miniature RF and Microwave Components and Methods for Fabricating
Such Components" provide examples of devices that may benefit from
a combination of partial etching, infiltration, completed etching,
and potentially a further infiltration. These devices (e.g. coaxial
devices) may benefit in terms of performance or characteristics
from a dielectric (or other) material filling the space between the
center conductor and shield as they may otherwise be subject to
shorting, which would render the devices useless, due to the thin,
poorly-supported center conductor coming into contact with the
shield. Indeed, even if there is no such contact, performance can
be compromised if the gaps between central conductor and shield are
not as-designed.
[0092] FIG. 11 shows a structure similar to some of the coaxial
devices set forth in the '521 and '931 applications, but simplified
for purposes of illustration. After the structure in FIG. 11 is
released by removal of sacrificial material, in principle a
dielectric material can then be introduced. Such introduction may
be achieved by allowing it to wick into the gap between center
conductor 320 and shield 302 by introducing it at an open end of
the structure or through etching holes 314. Alternatively, the
introduction may occur by subjecting the structure to a vacuum
covering the structure with a flowable material and then letting a
gas bleed into the vacuum chamber so as to force the flowable
material into the openings in the shield 302. However, if the
center conductor has already moved from its desired position,
introducing the dielectric material may not improve the
situation.
[0093] The process of FIG. 10(a) may be applied to ensure the
structure is appropriately fabricated. By etching a structure such
as that in FIG. 11 in two stages, it is possible to introduce a new
material (e.g., a dielectric) into at least part of the region
etched during the first stage, before continuing on to the second
stage of etching. Specifically, in the case of the coaxial device
of FIG. 11, the portion of the inner conductor 320 that is located
at the intersection of the two arms of the device may benefit
significantly if this intersection point is retained at its
intended position. Thus, in this example, it is desirable to
stabilize the position of a portion the structure relative to the
position of another portion the structure (e.g. the central
conductor 320 position relative to the position of the shield 302
near the intersection of the arms of the device) by introducing
dielectric material between the center conductor and shield in a
desired region prior to the final etch. After which the remaining
sacrificial material will be etched and if desired, additional
dielectric can be introduced into the rest of the regions between
the shield 320 and central conductor or even to capsulate the
entire structure with the possible exception of central conductor
and shield contact regions.
[0094] A preferred approach is exemplified schematically in FIG.
12(a)-12(e). In FIG. 12(a), a plane of a portion of the coaxial
element is shown from a top view where the plane is chosen to
intersect the plane of central conductor 332 ( 320 in FIG. 11) as
well as the etching and infiltration holes 326 (314 in FIG. 11)
with a sacrificial material 334 filling the space between center
conductor 332 and outer conductive shield 338 (302 in FIG. 11). In
some embodiments sacrificial material may also be located outside
the shield. In FIG. 12(b), one region 342 of the interior of the
coaxial element is shown as having been etched out while leaving
some sacrificial material 334 in place to stabilize the central
conductor 332 thereby preventing it from moving out of position.
Next, the etched region 342 is filled with a dielectric material
344 as shown in FIG. 12(c). With the dielectric material 344 now
stabilizing the central conductor 332, it is now possible to etch
out the remaining sacrificial material 334 leaving open internal
regions 346 and 348 as shown in FIG. 12(d). Finally, if desired,
the resulting open internal spaces may be filled with the same, or
with a different, dielectric 344 as shown in FIG. 12(e).
[0095] The etching and infiltration approach exemplified in FIGS.
12(a)-12(e) may be achieved in different ways. For example, such
approaches may involve etching performed in two or more stages.
[0096] A first example of an etching and infiltration embodiment is
explained with the aid of FIGS. 13 and 14(a) and 14(b). In this
example, a substantially complete shielding of selected regions not
to be etched is provided (with the exception of inside the
structure itself) such that etching will occur only in the
unshielded regions. Etching then occurs. After the initial etching
is performed, infiltration occurs which provides dielectric support
to a desired region. Next the shielding is at least partially
removed then etching of originally shielded regions occurs, and if
desired, dielectric infiltration of the originally shielded regions
occurs. More specifically in the present example, the shielding
includes a permanent structure which is part of the desired
structure, a permanent structure that is not part of the design's
desired or required functionality but which is added as a
processing convenience, and a temporary shielding structure that is
removed after use.
[0097] First a selected chimney region 350 (e.g. the crossing or
intersecting region) to be preferentially etched is surrounded by a
"chimney" structure 348 which is made of structural material. The
chimney structure 348 is electrochemically fabricated along with
the desired structure and it and the chimney may be seen in FIG.
13. The chimney region is further defined by a sheet of structural
material 356 which can be seen in FIG. 14(a). The sheet may be
formed as a layer of the structure (e.g. it may be called a
temporary layer) or it may be added to the structure after layer
formation. The sheet has an opening over the chimney region 350.
The chimney region allows preferential etching while the chimney
structure and sheet shield the sacrificial material elsewhere and
serve as an etch stop. FIG. 14(a) shows the temporary layer over
the structure of FIG. 13, with the entire structure including the
sacrificial material shown as if partially transparent. The sheet
(i.e. temporary layer) is fabricated like any layer, and may be
bonded to the side walls of the chimney structure until it is
planarized away or otherwise removed in a later operation.
[0098] Next a time-controlled etch is performed on the structure of
FIG. 14(a) which removes the sacrificial material within the
central chimney region, including the region between the center
conductor and shield as a result of etchant entering the etching
holes 352 in the sides of the shield. If the etch is stopped once
the central conductor is reached, remaining sacrificial material
somewhat outside the etching shield regions will be remain in place
holding the inner conductor in place. The state of the process is
shown in FIG. 14(b) where the plate is shown as opaque.
[0099] Next, a dielectric is introduced at least between the center
conductor and shield through the etch holes. The dielectric may
optionally fill the chimney area as well. This etch and
infiltration operation may be performed within an electrochemical
fabrication apparatus by inclusion of an appropriate etching
station and infiltration station.
[0100] Next, the previously formed temporary layer is removed or
erased. This removal may occur, for example, by planarization, e.g.
lapping. Alternatively, the removal may occur by etching using an
etchant that attacks the sheet but not the dielectric or the
structural material forming the desired structure. The selectively
between the sheet and the material of the desired structure may
result from either use of a different material for the sheet and
use of an etchant that is selective to that material or
alternatively due to restricted access to the material of the
desired structure as a result of sacrificial material that
separates the sheet and the material of the desired structure. The
removal of the sheet restores the structure to it open
configuration similar to that of FIG. 13 with the exception of the
"cross" region and potentially the chimney region being filled with
a dielectric.
[0101] Next, the remaining sacrificial material is etched. This may
occur after the structure is removed from an electrochemical
fabrication machine (e.g. if such a machine is used in fabrication
of the device) or may be performed within such a machine.
Additional infiltration may be performed if desired.
[0102] A second example of an etching and infiltration embodiment
is explained with the aid of FIGS. 15, 16, and 17(a). In this
example incomplete shielding is provided (i.e. shielding that
doesn't completely block entrance of etchant) in some areas to slow
the etching in those regions such that a differential etching rate
is achieved between shielded and unshielded regions. More
particularly in this example, shielding barriers do not adhere to
structural material that remains as part of the structure and they
do not adhere to the substrate. The barriers in this example are
surrounded by sacrificial material such that once all surrounding
sacrificial material is etched, the barriers can be removed or can
fall away from the structure (e.g. if the structure is etched
up-sided down) and thereby allow or cause a differential in etching
in the initially shielded regions to occur. As a result of the
shielding delays, etching preferably reaches completion in some
regions while not reaching completion in other regions. The initial
etching can then be terminated, the structure cleaned, infiltration
performed in selected regions (e.g. the regions where completion of
etching occurred), etching reinitiated and continued until etching
completion is reached in all regions and then a subsequent
infiltration may be performed if desired. In still other
embodiments, more than two etching stages may be used in
combination with two or more infiltrations being performed.
[0103] In some embodiments, the shields may be configured to form
etching paths of extended length that the etchant must travel along
to get to a desired etching location (i.e. etching is delayed as a
result of the extended path length). In other embodiments etching
delays may be achieved not based so much on extending the length of
the path but instead based on diminishing the sizes of the openings
through which the etchant must travel to access a desired etching
location (i.e. etching is delayed based on diminished etching of
flow path cross-section). In still other embodiments, etching
delays may be based on a more balanced combination of these two
alternative approaches. In some embodiments etching barriers may
have substantially solid walls where etchant is only allowed to
work on removing the shielding by working around the perimeter of
the shields, while in other embodiments the walls may be perforated
with holes such that the etchant can work on removing the barrier
in a less path oriented manner.
[0104] In a second approach, etch barriers are fabricated along
with the device which greatly slows the etching in the region of
the device outside the crossing or intersecting regions of the
arms. Eventually, these barriers become completely released and can
be removed from (or fall away from) the device. The advantage of
the second approach is that no planarization operation or other
operation is required to remove the temporary layer as was required
by the first approach. As a result, it is easy to perform the
entire release and infiltration process outside any electrochemical
fabrication machine that may be used in fabricating the
structure.
[0105] FIGS. 15, 16, and 17(a) show an RF component similar to that
of FIG. 11 but instead of using a chimney structure as was used in
FIGS. 12, 13, and 14(a) and 14(b), an etch barrier 362 is designed
so as to substantially but not completely surround selected
portions of the component. In this example the etch barrier 362
surrounds each of the four `arms` of the component while leaving
the intersecting region of the four arms open so that this central
regions is more directly exposed to the etchant. Where the barriers
are present, the etchant must first etch out the material between
the barrier and the external surface of the shield before the
etchant can access the holes in the sides of the outer conductor
and thereby begin the inward journey to the central conductor.
After a first-stage etch which is timed or otherwise controlled to
remove material between the center conductor and the shield in the
intersecting or crossing region, dielectric can be introduced into
this central region, after which etching can continue until all
sacrificial material is removed. At some point during the etching,
the barriers will be released and can be allowed to fall away
(assuming etching occurs in an upside down manner) or may be
otherwise removed. Since in this design the only etching holes are
in the side walls of the coaxial device, the tops of the etch
barriers might be deleted, so that only two vertical walls are
needed, although that will accelerate their separation from the
device.
[0106] FIG. 17(a) illustrates an end view of one of the arms where
the end of a central conductor 370 can be seen which is surrounded
by the outer conductor 372 of the coaxial line which outer
conductor includes etching holes 374 which cannot be accessed until
sacrificial material along paths 376 is removed, and still cannot
be openly accessed until all sacrificial material between barrier
382 and outer conductor 372 is removed and barrier 382 is
removed.
[0107] FIG. 17(b) illustrates a coaxial element including central
conductor 390 and outer conductor 392 filed with etchant 388 along
with surrounding barriers 394 and 398. The barriers taken together
result in an etching path 396 to reach openings 382 being extended
considerably compared to that illustrated in FIG. 17(a). In some
embodiments, such added delays may be necessary or desired to
ensure complete etching of the material in the intersecting
region.
[0108] FIGS. 18(a) and 18(b) depict block diagrams for two
different groups of embodiments that use multi-stage etching
operations for etching sacrificial material from a multi-layer
structure that is formed on a substrate where the substrate itself
a sacrificial material, e.g. located in passageways and the like,
and/or a component that is attached to the multi-layer structure
that includes a sacrificial material (e.g. located within
passageways and the like). These embodiments may be useful in a
variety of circumstances. For example, the embodiments associated
with the process of FIG. 18(a) may be useful for minimizing the
amount of time that the multi-layer structure is exposed to etchant
when a larger amount of time is needed to remove sacrificial
material from the substrate or other component than is required to
remove sacrificial material from the multi-layer structure. The
converse is true for embodiments related to the process of FIG.
18(b).
[0109] The process of FIG. 18(a) begins with Operation 1, element
402, which calls for the formation of a structure from a plurality
of layers where the structure is formed on a substrate that has
material to be etched or is attached to a component that contains
material to be etched. The layers include a structure of desired
configuration formed from at least one structural material and they
include a sacrificial support structure which is formed from at
least one sacrificial material.
[0110] After formation of the structure, or during formation of the
structure, the process moves forward to Operation 2, element 404.
Operation 2 calls for the formation of a barrier element, either in
conjunction with Operation 1 or alternatively after completion of
Operation 1.
[0111] From Operation 2 the process moves forward to Operation 3,
element 406. Operation 3 calls for performing one or more etching
operations with or without those operations being separated by
intermediate operations and where the etching operations remove at
least part of the sacrificial material from the substrate or
component.
[0112] After Operation 3 the process moves forward to Operation 4
which calls for the removal of at least one etching barrier which
was protecting, at least in part, the materials making up the
multi-layer structure.
[0113] From Operation 4 the process moves forward to Operation 5,
element 410. Operation 5 calls for the performance of one or more
additional etching operations to remove sacrificial material from
the plurality of layers of the multi-layer structure and where the
etching operations may or may not be separated by the performance
of intermediate operations.
[0114] The process of FIG. 18(b) is similar to that of FIG. 18(a)
with a few minor changes. Whereas Operation 2 of the process of
FIG. 18(a) formed or called for an etching barrier that protected
the material of the multi-layer structure, Operation 2 of FIG.
18(b) calls for an etching barrier that protects the substrate or
component from initial attack by an etchant.
[0115] Operation 3 of the process of FIG. 18(b) is similar to
Operation 5 of the process of FIG. 18(a) wherein etching operations
are performed to remove sacrificial material from the plurality of
layers making up the multi-layer structure.
[0116] Operation 4 in each of the processes of FIG. 18(a) and 18(b)
are similar in that they call for the removal of the etching
barrier.
[0117] Operation 5 of FIG. 18(b) is similar to Operation 3 of FIG.
18(a) in that it calls for the performance of one or more etching
operations to remove material from the substrate or component.
[0118] In these groups of embodiments, the fifth operations may
complete the release of the structure and substrate or component
from the sacrificial material or alternatively these operations may
be followed by additional operations that will complete the
process.
[0119] It should also be understood that Operation 5 of FIG. 18(a)
may not only involve etching of the sacrificial material from the
plurality of layers but may also involve the etching of sacrificial
material from the substrate or component. Similarly, Operation 5 of
FIG. 18(b) may not be limited to removing sacrificial material from
the substrate or component but may also involve removal of
additional sacrificial material from the plurality of layers making
up the structure.
[0120] An example embodiment, following the process of FIG. 18(a)
is depicted in FIGS. 19(a)-19(e).
[0121] FIG. 19(a) illustrates a multi-layer structure 452 located
on a substrate 454 where the substrate includes a passage 456
filled with a sacrificial material 462. The multi-layer structure
452 includes regions of sacrificial material 462 and regions of
structural material 464. Though it would be nice to perform an etch
on the sacrificial material of FIG. 19(a) to obtain the structure
of FIG. 19(e) using a single operation, this may not be possible.
If a long etching time is required to remove the sacrificial
material 462 from passage 456, significant damage to the structural
material 464 or interlayer interfaces may occur if the multi-layer
structure is exposed to etchant during entire time necessary to
etch out passage 456. As such, in some circumstances it may be
desirable not to jump from the state shown in FIG. 19(a) to the
state shown in FIG. 19(e) in a single operation. As such, in this
embodiment multiple operations will occur to reach the final goal
depicted in FIG. 19(e).
[0122] In FIG. 19(b) an additional layer 472, which is a barrier
layer, is added to the multi-layer structure. This barrier layer
may be formed of structural material or may be formed of a
different material. It is intended that this barrier layer inhibit
the etchant, which is used for removing the sacrificial material
from passage 456, from reaching the structural material 464. As
indicated, this barrier layer may be formed adjacent to the last
layer of structure or alternatively, with the exception of
connecting to an outer ring of structural material, the barrier
layer may be spaced from the desired structure by one or more
layers of sacrificial material. After the barrier layer 472 is put
in place, an etchant is applied to the combined multi-layer
structure, substrate, and barrier layer where by the etchant
attacks the sacrificial material 462 located in passage 456. The
etching is allowed to proceed for a time that is believed
appropriate for allowing the passage to become largely free of
sacrificial material or even completely free of sacrificial
material.
[0123] As indicated in FIG. 19(c) a small amount of sacrificial
material remains in the channel near the first layer of the
multi-layer structure. After the preliminary etch which
substantially clears channel 456, barrier layer 472 is removed as
indicated in FIG. 19(d). The removal of the barrier layer may occur
via a planarization operation or via an etching operation assuming
that a suitable etchant for preferentially removing the barrier
layer material without damaging the structural material is
possessed or assuming the structural material is separated from the
barrier layer material by a sufficient thickness of sacrificial
material.
[0124] Next, an etchant for removing the sacrificial material is
applied whereby the etchant can remove the sacrificial material
from the multi-layer structure starting at the top layer and
working down while simultaneously the etchant can continue to clear
the passage through the substrate whereby both the passage and the
multi-layer structure are cleared of sacrificial material while
maintaining the exposure of the structural material 464 to the
etchant to a minimum.
[0125] The resulting etched structure, part, component, or device
is shown in FIG. 19(e). The sidewall may or may not be intended to
stay with the final structure and if desired can be removed, for
example by dicing before or after the final etching operation.
[0126] It will be appreciated by those of skill in the art that the
approaches described herein are not limited to the particular
geometries or devices described, but may be applied to a wide
variety of situations in which it is desired to perform a
multi-stage etch, whether for purposes of incorporating an
additional material (e.g., while stabilizing a structure) or not or
whether for the purpose of protecting a specific material or
geometry from undue exposure to an etchant as compared to that
which is needed to achieve the intended purpose. Similarly it will
be understood by those of skill in the art that many variations of
the above processes are possible including, for example, variations
in the numbers of operations, variations in the parameters
associated with the operations, variations in etchants, variations
in the actual processes selected for forming a given multi-layer
structure or given portion of a multi-layer structure.
[0127] Numerous alternative embodiments are possible, for example
the barrier between two sacrificial materials may roughly conform
to the shaped of the desired structure or it may take on some other
complex shape if believed to be advantageous. In other
alternatives, not all etching barriers may completely surround a
desired multi-layer structure, in that certain etchants may be
allowed to contact certain regions of the desired multi-layer
structure but may not be allowed to contact other regions of the
structure where a different structural material is present. Two,
three, or more operations may be involved. Multiple structural
materials may be used. In additional alternative embodiments not
all materials need have contact with the substrate and not all
materials need completely surround other materials. In some
embodiments etching operations may be performed completely using
chemical etchants while in other embodiments electrochemical
etching operations may be performed.
[0128] The various multi-stage etching operations of the various
embodiments of the invention may be performed for a variety of
reasons. For example, such reasons include but are not limited to
(1) allowing separation of multiple structures that were
simultaneously formed on a common substrate prior to exposing what
may be a very fragile multi-layer structure 202 to potential harm;
(2) allowing a fast acting etchant to remove a large portion of the
sacrificial material (which etchant may react negatively with the
structural material) and then switching to a different etchant
before the desired multi-layer structure is exposed; (3) allowing a
more uniform etching time when the desired three-dimensional
structure is exposed to the etchant; and (4) allowing one etchant
to contact a certain portion of the desired multi-layer structure
so as to remove one sacrificial material but not contact another
portion of desired multi-layer structure as it could do damage to a
second structural material in that location.
[0129] The patent applications and patents set forth below are
hereby incorporated by reference herein as if set forth in full.
The teachings in these incorporated applications can be combined
with the teachings of the instant application in many ways: For
example, enhanced methods of producing structures may be derived
from some combinations of teachings, enhanced structures may be
obtainable, enhanced apparatus may be derived, and the like.
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10/434,494 - May 7, 2003 Zhang, "Methods and Apparatus for
Monitoring 2004-0000489A - Jan. 1, 2004 Deposition Quality During
Conformable Contact Mask Plating Operations" 10/434,289 - May 7,
2003 Zhang, "Conformable Contact Masking Methods and 20040065555A -
Apr. 8, 2004 Apparatus Utilizing In Situ Cathodic Activation of a
Substrate" 10/434,294 - May 7, 2003 Zhang, "Electrochemical
Fabrication Methods With 2004-0065550A - Apr. 8, 2004 Enhanced Post
Deposition Processing Enhanced Post Deposition Processing"
10/434,295 - May 7, 2003 Cohen, "Method of and Apparatus for
Forming Three- 2004-0004001A - Jan. 8, 2004 Dimensional Structures
Integral With Semiconductor Based Circuitry" 10/434,315 - May 7,
2003 Bang, "Methods of and Apparatus for Molding 2003-0234179 A -
Dec. 25, 2003 Structures Using Sacrificial Metal Patterns"
10/434,103 - May 7, 2004 Cohen, "Electrochemically Fabricated
Hermetically 2004-0020782A - Feb. 5, 2004 Sealed Microstructures
and Methods of and Apparatus for Producing Such Structures"
XX/XXX,XXX - May 7, 2004 Thompson, "Electrochemically Fabricated
Structures (Docket P-US104-A-MF) Having Dielectric or Active Bases
and Methods of and Apparatus for Producing Such Structures"
10/434,519 - May 7, 2003 Smalley, "Methods of and Apparatus for
2004-0007470A - Jan. 15, 2004 Electrochemically Fabricating
Structures Via Interlaced Layers or Via Selective Etching and
Filling of Voids" 10/724,515 - Nov. 26, 2003 Cohen, "Method for
Electrochemically Forming Structures Including Non-Parallel Mating
of Contact Masks and Substrates" XX/XXX,XXX - May 7, 2004 Cohen,
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Kumar, "Probe Arrays and Method for Making"
[0130] 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 planarization processes. Some
embodiments may involve the selective deposition of a plurality of
different materials on a single layer or on different layers. Some
embodiments may use blanket depositions processes that are not
electrodeposition processes. Some embodiments may use nickel as a
structural material while other embodiments may use different
materials such as gold, silver, copper, zinc, tin, or any other
depositable materials that can be separated from the a sacrificial
material. Some embodiments may use copper as a sacrificial material
while other embodiments may use silver, zinc, tin, or other
materials. Some embodiments using a nickel structural material and
a copper sacrificial material which may be selectively etched using
a sodium chlorite and ammonium hydroxide based etchant such as
Enstrip C-38 sold by Entone-OMI of New Haven, Conn. Such an etchant
may be used in a diluted form or even have components added such as
corrosion inhibitors (e.g. sodium nitrate) to further improve
selectivity of the process.
[0131] 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.
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