U.S. patent application number 12/504496 was filed with the patent office on 2010-01-14 for electrochemical fabrication method for producing compliant beam-like structures.
This patent application is currently assigned to Microfabrica Inc.. Invention is credited to Christopher A. Bang, Adam L. Cohen, Marvin M. Kilgo, III, Michael S. Lockard.
Application Number | 20100006443 12/504496 |
Document ID | / |
Family ID | 34228452 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100006443 |
Kind Code |
A1 |
Cohen; Adam L. ; et
al. |
January 14, 2010 |
Electrochemical Fabrication Method for Producing Compliant
Beam-Like Structures
Abstract
Embodiments of the invention are directed to the formation of
beam-like structures using electrochemical fabrication techniques
where the beam like structures have narrow regions and wider
regions such that a beam of desired compliance is obtained. In some
embodiments, narrower regions of the beam are thinner than a
minimum feature size but are formable as a result of the thicker
regions. In some embodiments the beam-like structures are formed
from a plurality of adhered layers.
Inventors: |
Cohen; Adam L.; (Los
Angeles, CA) ; Lockard; Michael S.; (Lake Elizabeth,
CA) ; Bang; Christopher A.; (San Diego, CA) ;
Kilgo, III; Marvin M.; (Oakland, CA) |
Correspondence
Address: |
MICROFABRICA INC.;ATT: DENNIS R. SMALLEY
7911 HASKELL AVENUE
VAN NUYS
CA
91406
US
|
Assignee: |
Microfabrica Inc.
Van Nuys
CA
|
Family ID: |
34228452 |
Appl. No.: |
12/504496 |
Filed: |
July 16, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10883891 |
Jul 2, 2004 |
|
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12504496 |
|
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60484636 |
Jul 3, 2003 |
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Current U.S.
Class: |
205/50 ;
205/118 |
Current CPC
Class: |
C25D 5/022 20130101;
B23H 9/00 20130101; B23H 3/00 20130101; G03F 7/00 20130101; C25D
1/003 20130101; C25D 5/10 20130101 |
Class at
Publication: |
205/50 ;
205/118 |
International
Class: |
C25D 5/02 20060101
C25D005/02; C25D 7/00 20060101 C25D007/00 |
Claims
1. An elongated structure having a desired compliance, comprising a
structural material that is configured with narrow regions
separated by wider regions, wherein the widths of the regions are
selected to yield desired mechanical properties.
2. The structure of claim 1 comprising a plurality of layers of
deposited material.
3. The structure of claim 1 wherein the narrow regions have a width
that is less than a general minimum feature size associated with a
build process which is used in fabricating the structure and where
the wider regions have a width that is greater than the general
minimum feature size.
4. A method of designing a structure, comprising: designing a
structure comprising one or more beam-like elements to have a
desired set of mechanical properties; comparing the dimensions of
the designed structure with minimum feature size dimensions and
determining that a width of at least one of the beam-like elements
is narrower than a minimum feature size; modifying the
configuration of the at least one beam-like element that has a
width narrower than the minimum feature size by, configuring
portions of the one beam-like element to have a width less than the
minimum feature size and at least one other portion of the at least
one beam-like element to have a width greater than the minimum
feature size.
5. A method for producing a multi-layer structure having an
elongated element having an effective compliance, comprising:
configuring a design of the elongated element to have portions that
have widths less than a minimum feature size and portions having
widths greater than the minimum feature size wherein a compliance
of the elongated elements is set at desired amount; producing the
structure using masking operations and electrochemical deposition
or etching operations, where the formation of the masks or use of
the masks at least in part dictate the minimum feature size.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/883,891 (Microfabrica Docket No.
P-US116-A-MF) filed on Jul. 2, 2004, which in turn claims benefit
of U.S. Provisional Patent Application No. 60/484,636 filed on Jul.
3, 2003. These referenced applications are hereby incorporated
herein by reference as if set forth in full.
FIELD OF THE INVENTION
[0002] The embodiments of various aspects of the invention relate
generally to the formation of three-dimensional structures using
electrochemical fabrication methods via a layer-by-layer build up
of deposited materials and more particularly to the formation of
beam-like structures that have a desired compliance.
BACKGROUND OF THE INVENTION
[0003] A technique for forming three-dimensional structures (e.g.
parts, components, devices, and the like) from a plurality of
adhered layers was invented by Adam L. Cohen and is known as
Electrochemical Fabrication. It is being commercially pursued by
Microfabrica.TM. Inc. (formerly MEMGen.RTM. Corporation) of Van
Nuys, Calif. under the name EFAB.RTM.. This technique was described
in U.S. Pat. No. 6,027,630, issued on Feb. 22, 2000. This
electrochemical deposition technique allows the selective
deposition of a material using a unique masking technique that
involves the use of a mask that includes patterned conformable
material on a support structure that is independent of the
substrate onto which plating will occur. When desiring to perform
an electrodeposition using the mask, the conformable portion of the
mask is brought into contact with a substrate while in the presence
of a plating solution such that the contact of the conformable
portion of the mask to the substrate inhibits deposition at
selected locations. For convenience, these masks might be
generically called conformable contact masks; the masking technique
may be generically called a conformable contact mask plating
process. More specifically, in the terminology of Microfabrica.TM.
Inc. (formerly MEMGen.RTM. Corporation) of Van Nuys, Calif. such
masks have come to be known as INSTANT MASKS.TM. and the process
known as INSTANT MASKING or INSTANT MASK.TM. plating. Selective
depositions using conformable contact mask plating may be used to
form single layers of material or may be used to form multi-layer
structures. The teachings of the '630 patent are hereby
incorporated herein by reference as if set forth in full herein.
Since the filing of the patent application that led to the above
noted patent, various papers about conformable contact mask plating
(i.e. INSTANT MASKING) and electrochemical fabrication have been
published: [0004] (1) A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U.
Frodis and P. Will, "EFAB: Batch production of functional,
fully-dense metal parts with micro-scale features", Proc. 9th Solid
Freeform Fabrication, The University of Texas at Austin, p 161,
August 1998. [0005] (2) A. Cohen, G. Zhang, F. Tseng, F. Mansfeld,
U. Frodis and P. Will, "EFAB: Rapid, Low-Cost Desktop
Micromachining of High Aspect Ratio True 3-D MEMS", Proc. 12th IEEE
Micro Electro Mechanical Systems Workshop, IEEE, p 244, January
1999. [0006] (3) A. Cohen, "3-D Micromachining by Electrochemical
Fabrication", Micromachine Devices, March 1999. [0007] (4) G.
Zhang, A. Cohen, U. Frodis, F. Tseng, F. Mansfeld, and P. Will,
"EFAB: Rapid Desktop Manufacturing of True 3-D Microstructures",
Proc. 2nd International Conference on Integrated
MicroNanotechnology for Space Applications, The Aerospace Co.,
April 1999. [0008] (5) F. Tseng, U. Frodis, G. Zhang, A. Cohen, F.
Mansfeld, and P. Will, "EFAB: High Aspect Ratio, Arbitrary 3-D
Metal Microstructures using a Low-Cost Automated Batch Process",
3rd International Workshop on High Aspect Ratio MicroStructure
Technology (HARMST'99), June 1999. [0009] (6) A. Cohen, U. Frodis,
F. Tseng, G. Zhang, F. Mansfeld, and P. Will, "EFAB: Low-Cost,
Automated Electrochemical Batch Fabrication of Arbitrary 3-D
Microstructures", Micromachining and Microfabrication Process
Technology, SPIE 1999 Symposium on Micromachining and
Microfabrication, September 1999. [0010] (7) F. Tseng, G. Zhang, U.
Frodis, A. Cohen, F. Mansfeld, and P. Will, "EFAB: High Aspect
Ratio, Arbitrary 3-D Metal Microstructures using a Low-Cost
Automated Batch Process", MEMS Symposium, ASME 1999 International
Mechanical Engineering Congress and Exposition, November, 1999.
[0011] (8) A. Cohen, "Electrochemical Fabrication (EFAB.TM.)",
Chapter 19 of The MEMS Handbook, edited by Mohamed Gad-EI-Hak, CRC
Press, 2002. [0012] (9) Microfabrication--Rapid Prototyping's
Killer Application", pages 1-5 of the Rapid Prototyping Report,
CAD/CAM Publishing, Inc., June 1999.
[0013] The disclosures of these nine publications are hereby
incorporated herein by reference as if set forth in full
herein.
[0014] The electrochemical deposition process may be carried out in
a number of different ways as set forth in the above patent and
publications. In one form, this process involves the execution of
three separate operations during the formation of each layer of the
structure that is to be formed: [0015] 1. Selectively depositing at
least one material by electrodeposition upon one or more desired
regions of a substrate. [0016] 2. Then, blanket depositing at least
one additional material by electrodeposition so that the additional
deposit covers both the regions that were previously selectively
deposited onto, and the regions of the substrate that did not
receive any previously applied selective depositions. [0017] 3.
Finally, planarizing the materials deposited during the first and
second operations to produce a smoothed surface of a first layer of
desired thickness having at least one region containing the at
least one material and at least one region containing at least the
one additional material.
[0018] After formation of the first layer, one or more additional
layers may be formed adjacent to the immediately preceding layer
and adhered to the smoothed surface of that preceding layer. These
additional layers are formed by repeating the first through third
operations one or more times wherein the formation of each
subsequent layer treats the previously formed layers and the
initial substrate as a new and thickening substrate.
[0019] Once the formation of all layers has been completed, at
least a portion of at least one of the materials deposited is
generally removed by an etching process to expose or release the
three-dimensional structure that was intended to be formed.
[0020] The preferred method of performing the selective
electrodeposition involved in the first operation is by conformable
contact mask plating. In this type of plating, one or more
conformable contact (CC) masks are first formed. The CC masks
include a support structure onto which a patterned conformable
dielectric material is adhered or formed. The conformable material
for each mask is shaped in accordance with a particular
cross-section of material to be plated. At least one CC mask is
needed for each unique cross-sectional pattern that is to be
plated.
[0021] The support for a CC mask is typically a plate-like
structure formed of a metal that is to be selectively electroplated
and from which material to be plated will be dissolved. In this
typical approach, the support will act as an anode in an
electroplating process. In an alternative approach, the support may
instead be a porous or otherwise perforated material through which
deposition material will pass during an electroplating operation on
its way from a distal anode to a deposition surface. In either
approach, it is possible for CC masks to share a common support,
i.e. the patterns of conformable dielectric material for plating
multiple layers of material may be located in different areas of a
single support structure. When a single support structure contains
multiple plating patterns, the entire structure is referred to as
the CC mask while the individual plating masks may be referred to
as "submasks". In the present application such a distinction will
be made only when relevant to a specific point being made.
[0022] In preparation for performing the selective deposition of
the first operation, the conformable portion of the CC mask is
placed in registration with and pressed against a selected portion
of the substrate (or onto a previously formed layer or onto a
previously deposited portion of a layer) on which deposition is to
occur. The pressing together of the CC mask and substrate occur in
such a way that all openings, in the conformable portions of the CC
mask contain plating solution. The conformable material of the CC
mask that contacts the substrate acts as a barrier to
electrodeposition while the openings in the CC mask that are filled
with electroplating solution act as pathways for transferring
material from an anode (e.g. the CC mask support) to the
non-contacted portions of the substrate (which act as a cathode
during the plating operation) when an appropriate potential and/or
current are supplied.
[0023] An example of a CC mask and CC mask plating are shown in
FIGS. 1A-1C. FIG. 1A shows a side view of a CC mask 8 consisting of
a conformable or deformable (e.g. elastomeric) insulator 10
patterned on an anode 12. The anode has two functions. FIG. 1A also
depicts a substrate 6 separated from mask 8. One is as a supporting
material for the patterned insulator 10 to maintain its integrity
and alignment since the pattern may be topologically complex (e.g.,
involving isolated "islands" of insulator material). The other
function is as an anode for the electroplating operation. CC mask
plating selectively deposits material 22 onto a substrate 6 by
simply pressing the insulator against the substrate then
electrodepositing material through apertures 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. The CC mask plating process is distinct from a
"through-mask" plating process in that in a through-mask plating
process the separation of the masking material from the substrate
would occur destructively. As with through-mask plating, CC mask
plating deposits material selectively and simultaneously over the
entire layer. The plated region may consist of one or more isolated
plating regions where these isolated plating regions may belong to
a single structure that is being formed or may belong to multiple
structures that are being formed simultaneously. In CC mask plating
as individual masks are not intentionally destroyed in the removal
process, they may be usable in multiple plating operations.
[0024] Another example of a CC mask and CC mask plating is shown in
FIGS. 1D-1F. FIG. 1D shows an anode 12' separated from a mask 8'
that includes a patterned conformable material 10' and a support
structure 20. FIG. 1D also depicts substrate 6 separated from the
mask 8'. FIG. 1E illustrates the mask 8' being brought into contact
with the substrate 6. FIG. 1F illustrates the deposit 22' that
results from conducting a current from the anode 12' to the
substrate 6. FIG. 1G illustrates the deposit 22' on substrate 6
after separation from mask 8'. In this example, an appropriate
electrolyte is located between the substrate 6 and the anode 12'
and a current of ions coming from one or both of the solution and
the anode are conducted through the opening in the mask to the
substrate where material is deposited. This type of mask may be
referred to as an anodeless INSTANT MASK.TM. (AIM) or as an
anodeless conformable contact (ACC) mask.
[0025] Unlike through-mask plating, CC mask plating allows CC masks
to be formed completely separate from the fabrication of the
substrate on which plating is to occur (e.g. separate from a
three-dimensional (3D) structure that is being formed). CC masks
may be formed in a variety of ways, for example, a
photolithographic process may be used. All masks can be generated
simultaneously, prior to structure fabrication rather than during
it. This separation makes possible a simple, low-cost, automated,
self-contained, and internally-clean "desktop factory" that can be
installed almost anywhere to fabricate 3D structures, leaving any
required clean room processes, such as photolithography to be
performed by service bureaus or the like.
[0026] An example of the electrochemical fabrication process
discussed above is illustrated in FIGS. 2A-2F. These figures show
that the process involves deposition of a first material 2 which is
a sacrificial material and a second material 4 which is a
structural material. The CC mask 8, in this example, includes a
patterned conformable material (e.g. an elastomeric dielectric
material) 10 and a support 12 which is made from deposition
material 2. The conformal portion of the CC mask is pressed against
substrate 6 with a plating solution 14 located within the openings
16 in the conformable material 10. An electric current, from power
supply 18, is then passed through the plating solution 14 via (a)
support 12 which doubles as an anode and (b) substrate 6 which
doubles as a cathode. FIG. 2A, illustrates that the passing of
current causes material 2 within the plating solution and material
2 from the anode 12 to be selectively transferred to and plated on
the cathode 6. After electroplating the first deposition material 2
onto the substrate 6 using CC mask 8, the CC mask 8 is removed as
shown in FIG. 2B. FIG. 2C depicts the second deposition material 4
as having been blanket-deposited (i.e. non-selectively deposited)
over the previously deposited first deposition material 2 as well
as over the other portions of the substrate 6. The blanket
deposition occurs by electroplating from an anode (not shown),
composed of the second material, through an appropriate plating
solution (not shown), and to the cathode/substrate 6. The entire
two-material layer is then planarized to achieve precise thickness
and flatness as shown in FIG. 2D. After repetition of this process
for all layers, the multi-layer structure 20 formed of the second
material 4 (i.e. structural material) is embedded in first material
2 (i.e. sacrificial material) as shown in FIG. 2E. The embedded
structure is etched to yield the desired device, i.e. structure 20,
as shown in FIG. 2F.
[0027] Various components of an exemplary manual electrochemical
fabrication system 32 are shown in FIGS. 3A-3C. The system 32
consists of several subsystems 34, 36, 38, and 40. The substrate
holding subsystem 34 is depicted in the upper portions of each of
FIGS. 3A to 3C and includes several components: (1) a carrier 48,
(2) a metal substrate 6 onto which the layers are deposited, and
(3) a linear slide 42 capable of moving the substrate 6 up and down
relative to the carrier 48 in response to drive force from actuator
44. Subsystem 34 also includes an indicator 46 for measuring
differences in vertical position of the substrate which may be used
in setting or determining layer thicknesses and/or deposition
thicknesses. The subsystem 34 further includes feet 68 for carrier
48 which can be precisely mounted on subsystem 36.
[0028] The CC mask subsystem 36 shown in the lower portion of FIG.
3A includes several components: (1) a CC mask 8 that is actually
made up of a number of CC masks (i.e. submasks) that share a common
support/anode 12, (2) precision X-stage 54, (3) precision Y-stage
56, (4) frame 72 on which the feet 68 of subsystem 34 can mount,
and (5) a tank 58 for containing the electrolyte 16. Subsystems 34
and 36 also include appropriate electrical connections (not shown)
for connecting to an appropriate power source for driving the CC
masking process.
[0029] The blanket deposition subsystem 38 is shown in the lower
portion of FIG. 3B and includes several components: (1) an anode
62, (2) an electrolyte tank 64 for holding plating solution 66, and
(3) frame 74 on which the feet 68 of subsystem 34 may sit.
Subsystem 38 also includes appropriate electrical connections (not
shown) for connecting the anode to an appropriate power supply for
driving the blanket deposition process.
[0030] 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.
[0031] The '630 patent also teaches that other methods may be used
to form contact masks (i.e. electroplating articles in the language
of the '630 patent) which include applying masking composition
selectively to a support by such processes as screen printing,
stencil printing and inkjet printing.
[0032] The '630 patent also teaches that methods similar to those
used in relief printing can also be used to fabricate
electroplating articles (i.e. contact masks). A cited example of
such a method includes: applying a liquid masking composition to a
relief pattern, which might be produced by patterning a high aspect
ratio photoresist such as AZ4620 or SU-8; pressing the relief
pattern/masking composition structure against a support such that
the masking composition adheres to the support; and removing the
relief pattern. The formed electroplating article includes a
support having a mask patterned with the inverse pattern of the
relief pattern.
[0033] The '630 patent additionally teaches the creation of an
electroplating article (i.e. a contact mask) by creating a relief
pattern on a support by etching of the support, or applying a
durable photoresist, e.g., SU-8; coating a flat, smooth sheet with
a thin, uniform layer of liquid masking composition; stamping the
support/resist against the coated sheet (i.e., like a stamp and
inkpad) to quickly mate and unmate the support/resist and the
masking composition (preferably the support and the sheet are kept
parallel); and curing the liquid masking composition.
[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] Another method for forming microstructures from
electroplated metals (i.e. using electrochemical fabrication
techniques) is taught in U.S. Pat. No. 5,190,637 to Henry Guckel,
entitled "Formation of Microstructures by Multiple Level Deep X-ray
Lithography with Sacrificial Metal layers". This patent teaches the
formation of metal structure utilizing mask exposures. A first
layer of a primary metal is electroplated onto an exposed plating
base to fill a void in a photoresist, the photoresist is then
removed and a secondary metal is electroplated over the first layer
and over the plating base. The exposed surface of the secondary
metal is then machined down to a height which exposes the first
metal to produce a flat uniform surface extending across the both
the primary and secondary metals. Formation of a second layer may
then begin by applying a photoresist layer over the first layer and
then repeating the process used to produce the first layer. The
process is then repeated until the entire structure is formed and
the secondary metal is removed by etching. The photoresist is
formed over the plating base or previous layer by casting and the
voids in the photoresist are formed by exposure of the photoresist
through a patterned mask via X-rays or UV radiation.
SUMMARY OF THE INVENTION
[0037] It is an object of some aspects of the invention is to
provide one or more beam-like structures having desired values of
compliance which are greater than normally considered possible.
[0038] Other objects and advantages of various aspects of the
invention will be apparent to those of skill in the art upon review
of the teachings herein. The various aspects of the invention, set
forth explicitly herein or otherwise ascertained from the teachings
herein, may address one or more of the above objects alone or in
combination, or alternatively they may address some other object of
the invention that may be 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.
[0039] In a first aspect of the invention an elongated structure
having a desired compliance, includes a structural material that is
deposited configured with narrow regions separated by wider
regions, wherein the widths of the regions are selected to yield
desired mechanical properties.
[0040] In a second aspect of the invention a method of designing a
structure, includes: designing the structure to one or more
beam-like elements and to have a desired set of mechanical
properties; comparing the dimensions of the designed structure with
minimum feature size dimensions and determining that a width of at
least one of the beam-like elements is narrower than a minimum
feature size; modifying the configuration of at least one beam-like
element that has a width narrower than the minimum feature size by,
configuring portions of the one beam-like element to have a width
greater than the minimum feature size and other portions of the
beam-like element to have widths greater than the minimum feature
size.
[0041] In a third aspect of the invention a method for producing a
multi-layer structure having an elongated element having an
effective compliance, includes: configuring a design of the
elongated element to have portions that have widths less than a
minimum feature size and portions having widths greater than the
minimum feature size wherein a compliance of the structure is set
at or below a desired amount; and producing the structure using
masking operations and electrochemical deposition operations, where
the formation of the masks or the use of the masks at least in part
dictate the minimum feature size.
[0042] Further aspects of the invention will be understood by those
of skill in the art upon reviewing the teachings herein. Other
aspects of the invention may involve combinations of the above
noted aspects of the invention and/or addition of various features
of one or more embodiments. Other aspects of the invention may
involve apparatus that can be used in implementing one or more of
the above method aspects of the invention. These other aspects of
the invention may provide various combinations of the aspects
presented above as well as provide other configurations,
structures, functional relationships, and processes that have not
been specifically set forth above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] 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.
[0044] 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.
[0045] 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.
[0046] FIGS. 4A-4I schematically depict the formation of a first
layer of a structure using adhered mask plating where the blanket
deposition of a second material overlays both the openings between
deposition locations of a first material and the first material
itself.
[0047] FIG. 5A depicts a top view of a beam which is too narrow to
be formed but which offers a desired compliance.
[0048] FIGS. 5B-5D depict beams of similar length dimension to that
shown in FIG. 5A but which have been modified according to various
embodiments of the invention to include hold-down structures which
enhance manufacturability.
[0049] FIG. 5E depicts a straight beam with a larger
cross-sectional width than that of the beam of FIG. 5A such that
the beam is manufacturable without hold-downs but which doesn't
offer a desired level of compliance.
[0050] FIGS. 5F-5G depict beams of similar dimension to that shown
in FIG. 5A but which have been modified according to a various
embodiments of the invention to include hold-down structures which
enhance manufacturability.
[0051] FIG. 6 depicts a structure containing multiple compliant
beams that include hold-down structures.
[0052] FIG. 7 depicts a multi-layer beam structure where the
hold-down elements are adhered to previous hold-down elements while
the thin portions of the beams may delaminate from one another.
[0053] FIG. 8 depicts a top view of an alternative beam structure
where the hold-downs for the main beam structure are also joined by
a secondary beam structure which may be used to tailor or control
deflection of the main beam structure.
[0054] FIG. 9 depicts a top view of a further alternative
embodiment where the size and positions of the hold-down elements
are varied to tailor the mechanical properties of the beam.
[0055] FIGS. 10A-10E depict top views of five example beam-like
structures that have a desired compliance and furthermore have
features that limit the amount of deflection (in the plane of the
page) that the beam-like structures can undergo or cause a change
in compliance when a certain deflection amount is reached.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0056] FIGS. 1A-1G, 2A-2F, and 3A-3C illustrate various features of
one form of electrochemical fabrication that are known. Other
electrochemical fabrication techniques are set forth in the '630
patent referenced above, in the various previously incorporated
publications, in various other patents and patent applications
incorporated herein by reference, still others may be derived from
combinations of various approaches described in these publications,
patents, and applications, or are otherwise known or ascertainable
by those of skill in the art from the teachings set forth herein.
All of these techniques may be combined with those of the various
embodiments of various aspects of the invention to yield enhanced
embodiments. Still other embodiments may be derived from
combinations of the various embodiments explicitly set forth
herein.
[0057] FIGS. 4A-4I illustrate various stages in the formation of a
single layer of a multi-layer fabrication process where a second
metal is deposited on a first metal as well as in openings in the
first metal where its deposition forms part of the layer. In FIG.
4A, a side view of a substrate 82 is shown, onto which patternable
photoresist 84 is cast as shown in FIG. 4B. In FIG. 4C, a pattern
of resist is shown that results from the curing, exposing, and
developing of the resist. The patterning of the photoresist 84
results in openings or apertures 92(a)-92(c) extending from a
surface 86 of the photoresist through the thickness of the
photoresist to surface 88 of the substrate 82. In FIG. 4D, a metal
94 (e.g. nickel) is shown as having been electroplated into the
openings 92(a)-92(c). In FIG. 4E, the photoresist has been removed
(i.e. chemically stripped) from the substrate to expose regions of
the substrate 82 which are not covered with the first metal 94. In
FIG. 4F, a second metal 96 (e.g., silver) is shown as having been
blanket electroplated over the entire exposed portions of the
substrate 82 (which is conductive) and over the first metal 94
(which is also conductive). FIG. 4G depicts the completed first
layer of the structure which has resulted from the planarization of
the first and second metals down to a height that exposes the first
metal and sets a thickness for the first layer. In FIG. 4H the
result of repeating the process steps shown in FIGS. 4B-4G several
times to form a multi-layer structure are shown where each layer
consists of two materials. For most applications, one of these
materials is removed as shown in FIG. 4I to yield a desired 3-D
structure 98 (e.g. component or device).
[0058] Various embodiments of various aspects of the invention are
directed to formation of three-dimensional structures from
materials some or all of which are to be electrodeposited. Some of
these structures may be formed form a single layer of one or more
deposited materials while others are formed from a plurality of
layers of deposited materials (e.g. 2 or more layers, more
preferably five or more layers, and most preferably ten or more
layers). 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.
[0059] Various embodiments of the invention may perform selective
patterning operations using conformable contact masks and masking
operations, 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). 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.
[0060] Various embodiments of the present invention are directed to
the design of structures which include at least one narrow
beam-like feature where the effective width of the beam-like
feature is less than that generally considered to be reliably
formable wherein the formation of the narrow feature is controlled
by the selective deposition of material via a patterned mask (e.g.
of the contact, proximity, or adhered type) or the selective
etching via a patterned mask. In other words, various embodiments
of the invention are directed to formation of structures having one
or more features that have dimensions that are smaller than a
minimum feature size, MFS. The MFS may vary based on the specifics
of the formation process but is generally related to the ability to
reliably form masks of desired patterning and to use those masks in
depositing either a sacrificial or structural material or in
etching a material in anticipation of filling created voids with a
sacrificial or structural material. The MFS, for example, may be
defined as the minimum width of a structure of defined length (e.g.
100-500 microns) that may be reliably formed (e.g. 90-99 times out
of 100).
[0061] Various embodiments of the invention are directed to the
formation of structures that, after formation and removal of
sacrificial material, have narrow unsupported features where the
width of the structure is at least in part based on it having a
desired compliance (e.g. in the plane of the layer in a direction
that has a component that is parallel to the width dimension (i.e.
perpendicular to the elongated portion of the structure).
[0062] As noted above, in some embodiments the formation process
involves the deposition of a sacrificial material as well as a
structural material on a particular layer of a structure. Some
embodiments allow a much narrower beam or similar structure to be
successfully fabricated than is typically considered possible. As
the beam width narrows the compliance of the beam increases most
particularly within the plane of the layer and perpendicular to the
length of the beam. However, for example, such beams may also be
designed to achieve increased compliance perpendicular to the layer
plane, or to achieve a required compliance in torsion.
[0063] In various embodiments of the invention the beam-like
structures are formed with alternating lengths of narrow structural
material and wider structural material. The lengths of narrow
structural material are designed to produce most if not all of the
compliance while the wider regions are designed such that they may
result in reliable formation of themselves as well as of the
intervening narrower regions. They are spaced within a distance of
each other such that the narrower portions of the structure may
also be formed reliably.
[0064] A first exemplary embodiment involves the selective
deposition of sacrificial material using a patterned photoresist
(or similar material) to define the pattern of openings for
receiving a sacrificial material. After deposition of the
sacrificial material, the resist is removed, and a deposition of
structural material occurs. The deposition of structural material
is typically performed in a blanket deposition manner but may be
selectively deposited in some alternative embodiments. In
embodiments where blanket deposition occurs, and even in some
embodiments where selective deposition of structural material
occurs, a planarization operation is performed to bring the net
height of deposition to a desired level. In these embodiments, the
pattern of structural material is initially manifest in the
photoresist. For example, a beam that is to be formed out of nickel
can be produced by patterning a beam in photoresist, plating
sacrificial material (e.g., copper), stripping the resist, plating
nickel, and then planarizing. For this process to work, the resist
needs to adhere reasonably well to the substrate (or to a
previously formed layer), since if it detaches and is washed away
(e.g., during developing, processing related to developing, or
plating) the beam will not be formed and the area intended to be
occupied by resist and later by structural material will be
occupied by sacrificial material. Similarly, the photoresist must
be completely removed prior to the deposition of structural
material, else structural material will not be deposited in at
least some desired regions and the desired structure will not be
properly formed.
[0065] It is observed that as features are designed smaller (e.g.,
as a beam is designed narrower) at some size, the resist (i.e.
patterning material) will no longer remain reliably attached and
the feature cannot be manufactured. Loss of the resist features may
make it impossible to manufacture structures such as beams which
are narrow enough, and thus sufficiently compliant, for the
intended application.
[0066] According to some embodiments narrow beam structures are
designed to include one or more wider "hold-down" features. These
embodiments provide a method for designing and forming structures
that can be manufactured with narrower elongated features and with
greater compliance than would otherwise be possible, by providing
`hold-down` features which prevent loss of the narrower patterned
resist structures.
[0067] FIG. 5A shows a top view (i.e. perpendicular to the plan of
the layer or layers) of a narrow beam 102. It is assumed that such
a beam is narrow enough that it would not be manufacturable due to
loss of the corresponding patterning structure, i.e. its width 104
is less than the MFS.
[0068] FIG. 5B shows a top view of a beam 112 having a width 114
which is similar to the width 104 of the beam of FIG. 5A, but which
is provided with hold-down features 116 which have widths 118 which
are greater than the MFS. In the example of FIG. 5B the hold-down
features are shown as being circular and thus the width 118
corresponds to a diameter of the circular structure. The width 118
of the hold-down features is made as small as possible while the
center-to-center spacing is made as large as possible. If it is
desired that the beam of FIG. 5B has the same compliance as that of
FIG. 5A, the narrow portions of the beam of FIG. 5B may be made
some what smaller than the width 104 of the beam of FIG. 5A to
account for diminished compliance associated with the portion of
the beam length which is occupied by hold-down features and which
offer little or no compliance.
[0069] FIG. 5C depicts a beam 122 having hold-down features with an
alternative configuration. The hold-down features 126 still have a
generally circular configuration but with fillets that form a
smooth transition between the hold-down feature and the narrow
portion of the beam. It is believed that this structure will reduce
stress concentrations during compliant movement. In still other
embodiments the tapering may continue through a large portion of
the narrow portion of the beam if not the entire length of the
narrow portion of the beam as indicated in FIG. 5D.
[0070] The hold-downs of FIGS. 5B-5D are intended to provide
additional area to attach the patterning structure to the substrate
during processing, thereby preventing total loss of the resist
structure (i.e. at least minimizing excessive misplacement of the
narrowest portions of the patterning structure). In some cases, the
hold-downs may even prevent delamination of the narrowest portions
of the patterning material and thus improve the likelihood of
adhesion between the narrowest structural material on the present
layer with structural material located on a previous layer.
[0071] The beams of FIGS. 5B-5D are very compliant due to their
effective narrow widths. They may not be quite as compliant as the
beam of FIG. 5A due to the low compliance of the hold-downs, but as
indicated above the compliance may increased by making the beams of
FIGS. 5B-5D have segments that are somewhat narrower than that of
FIG. 5A. In any event, the beams of FIGS. 5B-5D are more compliant
than the uniformly-wide beam 132 shown in top view in FIG. 5E. The
beam in FIG. 5E has a length similar to those of the beams of FIGS.
5B-5D but is designed wide enough to avoid loss of the resist
structure. The width 134 of the beam 132 may be similar to the
width of the hold-down structures 116 and 126 of FIGS. 5B and 5C or
may be somewhat narrower if hold-downs of FIGS. 5B and 5C required
some additional increment in width to reliably remain in place as a
result of their shorter length.
[0072] For a given length beam it is within the skill of the art to
determine the width (e.g. empirically) that is required to reliably
form a beam. Similarly for a given post or hold-down structure it
is within the ability of those of skill in the art to determine the
required dimensions for the structure so it will stay attached to a
substrate or previously formed layer whether the substrate or
previously formed layer comprises structural material or a
sacrificial material that will eventually be removed.
[0073] FIG. 5F shows a top view of a single or multi-layer beam 142
with hold-downs 146 of a different design. In this example, the
hold-down features are narrower than those in FIG. 5B, thus making
the beam more compliant than that of the FIG. 5B. However, the
hold-downs are themselves thin and may therefore not serve the
retention function as well as may be desired under some
circumstances.
[0074] If experimentation shows that sufficiently narrow hold-downs
(e.g. similar to those of FIG. 5F do not offer sufficient
robustness to the build process, the hold-downs 156 may include
relatively narrow side runners 154 and larger post-like structures
that do not themselves directly contact the beam 152 which is to
have improved compliance. An example of such a structure is shown
in FIG. 5G. In the embodiment of FIG. 5G, the hold-downs 156 will
not interfere with the bending of the beam 152 unless the bend
radius is very small.
[0075] In other embodiments the hold-down structures may take on
shapes that are other than circular in nature. For example, they
may have square or rectangular configurations or diamond shaped
configurations. In still other embodiments the position or shape of
the hold-downs need not be symmetric about the beam. For example,
in some embodiments the hold-downs may be located on a single side
of the beam or they may be located on alternating sides of the
beam.
[0076] FIG. 6 provides a perspective view of four relatively tall
beams 162(a)-162(d) which are made from structural material and
that are equipped with hold-downs similar to those shown in FIG.
5B. These beams may be formed from multiple adhered layers. These
four beams connect at one end to a support structure 164 which may
be adhered to structural material associated with previous layers
(not shown) or to subsequent layers (not shown). These beams are
shown with two different hold-down spacings 166 and 168. The fewer
the hold-downs (or the further apart they are spaced), the better
for compliance. But the greater the number of hold-downs (or the
more closely they are spaced), the better for retention. In a given
situation, the best compromise between reliable formation and
compliance can be determined experimentally.
[0077] FIG. 7 provides a perspective view of a beam 172 which is
similar to beam 162(d) of FIG. 6 and which is formed from 6 layers
of structural material and is adhered to a support 174. Here
however it is assumed that the narrow portions of the resist
structure (though not the hold-downs themselves) delaminated from
the substrate and there was therefore some deposition of
sacrificial material beneath them (i.e., a `flash` deposit). The
presence of sacrificial material between layers in the narrow
portions of the beam gives rise to thin gaps 176 between portions
of the layers (after removal of the sacrificial material). These
gaps may not substantially affect the mechanical performance of the
beam as a whole and particularly with regard to deflections in the
positive or negative X direction. Thus even if the narrow portions
of the beam delaminate and allow some under-deposition of the
sacrificial material, as long as the mask that patterns the beam is
properly formed and remains in place in a more-or-less undistorted
position, a satisfactory working compliant beam can be
fabricated.
[0078] Beams made according to various embodiments of the invention
can be arbitrarily tall (especially if made from multiple layers),
thus making them extremely stiff in the direction perpendicular to
the plane of the substrate and very compliant within the plane of
the substrate.
[0079] In some embodiments, beams may be formed in combination with
different structural elements that can be used to tailor the
mechanical properties of the beam or to provide preferential
bending locations and the like. In some embodiments, the beams may
have portions with varying widths such that some portions provide
less compliance than others. In other embodiments, as shown in FIG.
8, additional or secondary beam-like elements 184 may be added to
stiffen the primary beam 182 at specific locations so as to tailor
bending to occur at desired locations. In the example of FIG. 8,
the added beam-like element 184 is coplanar with at least one layer
of the primary beam, but may have a different total height than the
primary beam 182. If the location of the secondary beam is
appropriately selected it may be possible for a deflection along
the planes of the layers of the beam to translated into an out of
plane motion of the beam.
[0080] In other embodiments, the mechanical properties of the beam
may be tailored by varying the size and spacings of the hold-down
elements and even of the beam itself. FIG. 9. illustrates a beam
192 having hold-downs 194(a)-194(d) that vary in size and
spacing.
[0081] In other embodiments, beams may be formed in combination
with different structural elements that can be used to set
deflection limits or can be use to set controlled changes in
compliance when certain deflection amounts occur. For example, FIG.
10A provides a top view of a structure that includes two hold down
features 204 and 206 that includes stubs 214 and 216, respectively,
which extend from the same respective side of each hold down
feature. These stubs 214 and 216 may be used to limit the amount of
deflection that the intermediate portion of the beam can undergo
when bending upward in the plane of the layer. As FIG. 10A does not
include stubs on the opposite side of the hold down elements,
greater deflection is allowed when the beam bends in that
direction. In other embodiments, the stubs need not be supplied in
a symmetric or identical opposing fashion. FIG. 10B depicts an
alternative embodiment, where stubs 314(a) & (b) and 316(a)
& (b) extend from both sides of the hold down structures 304
and 306. FIG. 10C depicts another example, where three hold down
features exist where the central hold down structure includes four
stubs (two on one side of the beam and two on the other side). FIG.
10D depicts another alternative example where the stubs on either
side of the beam are of different lengths and thus set different
deflection limits depending direction of bending. FIG. 10E depicts
a further alternative where instead of the stubs providing a hard
stop when deflection reaches a certain amount, the stubs may
contact and slide beside one another to allow continued bending but
with a change in compliance.
[0082] The patent applications and patents set forth below are
hereby incorporated by reference herein as if set forth in full.
The teachings in these incorporated applications can be combined
with the teachings of the instant application in many ways: For
example, enhanced methods of producing structures may be derived
from some combinations of teachings, enhanced structures may be
obtainable, enhanced apparatus may be derived, and the like.
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[0083] Various other embodiments of the present invention exist.
Some of these embodiments may be based on a combination of the
teachings herein with various teachings incorporated herein by
reference. Some embodiments may not use any blanket deposition
process and/or they may not use a planarization process. Some
embodiments may use selective deposition processes or blanket
deposition processes on some layers that are not electrodeposition
processes. Some embodiments may use electroplating deposition
process, electrophoretic depositions process, electroless
deposition processes, sputtering processes, spreading processes,
and the like. Some embodiments, for example, may use nickel, gold,
copper, tin, silver, zinc, solder as structural materials while
other embodiments may use different materials. Some embodiments,
for example, may use copper, tin, zinc, solder or other materials
as sacrificial materials. Some embodiments may remove all
sacrificial material while other embodiments may not. Some
embodiments may use photoresist, polyimide, glass, ceramics, other
polymers, and the like as dielectric structural materials.
[0084] In some embodiments, two materials may be deposited in
association with individual layers but additional materials may be
added to the overall structure by using different pairs of
materials on different layers. For example, some layers may include
copper and a dielectric while other layers may include nickel and
copper. After the formation of the structure is completed, the
copper may be removed as a sacrificial material which leaves behind
a nickel and dielectric structure with hollowed out regions and/or
a nickel, dielectric, and copper structure if copper is entrapped
by regions of nickel and/or dielectric material. In other
embodiments, more than two materials may be deposited in
association with some layers.
[0085] It will be understood by those of skill in the art that
additional operations may be used in variations of the above
presented embodiments. These additional operations may, for
example, perform cleaning functions (e.g. between the primary
operations discussed above), they may perform activation functions,
they may perform monitoring functions, and the like.
[0086] 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.
* * * * *