U.S. patent application number 11/733195 was filed with the patent office on 2008-02-28 for methods of forming three-dimensional structures having reduced stress and/or curvature.
This patent application is currently assigned to Microfabrica Inc.. Invention is credited to Jorge Sotelo Albarran, Adam L. Cohen, Uri Frodis, Kieun Kim, Ananda H. Kumar, Michael S. Lockard, Dennis R. Smalley.
Application Number | 20080050524 11/733195 |
Document ID | / |
Family ID | 39113789 |
Filed Date | 2008-02-28 |
United States Patent
Application |
20080050524 |
Kind Code |
A1 |
Kumar; Ananda H. ; et
al. |
February 28, 2008 |
Methods of Forming Three-Dimensional Structures Having Reduced
Stress and/or Curvature
Abstract
Electrochemical fabrication processes and apparatus for
producing single layer or multi-layer structures where each layer
includes the deposition of at least two materials and wherein the
formation of at least some layers includes operations for reducing
stress and/or curvature distortion when the structure is released
from a sacrificial material which surrounded it during formation
and possibly when released from a substrate on which it was formed.
Six primary groups of embodiments are presented which are divide
into eleven primary embodiments. Some embodiments attempt to remove
stress to minimize distortion while others attempt to balance
stress to minimize distortion.
Inventors: |
Kumar; Ananda H.; (Fremont,
CA) ; Albarran; Jorge Sotelo; (Santa Clarita, CA)
; Cohen; Adam L.; (Van Nuys, CA) ; Kim; Kieun;
(Van Nuys, CA) ; Lockard; Michael S.; (Lake
Elizabeth, CA) ; Frodis; Uri; (Los Angeles, CA)
; Smalley; Dennis R.; (Newhall, CA) |
Correspondence
Address: |
MICROFABRICA INC.;ATT: DENNIS R. SMALLEY
7911 HASKELL AVENUE
VAN NUYS
CA
91406
US
|
Assignee: |
Microfabrica Inc.
|
Family ID: |
39113789 |
Appl. No.: |
11/733195 |
Filed: |
April 9, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60790327 |
Apr 7, 2006 |
|
|
|
Current U.S.
Class: |
427/289 ;
427/331 |
Current CPC
Class: |
B81C 1/00666 20130101;
C25D 5/022 20130101 |
Class at
Publication: |
427/289 ;
427/331 |
International
Class: |
B05D 1/38 20060101
B05D001/38; B05D 3/00 20060101 B05D003/00 |
Claims
1. In a method of forming a multi-layer three-dimensional
structure, including: (A) forming a plurality of successive layers
of the structure with each successive layer, except for a first
layer, adhered to a previously formed layer and with each
successive layer comprising at least two materials, one of which is
a structural material and the other of which is a sacrificial
material, and wherein each successive layer defines a successive
cross-section of the three-dimensional structure, and wherein the
forming of each of the plurality of successive layers includes: (i)
depositing a first of the at least two materials; (ii) depositing a
second of the at least two materials; and (B) after the forming of
the plurality of successive layers, separating at least a portion
of the sacrificial material from the structural material to reveal
the three-dimensional structure, wherein the improvement comprises:
in association with the formation of at least one of the successive
layers, dividing the layer into a first thin sublayer and a second
thicker sublayer and depositing a primary structural material in a
lateral region of the first sublayer to form at least a portion of
the sublayer, and thereafter planarizing the primary structural
material to a height that bounds the first sublayer, where the
thickness of the first sublayer is similar to a known or estimated
effective work hardened thickness (e.g. preferably having a
thickness between 1/3 and 3 times that of the estimated or known
effective work hardened thickness, more preferably between 1/2 and
2 times that of the estimated or known effective work hardened
thickness, even more preferably within 2/3 and 3/2 times that of
the estimated or known effective work hardened thickness, even more
preferably between 4/5 and 5/4 times that of the estimated or known
effective work hardened thickness, and most preferably between 9/10
and 10/9 times that of the estimated or known effective work
hardened thickness) or less than a known or estimated effective
work hardened thickness induced by the planarization operation, and
thereafter depositing the primary structural material in a lateral
region of the second sublayer, and thereafter planarizing the
primary structural material of the second sublayer.
2. In a method of forming a multi-layer three-dimensional
structure, including: (A) forming a plurality of successive layers
of the structure with each successive layer, except for a first
layer, adhered to a previously formed layer and with each
successive layer comprising at least two materials, one of which is
a structural material and the other of which is a sacrificial
material, and wherein each successive layer defines a successive
cross-section of the three-dimensional structure, and wherein the
forming of each of the plurality of successive layers includes: (i)
depositing a first of the at least two materials; (ii) depositing a
second of the at least two materials; and (B) after the forming of
the plurality of successive layers, separating at least a portion
of the sacrificial material from the structural material to reveal
the three-dimensional structure, wherein the improvement comprises:
in association with the formation of at least one of the successive
layers, depositing a primary structural material in a lateral
region of the layer to form at least a majority of the one
successive layer in the lateral region, and thereafter planarizing
the primary structural material to a height that bounds or exceeds
the desired height of the at least one successive layer and such
that at least a portion of the primary structural material is work
hardened, etching into the primary structural material to form one
or more openings that extend into the one successive layer in a
least a portion of the lateral region to remove at least a portion
of the work hardened primary structural material.
3. The method of claim2 further comprising depositing structural
material into the one or more openings after etching.
4. The method of claim 3 wherein the depositing of structural
material into the one or more openings occurs during deposition
associated with formation of a subsequent successive layer.
5. The method of claim 3 wherein the depositing of structural
material into the one or more openings occurs prior to being a
deposition associated with formation of a subsequent successive
layer.
6. The method of clam 1 where curvature during formation of the
structure is reduced by forming the structure on a thick rigid
substrate.
7. The method of claim 1 where curvature during formation of the
structure is reduced by plating material periodically on the back
side of the substrate as a thickness of deposited material on the
front side of increase.
8. The method of claim 8 wherein the material plated on the back
side of the substrate is planarized after it is deposited.
9. In a method of forming a multi-layer three-dimensional
structure, including: (A) forming a plurality of successive layers
of the structure with each successive layer, except for a first
layer, adhered to a previously formed layer and with each
successive layer comprising at least two materials, one of which is
a structural material and the other of which is a sacrificial
material, and wherein each successive layer defines a successive
cross-section of the three-dimensional structure, and wherein the
forming of each of the plurality of successive layers includes: (i)
depositing a first of the at least two materials; (ii) depositing a
second of the at least two materials; and (B) after the forming of
the plurality of successive layers, separating at least a portion
of the sacrificial material from the structural material to reveal
the three-dimensional structure, wherein the improvement comprises:
forming at least one layer such that a primary structural material
on the layer is provided with an upper surface configuration,
planarizing the upper surface, and thereafter forming notches in
the planarized surface in a desired pattern where the notches
provide decoupling of stress located in separated regions of
structural material.
Description
RELATED APPLICATIONS
[0001] This application claims benefit to U.S. Provisional Patent
Application No. 60/790,327, filed Apr. 7, 2006 and this application
is a continuation-in-part of U.S. patent application Ser. No.
10/434,519, filed May 7, 2003 which in turn claims benefit of U.S.
Provisional Patent Application No. 60/379,130, filed May 7, 2002;
the present application is also a continuation in part of U.S.
patent application Ser. No. 11/029,220, filed Jan. 3, 2005 which
claims benefit of U.S. Provisional Patent Application Nos.
60/534,159 and 60/534,183, both filed Dec. 31, 2003. These
referenced applications are incorporated herein by reference as if
set forth in full herein
FIELD OF THE INVENTION
[0002] Embodiments of this invention relate to the field of
electrochemical fabrication and the associated formation of
micro-scale or meso-scale single layer or multi-layer
three-dimensional structures and more specifically to the use of
electrochemical fabrication processes that produce
three-dimensional single layer or multi-layer structures having
reduced stress, curvature, and/or other stress induced
distortions.
BACKGROUND OF THE INVENTION
[0003] An electrochemical fabrication technique for forming
three-dimensional structures from a plurality of adhered layers is
being commercially pursued by Microfabrica Inc. (formerly
MEMGen.RTM. Corporation) of Van Nuys, Calif. under the name
EFAB.TM..
[0004] Various electrochemical fabrication techniques were
described in U.S. Pat. No. 6,027,630, issued on Feb. 22, 2000 to
Adam Cohen. Some embodiments of this electrochemical fabrication
technique allows the selective deposition of a material using a
mask that includes a patterned conformable material on a support
structure that is independent of the substrate onto which plating
will occur. When desiring to perform an electrodeposition using the
mask, the conformable portion of the mask is brought into contact
with a substrate, but not adhered or bonded to the substrate, while
in the presence of a plating solution such that the contact of the
conformable portion of the mask to the substrate inhibits
deposition at selected locations. For convenience, these masks
might be generically called conformable contact masks; the masking
technique may be generically called a conformable contact mask
plating process. More specifically, in the terminology of
Microfabrica Inc. such masks have come to be known as INSTANT
MASKS.TM. and the process known as INSTANT MASKING.TM. or INSTANT
MASK.TM. plating. Selective depositions using conformable contact
mask plating may be used to form single selective deposits of
material or may be used in a process to form multi-layer
structures. The teachings of the '630 patent are hereby
incorporated herein by reference as if set forth in full herein.
Since the filing of the patent application that led to the above
noted patent, various papers about conformable contact mask plating
(i.e. INSTANT MASKING) and electrochemical fabrication have been
published: [0005] (1) A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U.
Frodis and P. Will, "EFAB:
[0006] 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. [0007] (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. [0008] (3) A. Cohen, "3-D
Micromachining by Electrochemical Fabrication", Micromachine
Devices, March 1999. [0009] (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. [0010] (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. [0011] (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. [0012] (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.
[0013] (8) A. Cohen, "Electrochemical Fabrication (EFAB.TM.)",
Chapter 19 of The MEMS Handbook, edited by Mohamed Gad-El-Hak, CRC
Press, 2002. [0014] (9) Microfabrication--Rapid Prototyping's
Killer Application", pages 1-5 of the Rapid Prototyping Report,
CAD/CAM Publishing, Inc., June 1999.
[0015] The disclosures of these nine publications are hereby
incorporated herein by reference as if set forth in full
herein.
[0016] An electrochemical deposition for forming multilayer
structures may be carried out in a number of different ways as set
forth in the above patent and publications. In one form, this
process involves the execution of three separate operations during
the formation of each layer of the structure that is to be formed:
[0017] 1. Selectively depositing at least one material by
electrodeposition upon one or more desired regions of a substrate.
Typically this material is either a structural material or a
sacrificial material. [0018] 2. Then, blanket depositing at least
one additional material by electrodeposition so that the additional
deposit covers both the regions that were previously selectively
deposited onto, and the regions of the substrate that did not
receive any previously applied selective depositions. Typically
this material is the other of a structural material or a
sacrificial material. [0019] 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.
[0020] After formation of the first layer, one or more additional
layers may be formed adjacent to an immediately preceding layer and
adhered to the smoothed surface of that preceding layer. These
additional layers are formed by repeating the first through third
operations one or more times wherein the formation of each
subsequent layer treats the previously formed layers and the
initial substrate as a new and thickening substrate.
[0021] Once the formation of all layers has been completed, at
least a portion of at least one of the materials deposited is
generally removed by an etching process to expose or release the
three-dimensional structure that was intended to be formed. The
removed material is a sacrificial material while the material that
forms part of the desired structure is a structural material.
[0022] The preferred method of performing the selective
electrodeposition involved in the first operation is by conformable
contact mask plating. In this type of plating, one or more
conformable contact (CC) masks are first formed. The CC masks
include a support structure onto which a patterned conformable
dielectric material is adhered or formed. The conformable material
for each mask is shaped in accordance with a particular
cross-section of material to be plated (the pattern of conformable
material is complementary to the pattern of material to be
deposited). At least one CC mask is used for each unique
cross-sectional pattern that is to be plated.
[0023] The support for a CC mask is typically a plate-like
structure formed of a metal that is to be selectively electroplated
and from which material to be plated will be dissolved. In this
typical approach, the support will act as an anode in an
electroplating process. In an alternative approach, the support may
instead be a porous or otherwise perforated material through which
deposition material will pass during an electroplating operation on
its way from a distal anode to a deposition surface. In either
approach, it is possible for multiple CC masks to share a common
support, i.e. the patterns of conformable dielectric material for
plating multiple layers of material may be located in different
areas of a single support structure. When a single support
structure contains multiple plating patterns, the entire structure
is referred to as the CC mask while the individual plating masks
may be referred to as "submasks". In the present application such a
distinction will be made only when relevant to a specific point
being made.
[0024] In preparation for performing the selective deposition of
the first operation, the conformable portion of the CC mask is
placed in registration with and pressed against a selected portion
of (1) the substrate, (2) a previously formed layer, or (3) a
previously deposited portion of a layer on which deposition is to
occur. The pressing together of the CC mask and relevant substrate
occur in such a way that all openings, in the conformable portions
of the CC mask contain plating solution. The conformable material
of the CC mask that contacts the substrate acts as a barrier to
electrodeposition while the openings in the CC mask that are filled
with electroplating solution act as pathways for transferring
material from an anode (e.g. the CC mask support) to the
non-contacted portions of the substrate (which act as a cathode
during the plating operation) when an appropriate potential and/or
current are supplied.
[0025] An example of a CC mask and CC mask plating are shown in
FIGS. 1A-1C. FIG. 1A shows a side view of a CC mask 8 consisting of
a conformable or deformable (e.g. elastomeric) insulator 10
patterned on an anode 12. The anode has two functions. 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.
FIG. 1A also depicts a substrate 6, separated from mask 8,onto
which material will be deposited during the process of forming a
layer. CC mask plating selectively deposits material 22 onto
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. 1B. After deposition, the CC mask is
separated, preferably non-destructively, from the substrate 6 as
shown in FIG. 1C.
[0026] The CC mask plating process is distinct from a
"through-mask" plating process in that in a through-mask plating
process the separation of the masking material from the substrate
would occur destructively. Furthermore in a through mask plating
process, opening in the masking material are typically formed while
the masking material is in contact with and adhered to the
substrate. As with through-mask plating, CC mask plating deposits
material selectively and simultaneously over the entire layer. The
plated region may consist of one or more isolated plating regions
where these isolated plating regions may belong to a single
structure that is being formed or may belong to multiple structures
that are being formed simultaneously. In CC mask plating as
individual masks are not intentionally destroyed in the removal
process, they may be usable in multiple plating operations.
[0027] Another example of a CC mask and CC mask plating is shown in
FIGS. 1D-1G. FIG. 1D shows an anode 12' separated from a mask 8'
that includes a patterned conformable material 10' and a support
structure 20. FIG. 1D also depicts substrate 6 separated from the
mask 8'. FIG. 1E illustrates the mask 8' being brought into contact
with the substrate 6. FIG. 1F illustrates the deposit 22' that
results from conducting a current from the anode 12' to the
substrate 6. FIG. 1G illustrates the deposit 22' on substrate 6
after separation from mask 8'. In this example, an appropriate
electrolyte is located between the substrate 6 and the anode 12'
and a current of ions coming from one or both of the solution and
the anode are conducted through the opening in the mask to the
substrate where material is deposited. This type of mask may be
referred to as an anodeless INSTANT MASK.TM. (AIM) or as an
anodeless conformable contact (ACC) mask.
[0028] Unlike through-mask plating, CC mask plating allows CC masks
to be formed completely separate from the substrate on which
plating is to occur (e.g. separate from a three-dimensional (3D)
structure that is being formed). CC masks may be formed in a
variety of ways, for example, using a photolithographic process.
All masks can be generated simultaneously, e.g. prior to structure
fabrication rather than during it. This separation makes possible a
simple, low-cost, automated, self-contained, and internally-clean
"desktop factory" that can be installed almost anywhere to
fabricate 3D structures, leaving any required clean room processes,
such as photolithography to be performed by service bureaus or the
like.
[0029] An example of the electrochemical fabrication process
discussed above is illustrated in FIGS. 2A-2F. These figures show
that the process involves deposition of a first material 2 which is
a sacrificial material and a second material 4 which is a
structural material. The CC mask 8, in this example, includes a
patterned conformable material (e.g. an elastomeric dielectric
material) 10 and a support 12 which is made from deposition
material 2. The conformal portion of the CC mask is pressed against
substrate 6 with a plating solution 14 located within the openings
16 in the conformable material 10. An electric current, from power
supply 18, is then passed through the plating solution 14 via (a)
support 12 which doubles as an anode and (b) substrate 6 which
doubles as a cathode. FIG. 2A illustrates that the passing of
current causes material 2 within the plating solution and material
2 from the anode 12 to be selectively transferred to and plated on
the substrate 6. After electroplating the first deposition material
2 onto the substrate 6 using CC mask 8, the CC mask 8 is removed as
shown in FIG. 2B. FIG. 2C depicts the second deposition material 4
as having been blanket-deposited (i.e. non-selectively deposited)
over the previously deposited first deposition material 2 as well
as over the other portions of the substrate 6. The blanket
deposition occurs by electroplating from an anode (not shown),
composed of the second material, through an appropriate plating
solution (not shown), and to the cathode/substrate 6. The entire
two-material layer is then planarized to achieve precise thickness
and flatness as shown in FIG. 2D. After repetition of this process
for all layers, the multi-layer structure 20 formed of the second
material 4 (i.e. structural material) is embedded in first material
2 (i.e. sacrificial material) as shown in FIG. 2E. The embedded
structure is etched to yield the desired device, i.e. structure 20,
as shown in FIG. 2F.
[0030] Various components of an exemplary manual electrochemical
fabrication system 32 are shown in FIGS. 3A-3C. The system 32
consists of several subsystems 34, 36, 38, and 40. The substrate
holding subsystem 34 is depicted in the upper portions of each of
FIGS. 3A-3C and includes several components: (1) a carrier 48, (2)
a metal substrate 6 onto which the layers are deposited, and (3) a
linear slide 42 capable of moving the substrate 6 up and down
relative to the carrier 48 in response to drive force from actuator
44. Subsystem 34 also includes an indicator 46 for measuring
differences in vertical position of the substrate which may be used
in setting or determining layer thicknesses and/or deposition
thicknesses. The subsystem 34 further includes feet 68 for carrier
48 which can be precisely mounted on subsystem 36.
[0031] The CC mask subsystem 36 shown in the lower portion of FIG.
3A includes several components: (1) a CC mask 8 that is actually
made up of a number of CC masks (i.e. submasks) that share a common
support/anode 12, (2) precision X-stage 54, (3) precision Y-stage
56, (4) frame 72 on which the feet 68 of subsystem 34 can mount,
and (5) a tank 58 for containing the electrolyte 16. Subsystems 34
and 36 also include appropriate electrical connections (not shown)
for connecting to an appropriate power source (not shown) for
driving the CC masking process.
[0032] The blanket deposition subsystem 38 is shown in the lower
portion of FIG. 3B and includes several components: (1) an anode
62, (2) an electrolyte tank 64 for holding plating solution 66, and
(3) frame 74 on which 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 (not shown) for
driving the blanket deposition process.
[0033] The planarization subsystem 40 is shown in the lower portion
of FIG. 3C and includes a lapping plate 52 and associated motion
and control systems (not shown) for planarizing the
depositions.
[0034] In addition to teaching the use of CC masks for
electrodeposition purposes, the '630 patent also teaches that the
CC masks may be placed against a substrate with the polarity of the
voltage reversed and material may thereby be selectively removed
from the substrate. It indicates that such removal processes can be
used to selectively etch, engrave, and polish a substrate, e.g., a
plaque.
[0035] The '630 patent further indicates that the electroplating
methods and articles disclosed therein allow fabrication of devices
from thin layers of materials such as, e.g., metals, polymers,
ceramics, and semiconductor materials. It further indicates that
although the electroplating embodiments described therein have been
described with respect to the use of two metals, a variety of
materials, e.g., polymers, ceramics and semiconductor materials,
and any number of metals can be deposited either by the
electroplating methods therein, or in separate processes that occur
throughout the electroplating method. It indicates that a thin
plating base can be deposited, e.g., by sputtering, over a deposit
that is insufficiently conductive (e.g., an insulating layer) so as
to enable subsequent electroplating. It also indicates that
multiple support materials (i.e. sacrificial materials) can be
included in the electroplated element allowing selective removal of
the support materials.
[0036] The '630 patent additionally teaches that the electroplating
methods disclosed therein can be used to manufacture elements
having complex microstructure and close tolerances between parts.
An example is given with the aid of FIGS. 14A-14E of that patent.
In the example, elements having parts that fit with close
tolerances, e.g., having gaps between about 1-5 um, including
electroplating the parts of the device in an unassembled,
preferably pre-aligned, state and once fabricated. In such
embodiments, the individual parts can be moved into operational
relation with each other or they can simply fall together. Once
together the separate parts may be retained by clips or the
like.
[0037] Another method for forming microstructures from
electroplated metals (i.e. using electrochemical fabrication
techniques) is taught in U.S. Pat. No. 5,190,637 to Henry Guckel,
entitled "Formation of Microstructures by Multiple Level Deep X-ray
Lithography with Sacrificial Metal layers". This patent teaches the
formation of metal structure utilizing through mask exposures. A
first layer of a primary metal is electroplated onto an exposed
plating base to fill a void in a photoresist (the photoresist
forming a through mask having a desired pattern of openings), the
photoresist is then removed and a secondary metal is electroplated
over the first layer and over the plating base. The exposed surface
of the secondary metal is then machined down to a height which
exposes the first metal to produce a flat uniform surface extending
across both the primary and secondary metals. Formation of a second
layer may then begin by applying a photoresist over the first layer
and patterning it (i.e. to form a second through mask) and then
repeating the process that was used to produce the first layer to
produce a second layer of desired configuration. The process is
repeated until the entire structure is formed and the secondary
metal is removed by etching. The photoresist is formed over the
plating base or previous layer by casting and patterning of the
photoresist (i.e. voids formed in the photoresist) are formed by
exposure of the photoresist through a patterned mask via X-rays or
UV radiation and development of the exposed or unexposed areas.
[0038] The '637 patent teaches the locating of a plating base onto
a substrate in preparation for electroplating materials onto the
substrate. The plating base is indicated as typically involving the
use of a sputtered film of an adhesive metal, such as chromium or
titanium, and then a sputtered film of the metal that is to be
plated. It is also taught that the plating base may be applied over
an initial layer of sacrificial material (i.e. a layer or coating
of a single material) on the substrate so that the structure and
substrate may be detached if desired. In such cases after formation
of the structure the sacrificial material forming part of each
layer of the structure may be removed along the initial sacrificial
layer to free the structure. Substrate materials mentioned in the
'637 patent include silicon, glass, metals, and silicon with
protected semiconductor devices. A specific example of a plating
base includes about 150 angstroms of titanium and about 300
angstroms of nickel, both of which are sputtered at a temperature
of 160.degree. C. In another example it is indicated that the
plating base may consist of 150 angstroms of titanium and 150
angstroms of nickel where both are applied by sputtering.
[0039] Electrochemical Fabrication provides the ability to form
prototypes and commercial quantities of miniature objects, parts,
structures, devices, and the like at reasonable costs and in
reasonable times. In fact, Electrochemical Fabrication is an
enabler for the formation of many structures that were hitherto
impossible to produce. Electrochemical Fabrication opens the
spectrum for new designs and products in many industrial fields.
Even though Electrochemical Fabrication offers this new capability
and it is understood that Electrochemical Fabrication techniques
can be combined with designs and structures known within various
fields to produce new structures, certain uses for Electrochemical
Fabrication provide designs, structures, capabilities and/or
features not known or obvious in view of the state of the art.
[0040] A need exists in various fields for miniature devices having
improved characteristics, reduced fabrication times, reduced
fabrication costs, simplified fabrication processes, greater
versatility in device design, improved selection of materials,
improved material properties, more cost effective and less risky
production of such devices, and/or more independence between
geometric configuration and the selected fabrication process.
SUMMARY OF THE INVENTION
[0041] It is an object of some embodiments of the invention to
provide an enhanced electrochemical fabrication process capable of
forming structures with reduced internal stress.
[0042] It is an object of some embodiments of the invention to
provide an enhanced electrochemical fabrication process capable of
forming structures exhibiting reduced curvature distortion.
[0043] Other objects and advantages of various embodiments of the
invention will be apparent to those of skill in the art upon review
of the teachings herein. The various embodiments of the invention,
set forth explicitly herein or otherwise ascertained from the
teachings herein, may address one or more of the above objects
alone or in combination, or alternatively may address some other
object of the invention ascertained from the teachings herein. It
is not necessarily intended that all objects be addressed by any
single aspect of the invention even though that may be the case
with regard to some aspects.
[0044] Each of the first through fourteenth aspects of the
invention provide a method of forming a multi-layer
three-dimensional structure, including: (A) forming a plurality of
successive layers of the structure with each successive layer,
except for a first layer, adhered to a previously formed layer and
with each successive layer comprising at least two materials, one
of which is a structural material and the other of which is a
sacrificial material, and wherein each successive layer defines a
successive cross-section of the three-dimensional structure, and
wherein the forming of each of the plurality of successive layers
includes: (i) depositing a first of the at least two materials;
(ii) depositing a second of the at least two materials; and (B)
after the forming of the plurality of successive layers, separating
at least a portion of the sacrificial material from the structural
material to reveal the three-dimensional structure.
[0045] The first aspect of the invention additionally includes, in
association with the formation of at least one of the successive
layers, dividing the layer into a first thin sublayer and a second
thicker sublayer and depositing a primary structural material in a
lateral region of the first sublayer to form at least a portion of
the sublayer, and thereafter planarizing the primary structural
material to a height that bounds the first sublayer, where the
thickness of the first sublayer is similar to a known or estimated
effective work hardened thickness (e.g. preferably having a
thickness between 1/3 and 3 times that of the estimated or known
effective work hardened thickness, more preferably between 1/2 and
2 times that of the estimated or known effective work hardened
thickness, even more preferably within 2/3 and 3/2 times that of
the estimated or known effective work hardened thickness, even more
preferably between 4/5 and 5/4 times that of the estimated or known
effective work hardened thickness, and most preferably between 9/10
and 10/9 times that of the estimated or known effective work
hardened thickness) or less than a known or estimated effective
work hardened thickness induced by the planarization operation, and
thereafter depositing the primary structural material in a lateral
region of the second sublayer, and thereafter planarizing the
primary structural material of the second sublayer.
[0046] The second aspect of the invention additionally includes, in
association with the formation of at least one of the successive
layers, dividing the layer into a first thin sublayer and a second
thicker sublayer, where the thickness of the first sublayer is
substantially less than that of the second sublayer thickness (e.g.
it is preferably less than 30%, more preferably less than 20%, and
most preferably less than 10% of the second sublayer thickness) and
depositing a primary structural material in a lateral region of the
first sublayer to form at least a portion of the sublayer, and
thereafter planarizing the primary structural material to a height
that bounds the first sublayer, and thereafter depositing the
primary structural material in a lateral region of the second
sublayer, and thereafter planarizing the primary structural
material of the second sublayer.
[0047] The third aspect of the invention additionally includes, in
association with the formation of a first layer to which each
successive layer will be adhered, depositing a primary structural
material in a lateral region of the first layer to form at least a
portion of the first layer, thereafter planarizing the upper
surface of the first layer, prior to or after forming one or more
successive layers, planarizing the bottom surface of the first
layer.
[0048] The fourth aspect of the invention additionally includes,
forming one or more successive layers on one or more previously
formed layers such that the one or more layers are formed on the
upper surfaces of the one or more previously formed layers and then
reversing a build orientation such that one or more additional
layers are formed on the bottom surface of a first formed layer of
the previously formed layer or layers.
[0049] The fifth aspect of the invention additionally includes, in
association with the formation of at least one of the successive
layers, depositing a primary structural material in a lateral
region of the layer to form at least a majority of the one
successive layer in the lateral region, and thereafter planarizing
the primary structural material to a height that bounds or exceeds
the desired height of the at least one successive layer and such
that at least a portion of the primary structural material is work
hardened, etching into the primary structural material to form one
or more openings that extend into the one successive layer in a
least a portion of the lateral region to remove at least a portion
of the work hardened primary structural material.
[0050] The sixth aspect of the invention additionally includes, in
association with the formation of at least one of the successive
layers, depositing a primary structural material in a lateral
region of the layer to form at least a majority of the one
successive layer in the lateral region, and thereafter planarizing
the primary structural material to form a surface of the one
successive layer, and thereafter sequentially exposing portions of
the surface to selected radiation that provides the exposed
portions with an elevated temperature and results in less
distortion of the lateral region after the separating than would
exist in absence of the exposing.
[0051] The seventh aspect of the invention additionally includes,
in association with the formation of at least one of the successive
layers, depositing a primary structural material in a lateral
region of the layer to form at least a majority of the one
successive layer in the lateral region, and thereafter planarizing
the primary structural material to form a surface of the one
successive layer, and thereafter sequentially exposing portions of
the surface to selected laser radiation which results in less
distortion of the lateral region after the separating than would
exist in absence of the exposing.
[0052] The eighth aspect of the invention additionally includes, in
association with the formation of at least one of the successive
layers, depositing a primary structural material in a lateral
region of the layer to form at least a majority of the one
successive layer in the lateral region, and thereafter planarizing
the primary structural material to form a surface of the one
successive layer, and thereafter exposing at least a portion of the
surface to selected radiation which results in less distortion of
the lateral region after the separating than would exist in absence
of the exposing.
[0053] The ninth aspect of the invention additionally includes, in
association with the formation of at least one of the successive
layers, depositing a primary structural material in a lateral
region of the layer to form at least a majority of the one
successive layer in the lateral region, and thereafter planarizing
the primary structural material to form a surface of the one
successive layer, and thereafter applying heat to selected portions
of the surface or to the surface as a whole which results in less
distortion of the lateral region after the separating than would
exist in absence of the heating
[0054] The tenth aspect of the invention additionally includes
forming at least one layer such that a primary structural material
on the layer is provided with an upper surface configuration that
is not planar but instead is made to include a plurality of
alternating surface recessions and elevations (e.g. where the
recessions are relatively narrow. e.g. preferably narrower than 10
um, more preferably narrower than 5 um, even more preferably
thinner than 2 um, and most preferably thinner than 1 um) and where
the height difference between the recessions and elevations is
preferably larger than a depth of work hardening that the surface
of the layer may experience during a planarization operations)
which provide decoupling of stress found within the elevations
[0055] The eleventh aspect of the invention additionally includes,
forming at least one layer such that a primary structural material
on the layer is provided with an upper surface configuration,
planarizing the upper surface, and thereafter forming notches in
the planarized surface in a desired pattern where the notches
provide decoupling of stress located in separated regions of
structural material.
[0056] The twelfth aspect of the invention additionally includes,
in association with the formation of at least one of the successive
layers, depositing a primary structural material in a lateral
region of the layer to form the majority of the one successive
layer in the lateral region, wherein the primary structural
material is a material that cannot be planarized reasonably and
effectively by diamond fly cutting and thereafter depositing a
secondary structural material in the lateral region of the one
successive layer over the primary structural material, wherein the
secondary structural material can be planarized reasonably and
effectively by diamond fly cutting, and then planarizing the
secondary structural material using diamond fly cutting.
[0057] The thirteenth aspect of the invention additionally
includes, in association with the formation of at least one of the
successive layers, depositing a primary structural material in a
lateral region of the layer to form the majority of the one
successive layer in the lateral region, and thereafter depositing a
secondary structural material in the lateral region of the one
successive layer over the primary structural material, wherein the
secondary structural material has a higher tensile stress than the
primary structural material, and then planarizing the secondary
structural material without planarizing the primary structural
material.
[0058] The fourteenth aspect of the invention additionally includes
in association with the formation of at least one of the successive
layers, depositing a primary structural material in a lateral
region of the layer to form at least a majority of the one
successive layer in the lateral region, and thereafter planarizing
the primary structural material to a height that is less than a
desired height of the layer and thereafter depositing at least one
secondary structural material to the lateral region to bring the
height of the deposited primary and secondary structural materials
to a height at least as great as the desired height of the layer,
wherein the secondary structural material has a tensile stress
greater than a tensile stress of the primary structural material
prior to the planarization of the primary structural material.
[0059] Additional aspects of the invention provide the additions of
the above noted aspects to the formation of the single layers
structures as opposed to multiple layer structures.
[0060] Additional aspects of the invention provide products
produced by the above noted method aspects of the invention.
[0061] Further aspects of the invention will be understood by those
of skill in the art upon reviewing the teachings herein. Other
aspects of the invention may involve apparatus that can be used in
implementing one or more of the above process aspects of the
invention or devices formed using one of the above process aspects
of the invention. These other aspects of the invention may provide
various combinations of the aspects, embodiments, and associated
alternatives explicitly set forth herein as well as provide other
configurations, structures, functional relationships, and processes
that have not been specifically set forth above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0062] FIGS. 1A-1C schematically depict side views of various
stages of a CC mask plating process, while FIGS. 1D-G schematically
depict a side views of various stages of a CC mask plating process
using a different type of CC mask.
[0063] FIGS. 2A-2F schematically depict side views of various
stages of an electrochemical fabrication process as applied to the
formation of a particular structure where a sacrificial material is
selectively deposited while a structural material is blanket
deposited.
[0064] FIGS. 3A-3C schematically depict side views of various
example subassemblies that may be used in manually implementing the
electrochemical fabrication method depicted in FIGS. 2A-2F.
[0065] FIGS. 4A-4F 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
[0066] FIG. 4G depicts the completion of formation of the first
layer resulting from planarizing the deposited materials to a
desired level.
[0067] FIGS. 4H and 4I respectively depict the state of the process
after formation of the multiple layers of the structure and after
release of the structure from the sacrificial material.
[0068] FIGS. 5A-5D provides a comparison between a structure,
formed from one layer, that is curvature free and one that has
unintended curvature which is released from a substrate.
[0069] FIGS. 6A-6D provides a comparison between a structure,
formed from two layers, that is curvature free and one that has
unintended curvature where the second layer is cantilevered
relative to the first layer and where the first layer remains
adhered to a substrate.
[0070] FIGS. 7A-7D provides a comparison between a structure,
formed from two layers, that is curvature free and one that has
unintended curvature which is released from a substrate via a
sacrificial release layer (i.e. a material layer) located between
structure and the substrate.
[0071] FIGS. 8A-8D provides a comparison between a structure,
formed from three layers, that is curvature free and one that has
unintended curvature where the second layer is cantilevered
relative to the first layer and wherein the first layer remains
adhered to a substrate.
[0072] FIG. 9 depicts a side view of an example structure where
different portions of the layers of the structure are divided into
different categories (up-facing, down-facing, both up- and
down-facing, or continuing) based on their geometric relationship
to elements of an immediately succeeding layer and to elements of
an immediately preceding layer.
[0073] FIGS. 10A and 10B provide side views of two designs of
three-dimensional structures that may be cross-sectioned into
layers (e.g. eight layers) to produce identical cross-sectional
representations that may be the basis for driving the fabrication
of identical three-dimensional multi-layer structures.
[0074] FIGS. 10C-10M provide examples of how different portions of
the various cross-sections may be categorized differently to define
distinct structural regions so that different fabrication
techniques (e.g. curvature reduction techniques) may be applied to
the formation of distinct portions of the structure.
[0075] FIGS. 11A-12B provide side views of cantilever structures
supported from a single side where length and thickness
requirements are specified for special identification or where
layers of structural material are distinguished depending on
whether or not they meet the identification requirements.
[0076] FIGS. 13A-14B provide side views of cantilever structures
supported from both ends where length and thickness requirements
are specified for special identification or where layers of
structural material are distinguished depending on whether or not
they meet the identification requirements.
[0077] FIG. 15 provides a block diagram setting forth a brief
description of each of the six groups of embodiments and each of
the eleven primary embodiments set forth herein.
[0078] FIG. 16 provide block diagram setting forth examples of
options associated with with fourth embodiment of the
invention.
[0079] FIG. 17A provides a generalized flowchart of a first
embodiment of invention where the process of forming at least one
layer of the structure is modified to reduced curvature by forming
the at least one layer from a first sublayer having a thickness
that is less than or equal to work hardening thickness and a second
sublayer that has a thickness that is the layer thickness minus the
thickness of the first sublayer.
[0080] FIG. 17B provides a more specific set of steps or operations
for a specific implementation of the first embodiment of the
invention.
[0081] FIG. 17C provides a variation of the first embodiment of the
invention where the curvature reduction technique may be applied to
only selected lateral portions of layers as opposed to the entire
layers and where two optional branches of the process are
illustrated
[0082] FIGS. 18A-18I depict various states of an implementation of
the first embodiment according to the process of FIG. 17B as
applied to the formation of the structure of FIG. 6B where CRP is
applied to the entire second layer of the structure.
[0083] FIG. 19A provides a generalized flowchart of the second
embodiment of the invention where the structure will be formed,
transferred to a second substrate or carrier, the original
substrate or carrier removed and the bottom side of the first layer
planarized to induce work hardening therein.
[0084] FIG. 20A depicts a side view of a three layer structure made
from two different structural materials (e.g. a pin probe formed on
its side having a nickel body and a rhodium tip).
[0085] FIG. 20B depicts a side view of the structure of FIG. 20A
while still surrounded by sacrificial material.
[0086] FIG. 20C depicts a side view of the structure of FIG. 20B
where work hardened upper portions of each layer are indicated
(these portions may result from planarization of each layer, e.g.
by lapping, as it is formed).
[0087] FIG. 20D depicts a side view of the structure of FIG. 20B
where work hardened upper portions of each layer are indicated and
where the bottom portion of the first layer is shown as worked
hardened according to an embodiment of the second embodiment of the
invention so as to help balance any stresses (e.g. compressive
forces) within the structure that may tend to make the structure
curve after release from a build substrate and sacrificial material
used in forming the structure.
[0088] FIGS. 21A-21W provide side views of various states of an
example process involved in forming the structure of FIG. 3
according to an embodiment of the invention
[0089] FIG. 22A-22F depict states of the process that may replace
states 21S-21V in an alternative embodiment where a release layer
and a substrate or other carrier is added to the top of the 3rd
layer so that continued operations (e.g. planarization of the
bottom of the 1st layer may occur.
[0090] FIG. 23 provides a flowchart of an implementation of the
third embodiment of the invention.
[0091] FIG. 24A-24G-2 depict states of an example process as
applied to a one layer cantilever structure implementing the fourth
embodiment of the invention where the curvature reduction technique
etches away the upper surface of the second layer and where the
etching occurs in either a selective manner (FIG. 24G1) base on the
selectivity of an etchant used and not on masking (as would be the
case in some other embodiments) or a non-selective manner FIG.
24G-2 based on the non-selectivity of and etchant used and where
the etched structural material is not replaced via a subsequent
deposition process (as would be the case for some alternative
embodiments).
[0092] FIGS. 25A-25H depict states of an example process as applied
to a one layer structure implementing the fifth embodiment of the
invention where annealing of the upper surface structural material
is used to eliminate or reduced stress and/or curvature
distortion.
[0093] FIGS. 26A-26F depict states of an example process as applied
to either a one layer structure that is divided into two layers or
a two layer structure implementing the seventh embodiment of the
invention where the upper sublayer or the second layer has its
structural configuration modified to reduce stress and/or curvature
distortion by inserting vertical stress relief into it (in
alternative embodiments the breaks may be implemented so that they
only extend into the layer to a depth necessary to extend through
or nearly through any work hardened upper surface portion of the
layer).
[0094] FIGS. 27A-27H depict states of an example process as applied
to a one layer cantilever structure 700 (the whole structure is
formed with two layers) implementing the eighth embodiment of the
invention where stress induced in worked hardened regions is
isolated by the formation of breaks in the worked hardened material
after it is formed to eliminate or reduced stress and/or curvature
distortion.
[0095] FIGS. 28A-28H depict state of an example process as applied
to a single layer cantilever structure which is divided into two
sublayers implementing the an example of the ninth embodiment where
the structural portion of the layers is formed from two vertically
stacked materials where planarization of the upper structural
material occurs and where the upper material is planarizable by a
non-stress inducing process (e.g. diamond fly cutting).
[0096] FIGS. 29A-29H depict state of an example process as applied
to a single layer cantilever structure which is divided into two
sublayers implementing an example of the tenth primary embodiment
of the invention where the structural portion of the layer is
formed from two vertically stacked materials where planarization of
the upper structural material occurs and where the lower material
is deposited in a low stress state while the upper material is
deposited in a higher tensile stress state and where the upper
material is planarized using a process (e.g. lapping) that
introduces compression into the material such that the tensile and
compressive forces at least partially cancel one another so that
stress and/or distortion is reduced.
[0097] FIGS. 30A-30G-2 depict state of an example process as
applied to a single layer cantilever structure which is divided
into two sublayers implementing an example of the eleventh primary
embodiment of the invention where the structural portion of the
layer is formed from two vertically stacked materials where
planarization of the lower structural material occurs and sets the
planed height of the deposited material at some distance below the
desired layer thickness and where the planarization introduces work
hardening into the upper surface of the first structural material
and thereafter a thin coating of second structural material is
deposited to raise the height of the deposited materials to the
desired layer level and wherein the second material is chosen or
deposited in such a way that it results in a high tensile stress
deposit that helps compensate for the compress stress in the work
hardened region of the first material.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Electrochemical Fabrication in General
[0098] FIGS. 1A-1G, 2A-2F, and 3A-3C illustrate various features of
one form of electrochemical fabrication. Other electrochemical
fabrication techniques are set forth in the '630 patent referenced
above, in the various previously incorporated publications, in
various other patents and patent applications incorporated herein
by reference. Still others may be derived from combinations of
various approaches described in these publications, patents, and
applications, or are otherwise known or ascertainable by those of
skill in the art from the teachings set forth herein. All of these
techniques may be combined with those of the various embodiments of
various aspects of the invention to yield enhanced embodiments.
Still other embodiments may be derived from combinations of the
various embodiments explicitly set forth herein.
[0099] FIGS. 4A-4I illustrate various stages in the formation of a
single layer of a multi-layer fabrication process where a second
metal is deposited on a first metal as well as in openings in the
first metal so that the first and second metal form part of the
layer. In FIG. 4A a side view of a substrate 82 is shown, onto
which patternable photoresist 84 is cast as shown in FIG. 4B. In
FIG. 4C, a pattern of resist is shown that results from the curing,
exposing, and developing of the resist. The patterning of the
photoresist 84 results in openings or apertures 92(a)-92(c)
extending from a surface 86 of the photoresist through the
thickness of the photoresist to surface 88 of the substrate 82. In
FIG. 4D a metal 94 (e.g. nickel) is shown as having been
electroplated into the openings 92(a)-92(c). In FIG. 4E the
photoresist has been removed (i.e. chemically stripped) from the
substrate to expose regions of the substrate 82 which are not
covered with the first metal 94. In FIG. 4F a second metal 96 (e.g.
silver) is shown as having been blanket electroplated over the
entire exposed portions of the substrate 82 (which is conductive)
and over the first metal 94 (which is also conductive). FIG. 4G
depicts the completed first layer of the structure which has
resulted from the planarization of the first and second metals down
to a height that exposes the first metal and sets a thickness for
the first layer. In FIG. 4H the result of repeating the process
steps shown in FIGS. 4B-4G several times to form a multi-layer
structure are shown where each layer consists of two materials. For
most applications, one of these materials is removed as shown in
FIG. 4I to yield a desired 3-D structure 98 (e.g. component or
device).
[0100] Various embodiments of various aspects of the invention are
directed to formation of three-dimensional structures from
materials some of which may be electrodeposited or electroless
deposited. Some of these structures may be formed form a single
build level formed from one or more deposited materials while
others are formed from a plurality of build layers each including
at least two materials (e.g. two or more layers, more preferably
five or more layers, and most preferably ten or more layers). In
some embodiments, layer thicknesses may be as small as one micron
or as large as fifty microns. In other embodiments, thinner layers
may be used while in other embodiments, thicker layers may be used.
In some embodiments structures having features positioned with
micron level precision and minimum features size on the order of
tens of microns are to be formed. In other embodiments structures
with less precise feature placement and/or larger minimum features
may be formed. In still other embodiments, higher precision and
smaller minimum feature sizes may be desirable.
[0101] The various embodiments, alternatives, and techniques
disclosed herein may form multi-layer structures using a single
patterning technique on all layers or using different patterning
techniques on different layers. For example, Various embodiments of
the invention may perform selective patterning operations using
conformable contact masks and masking operations (i.e. operations
that use masks which are contacted to but not adhered to a
substrate), proximity masks and masking operations (i.e. operations
that use masks that at least partially selectively shield a
substrate by their proximity to the substrate even if contact is
not made), non-conformable masks and masking operations (i.e. masks
and operations based on masks whose contact surfaces are not
significantly conformable), and/or adhered masks and masking
operations (masks and operations that use masks that are adhered to
a substrate onto which selective deposition or etching is to occur
as opposed to only being contacted to it). Conformable contact
masks, proximity masks, and non-conformable contact masks share the
property that they are preformed and brought to, or in proximity
to, a surface which is to be treated (i.e. the exposed portions of
the surface are to be treated). These masks can generally be
removed without damaging the mask or the surface that received
treatment to which they were contacted, or located in proximity to.
Adhered masks are generally formed on the surface to be treated
(i.e. the portion of that surface that is to be masked) and bonded
to that surface such that they cannot be separated from that
surface without being completely destroyed damaged beyond any point
of reuse. Adhered masks may be formed in a number of ways including
(1) by application of a photoresist, selective exposure of the
photoresist, and then development of the photoresist, (2) selective
transfer of pre-patterned masking material, and/or (3) direct
formation of masks from computer controlled depositions of
material.
[0102] Patterning operations may be used in selectively depositing
material and/or may be used in the selective etching of material.
Selectively etched regions may be selectively filled in or filled
in via blanket deposition, or the like, with a different desired
material. In some embodiments, the layer-by-layer build up may
involve the simultaneous formation of portions of multiple layers.
In some embodiments, depositions made in association with some
layer levels may result in depositions to regions associated with
other layer levels (i.e. regions that lie within the top and bottom
boundary levels that define a different layer's geometric
configuration). Such use of selective etching and interlaced
material deposition in association with multiple layers is
described in U.S. patent application Ser. No. 10/434,519, by
Smalley, and entitled "Methods of and Apparatus for
Electrochemically Fabricating Structures Via Interlaced Layers or
Via Selective Etching and Filling of Voids layer elements" which is
hereby incorporated herein by reference as if set forth in
full.
[0103] Temporary substrates on which structures may be formed may
be of the sacrificial-type (i.e. destroyed or damaged during
separation of deposited materials to the extent they can not be
reused), non-sacrificial-type (i.e. not destroyed or excessively
damaged, i.e. not damaged to the extent they may not be reused,
e.g. with a sacrificial or release layer located between the
substrate and the initial layers of a structure that is formed).
Non-sacrificial substrates may be considered reusable, with little
or no rework (e.g. replanarizing one or more selected surfaces or
applying a release layer, and the like) though they may or may not
be reused for a variety of reasons.
DEFINITIONS
[0104] This section of the specification is intended to set forth
definitions for a number of specific terms that may be useful in
describing the subject matter of the various embodiments of the
invention. It is believed that the meanings of most if not all of
these terms is clear from their general use in the specification
but they are set forth hereinafter to remove any ambiguity that may
exist. It is intended that these definitions be used in
understanding the scope and limits of any claims that use these
specific terms. As far as interpretation of the claims of this
patent disclosure are concerned, it is intended that these
definitions take presence over any contradictory definitions or
allusions found in any materials which are incorporated herein by
reference.
[0105] "Build" as used herein refers, as a verb, to the process of
building a desired structure or plurality of structures from a
plurality of applied or deposited materials which are stacked and
adhered upon application or deposition or, as a noun, to the
physical structure or structures formed from such a process.
Depending on the context in which the term is used, such physical
structures may include a desired structure embedded within a
sacrificial material or may include only desired physical
structures which may be separated from one another or may require
dicing and/or slicing to cause separation.
[0106] "Build axis" or "build orientation" is the axis or
orientation that is substantially perpendicular to substantially
planar levels of deposited or applied materials that are used in
building up a structure. The planar levels of deposited or applied
materials may be or may not be completely planar but are
substantially so in that the overall extent of their
cross-sectional dimensions are significantly greater than the
height of any individual deposit or application of material (e.g.
100, 500, 1000, 5000, or more times greater). The planar nature of
the deposited or applied materials may come about from use of a
process that leads to planar deposits or it may result from a
planarization process (e.g. a process that includes mechanical
abrasion, e.g. lapping, fly cutting, grinding, or the like) that is
used to remove material regions of excess height. Unless explicitly
noted otherwise, "vertical" as used herein refers to the build axis
or nominal build axis (if the layers are not stacking with perfect
registration) while "horizontal" refers to a direction within the
plane of the layers (i.e. the plane that is substantially
perpendicular to the build axis).
[0107] "Build layer" or "layer of structure" as used herein does
not refer to a deposit of a specific material but instead refers to
a region of a build located between a lower boundary level and an
upper boundary level which generally defines a single cross-section
of a structure being formed or structures which are being formed in
parallel. Depending on the details of the actual process used to
form the structure, build layers are generally formed on and
adhered to previously formed build layers. In some processes the
boundaries between build layers are defined by planarization
operations which result in successive build layers being formed on
substantially planar upper surfaces of previously formed build
layers. In some embodiments, the substantially planar upper surface
of the preceding build layer may be textured to improve adhesion
between the layers. In other build processes, openings may exist in
or be formed in the upper surface of a previous but only partially
formed build layers such that the openings in the previous build
layers are filled with materials deposited in association with
current build layers which will cause interlacing of build layers
and material deposits. Such interlacing is described in U.S. patent
application Ser. No. 10/434,519. This referenced application is
incorporated herein by reference as if set forth in full. In most
embodiments, a build layer includes at least one primary structural
material and at least one primary sacrificial material. However, in
some embodiments, two or more primary structural materials may used
without a primary sacrificial material (e.g. when one primary
structural material is a dielectric and the other is a conductive
material). In some embodiments, build layers are distinguishable
from each other by the source of the data that is used to yield
patterns of the deposits, applications, and/or etchings of material
that form the respective build layers. For example, data
descriptive of a structure to be formed which is derived from data
extracted from different vertical levels of a data representation
of the structure define different build layers of the structure.
The vertical separation of successive pairs of such descriptive
data may define the thickness of build layers associated with the
data. As used herein, at times, "build layer" may be loosely
referred simply as "layer". In many embodiments, deposition
thickness of primary structural or sacrificial materials (i.e. the
thickness of any particular material after it is deposited) is
generally greater than the layer thickness and a net deposit
thickness is set via one or more planarization processes which may
include, for example, mechanical abrasion (e.g. lapping, fly
cutting, polishing, and the like) and/or chemical etching (e.g.
using selective or non-selective etchants). The lower boundary and
upper boundary for a build layer may be set and defined in
different ways. From a design point of view they may be set based
on a desired vertical resolution of the structure (which may vary
with height). From a data manipulation point of view, the vertical
layer boundaries may be defined as the vertical levels at which
data descriptive of the structure is processed or the layer
thickness may be defined as the height separating successive levels
of cross-sectional data that dictate how the structure will be
formed. From a fabrication point of view, depending on the exact
fabrication process used, the upper and lower layer boundaries may
be defined in a variety of different ways. For example by
planarization levels or effective planarization levels (e.g.
lapping levels, fly cutting levels, chemical mechanical polishing
levels, mechanical polishing levels, vertical positions of
structural and/or sacrificial materials after relatively uniform
etch back following a mechanical or chemical mechanical
planarization process). For example, by levels at which process
steps or operations are repeated. At levels at which, at least
theoretically, lateral extends of structural material can be
changed to define new cross-sectional features of a structure.
[0108] "Layer thickness" is the height along the build axis between
a lower boundary of a build layer and an upper boundary of that
build layer.
[0109] "Planarization" is a process that tends to remove materials,
above a desired plane, in a substantially non-selective manner such
that all deposited materials are brought to a substantially common
height or desired level (e.g. within 20%, 10%, 5%, or even 1% of a
desired layer boundary level). For example, lapping removes
material in a substantially non-selective manner though some amount
of recession one material or another may occur (e.g. copper may
recess relative to nickel). Planarization may occur primarily via
mechanical means, e.g. lapping, grinding, fly cutting, milling,
sanding, abrasive polishing, frictionally induced melting, other
machining operations, or the like (i.e. mechanical planarization).
Mechanical planarization maybe followed or proceeded by thermally
induced planarization (.e.g. melting) or chemically induced
planarization (e.g. etching). Planarization may occur primarily via
a chemical and/or electrical means (e.g. chemical etching,
electrochemical etching, or the like). Planarization may occur via
a simultaneous combination of mechanical and chemical etching (e.g.
chemical mechanical polishing (CMP)).
[0110] "Structural material" as used herein refers to a material
that remains part of the structure when put into use.
[0111] "Supplemental structural material" as used herein refers to
a material that forms part of the structure when the structure is
put to use but is not added as part of the build layers but instead
is added to a plurality of layers simultaneously (e.g. via one or
more coating operations that applies the material, selectively or
in a blanket fashion, to a one or more surfaces of a desired build
structure that has been released from a sacrificial material.
[0112] "Primary structural material" as used herein is a structural
material that forms part of a given build layer and which is
typically deposited or applied during the formation of that build
layer and which makes up more than 20% of the structural material
volume of the given build layer. In some embodiments, the primary
structural material may be the same on each of a plurality of build
layers or it may be different on different build layers. In some
embodiments, a given primary structural material may be formed from
two or more materials by the alloying or diffusion of two or more
materials to form a single material.
[0113] "Secondary structural material" as used herein is a
structural material that forms part of a given build layer and is
typically deposited or applied during the formation of the given
build layer but is not a primary structural material as it
individually accounts for only a small volume of the structural
material associated with the given layer. A secondary structural
material will account for less than 20% of the volume of the
structural material associated with the given layer. In some
preferred embodiments, each secondary structural material may
account for less than 10%, 5%, or even 2% of the volume of the
structural material associated with the given layer. Examples of
secondary structural materials may include seed layer materials,
adhesion layer materials, barrier layer materials (e.g. diffusion
barrier material), and the like. These secondary structural
materials are typically applied to form coatings having thicknesses
less than 2 microns, 1 micron, 0.5 microns, or even 0.2 microns).
The coatings may be applied in a conformal or directional manner
(e.g. via CVD, PVD, electroless deposition, or the like). Such
coatings may be applied in a blanket manner or in a selective
manner. Such coatings may be applied in a planar manner (e.g. over
previously planarized layers of material) as taught in U.S. patent
application Ser. No. 10/607,931. In other embodiments, such
coatings may be applied in a non-planar manner, for example, in
openings in and over a patterned masking material that has been
applied to previously planarized layers of material as taught in
U.S. patent application Ser. No. 10/841,383. These referenced
applications are incorporated herein by reference as if set forth
in full herein.
[0114] "Functional structural material" as used herein is a
structural material that would have been removed as a sacrificial
material but for its actual or effective encapsulation by other
structural materials. Effective encapsulation refers, for example,
to the inability of an etchant to attack the functional structural
material due to inaccessibility that results from a very small area
of exposure and/or due to an elongated or tortuous exposure path.
For example, large (10,000 .mu.m.sup.2) but thin (e.g. less than
0.5 microns) regions of sacrificial copper sandwiched between
deposits of nickel may define regions of functional structural
material depending on ability of a release etchant to remove the
sandwiched copper.
[0115] "Sacrificial material" is material that forms part of a
build layer but is not a structural material. Sacrificial material
on a given build layer is separated from structural material on
that build layer after formation of that build layer is completed
and more generally is removed from a plurality of layers after
completion of the formation of the plurality of layers during a
"release" process that removes the bulk of the sacrificial material
or materials. In general sacrificial material is located on a build
layer during the formation of one, two, or more subsequent build
layers and is thereafter removed in a manner that does not lead to
a planarized surface. Materials that are applied primarily for
masking purposes, i.e. to allow subsequent selective deposition or
etching of a material, e.g. photoresist that is used in forming a
build layer but does not form part of the build layer) or that
exist as part of a build for less than one or two complete build
layer formation cycles are not considered sacrificial materials as
the term is used herein but instead shall be referred as masking
materials or as temporary materials. These separation processes are
sometimes referred to as a release process and may or may not
involve the separation of structural material from a build
substrate. In many embodiments, sacrificial material within a given
build layer is not removed until all build layers making up the
three-dimensional structure have been formed. Of course sacrificial
material may be, and typically is, removed from above the upper
level of a current build layer during planarization operations
during the formation of the current build layer. Sacrificial
material is typically removed via a chemical etching operation but
in some embodiments may be removed via a melting operation or
electrochemical etching operation. In typical structures, the
removal of the sacrificial material (i.e. release of the structural
material from the sacrificial material) does not result in
planarized surfaces but instead results in surfaces that are
dictated by the boundaries of structural materials located on each
build layer. Sacrificial materials are typically distinct from
structural materials by having different properties therefrom (e.g.
chemical etchability, hardness, melting point, etc.) but in some
cases, as noted previously, what would have been a sacrificial
material may become a structural material by its actual or
effective encapsulation by other structural materials. Similarly,
structural materials may be used to form sacrificial structures
that are separated from a desired structure during a release
process via the sacrificial structures being only attached to
sacrificial material or potentially by dissolution of the
sacrificial structures themselves using a process that is
insufficient to reach structural material that is intended to form
part of a desired structure. It should be understood that in some
embodiments, small amounts of structural material may be removed,
after or during release of sacrificial material. Such small amounts
of structural material may have been inadvertently formed due to
imperfections in the fabrication process or may result from the
proper application of the process but may result in features that
are less than optimal (e.g. layers with stairs steps in regions
where smooth sloped surfaces are desired. In such cases the volume
of structural material removed is typically minuscule compared to
the amount that is retained and thus such removal is ignored when
labeling materials as sacrificial or structural. Sacrificial
materials are typically removed by a dissolution process, or the
like, that destroys the geometric configuration of the sacrificial
material as it existed on the build layers. In many embodiments,
the sacrificial material is a conductive material such as a metal.
As will be discussed hereafter, masking materials though typically
sacrificial in nature are not termed sacrificial materials herein
unless they meet the required definition of sacrificial
material.
[0116] "Supplemental sacrificial material" as used herein refers to
a material that does not form part of the structure when the
structure is put to use and is not added as part of the build
layers but instead is added to a plurality of layers simultaneously
(e.g. via one or more coating operations that applies the material,
selectively or in a blanket fashion, to a one or more surfaces of a
desired build structure that has been released from an initial
sacrificial material. This supplemental sacrificial material will
remain in place for a period of time and/or during the performance
of certain post layer formation operations, e.g. to protect the
structure that was released from a primary sacrificial material,
but will be removed prior to putting the structure to use.
[0117] "Primary sacrificial material" as used herein is a
sacrificial material that is located on a given build layer and
which is typically deposited or applied during the formation of
that build layer and which makes up more than 20% of the
sacrificial material volume of the given build layer. In some
embodiments, the primary sacrificial material may be the same on
each of a plurality of build layers or may be different on
different build layers. In some embodiments, a given primary
sacrificial material may be formed from two or more materials by
the alloying or diffusion of two or more materials to form a single
material.
[0118] "Secondary sacrificial material" as used herein is a
sacrificial material that is located on a given build layer and is
typically deposited or applied during the formation of the build
layer but is not a primary sacrificial materials as it individually
accounts for only a small volume of the sacrificial material
associated with the given layer. A secondary sacrificial material
will account for less than 20% of the volume of the sacrificial
material associated with the given layer. In some preferred
embodiments, each secondary sacrificial material may account for
less than 10%, 5%, or even 2% of the volume of the sacrificial
material associated with the given layer. Examples of secondary
structural materials may include seed layer materials, adhesion
layer materials, barrier layer materials (e.g. diffusion barrier
material), and the like. These secondary sacrificial materials are
typically applied to form coatings having thicknesses less than 2
microns, 1 micron, 0.5 microns, or even 0.2 microns). The coatings
may be applied in a conformal or directional manner (e.g. via CVD,
PVD, electroless deposition, or the like). Such coatings may be
applied in a blanket manner or in a selective manner. Such coatings
may be applied in a planar manner (e.g. over previously planarized
layers of material) as taught in U.S. patent application Ser. No.
10/607,931. In other embodiments, such coatings may be applied in a
non-planar manner, for example, in openings in and over a patterned
masking material that has been applied to previously planarized
layers of material as taught in U.S. patent application Ser. No.
10/841,383. These referenced applications are incorporated herein
by reference as if set forth in full herein.
[0119] "Adhesion layer", "seed layer", "barrier layer", and the
like refer to coatings of material that are thin in comparison to
the layer thickness and thus generally form secondary structural
material portions or sacrificial material portions of some layers.
Such coatings may be applied uniformly over a previously formed
build layer, they may be applied over a portion of a previously
formed build layer and over patterned structural or sacrificial
material existing on a current (i.e. partially formed) build layer
so that a non-planar seed layer results, or they may be selectively
applied to only certain locations on a previously formed build
layer. In the event such coatings are non-selectively applied,
selected portions may be removed (1) prior to depositing either a
sacrificial material or structural material as part of a current
layer or (2) prior to beginning formation of the next layer or they
may remain in place through the layer build up process and then
etched away after formation of a plurality of build layers.
[0120] "Masking material" is a material that may be used as a tool
in the process of forming a build layer but does not form part of
that build layer. Masking material is typically a photopolymer or
photoresist material or other material that may be readily
patterned. Masking material is typically a dielectric. Masking
material, though typically sacrificial in nature, is not a
sacrificial material as the term is used herein. Masking material
is typically applied to a surface during the formation of a build
layer for the purpose of allowing selective deposition, etching, or
other treatment and is removed either during the process of forming
that build layer or immediately after the formation of that build
layer.
[0121] "Multilayer structures" are structures formed from multiple
build layers of deposited or applied materials.
[0122] "Multilayer three-dimensional (or 3D or 3-D) structures" are
Multilayer Structures that meet at least one of two criteria: (1)
the structural material portion of at least two layers of which one
has structural material portions that do not overlap structural
material portions of the other.
[0123] "Complex multi layer three-dimensional (or 3D or 3-D)
structures" are multilayer three-dimensional structures formed from
at least three layers where a line may be defined that
hypothetically extends vertically through at least some portion of
the build layers of the structure will extend from structural
material through sacrificial material and back through structural
material or will extend from sacrificial material through
structural material and back through sacrificial material (these
might be termed vertically complex multilayer three-dimensional
structures). Alternatively, complex multilayer three-dimensional
structures may be defined as multilayer three-dimensional
structures formed from at least two layers where a line may be
defined that hypothetically extends horizontally through at least
some portion of a build layer of the structure that will extend
from structural material through sacrificial material and back
through structural material or will extend from sacrificial
material through structural material and back through sacrificial
material (these might be termed horizontally complex multilayer
three-dimensional structures). Worded another way, in complex
multilayer three-dimensional structures, a vertically or
horizontally extending hypothetical line will extend from one or
structural material or void (when the sacrificial material is
removed) to the other of void or structural material and then back
to structural material or void as the line is traversed along at
least a portion of the line.
[0124] "Moderately complex multilayer three-dimensional (or 3D or
3-D) structures are complex multilayer 3D structures for which the
alternating of void and structure or structure and void not only
exists along one of a vertically or horizontally extending line but
along lines extending both vertically and horizontally.
[0125] "Highly complex multi layer (or 3D or 3-D) structures are
complex multilayer 3D structures for which the
structure-to-void-to-structure or void-to-structure-to-void
alternating occurs once along the line but occurs a plurality of
times along a definable horizontally or vertically extending
line.
[0126] "Up-facing feature" is an element dictated by the
cross-sectional data for a given build layer "n" and a next build
layer "n+1" that is to be formed from a given material that exists
on the build layer "n" but does not exist on the immediately
succeeding build layer "n+1". For convenience the term "up-facing
feature" will apply to such features regardless of the build
orientation.
[0127] "Down-facing feature" is an element dictated by the
cross-sectional data for a given build layer "n" and a preceding
build layer "n-1" that is to be formed from a given material that
exists on build layer "n" but does not exist on the immediately
preceding build layer "n-1". As with up-facing features, the term
"down-facing feature" shall apply to such features regardless of
the actual build orientation.
[0128] "Continuing region" is the portion of a given build layer
"n" that is dictated by the cross-sectional data for the given
build layer "n", a next build layer "n+1" and a preceding build
layer "n-1" that is neither up-facing nor down-facing for the build
layer "n".
[0129] "Minimum feature size" refers to a necessary or desirable
spacing between structural material elements on a given layer that
are to remain distinct in the final device configuration. If the
minimum feature size is not maintained on a given layer, the
fabrication process may result in structural material inadvertently
bridging the two structural elements due to masking material
failure or failure to appropriately fill voids with sacrificial
material during formation of the given layer such that during
formation of a subsequent layer structural material inadvertently
fills the void. More care during fabrication can lead to a
reduction in minimum feature size or a willingness to accept
greater losses in productivity can result in a decrease in the
minimum feature size. However, during fabrication for a given set
of process parameters, inspection diligence, and yield (successful
level of production) a minimum design feature size is set in one
way or another. The above described minimum feature size may more
appropriately be termed minimum feature size of sacrificial
material regions. Conversely a minimum feature size for structure
material regions (minimum width or length of structural material
elements) may be specified. Depending on the fabrication method and
order of deposition of structural material and sacrificial
material, the two types of minimum feature sizes may be different.
In practice, for example, using electrochemical fabrication methods
and described herein, the minimum features size on a given layer
may be roughly set to a value that approximates the layer thickness
used to form the layer and it may be considered the same for both
structural and sacrificial material widths and lengths. In some
more rigorously implemented processes, examination regiments, and
rework requirements, it may be set to an amount that is 80%, 50%,
or even 30% of the layer thickness. Other values or methods of
setting minimum feature sizes may be set.
[0130] "Sublayer" as used herein refers to a portion of a build
layer that typically includes the full lateral extents of that
build layer but only a portion of its height. A sublayer is usually
a vertical portion of build layer that undergoes independent
processing compared to another sublayer of that build layer.
Stress, Curvature, and Regions of Structures
[0131] When forming structures using the electrochemical
fabrication methods discussed above, structures or portions of
structures may be formed with unintended curvature. This curvature
appears to be more prevalence when the thickness between
down-facing and overlying up-facing regions is relatively thin
(e.g. under 30-60 microns). It appears as the thickness of the
structural elements increase the tendency to curve decreases as the
overall structure becomes more rigid and less capable of distorting
under the load of any unbalanced stresses that were built into the
structure. The unintended curvature in the structures themselves
cannot be seen prior to the release of the structures (i.e.
structural material) from the surrounding sacrificial materials and
possibly from the substrate itself. However, at times, unintended
curvature can be seen in the build layers themselves particularly
when the total thickness of deposited layers becomes relatively
thick (e.g. in excess of 700 to 1500 microns) and the lateral (i.e.
horizontal extents when the build axis is considered to extend
vertically) of the build layers increase (e.g. beyond 100 mm). The
build layer curvature may or may not translate into curvature of
the build structures themselves depending on the horizontal
dimensions of the build structures themselves, the thickness of the
structures, whether or not they remained adhered to the substrate,
their overall configurations, and the like. Though this application
is primarily focused on reducing stress and/or unintended curvature
in structures themselves, curvature of build layers is something
that can lead to formational difficulties and illustrates the
inherent stress, or at least unbalanced stress, that can exist in
build layers.
[0132] Various techniques exist for minimizing build layer
curvature. One such technique includes the use of a thick and very
rigid substrate particularly when it is intended that a relatively
large thickness of build layers be deposited thereon. Another
technique involves the attachment of the substrate to a carrier
that tends to stiffen it. Another technique involves the deposition
and planarization of material onto the back side of the substrate
during the build process to balance the stresses that are induced
by the build up of layers on the front side of the substrate. The
net amount of material deposited on the back side of the substrate
need not be identical to that deposited on the front side and it
need not even be the same material. The material deposited onto the
back side of the substrate is typically a sacrificial material
though it can be structural material or even a mixture of
structural and sacrificial material. In fact, in some cases it may
be possible to build structures on both sides of the substrate
wherein after formation, the structures on both sides of the
substrate are released from the sacrificial material and even from
the substrate. If the structures are to remain on the substrate
they can remain joined with their counterparts on the opposite side
of the substrate or they can be separated from their counterparts
by slicing the substrate in half (i.e. along a horizontal plane
through the substrate.
[0133] FIGS. 5A-5D provides a comparison between a structure,
formed from one layer, that is curvature free and one that has
unintended curvature which is released from a substrate. FIG. 5A
provides a schematic side view of a structure 1204 formed as a
single build layer L1 on a substrate 1202 and which is surrounded
by sacrificial material 1206. FIG. 5B depicts the structure 1204 of
FIG. 5A as it is intended to look after it is separated from the
substrate 1202 and sacrificial material 1206. FIG. 5C depicts the
structure 1202 of FIG. 5A as it is intended to look after it is
separated from the substrate 1202 and sacrificial material 1206 and
wherein worked hardened regions 1204B on the upper portion of each
layer are shown along with the lower portion 1204A of structure
1204. Worked hardened regions 1204B may occur via planarization
operations that were used to set the upper boundary portion of the
build layer L1 from which the structure was formed. The
planarization operations setting the boundary level may have
involved one or more lapping operations. FIG. 5D depicts the
structure of FIG. 5A as it may exist after being formed by a prior
art technique where the structure is curved due to excessive
unbalanced stresses that were induced in the structure during its
formation. In particular, the work hardened region 1204B, prior to
separation of the structure 1204 from the substrate 1202, may
experience a compressive stress and upon separation from the
substrate, the layer as a whole may be insufficiently rigid to
resist the release of the compressive stress so that the stress is
relieved by the bending of the structure downward thereby providing
a slight expansion of the upper portion of the structure and a
relief of the compressive force. The structure 1204 of FIG. 5A may
be released from the substrate 1202 via destructive removal of a
sacrificial substrate (e.g. dissolution by etching) or via a
release material located between the structure and a
non-sacrificial substrate (not shown).
[0134] FIGS. 6A-6D provides a comparison between a structure,
formed from two layers, that is curvature free and one that has
unintended curvature where the second layer is cantilevered
relative to the first layer and where the first layer remains
adhered to a substrate. FIG. 6A provides a schematic side view of a
two layer structure 1224, formed from a first layer L1 and a second
layer L2, attached to a substrate 1222 and which is surrounded by
sacrificial material 1226 and where the structural material 1224-2
of the second layer extends beyond the structural material 1224-1
of the first layer L1. FIG. 6B depicts the structure 1224 of FIG.
6A as it is intended to look after it is separated from the
sacrificial material 1226 which results in a portion 1228 of the
structural material 1224-2 of second layer L2 forming an
unsupported cantilever section relative to the structural material
1224-1 of the first layer L1. FIG. 6C depicts the structure 1224 of
FIG. 6A as it is intended to look after it is separated from the
sacrificial material 1226 and wherein worked hardened regions
1224-1B and 1224-2B on the upper portions of the structural
material of each of layers L1 and L2 are shown as well as the
non-work hardened regions 1224-1A and 1224-2A. FIG. 6D depicts the
structure 1224 of FIG. 6A as it may exist after being formed by a
prior art technique where the unsupported portion 1228 (i.e.
cantilever portion) of second layer 1224-2 is curved downward due
to excessive unbalanced stresses that were induced in the structure
1224 during its formation. As shown in this FIG. 6D, the left side
of the structural material on the second layer L2 appears to be
un-distorted as it is constrained by its doubled thicknesses (i.e.
the thickness of layers L1 and L2) and by its attachment to the
substrate. As with the structure 1204 of FIG. 5D, the curvature is
downward as a result of compressive strain induced in the upper
most portion of each layer probably as a result of surface damage
introduced in the upper portion of each layer as a result of a
stress inducing planarization process (e.g. lapping) that was used
to set the boundary level of the layers.
[0135] FIGS. 7A-7D provides a comparison between a structure,
formed from two layers, that is curvature free and one that has
unintended curvature which is released from a substrate via a
sacrificial release layer (i.e. a material layer) located between
structure and the substrate. FIG. 7A provides a schematic side view
of a two layer structure 1244 attached to a substrate 1242, via a
sacrificial layer, LO, 1248 (i.e. a single material layer) and
which is surrounded by sacrificial material 1246. The structure is
formed from structural material 1244-1, on a first build layer L1,
and 1244-2, on a second build layer L2. FIG. 7B depicts the
structure 1244 of FIG. 7A as it is intended to look after it is
separated from the substrate 1242 and sacrificial material 1246.
FIG. 7C depicts the structure of FIG. 7A as it is intended to look
after it is separated from the substrate and sacrificial material
and wherein work hardened regions 1244-1B and 1244-2B on the upper
portion of each layer L1 and L2 are shown as well as the non-work
hardened regions 1224-1A and 1224-2A. FIG. 7D depicts the structure
1244 of FIG. 7A as it may exist after being formed by a prior art
technique where the structure 1244 is curved due to excessive
unbalanced stresses that were induced in the structure during its
formation.
[0136] FIGS. 8A-8D provides a comparison between a structure,
formed from three layers, that is curvature free and one that has
unintended curvature where the second layer is cantilevered
relative to the first layer and wherein the first layer remains
adhered to a substrate. FIG. 8A provides a schematic side view of a
three layer structure 1264 attached to a substrate 1262 and which
is surrounded by sacrificial material 1266 and where the structural
material 1264-2 and 1264-3 of the second and third layers, L2 and
L3, respectively extends beyond the structural material 1264-1 of
the first layer L1. FIG. 8B depicts the structure 1264 of FIG. 8A
as it is intended to look after it is separated from the
sacrificial material 1266 but remains adhered to the substrate 1262
which results in a portion of the structural material on the second
and third layers, L2 and L3, defining cantilever 1268 (i.e. a
horizontally structure that is unsupported by material existing on
previously formed layers). FIG. 8C depicts the structure 1264 of
FIG. 8A as it is intended to look after it is separated from the
sacrificial material and wherein work hardened regions 1264-1B,
1264-2B, and 1264-3B on the upper portion of each layer L1, L2, and
L3 are shown along with regions that are non-work hardened 1264-1A,
1264-2A, and 1264-3A. FIG. 8D depicts the structure 1244 of FIG. 8A
as it may exist after being formed by a prior art technique where
the unsupported portion 1268 of second and third layers are curved
due to excessive unbalanced stresses that were induced in the
structure 1264 during its formation.
[0137] FIG. 9 depicts a side view of an example structure where
different portions of the layers of the structure are divided into
different categories (up-facing, down-facing, both up-facing and
down-facing, or continuing) based on their geometric relationship
to elements of an immediately succeeding layer and to elements of
an immediately preceding layer. In FIG. 9, a structure 1284 is
shown surrounded by sacrificial material 1286 and adhered to a
substrate 1282. For illustrative purposes the structure is
considered to be an extrusion along the y-axis with layers stacked
along the z-axis (i.e. the build axis is the x-axis). The
structural portion of each layer may be considered to consist of
one or more regions depending on the geometric relationship of the
structural material to structural material on previous and
succeeding layers. The region portions as illustrate here may
consist of down-facing regions DF, continuation regions C,
up-facing regions UF, and regions that re both up-facing and down
facing UF & DF. In the present example the material of
structure 1284 is considered to be of a single type, e.g. nickel,
nickel-cobalt, nickel phosphorous, silver, or the like. In other
embodiments, the structural material on each layer may be different
or different on different parts of the same layer. In such cases,
regions designations may be base on the distinction between
structural materials and sacrificial material, as above, or may be
based on distinctions between different structural materials. In
still other cases, other region designations may be defined and
use. Regions, for example, may be defined (1) as down-facing for
one structural material but also as being bounded from below by
different structural material, (2) as being only one layer above a
down-facing region, (3) as being only two layers below an up-facing
region. Regions may be distinguished based on a required horizontal
width or length. Regions may be divided into boundary portions and
deeper interior portions. A scheme for defining regions should take
into account at least two criteria: (1) the scheme provides
sufficient information to allow desired formation techniques to be
used on different portions of each layer, and (2) the desired
regions can be adequately identified and distinguished.
[0138] FIGS. 10A and 10B provide side views of two designs of
three-dimensional structures that may be cross-sectioned into
layers (e.g. eight layers) to produce identical cross-sectional
representations that may be the basis for driving the fabrication
of identical three-dimensional multi-layer structures. FIG. 10A
depicts a structure 1302 that is designed with a stair stepped
configuration, along the z-axis, while FIG. 10B depicts a structure
1312 that has smoothly sloping surfaces 1314 along the z-axis.
These three-dimensional representations may each be converted into
a plurality of cross-sectional representations which may be useful
in driving the fabrication of physical multilayer three-dimensional
structures. As these cross-sectional representations provide only a
quantized approximation of the original three-dimensional designs,
it is conceivable that different approximations are possible
depending on the sophistication of the data processing used and the
structural features that are desired to be emphasized. Rather
detailed methods for distinguishing cross-sectional regions and
producing cross-sectional representations of three-dimensional
structures that emphasis different geometric attributes of original
structures are provided in the following U.S. Patents: (1) U.S.
Pat. No. 5,321,622, entitled "Boolean Layer Comparison Slice", by
Snead et al; and U.S. Pat. No. 6,366,825, entitled "Simultaneous
Multiple Layer Curing in Stereolithography", Smalley et al. Each of
these patents is incorporated herein by reference as if set forth
in full. If it is desired that physically reproduced structures
define oversized structures (e.g. structures whose layered solid
regions cover all portions of the solid regions of the original
design), the basic cross-sectional data and thus the basic
configuration of the structural material associated with each build
layer, for the designs of FIGS. 10A and 10B, may be identical
particularly when these designs are divided into eight
cross-sections.
[0139] FIGS. 10C-10M provide examples of how different portions of
the various cross-sections may be categorized differently to define
distinct structural regions so that different fabrication
techniques (e.g. curvature reduction techniques) may be applied to
the formation of distinct portions of the structure. The
cross-sectional data associated with each of these figures is, for
example, extractable from the three-dimensional design of either
FIG. 10A or 10B.
[0140] FIG. 10C depicts a schematic side view of an example
structure formed from eight layers, L1-L8, where the structural
material portions 1320 of each layer are shown with identical
patterns which are intended to indicate that each structural
material portion is defined as having the same attributes (e.g. the
cross-sectional data for each layer does not distinguish any
special regions of the layers, such as up-facing, down-facing, or
continuing regions). Representations of each cross-section have
similar attributes and thus be used to drive an electrochemical
fabrication process according to some embodiments of the invention
where similar curvature reduction techniques will be equally
applied to all portions of all layers of the structure.
[0141] FIG. 10D depicts a schematic side view of an example eight
layer structure where up-facing portions 1322 of the structural
material for each layer are identified differently from
non-up-facing portions 1320 allowing such data to be used to
control the formation of the two identified regions differently
such that one or the other may be formed using a curvature
reduction technique or such that both may be formed using different
curvature reduction techniques.
[0142] FIG. 10E depicts a schematic side view of an example eight
layer structure where special portions 1324 of the structural
material 1320 of the layers are identified differently from other
structural material portions 1320 when those portions are up-facing
and overlay a single layer of structure (i.e. the up-facing
portions cap a thin portion of the structure). In other words the
special portions are up-facing regions that do not overlie thick
regions of structural material (i.e. structural material thicker
than one layer). The cut off thickness distinguishing special
portions from standard portions is labeled with Ti. Such data may
be used to control the formation of the two identified regions
differently such that one or the other may be formed using a
curvature reduction technique or such that both may be formed using
different curvature reduction techniques. This data may be used in
situations where it is believed that only those portions of a
structure thinner than two layer thicknesses are subject to
appreciable curvature or where such portions should be subjected to
different curvature reduction techniques.
[0143] FIG. 10F depicts a schematic side view of an example eight
layer structure where special portions 1326 of the structural
material of the layers are identified differently from other
structural material portions 1320 when those portions are up-facing
and overlay structural features thinner than three layer
thicknesses (i.e. up-facing regions that do not include up-facing
regions that overly structural thicknesses of at least three
layers) allowing such data to be used to control the formation of
the two identified regions differently such that one or the other
may be formed using a curvature reduction technique or such that
both may be formed using different curvature reduction techniques.
The cut off thickness distinguishing special portions from standard
portions is labeled with T1&2.
[0144] FIG. 10G depicts a schematic side view of an example eight
layer structure where special portions 1332 and 1334 of the
structural material of layers are identified differently from other
structural material portions 1320. Special portions 1332 define
up-facing regions that overlay structural material thinner than
three layer thicknesses. Special portions 1334 are those portions
that immediately underlay up-facing portions where net structural
thickness remains less than three layer thicknesses. Defining
distinct data for three such regions allows the formation of the
structure to occur using up to three different building processes
that are geometry specific (e.g. up to three different curvature
reduction techniques. The cut off thickness distinguishing special
portions from standard portions is labeled with T1&2.
[0145] FIG. 10H depicts a schematic side view of an example eight
layer structure where structural material portions of layers
containing an up-facing features that overlay structural features
thinner than three layer thicknesses or layers containing
non-facing regions thinner than two layer thickness 1336 are
identified differently from layers not containing those regions
1320 thereby allowing such data to be used to control the formation
of the two identified regions (i.e. types of layers) differently
and such that one or both may be formed using similar or different
curvature reduction techniques. This type of identification allows
the curvature reduction technique to be selected on a layer by
layer basis depending on the geometric configurations which are
present on the structural material portion of each layer. The cut
off thickness distinguishing special portions from standard
portions is labeled with T1&2.
[0146] FIG. 10I depicts a schematic side view of an example eight
layer structure where up-facing portions 1342 of the structural
material portions of layers that overlay structural material
features thinner than four layer thicknesses are identified
differently from other regions 1320 (i.e. different from
non-up-facing regions and up-facing regions that overly structural
thicknesses of at least four layers) allowing such data to be used
to control the formation of the two identified regions differently
such that one or the other may be formed using a curvature
reduction technique or such that both may be formed using different
curvature reduction techniques. The cut off thickness
distinguishing special portions from standard portions is labeled
with T1-3.
[0147] FIG. 10J depicts a schematic side view of an example eight
layer structure where up-facing portions 1344 of structural
material portions layers that overlay structural features thinner
than four layer thicknesses and underlying non-facing regions 1346
are identified differently from other regions 1320 (i.e. different
from thick non-up-facing regions, i.e. non-up-facing regions at
least three layers in thickness, and up-facing regions that overly
structural thicknesses of at least four layers) thereby allowing
such data to be used to control the formation of the three
identified regions differently and such that one or more may be
formed using similar or different curvature reduction techniques.
The cut off thickness distinguishing special portions from standard
portions is labeled with T1-3.
[0148] FIG. 10K depicts a schematic side view of an example eight
layer structure where layers 1348 containing an up-facing feature
that overlays structural features thinner than four layer
thicknesses or layers containing non-facing regions thinner than
three layer thickness are identified differently from layers not
containing those regions. Such identification of layers allows such
data to be used to control the formation of the two differently
identified regions (in this example only one region results from
the specified parameters) differently and such that one or both may
be formed using similar or different curvature reduction
techniques. The cut off thickness distinguishing special portions
from standard portions is labeled with T1-3.
[0149] FIG. 10L depicts a schematic side view of an example eight
layer structure where down-facing portions 1352 of the structural
material of the layers underlay up-facing portions of the
structural material on the immediately succeeding layer are
distinguished differently from other regions 1320 (i.e. the
specially identified portions are those that are both non-up-facing
and which are also less than two layers in thickness) thereby
allowing such data to be used to control the formation of the two
identified regions differently and such that one or both may be
formed using different curvature reduction techniques.
[0150] FIG. 10M depicts a schematic side view of a final eight
layer example where special regions 1354 are identified as those
that are (1) not up-facing portions of layers, (2) define portions
of the structural material that having a net thickness less than
four layer thicknesses. These special regions 1354 are
distinguished from other structural material portions 1320 (i.e.
the specially identified portions are those that are both
non-up-facing and have thickness of structure that is below them of
less than the thickness of three layers. Such data may be used to
control the formation of the two identified regions differently and
such that one or both may be formed using different curvature
reduction techniques.
[0151] The identification schemes of FIGS. 10D-10G, 10H-10J, 10L,
and 10M may be considered to identify layers containing different
feature types as well as defining specific regions within layers,
so that distinct curvature reduction techniques may be implemented
on region-by-region basis as previously noted or on a
layer-by-layer basis depending on the feature types present on
individual layers.
[0152] FIGS. 11A-12B provide side views of cantilever structures
supported from a single side where length and thickness
requirements are specified for special identification or where
layers of structural material are distinguished depending on
whether or not they meet the identification requirements.
[0153] FIG. 11A depicts a schematic side view of an example five
layer structure 1402 where the top two layers (L4 and L5) form a
relative short cantilever structure 1404 where the length of the
cantilever LC is less than a target length TL and where the height
of the cantilever is within a target height (i.e. less than a
target height) and where the target length sets a minimum
cantilever length beyond which the cantilever may particularly
benefit from implementation of a curvature reduction technique and
wherein target height sets a level beyond which a cantilever
structure does not require implementation of a curvature reduction
technique.
[0154] FIG. 11B depicts a schematic side view of the structure of
FIG. 11A where no distinction is made between different portions of
any of layers L1-L5 because the structure didn't meet both the
thinness and length requirements indicated in FIG. 11A. In
alternative examples, special distinction may have been granted if
only one of the criteria were met.
[0155] FIG. 12A depicts a schematic side view of an example five
layer L1-L5 structure 1412 where the top two layers L4 & L5
form a cantilever structure 1414 whose length exceed a target
length and whose thickness is within a minimum height range such
that the cantilever portion may be subject to excessive curvature
upon standard formation and thus may benefit from application of
special formation techniques to help reduce curvature.
[0156] FIG. 12B depicts a schematic side view of the structure of
FIG. 12A where the two layers L4 & L5 forming the thin and long
cantilever 1414 are shown as being defined differently than the
first three layers L1-L3 such that the difference may be used to
drive structure formation, according to one or more embodiments of
the invention, to help minimize distortion.
[0157] FIGS. 13A-14B provide side views of cantilever structures
supported from both ends where length and thickness requirements
are specified for special identification or where layers of
structural material are distinguished depending on whether or not
they meet the identification requirements.
[0158] FIG. 13A depicts a schematic side view of an example five
layer L1-L5 structure 1422where the structural material of top two
layers L4 & L5 form a relative short unsupported central bridge
1424 that is supported on each end by structural material of the
third layer L3 where the length of the unsupported region is less
than twice cantilever target length TL and where the height of the
unsupported portion is within a target height TH and where the
target length sets a minimum cantilever length (length from each
side) beyond which the unsupported portion may benefit from
implementation of a curvature reduction technique and wherein
target height sets a level beyond which a cantilever structure does
not require implementation of a curvature reduction technique.
[0159] FIG. 13B depicts a schematic side view of the structure 1422
of FIG. 13A where no distinction is made between different portions
of any layers because the structure didn't meet both the thinness
and length requirements indicated in FIG. 13A.
[0160] FIG. 14A depicts a schematic side view of an example five
layer L1-L5 structure 1432 where the top two layers L4 & L5
form an unsupported central bridge 1434 portion where length of the
bridge portion from each end exceeds a target cantilever length TL
and whose thickness is within a minimum height range TH such that
the cantilever portion 1434 may be subject to excessive curvature
upon standard formation and thus may benefit from application of
special formation techniques to help reduce curvature.
[0161] FIG. 14B depicts a schematic side view of the structure 1432
of FIG. 14A where the two layers L4 and L5 forming the thin but
long bridge portion 1434 are shown as being defined differently
than the first three layers L1-L3 such that the difference may be
used to drive structure formation, according to one or more
embodiments of the invention, to help minimize distortion.
Groups and Primary Embodiments
[0162] The disclosure of the present invention provides six groups
of embodiments which are further broken into a total of eleven
primary embodiments for reducing stress or curvature distortion.
Though the embodiments present herein are focused on forming
multi-layer three-dimensional structures, some of them have
application to forming single layer structures with less stress
and/or less curvature.
[0163] FIG. 15 provides a block diagram setting forth a brief
description of the eleven primary embodiments set forth herein.
[0164] The primary embodiments 99 of the present invention form
multi-layer structures with reduced curvature distortion by
modifying a process that is used to form at least one layer of the
structure or by modifying the design of the structure or of at
least one layer of the structure. The first group of embodiments
100 (i.e. Group 1) involves the balancing of stress via creative
use of planarization. This group of embodiments includes: (1) a
first embodiment 101 that includes formation of at least one layer
of the structure that includes a very thin, planarized sub-layer
and a thicker planarized sublayer; (2) a second embodiment 102 that
includes planarization of the bottom surface of the first layer,
and (3) a third embodiment 103 that starts formation of the
multi-layer structure by stacking layers using a building axis with
a first orientation and then continuing the formation with the
orientation of the building axis reversed.
[0165] The first embodiment 101 involves the following operations
or steps: (1) Determining the critical layers of a structure (e.g.
the bottom of the structure, layers including extended down-facing
regions, etc.) and (2) forming each critical layer as two
sublayers. The first sublayer for each layer has a thickness
approximating that of the work hardening depth of the planarization
operation so that it becomes substantially compressively stressed.
The second sublayer is thicker so that only its upper portion is
compressively stressed via planarization. The use of these two
sublayers results in a build layer, as a whole, having more
balanced stress and thus preferably having less distortion or
curvature.
[0166] The second embodiment 102 involves the formation of a
structure by stacking layers one above one another and planarizing
the top of each layer including the potential of inducing stress in
each layer. For example, some planarization operations may include
the lapping of both sacrificial and structural materials that form
the layer. After formation of one or more layers, (e.g. via
lapping) and after formation of one or more layers, planarizing the
bottom of the first layer using an appropriate technique to induce
a balancing stress therein (e.g. via lapping).
[0167] The third embodiment 103 involves forming a structure by
stacking successive layers one above one another. Starting with the
first layer, the top of each of plurality of layers is planarized
with stress being induced into each. Planarizing, for example, may
occur via lapping. After formation of one or more layers, the
orientation of the build axis is reversed and the formation of the
structure is continued by adding one or more additional layers to
the bottom side of the first layer. During the formation of these
additional layers, the top side of one or more of the additional
layers is planarized. With respect to the original orientation, the
bottom side of the additional layers is planarized.
[0168] The second group of embodiments 200 includes the reduction
of stress in one or more layers of a structure by removal of worked
hardened material. This group of embodiments includes a fourth
embodiment 201 that involves etching away at least a portion of any
work hardened material and possibly depositing additional material
to partially or completely fill any void crated by the etching.
[0169] The fourth embodiment 201 includes forming structures by
depositing materials, planarizing the materials, and etching back
at least one of the materials. The etching back may, for example,
be performed with either wet etching or dry etching. Wet etching
may be performed chemically or in some circumstances
electrochemically. Dry etching may be isotropic or anisotropic. If
anisotropic, dry etching may be performed without a mask assuming
both structural and sacrificial materials are etched at a
reasonably uniform rate. The etching may be performed in a variety
of alternative manners, for example: (1) masks may be used if
structural material is being etched and if sacrificial material
will be damaged by etchant, (2) masks may use "smaller" openings
for etching if edge placement is critical and if etchant attacks
the sacrificial material, (3) etching may be applied to only those
portions of structural material that are non-up-facing surfaces of
the structure, (4) etching may be applied to regions that are
non-up-facing and that are inset from sidewalls and up-facing
regions by an "offset" amount, and/or 5) etching may be applied
only to regions whose net thickness (i.e. thickness between
up-facing and down-facing regions) is less than a cut off amount
which may be a fixed amount or a variable amount based on length of
the region, whether the regions is supported from only one side or
opposite sides, the thickness of the region etc. Additional
operations or steps may be optionally performed, for example: (1)
material may be re-deposited to non-up-facing regions during
formation of the next layer, (2) material may be re-deposited to
up-facing regions if etching was uniform enough and if
re-deposition can occur in a uniform enough manner, (3) it may be
possible to use a combination of alternating etching and plating to
remove the stressed material and re-deposit a material having less
stressed.
[0170] The third group of embodiments 300 involves the removal of
stress without the removal of the work hardened material. This
group of embodiments includes: (1) a fifth embodiment 301 involving
the use of focused heating to anneal work hardened material and a
(2) sixth embodiment 302 involving the use of blanket or selective
heating to anneal work hardened material.
[0171] The fifth embodiment 301 includes the use of focused heating
(e.g. from a laser beam) to anneal one or more small lateral
regions of the surface of the layer preferably to a shallow depth
(e.g..about.the depth of work hardening) and then scanning or
jumping the focused heating in a desired pattern over the surface
to be annealed. In this embodiment the annealing is preferably,
though not necessarily performed prior to release from any
sacrificial material. In this embodiment, the annealing may occur
over only a selected portion of the structural material of the
layer (e.g. the portion that is part of a thin, e.g. less than
50-100 um, structural thickness), over all of the structural
material of the layer, or even over both structural and sacrificial
material regions. The annealing of this embodiment preferably
occurs after planarization of the layer is completed. However, if
sufficient heat is applied annealing of work hardened material on
the previously formed layer may occur.
[0172] The sixth embodiment 302 includes the use of blanket or
selectively applied heating to anneal the surface of a layer
preferably to a shallow depth (e.g..about.the depth of work
hardening) potentially using one or more flash exposures of heat
energy. In this embodiment annealing is preferably, though not
necessarily, performed prior to release from any sacrificial
material. Selective application may include heating of desired
structural material regions, heating of all structural material
regions, or heating of selected structural and sacrificial material
regions. The annealing of this embodiment preferably occurs after
planarization of the layer is completed. However, if sufficient
heat is applied annealing of work hardened material on the
previously formed layer may occur.
[0173] The fourth group of embodiments 400 involves the reduction
of stress via the isolation of stress. This group of embodiments
includes (1) a seventh embodiment 401 involving modifying the
structure by inserting breaks into what would otherwise be
contiguous regions of work hardened structural material and (2) an
eighth embodiment 402 involves modifying the structure by removing
selected regions of work hardened material.
[0174] The seventh embodiment 401 includes forming a desired
structure with at least one surface (which would be preferentially
formed of structural material in the absence of undesired stress
and/or curvature distortion) being formed from alternating regions
of structural material with either no material or with sacrificial
material, wherein the regions of no material or sacrificial
material are preferably narrower than the regions of structural
material and wherein after planarization the sacrificial material,
if present, is removed.
[0175] The eighth embodiment 402 includes forming a desired
structure with at least one surface (which would be preferentially
formed of continuous structural material in the absence of
undesired stress and/or curvature distortion) being formed from
structural material and after planarization etching, dicing, laser
ablation, or otherwise forming notches in the structural material
that are preferably though not necessarily thin relative to the
width of the structural material islands being formed and wherein
the depth of notching is preferably, though not necessarily, thin
(e.g..about.the depth of work hardening)
[0176] The fifth group of embodiments 500 involves reducing the
stress by planarizing using a non-stress inducing technique or a
technique. This group includes a ninth embodiment 501 involving
formation of a layer from two structural materials one of which is
subject to planarization and may be planarized without inducing
work hardening.
[0177] The ninth embodiment 501 includes formation of a layer of a
structure where first structural material deposited is low stress
(compressive or tensile) and where second structural material
deposited is low stress and is planarizable by a low or non-stress
inducing method (e.g. diamond turning or fly cutting) and where low
or non-stress inducing planarization of the second material occurs
leaving a layer having reduced stress.
[0178] The sixth group of embodiments 600 involves reducing stress
in a build layer which is formed using different materials having
different stress levels after deposition and planarizing one of
them. This group of embodiments includes: (1) a tenth embodiment
601 involving forming a build layer using a low stress material and
a tensile stress material (TSM), & planarizing the TSM and (2)
an eleventh embodiment 602 involving forming a build layer that
deposition of a low stress material, planarization of the low
stress material followed by deposition of a relatively thin
TSM.
[0179] The tenth embodiment 601 includes formation of a build layer
of a structure where a first structural material deposited is low
stress (compressive or tensile) and where second structural
material deposited is higher tensile stress and where the layer is
planarized through the higher tensile stress material such that
compressive stresses induced by planarization are at least
partially balanced so that stress and/or curvature is reduced.
[0180] The eleventh embodiment 602 includes formation of a build
layer of a structure where a first structural material deposited is
low stress (compressive or tensile) and where the planarization
sets the height of the material at somewhat less than the desired
layer thickness or layer level and where compressive stress induced
by planarization occurs and thereafter a thin high tensile stress
material is deposited to at least partially balance the compressive
stress and bring the thickness to the layer thickness or the upper
surface of the layer to the desired layer level.
[0181] FIGS. 16 provides a block diagram setting forth examples of
options associated with the fourth embodiment of the invention.
Similar options exist for the other embodiments of the
invention.
An Implementation of the First Preferred Embodiment and Some
Alternatives
[0182] FIG. 17A provides a generalized flowchart of a first
embodiment of invention where either (1) the process of forming at
least one layer of the structure is modified to reduced curvature
by forming the at least one layer from a first sublayer having a
thickness that is less than or equal to work hardening thickness
and a second sublayer that has a thickness that is the layer
thickness minus the thickness of the first sublayer, or (2) the
data descriptive of the three-dimensional structure or of
cross-sections of the three-dimensional structure are analyzed to
determine if certain criteria are met, such as those exemplified in
FIGS. 11D-11M to determine if the curvature reduction process
technique of the current process should be used.
[0183] The process start with block 109 and proceeds to block 110
which calls for defining the layers n=1 to N which are required to
fabricate a desired structure or structures and which calls for
defining which layers of the structure will receive modified
processing for curvature of stress reduction (i.e. which layers
will be processed using curvature reduction processing or CRP).
Block 111 set the value of the layer number variable "n" equal to
one. Block 112 enquires as to whether or not the current layer "n"
will be formed using CRP. If response is "no", the process moves to
block 113 which calls for the formation of layer "n" using a
desired formation process (i.e. one that may not be tailored to
reduce curvature or stress). After formation of layer "n" the
process moves forward to block 114 which increments the layer
number variable "n" by one (i.e. n=n+1). After block 114 the
process moves to the enquiry of block 115 which enquires as to
whether n>N, where N is the number of the final layer to be
formed. If the answer is "yes" the process moves to block 116 and
ends otherwise it loops back to block 112.
[0184] If the answer to the enquiry of block 112, for the current
layer is "yes" the process moves forward to blocks 117, 118, and
119 to implement the curvature reduction technique of this
embodiment. Block 117, calls for the division of layer "n" into
sublayers "n.sub.a" and "n.sub.b" where "n.sub.a" defines the lower
portion of layer "n" and represents a thin layer that can be made
to undergo work hardening (e.g. via planarization) through the
majority, if not all, of its thickness while sublayer "n.sub.b"
defines the majority of the thickness of layer "n". In alternative
embodiments, the data manipulations of block 117 may be performed
prior to the initiation of any physical formation of the structure.
From block 117 the process moves forward to block 118 which calls
for the formation of sublayer "n.sub.a" according to its build
instructions where deposited materials will be planarized to set
the height of sublayer "n.sub.a" equal to the desired height and
where the planarization will cause stress and/or work hardening of
the sub layer "n.sub.a" through most if not all of its
thickness.
[0185] After completion of sublayer "n.sub.a", the process moves
forward to block 119 which calls for the formation of sublayer
"n.sub.b" where the planarization process used only work hardens a
portion of the thickness of sublayer "n.sub.b". In effect, this
process results in the work hardening or stressing of both the
bottom and top of layer "n" which should help balance the stress
induced in the layer and help reduce an net stress that would lead
to curvature of the layer. From step 119 the process loops back to
block 114. The process is then continued until all layers 1 to N of
the structure are formed.
[0186] FIG. 17B provides a more specific set of steps or operations
for a specific implementation of the first embodiment of the
invention. In this more implementation, blocks that are similar to
those in FIG. 17A are similarly labeled. In this more specific
embodiments the steps 113, 118, and 119 are further defined to
include steps of operations 113-A to 113-C, 118-A to 11 8-C, and
119-A to 119-C, respectively.
[0187] Step 113-A calls for the selectively depositing a first
material according to a desired pattern of layer "n", step 113-B
calls for depositing a second material to fill voids in the 1 st
material on layer "n", while step calls for planarizing the
deposited first and second materials. In the present embodiment,
these steps complete the formation of layer "n". Typically one of
the first material or the second material is a sacrificial material
while the other is a structural material. In other embodiments,
different operations/steps may be used in forming layers.
[0188] Step 118-A calls for forming selectively depositing a first
material according to a desired pattern of layer "n" with a height
appropriate for yielding a desired thickness of sublayer "n.sub.a",
step 118-B calls for depositing a second material to fill voids in
the first material on sublayer "n.sub.a", and step 118-C calls for
planarizing the deposited first and second materials such that
stress/work hardening is introduced into "n.sub.a". In the present
embodiment, these steps complete the formation of sublayer
"n.sub.a". Typically one of the first material or the second
material is a sacrificial material while the other is a structural
material. In other embodiments, different operations/steps may be
used in forming sublayer "n.sub.a".
[0189] Step 119-A calls for selectively depositing a first material
according to a desired pattern of layer "n" with a height
appropriate for yielding a desired thickness of sublayer "n.sub.b",
step 119-B calls for depositing a second material to fill voids in
the first material on sublayer "n.sub.b", and Step 119-C calls for
planarizing the deposited first and second materials with work
hardening introduced into only a minority of the thickness of
n.sub.b". In the present embodiment, these steps complete the
formation of sublayer "n.sub.b". Typically one of the first
material or the second material is a sacrificial material while the
other is a structural material. In other embodiments, different
operations/steps may be used in forming sublayer "n.sub.b".
[0190] FIG. 17C provides a variation of the first embodiment of the
invention where the curvature reduction technique may be applied to
only selected lateral portions of layers as opposed to the entire
layers and where two optional branches of the process are
illustrated. In this alternative implementation, blocks that are
similar to those in FIG. 17A are similarly labeled. In alternative
embodiment, step 110 is modified to become step 110' as one does
not simply define which layers will receive CRP but instead
individual portions of layers are defined to receive CRP. Step 120
is inserted between 110' and 111 and calls for the supplying of a
substrate on which to form layers. The enquiry of step 112 is
modified to become the enquiry of step 112' as the question is
posed as to whether or not layer "n" has portion that is to receive
CRP. If the answer to the enquiry of step 112' is "yes" the process
move forward to block 121 which enquires as to whether CRP will be
applied to all of the layer "n". If the answer is yes the process
moves forward to blocks 117-119 and back to 114, as previously
discussed with regard to FIG. 17A. If the answer is "no" the
process moves forward to the process moves forward to block 122.
Block 122 calls for the dividing of layer "n" into lateral portions
that are to receive curvature reduction processing (CRP) and
lateral portions that are not to receive CRP. It also calls for
dividing the portion that is to receive CRP into vertical sublayer
regions "n.sub.a" and "n.sub.b", where "n.sub.a" is the lower
portion of a CRP region of the layer that undergoes stress
hardening thoughout the majority, and preferrably throughout, its
entire thickness and where "n.sub.b" defines a vertical region
above "n.sub.a" and has thickness equal to LT.sub.n-LT.sub.na. From
Blcok 122 the process moves forward to block 123.
[0191] Block 123 calls for forming a sublayer region "n.sub.a"
according to its build instructions while filling non-CRP
structural regions using sacrifical material, e.g. by selectively
depositing a first material, blanket depositing a second material,
and planarizing the materials where the planarization induces work
hardening.
[0192] From Block 123 the process moves forward to either block
124-1A or 124-2A depending on whether a first option is chosen or a
second option. Block 124-1A calls for etching away sacrificial
material deposited to the non-CRP structural material region(s).
This etching may be formed selective after masking has occurred.
After block 124-1A, the process moves to block 124-B which calls
for forming sublayer "n.sub.b" according to its build instructions
while depositing structural material to fill the non-CRP structural
material region(s) that were initially filled with sacrificial
material, e.g. by selectively depositing a first material, blanket
depositing 2.sup.nd material, and then planarizing. As noted above
the second option takes the process to block 124-2A which calls for
forming sublayer "n.sub.b" according to its build instructions
while depositing sacrificial material to the non-CRP structural
material region(s) and thereafter moving to block 124-2B which
calls for the etching away of sacrificial material deposited to the
non-CRP structural material region(s) from both the "n.sub.a" and
"n.sub.b" portions of layer "n" after which the process moves
forward to block 124-2C which calls for depositing structural
material to the etched region(s) and then planarizing.
[0193] FIGS. 18A-18I depict various states of an implementation of
the first embodiment according to the process of FIG. 17B as
applied to the formation of the structure of FIG. 6B where CRP is
applied to the entire second layer of the structure.
[0194] FIG. 18A depicts a side view of the state of the process
after a first layer L1 is formed using a structural material 131
and a sacrificial material 141 wherein the upper surface portion
131-B of the structural material is shown as being different from
the remainder 131-A of the structural material as it has undergone
work hardening from a planarization operation that was used to set
the level of the first layer.
[0195] FIGS. 18B-18E depict states of the process involving the
formation of the first sublayer of the second layer. FIG. 18B
depicts a side view of the state of the process after a mask 137 is
applied and patterned and after a structural material 132-A has
been deposited as part of forming a first sublayer L2-A of the
second layer L2. FIG. 18C depicts a side view of the state of the
process after the mask has been removed. FIG. 18D depicts a side
view of the state of the process after a blanket deposit of a
sacrificial material 142-A has been made as part of the process of
forming the first sublayer L2-A of the second layer L2. FIG. 18E
depicts a side view of the state of the process after the materials
forming the first sublayer L2-A of the second layer L2 have been
planarized where it is shown that substantially all of the
structural material 132-A' on the first sublayer L2-A of the second
layer has undergone work hardening.
[0196] FIGS. 18F-18H depict states of the process involving
formation of the second sublayer of the second layer. FIG. 18F
depicts a side view of the state of the process after a mask 147 is
applied and patterned and after a structural material 132-B has
been deposited as part of forming a second sublayer L2-B of the
second layer L2. FIG. 18G depicts a side view of the state of the
process after the mask 147 has been removed and a blanket deposit
of sacrificial material 142-B has been made as part of the process
of forming the second sublayer L2-B of the second layer L2. FIG.
18H depicts a side view of the state of the process after the
materials 132-B and 142-B forming the second sublayer L2-B of the
second layer L2 have been planarized where it is shown that only
the top portion of the structural material 132-B' on the second
sublayer of the second layer has undergone work hardening.
[0197] FIG. 18I depicts a side view of the state of the process
after the sacrificial material has been removed to release/reveal
the structure/device formed. FIG. 18I can be compared to 6C to see
the difference in work hardening regions that result from the use
of CRP of the present embodiment and which it is believed will lead
to a reduction in curvature of the structural material portion of
the second layer L2 after it is released from the sacrificial
material.
An Implementation of the Second Preferred Embodiment and Some
Alternatives
[0198] FIG. 19 provides a generalized flowchart for the second
embodiment of the invention where the structure will be formed,
transferred to a second substrate or carrier, the original
substrate or carrier removed and the bottom side of the first layer
planarized to induce work hardening therein.
[0199] The process of FIG. 19 start with block 208 and then moves
to block 209 which calls for supplying a substrate on which layers
will be formed. The process then moves to block 210 which calls for
the defining of each layer from the first to the Nth from which the
structure will be formed. After layers are defined, the process
moves forward to block 211 which calls for setting the layer number
variable equal to one. Next, with block 212, the "nth" layer is
formed according to its build instructions. Next the layer number
variable "n" is incremented by one (i.e. per block 213, n=n+1).
Next the block 214 makes the enquiry as to whether the layer number
variable has exceed the number of the final layer (i.e. has the
last layer been formed?). If "no" the process loops back to block
212, if "yes" the process moves forward to block 215. Block 215
calls for the formation of one or more additional layers if
desired. Such additional layers may include, for example, a release
layer. From block 215 the process moves forward to block 216 which
calls for attaching the upper surface of the layer stack (i.e. the
upper surface of the last formed layer) to a temporary substrate or
carrier). Next, according to block 217, the original substrate is
removed. The originally substrate may have been destructively
removed or removed via a release layer or the like. Next, according
to block 218, the bottom surface of the first layer is planarized
in a manner to induce work hardening in it. This is done with the
hopes of balancing the stress induced in the upper portion of each
layer, by other planarization operations, with the downward stress
introduced by this operation. Finally, according to block 220, the
structure is separated from the sacrificial material and from the
second substrate (if desired) or from the carrier. The process then
moves forward to block 221 and ends. It is believed that the
structure will have more balanced stress due to the final
planarization operation and therefore will have less intended
curvature.
[0200] FIG. 20A depicts a side view of a three layer L1-L3
structure 230 made from two different structural materials 232 and
234 (e.g. a pin probe formed on its side having a nickel or nickel
cobalt body 232 and a rhodium tip 234). The structure may be
relatively thin 50-60 microns in height, or less, and may be
subject to significant unintended curvature when formed by an
electrodeposition process as discussed herein and released from
sacrificial material and a substrate on which it was formed. FIG.
20B depicts a side view of the structure of FIG. 20A while it is
still surrounded by sacrificial material 236.
[0201] FIG. 20C depicts a side view of the structure of FIG. 20B
where work hardened upper portions of each layer L1-B, L2-B, and
L3-B are shown along with regions that did not undergo significant
work hardening L1-A, L2-A, L3-A. The work hardened regions may
result from planarization of each layer, e.g. by lapping, as it is
formed. FIG. 20D depicts a side view of the structure of FIG. 20B
where work hardened upper portions of each layer are indicated and
where the bottom portion L1-C of the first layer is shown as work
hardened according to an implementation of the second embodiment of
the invention so as to help balance any stresses (e.g. compressive
forces) within the structure that may tend to make the structure
curve after release from a build substrate and sacrificial material
used in forming the structure.
[0202] FIGS. 21A-21W provide side views of various states of an
example process involved in forming the structure of FIG. 20A &
20B in an implementation of the second embodiment of the invention.
This process falls within process description defined by the
flowchart of FIG. 19.
[0203] FIGS. 21A-21E depict various states of the process involved
in forming a first layer L1 of the structure where the height of
the first layer will not be completely finalized until after all
layers are formed. FIG. 21A depicts a side view of the state of the
process after a photoresist 243 has been patterned deposited onto a
substrate 242 in preparation for selectively depositing a 1st
structural material during formation of a 1st layer of the
structure. FIG. 21B depicts a side view of the state of the process
after deposition of the first structural material 244. FIG. 21C
depicts a side view of the state of the process after removal of
the photoresist 243. FIG. 21D depicts a side view of the state of
the process after blanket deposition of a sacrificial material 246
that will form a portion of the 1st layer. FIG. 21E depicts a side
view of the state of the process after planarization of the
materials deposited on the first layer L1 but where the resulting
height of the first layer is greater than a desired final height
for the first layer. The upper portion 244' of material 244 is
shown differently as it is assumed that it has been work hardened
by the planarization process.
[0204] FIGS. 21F-21M depict a side view of various states of the
process involved informing the second layer L2 of the structure.
FIG. 21F depicts a side view of the state of the process after
application and patterning of a photoresist 253 in preparation for
deposition of a first structural material 254 for the second layer
L2. FIG. 21G depicts a side view of the state of the process after
deposition of the first structural material 254 associated with the
second layer. FIG. 21H depicts a side view of the state of the
process after removal of the photoresist 253. FIG. 21I depicts a
side view of the state of the process after application and
patterning of a second photoresist 257 on the second layer where an
opening is created that will allow deposition of a second
structural material 255 along side the first structural material
254 (it may also allow some deposition over the first structural
material if such patterning is necessary to allow appropriate and
reliable exposure and development of the photoresist to occur. FIG.
21J depicts a side view of the state of the process after
deposition of the 2nd structural material 255. FIG. 21K depicts a
side view of the state of the process after removal of the
photoresist 257. FIG. 21L depicts a side view of the state of the
process after deposition of sacrificial material 256 which will
form a part of the second layer. FIG. 21M depicts a side view of
the state of the process after planarization of the three materials
deposited to form the second layer where the upper surface 254' and
255' of materials 254 and 255 are indicated as being subjected to
work hardening and associated compressive stress and where the
height of the second layer is equal to a desired height of the
second layer.
[0205] FIGS. 21N-21S depict side view of various states of the
process associated with forming the third layer L3 of the
structure. FIG. 21N depicts a side view of the state of the process
after a photoresist 263 is applied and patterned onto the second
layer in preparation for selectively depositing a first structural
material during formation of a third layer of the structure. FIG.
210 depicts a side view of the state of the process after
deposition of the first structural material 364. FIG. 21 P depicts
a side view of the state of the process after removal of the
photoresist 363. FIG. 21Q depicts a side view of the state of the
process after blanket deposition of a sacrificial material 366 that
will form a portion of the 3rd layer. FIG. 21R depicts a side view
of the state of the process after planarization of the materials
deposited on the third layer where the resulting height of the 3rd
layer is equal to a desired height of the third layer and where the
upper portion 364' of the structural material 364 is shown as
having been work hardened.
[0206] FIG. 21S depicts a side view of the state of the process
after attachment of a secondary substrate or carrier 372 (e.g. a
vacuum chuck). FIG. 21T depicts a side view of the state of the
process after removal of the original substrate 242. In some
alternative embodiments there may have been a release material
located between the substrate and the first layer so that the
substrate may be removed in a nondestructive manner. FIG. 21 U
depicts a side view of the state of the process after planarization
of the bottom side of the first layer thereby providing some
balancing compressive work hardening of the structural material
244'' on the bottom of the first layer which may tend to reduce the
amount of curvature the structure will undergo. FIG. 21V depicts a
side view of the state of the process after the structure is
released from the sacrificial material and from the secondary
substrate or carrier 272.
[0207] FIG. 22A-22F depict states of the process that may be used
to replace states 21S-21V in an alternative implementation of the
second embodiment where a release layer and a substrate or other
carrier is added to the top of the 3rd layer so that continued
operations (e.g. planarization of the bottom of the 1st layer may
occur). FIG. 22A depicts the state of the process after a release
layer 271 of sacrificial material (this is a one material layer) is
deposited on top of the third layer. FIG. 22B depicts the state of
the process after the release layer 271 of sacrificial material is
planarized with the potential work hardened portion of the release
layer is indicated 271'. FIG. 22C depicts the state of the process
after a transfer substrate or carrier 272 is bonded or otherwise
attached to the release layer 271. FIG. 22D depicts the state of
the process after the original substrate 242 is removed. FIG. 22E
depicts a side view of the state of the process after planarization
of the bottom side of the first layer thereby providing some
balancing compressive work hardening 244' of the bottom of the
first layer which may tend to reduce the amount of curvature the
structure will undergo. FIG. 22F depicts a side view of the state
of the process after the structure is released from the sacrificial
material and the release layer.
[0208] An example of the third embodiment of the invention may be
implemented by inserting additional steps into the process of FIG.
19 as shown in block 219 of FIG. 23.
An Implementation of the Fourth Embodiment of the Invention and
Some Alternatives
[0209] FIG. 24A-24G-2 depict states of an example process as
applied to a one layer cantilever structure (the whole structure is
formed with two layers) implementing the fourth embodiment of the
invention where the curvature reduction technique etches away the
upper surface of the second layer and where the etching occurs in
either a selective manner (FIG. 24G1) based on the selectivity of
an etchant used and not on masking (as would be the case in some
other embodiments) or a non-selective manner FIG. 24G-2 based on
the non-selectivity of and etchant used and where the etched
structural material is not replaced via a subsequent deposition
process (as would be the case for some alternative
embodiments).
[0210] FIG. 24A depicts a side view of the state of the process
after formation of a first layer L1, including structural material
404 and sacrificial material 406, on a substrate 402 where it is
not indicated whether or not work hardening of the upper surface of
the first layer has occurred. FIG. 24B depicts a side view of the
state of the process after a mask 417 is formed and a second layer
of structural material 412 is deposited. FIG. 24C depicts a side
view of the state of the process after the mask is removed. FIG.
24D depicts a side view of the state of the process after blanket
deposition of a sacrificial material 414 is deposited (in
alternative embodiments the order of depositing the structural and
sacrificial material may be reversed). FIG. 24E depicts a side view
of the state of the process after the surface of the second layer
L2 of deposited materials 414 and 416 is planarized at a level that
is slightly above the desired level for the second layer (assuming
that re-deposition of etched structural material will not occur).
The upper surface 414' of the structural material 414 is shown as
having been work hardened. FIG. 24F-1 depicts a side view of the
state of the process after a selective etchant primarily attacks
and removes the upper surface of the structural material (e.g. the
portion of the structural material that has been work hardened as a
result of the planarization process) to bring the level of the
deposit to the boundary level of the layer whereas FIG. 24F-2
depicts the state of the process after a substantially
non-selective etchant attacks and removes the upper surface of both
the structural and sacrificial materials. FIG. 24G-1 depicts the
state of the process after the sacrificial material 416 and 406
have been removed and where FIG. 24G-2 depicts the state of the
process after separation of the structure from the substrate 402
(which may not occur in some alternative embodiments)
An Implementation of the Fifth Embodiment of the Invention and Some
Alternatives
[0211] FIGS. 25A-25H depict states of an example process as applied
to a one layer structure implementing the fifth embodiment of the
invention where annealing of the upper surface of the structural
material is used to eliminate or reduced stress and/or curvature
distortion. FIG. 25A depicts a side view of the state of the
process after supplying a substrate 502 on which a layer or layers
will be formed. FIG. 25B depicts a side view of the state of the
process after a release layer 503 is formed on the substrate (such
a release layer may not be necessary or appropriate in some
embodiments). FIG. 25C depicts a side view of the state of the
process after a patterned mask 507 is formed and adhered to the
substrate (i.e. to the release layer on the substrate). In some
alternative embodiments, the mask may be a photoresist mask which
is adhered, exposed, and developed to yield desired openings. FIG.
25D depicts a side view of the state of the process after a
structural material 504 is deposited. FIG. 25E depicts a side view
of the state of the process after the surface of the masking
material and structural material are planarized (in an alternative
embodiments the masking material may have been removed and a
sacrificial material deposited prior to planarization occurring)
wherein the upper surface 504' of the structural material is shown
as having been work hardened. FIG. 25F depicts a side view of the
state of the process after a portion 504'' of the upper surface of
the first layer L1 has been annealed by beam 508 of a laser (not
shown). FIG. 25G depicts a side view of the state of the process
after the entire upper surface of the structural material has
annealed to yield 504''. FIG. 25H depicts the state of the process
after the mask and substrate have been separated from the
structural material 504/504'' to yield structure 500.
[0212] As with the other embodiments, presented herein, the sixth
embodiment may be implemented in a number of different ways. The
heating that induces annealing may (1) expose the entire upper
surface of the layer, (2) a mask may be formed on the upper surface
of the layer to shield portions of the layer, (3) be supplied via
an array of sources so with only selected sources powered. Various
other alternatives are also possible and will be understood by
those of skill in the art.
An Implementation of the Seventh Embodiment of the Invention and
Some Alternatives
[0213] FIGS. 26A-26F depict states of an example process as applied
to either a one layer structure that is divided into two layers or
a two layer structure implementing an example of the seventh
embodiment of the invention where the upper sublayer or the second
layer has its structural configuration modified to reduce stress
and/or curvature distortion by inserting vertical stress reliefs
into it (in alternative embodiments the breaks may be implemented
so that they only extend into the layer to a depth necessary to
extend through or nearly through any work hardened upper surface
portion of the layer). FIG. 26A depicts a side view of the state of
the process after supplying a substrate 702 on which a layer or
layers of a structure will be formed, after a release layer 703 is
formed on the substrate (such a release layer may not be necessary
or appropriate in some embodiments), after a patterned mask 707 is
formed and adhered to the substrate (i.e. to the release layer on
the substrate), and after a structural material 704 is deposited to
form a first layer or first sublayer of the first layer. FIG. 26B
depicts a side view of the state of the process after a second
layer or second sublayer of masking material 717 is applied to the
surface of the first layer or first sublayer and patterned to form
breaks 715 at periodic intervals along region that would be
occupied by structural material if it were not for the stress
and/or curvature that the process is attempting to minimize. FIG.
26C depicts a side view of the state of the process after plating
of structural material 714(e.g. nickel or a nickel alloy) into the
openings in the mask 717. FIG. 26D depicts a side view of the state
of the process after planarization of the upper surface of the
second layer or second sublayer is performed to set the height of
the second layer or second sublayer at the boundary level for that
layer or sublayer. FIG. 26E depicts a side view of the state of the
process after the mask and substrate have been separated from the
structural material while FIG. 26F depicts a top view of the same
state of the process (in this example it is noted that the notches
formed in the upper surface extend in a single direction
perpendicular to the length of the structure so as to maximize the
stress relief that has occurred while in other embodiments other
patterns of notches may be used and in still other embodiments, the
notches may be filled with a material, e.g. by spreading, wiping
clean, and solidifying.
An Implementation of the Eight Embodiment of the Invention and Some
Alternatives
[0214] FIGS. 27A-27H depict states of an example process as applied
to a one layer cantilever structure 700 (the whole structure is
formed with two layers) implementing the eighth embodiment of the
invention where stress induced in worked hardened regions is
isolated by the formation of breaks in the worked hardened material
after it is formed to eliminate or reduced stress and/or curvature
distortion. The breaks that are formed in the upper surface of the
second layer of this example, may be designed into the structure or
may be placed in the structure by implementation of an algorithm
that modifies the structure based on a pre-designed pattern or
based on a pattern that is created in response to design parameters
specified by the builder in order optimize stress and/or curvature
reduction.
[0215] FIG. 27A depicts a side view of the state of the process
after formation of a first layer L1, including structural material
704 and sacrificial material 706, on a substrate 702 where it is
not indicated whether or not work hardening of the upper surface of
the first layer has occurred (it is irrelevant to this example as
if is intended to only deal with work hardening that has occurred
on the second layer. FIG. 27B depicts a side view of the state of
the process after a mask 717 is formed and a second layer of
structural material 714 is deposited. FIG. 27C depicts a side view
of the state of the process after the mask is removed. FIG. 27D
depicts a side view of the state of the process after blanket
deposition of a sacrificial material 716 is deposited (in
alternative embodiments the order of depositing the structural and
sacrificial material may be reversed). FIG. 27E depicts a side view
of the state of the process after the surface of the second layer
L2 of deposited materials 714 and 716 is planarized at a level that
is slightly above the desired level for the second layer (assuming
that re-deposition of etched structural material will not occur).
The upper surface 714' of the structural material 714 is shown as
having been work hardened. FIG. 27F depicts a side view of the
state of the process after selectively removal of at least a
desired depth of work hardened material has been removed, for
example via patterned etching (dry or wet), partial depth dicing,
laser ablation, or the like, FIGS. 27G and 27H depict the state of
the process after removal of the sacrificial material and substrate
respectively to yield the structure 700.
[0216] As with the other embodiments, presented herein, this
embodiment may be implemented in a number of different ways
including use of the CRP on a plurality of layers (instead of just
the one illustrate). The stress relief gaps may filled in with a
material that does not reintroduce stress, reintroduces less stress
or even introduces stress that is opposite to that induced by the
work hardening.
An Implementation of the Ninth Embodiment of the Invention and Some
Alternatives
[0217] FIGS. 28A-28G-2 depict the state of an example process as
applied to a single layer cantilever structure, which is formed
along with a post, where the layer of the cantilever structure is
divided into two sublayers implementing the an example of the ninth
embodiment where the structural portion of the layers is formed
from two vertically stacked materials where planarization of the
upper structural material occurs and where the upper material is
planarizable by a non-stress inducing process (e.g. diamond fly
cutting).
[0218] FIG. 28A depicts a side view of the state of the process
after formation of a first layer L1 where it is not indicated
whether or not work hardening of the upper surface of the first
layer has occurred as it is not relevant to the present example as
the CRP is only to be implement in conjunction with formation of
the second layer. FIG. 28B depicts a side view of the state of the
process after a mask 917 is formed and a first portion (e.g.
sublayer of the second layer) of a first structural material 914-A
is deposited, where the first structural material 914-A is a
material that cannot be readily planarized (e.g. nickel, or nickel
cobalt, rhodium, or the like) without inducing significant stress
into it. FIG. 28C depicts a side view of the state of the process
after a second structural material 914-B is deposited over the
first structural material, wherein the second structural material
is a material (e.g. amorphous nickel phosphorous) that can be
readily planarized without inducing significant stress (e.g. by
diamond fly cutting). FIG. 28D depicts a side view of the state of
the process after the mask is removed. FIG. 28E depicts a side view
of the state of the process after blanket deposition of a
sacrificial material 716 has occurred (in alternative embodiments
the order of depositing the structural and sacrificial material may
be reversed). FIG. 28F depicts a side view of the state of the
process after the surface of the second structural material 914-B
is planarized at a level that corresponds to the boundary of the
layer using a non-stress inducing planarization process. FIG. 28G
depicts the state of the process after the sacrificial material has
been removed and where FIG. 28H depicts the state of the process
after separation of the structure 900 from the substrate (which may
not occur in some alternative embodiments).
[0219] As with the other embodiments, presented herein, this
embodiment may be implemented in a number of different ways
including use of the CRP on a plurality of layers (instead of just
the one illustrated). In some embodiments it may be acceptable if
some portion of the material 914-A reaches the planarization level
so long as it doesn't represent a large area that could negatively
impact the effectiveness of the planarization process.
An Implementation of the Tenth Embodiment of the Invention and Some
Alternatives
[0220] FIGS.29A-29H depict the states of an example process as
applied to a single layer cantilever structure which is divided
into two sublayers implementing an example of the tenth primary
embodiment of the invention where the structural portion of the
layer is formed from two vertically stacked materials where
planarization of the upper structural material occurs and where the
lower material is deposited in a low stress state while the upper
material is deposited in a higher tensile stress state and where
the upper material is planarized using a process (e.g. lapping)
that introduces compression into the material such that the tensile
and compressive forces at least partially cancel one another so
that stress and/or distortion is reduced.
[0221] FIG. 29A depicts a side view of the state of the process
after formation of a first layer that includes structural material
1004 and sacrificial material 1006 which have been deposited on
substrate 1002 and then planarized. In this figure it is not
indicated whether or not work hardening of the upper surface of the
first layer has occurred as it is irrelevant to the present example
as CRP is only intended to be applied to the second layer. FIG. 29B
depicts a side view of the state of the process after a mask is
formed and a first structural material 1014-A (e.g. first sublayer
of the second layer) is deposited, where the first structural
material 1014-A is a material that is preferably deposited with
minimal tensile or compressive stress. FIG. 29C depicts a side view
of the state of the process after a second structural material
1014-B is deposited over the first structural material, wherein the
second structural material is deposited with significant tensile
stress. FIG. 29D depicts a side view of the state of the process
after the mask is removed. FIG. 29E depicts a side view of the
state of the process after blanket deposition of a sacrificial
material 1016 occurs(in alternative embodiments the order of
depositing the structural and sacrificial material may be
reversed). FIG. 29F depicts a side view of the state of the process
after the surface of the second structural material 1014-B is
planarized at a level that corresponds to the boundary of the
layer. Planarization includes use of process that induces
compressive stress into the second material, wherein after
planarization substantially all of or at least most of the
remaining second material undergoes work hardening (which tends to
induce compressive stress). FIG. 29G depicts the state of the
process after the sacrificial material has been removed and where
FIG. 29H depicts the state of the process after separation of the
structure 1000 from the substrate (which may not occur in some
alternative embodiments).
[0222] As with the other embodiments, presented herein, this
embodiment may be implemented in a number of different ways
including use of the CRP on a plurality of layers (instead of just
the one illustrated).
An Implementation of the Eleventh Embodiment of the Invention and
Some Alternatives
[0223] FIGS. 30A-30G-2 depict state of an example process as
applied to a single layer cantilever structure which is formed on a
post and which is divided into two sublayers implementing an
example of the eleventh primary embodiment of the invention where
the structural portion of the layer is formed from two vertically
stacked materials where planarization of the lower structural
material occurs and sets the planned height of the deposited
material at some distance below the desired layer thickness and
where the planarization introduces work hardening into the upper
surface of the first structural material and thereafter a thin
coating of second structural material is deposited to raise the
height of the deposited materials to the desired layer level and
wherein the second material is chosen or deposited in such a way
that it results in a high tensile stress deposit that helps
compensate for the compressive stress in the work hardened region
of the first material.
[0224] FIG. 30A depicts a side view of the state of the process
after formation of a first layer that includes structural material
1104 and sacrificial material 1106 which were deposited onto
substrate 1102 where it is not indicated whether or not work
hardening of the upper surface of the first layer has occurred as
it is irrelevant to the present example as the CRP is only to be
applied to the second layer. FIG. 30B depicts a side view of the
state of the process after a mask 1117-A is formed and a first
structural material 1114-A (e.g. first sublayer of the second
layer) is deposited, where the first structural material is a
material that is preferably deposited with minimal tensile or
compressive stress. FIG. 30C depicts a side view of the state of
the process after the mask is removed. FIG. 30D depicts a side view
of the state of the process after blanket deposition of a
sacrificial material 1116 occurs (in alternative embodiments the
order of depositing the structural and sacrificial material may be
reversed). FIG. 30E depicts a side view of the state of the process
after the surface of the first structural material 1114-A is
planarized at a level that is somewhat below the desired boundary
level of the layer using a planarization process that induces
compressive stress into the first structural material, wherein
planarization induces work hardening in only a portion 1114-A' of
the thickness of the deposit of the first structural material. FIG.
30F depicts a side view of the state of the process after mask
1117-B is applied and a thin, high tensile stress coating of a
second structural material 1114-B is deposited over work hardened
portion 1114-A' of the first structural material. The amount of
material 1114-B that is deposited is thin and it is believed it can
be deposited with a sufficient uniform texture so as to no require
further planarization. The second material 1114-B either inherently
has a high tensile stress or is deposited in such away so as to
incur a high tensile stress. It is believed that such stressing can
help to compensate for the compressive stress induced in the upper
portion 1114-A' of the first structural material such that stress
and/or curvature distortion is reduced. FIG. 30G depicts the state
of the process after the sacrificial material has been removed and
FIG. 30H depicts the state of the process after separation of the
structure 1100 from the substrate (which may not occur in some
alternative embodiments).
[0225] As with the other embodiments, presented herein, this
embodiment may be implemented in a number of different ways
including use of the CRP on a plurality of layers (instead of just
the one illustrated).
Further Alternatives and Conclusions
[0226] The various embodiments explicitly set forth in this
application may take on a variety of alternative forms. For
example, the orders of depositing structural and sacrificial
material may be varied, different numbers of sacrificial and
structural materials may be used, different mechanical, chemical,
and electrochemical etching and planarization processes may be
used. Depositions may be made using electrochemical techniques,
electroless deposition techniques, sputtering, spraying, spreading,
as well as via other processes. Electrochemical deposition may take
the form of electroplating of fixed current density, pulsed
electroplating, reverse pulse plating.
[0227] Curvature reduction processes may involve or additionally
include techniques to change grain structure within layers, such as
for example, reverse pulse plating, formation of grain nucleation
sites within a layer. Curvature reduction processes may involve
theoretical or empirically determined process parameters that are
optimized for a given situation. Though a portion of this
application has been written based on the assumption that work
hardening occurs near the surface of some materials (e.g. nickel,
nickel-cobalt, other nickel alloys, and the like) when subjected to
some planarization processes (e.g. lapping), the effectiveness of
any stress reduction process or curvature reduction process should
dictate the appropriateness of the process and not whether the
assumed work hardening theory is determined to be accurate,
inaccurate, or simply incomplete.
[0228] The curvature reduction techniques may be implemented on a
critical or selected region basis, critical of selected layer
basis, based on locations or layers containing up-facing regions,
locations or layers containing non-up-facing regions, regions that
are thin relative to a predefined value, regions have length to
thickness aspect ratio that meet or do not meet certain criteria.
Rework of layers that are determined to be, or are suspected of
being faulty may be performed.
[0229] It will be understood by those of skill in the art or will
be readily ascertainable by them that various additional operations
may be added to the processes set forth herein. For example,
between performances of the various deposition operations, the
various etching operations, and the various planarization
operations cleaning operations, activation operations, and the like
may be desirable.
[0230] Some embodiments may employ diffusion bonding or the like to
enhance adhesion between successive layers of material. Various
teachings concerning the use of diffusion bonding in
electrochemical fabrication processes are set forth in U.S. patent
application Ser. No. 10/841,384 which was filed May 7, 2004 by
Cohen et al. which is entitled "Method of Electrochemically
Fabricating Multilayer Structures Having Improved Interlayer
Adhesion" and which is hereby incorporated herein by reference as
if set forth in full. This application is hereby incorporated
herein by reference as if set forth in full.
[0231] Further teachings about planarizing layers and setting
layers thicknesses and the like are set forth in the following U.S.
patent applications which were filed Dec. 31, 2003: (1) U.S. Patent
Application No. 60/534,159 by Cohen et al. and which is entitled
"Electrochemical Fabrication Methods for Producing Multilayer
Structures Including the use of Diamond Machining in the
Planarization of Deposits of Material" and (2) U.S. Patent
Application No. 60/534,183 by Cohen et al. and which is entitled
"Method and Apparatus for Maintaining Parallelism of Layers and/or
Achieving Desired Thicknesses of Layers During the Electrochemical
Fabrication of Structures". The techniques disclosed explicitly
herein may benefit by combining them with the techniques disclosed
in U.S. patent application Ser. No. 11/029,220, filed Jan. 3, 2005
by Frodis, et al., and which is entitled "Method and Apparatus for
Maintaining Parallelism of Layers and/or Achieving Desired
Thicknesses of Layers During the Electrochemical Fabrication of
Structures". These patent filings are each hereby incorporated
herein by reference as if set forth in full herein.
[0232] Additional teachings concerning the formation of structures
on dielectric substrates and/or the formation of structures that
incorporate dielectric materials into the formation process and
possibility into the final structures as formed are set forth in a
number of patent applications: (1) U.S. Patent Application No.
60/534,184, by Cohen, which as filed on Dec. 31, 2003, and which is
entitled "Electrochemical Fabrication Methods Incorporating
Dielectric Materials and/or Using Dielectric Substrates"; (2) U.S.
Patent Application No. 60/533,932, by Cohen, which was filed on
Dec. 31, 2003, and which is entitled "Electrochemical Fabrication
Methods Using Dielectric Substrates"; (3) U.S. Patent Application
No. 60/534,157, by Lockard et al., which was filed on Dec. 31,
2004, and which is entitled "Electrochemical Fabrication Methods
Incorporating Dielectric Materials"; (4) U.S. Patent Application
No. 60/574,733, by Lockard et al., which was filed on May 26, 2004,
and which is entitled "Methods for Electrochemically Fabricating
Structures Using Adhered Masks, Incorporating Dielectric Sheets,
and/or Seed Layers that are Partially Removed Via Planarization";
and U.S. Patent Application No. 60/533,895, by Lembrikov et al.,
which was filed on Dec. 31, 2003, and which is entitled
"Electrochemical Fabrication Method for Producing Multi-layer
Three-Dimensional Structures on a Porous Dielectric". The
techniques disclosed explicitly herein may benefit by combining
them with the techniques disclosed in U.S. patent application Ser.
No. 11/029,216 filed Jan. 3, 2005 by Cohen et al. and entitled
"Electrochemical Fabrication Methods Incorporating Dielectric
Materials and/or Using Dielectric Substrates". These patent filings
are each hereby incorporated herein by reference as if set forth in
full herein.
[0233] Some embodiments may not use any blanket deposition process.
Some embodiments may involve the selective deposition of a
plurality of different materials on a single layer or on different
layers. Some embodiments may use blanket or selective depositions
processes that are not electrodeposition processes. Some
embodiments may form structures from two or more materials where
one or more of the materials are coated with thin deposits of
dielectric material and one or more materials are treated as a
sacrificial material and removed after the formation of a plurality
of layers. Some embodiments may use nickel or a nickel alloy as a
structural material while other embodiments may use different
materials such as gold, silver, or any other electrodepositable or
electroless depositable materials. Some embodiments may use copper
as the structural material with or without a sacrificial material.
Some embodiments may remove a sacrificial material while other
embodiments may not.
[0234] Though various portions of this specification have been
provided with headers, it is not intended that the headers be used
to limit the application of teachings found in one portion of the
specification from applying to other portions of the specification.
For example, it should be understood that alternatives acknowledged
in association with one embodiment, are intended to apply to all
embodiments to the extent that the features of the different
embodiments make such application functional and do not otherwise
contradict or remove all benefits of the adopted embodiment.
Various other embodiments of the present invention exist. Some of
these embodiments may be based on a combination of the teachings
herein with various teachings incorporated herein by reference.
[0235] As noted above, embodiments of the invention may take a
variety of forms some of which have been set forth herein in detail
while others are described or summarized in a more cursory manner,
while still others will be apparent to those of skill in the art
upon review of the teachings herein though they are not explicitly
set forth herein. Further embodiments may be formed from a
combination of the various teachings explicitly set forth in the
body of this application. Even further embodiments may be formed by
combining the teachings set forth explicitly herein with teachings
set forth in the various applications and patents referenced
herein, each of which is incorporated herein by reference. In view
of the teachings herein, many further embodiments, alternatives in
design and uses of the instant invention will be apparent to those
of skill in the art. As such, it is not intended that the invention
be limited to the particular illustrative embodiments,
alternatives, and uses described above but instead that it be
solely limited by the claims presented hereafter.
* * * * *