U.S. patent application number 12/046147 was filed with the patent office on 2008-11-20 for method for producing patterned structures by printing a surfactant resist on a substrate for electrodeposition.
This patent application is currently assigned to JOHNS HOPKINS UNIVERSITY. Invention is credited to Noshir Sheriar Pesika, Peter Searson, Kathleen Joan Stebe.
Application Number | 20080283405 12/046147 |
Document ID | / |
Family ID | 40026406 |
Filed Date | 2008-11-20 |
United States Patent
Application |
20080283405 |
Kind Code |
A1 |
Pesika; Noshir Sheriar ; et
al. |
November 20, 2008 |
Method for Producing Patterned Structures by Printing a Surfactant
Resist on a Substrate for Electrodeposition
Abstract
Methods for electrodeposition of conductive material on a
conductive substrate that contains a pattern of a chemisorbed
surfactant formed by a stamp having a patterned surface which is
pressed onto the surface of the substrate for printing the
substrate. Electrodeposition occurs by immersing the patterned
substrate in a plating bath upon application of deposition
potential or current to the conductive substrate. In embodiment,
the chemisorbed surfactant on the surface of the substrate acts as
a positive resist so that electrodeposition occurs on regions of
the substrate not covered with surfactant. In another embodiment,
electrodeposition occurs preferentially in regions of the substrate
covered with the chemisorbed surfactant.
Inventors: |
Pesika; Noshir Sheriar;
(Goleta, CA) ; Stebe; Kathleen Joan; (Baltimore,
MD) ; Searson; Peter; (Baltimore, MD) |
Correspondence
Address: |
PATENT DOCKET ADMINISTRATOR;LOWENSTEIN SANDLER PC
65 LIVINGSTON AVENUE
ROSELAND
NJ
07068
US
|
Assignee: |
JOHNS HOPKINS UNIVERSITY
Baltimore
MD
|
Family ID: |
40026406 |
Appl. No.: |
12/046147 |
Filed: |
March 11, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11638137 |
Dec 13, 2006 |
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12046147 |
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10836021 |
Apr 29, 2004 |
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11638137 |
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60523498 |
Nov 19, 2003 |
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60467248 |
May 1, 2003 |
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Current U.S.
Class: |
205/135 |
Current CPC
Class: |
H05K 3/108 20130101;
C23C 18/1603 20130101; H05K 3/243 20130101; H05K 2203/0537
20130101; H05K 2203/0108 20130101; B82Y 30/00 20130101; B05D 1/283
20130101; C25D 5/022 20130101; C25D 5/34 20130101; B82Y 40/00
20130101 |
Class at
Publication: |
205/135 |
International
Class: |
C25D 5/02 20060101
C25D005/02 |
Goverment Interests
GOVERNMENT INTEREST
[0002] This invention was made with government support under NASA
Contract NGT5-50372 and NSF Grant DMR05-20491. The government has
certain rights in the invention.
Claims
1. A method for patterning a substrate with a conductive material,
comprising the steps of: (a) providing a substrate; (b) contacting
the substrate with a stamp comprising a surfactant layer, wherein
the surfactant chemisorbs to a portion of the substrate in contact
with the stamp, thereby creating a surfactant-covered region and a
surfactant-free region; and (c) removing the stamp from the
substrate; and (d) electrodepositing a conductive material onto the
substrate, whereby the conductive material adheres to the
surfactant-free region of the substrate.
2. The method of claim 1, wherein the stamp comprises
polydimethylsiloxane (PDMS).
3. The method of claim 1, wherein the surfactant layer is applied
to the stamp by immersing the stamp into a solution comprising the
surfactant.
4. The method of claim 3, wherein the solution comprises alkane
thiol CH.sub.3(CH.sub.2).sub.nSH.
5. The method of claim 1, wherein the stamp comprises a nanoscale
pattern.
6. The method of claim 1, wherein the stamp comprises microscale
pattern.
7. The method of claim 1 wherein electrodeposition occurs
preferentially in areas of the surfactant-covered region.
8. The method of claim 1, wherein the method is performed a
plurality of times onto the same substrate.
9. The method of claim 8, wherein a different conductive material
is electrodeposited onto the substrate each time the method is
performed.
10. A method for patterning a substrate with conductive materials,
comprising the steps of: (a) providing a substrate; (b) contacting
the substrate with a first stamp comprising a layer of a first
surfactant, wherein the first surfactant chemisorbs to a portion of
the substrate in contact with the stamp, thereby creating a first
surfactant-covered region and a first surfactant-free region; (c)
removing the first stamp from the substrate; (d) electrodepositing
a first conductive material onto the substrate, whereby the
conductive material adheres to the first surfactant-free region of
the substrate; (e) contacting the portion of the substrate
comprising the first conductive material with a second stamp
comprising a layer of a second surfactant, wherein the second
surfactant chemisorbs onto the first conductive material in contact
with the second stamp, thereby creating a second surfactant covered
region on the first conductive material and a second
surfactant-free region on the substrate; (f) removing the second
stamp from the substrate; and (g) electrodepositing a second
conductive material onto the substrate, whereby the second
conductive material adheres to the second surfactant-free
region.
11. A method for patterning a conductive substrate, comprising the
steps of: (a) providing a conductive substrate; (b) contacting the
substrate with a stamp comprising a surfactant layer, wherein the
surfactant chemisorbs to the portion of the substrate in contact
with the stamp, thereby creating a surfactant-covered region and a
surfactant-free region; and (c) removing the stamp from the
conductive substrate.
12. The method of claim 11, further comprising electrodepositing a
conductive material onto the conductive substrate, whereby the
conductive material adheres to the surfactant-free region of the
substrate.
13. The method of claim 11, wherein the stamp comprises
polydimethylsiloxane (PDMS).
14. The method of claim 11, wherein the surfactant layer is applied
to the stamp by immersing the stamp into a solution comprising the
surfactant.
15. The method of claim 14, wherein the solution comprises alkane
thiol CH.sub.3(CH.sub.2).sub.nSH.
16. The method of claim 11, wherein the stamp comprises nanoscale
feature(s).
17. The method of claim 11, wherein the stamp comprises microscale
feature(s)
18. The method of claim 12 wherein electrodeposition occurs
preferentially in areas of the surfactant-covered region.
19. The method of claim 12, wherein the method is performed a
plurality of times onto the same substrate.
20. The method of claim 19, wherein a different conductive material
is electrodeposited onto the substrate each time the method is
performed.
21. A method for patterning a substrate with conductive materials
comprising electrodepositing conductive materials onto a substrate
comprising a chemisorbed surfactant.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 11/638,137, filed Dec. 13, 2006, which is a
divisional of U.S. application Ser. No. 10/836,021, filed Apr. 29,
2004, now abandoned, which claims priority to U.S. Provisional
Application Nos. 60/523,498, filed Nov. 19, 2003 and 60/467,248,
filed May 1, 2003, the disclosures of which are hereby incorporated
by reference in their entireties.
FIELD OF THE INVENTION
[0003] This invention relates to lithography and, in particular, to
a method of high resolution lithography using a surfactant pattern
to direct the electrolytic deposition of materials on a substrate
surface. The process can be used to produce structures patterned in
one, two and three dimensions.
BACKGROUND OF THE INVENTION
[0004] Electrodeposition of conductive materials, such as metals,
onto the surface of a substrate including a patterned resist is a
well-known process for producing fine metal patterns on a
substrate. Electrodeposition is a process which occurs when using a
conductive substrate that serves as a cathode. According to
conventional methods, the cation of the metal to be deposited is
reduced from a plating bath at the cathode by application of a
potential or current. As such, electrodeposition occurs in the
regions where the conductive substrate is in contact with the
plating solution, but does not occur in regions of the substrate
that are covered with the resist. Conventional methods for creating
patterned resists rely on optical or electron-beam lithography to
define a pattern on the substrate. These methods, however, requires
expensive lithographic tools and facilities.
[0005] Another approach for producing a patterned substrate for
electrodeposition is to use soft lithography (or micro-contact
printing) to transfer a molecule that self-assembles on the
substrate. According to this technique, a polymer stamp having a
desired pattern is exposed to a solution of the surfactant
molecule. The stamp is then brought into contact with the
substrate, transferring the surfactant molecules from the polymer
stamp to the substrate in regions defined by the pattern on the
stamp. The surfactant molecules are chemisorbed to the substrate,
that is, the surfactant molecules are tethered to the surface
through a chemical bond.
[0006] The prior art describes methods wherein patterned
self-assembled monolayers are used as resists in combination with
electrodeposition. (See, e.g., Sondaghuethorst, J. A. M. et al.,
Generation of Electrochemically Deposited Metal Patterns by Means
of Electron-Beam (Nano)Lithography of Self-Assembled Monolayer
Resists, Applied Physics Letters 1994, 64, (3), pages 285-287;
Felgenhauer, T. et al., Electrode modification by electron-induced
patterning of aromatic self-assembled monolayers, Applied Physics
Letters 2001, 79, (20), pages 3323-3325; Kaltenpoth, G. et al.,
Electrode modification by electron-induced patterning of
self-assembled monolayers, Journal of Vacuum Science &
Technology B 2002, 20, (6), pages 2734-2738; Volkel, B., et al.,
Electrodeposition of copper and cobalt nanostructures using
self-assembled monolayer templates Surface Science (2005), 597,
pages 32-41. In the examples set forth in the references identified
above, the self-assembled monolayer is formed over the entire
conductive surface, and the pattern is created by irradiation to
selectively degrade the monolayer using an electron beam.
Irradiation of thiol monolayers can result in degradation of the
monolayer forming various fragments, unsaturated bonds, and
sulfides. The substrates covered with the degraded fragments can be
used as-is, or the fragments can be etched away to provide open
regions on the conductive surface at which electrodeposition can
proceed. Alternatively, irradiation may induce cross-linking in
adsorbed layers that contain cross-linkable groups (e.g.,
1,12-biphenyl-4-thiol), resulting in selective deposition or
etching in the regions that were not irradiated, analogous to using
a negative resist in conventional lithography. As mentioned above,
these electron beam-based lithography processes require the use of
expensive lithographic tools.
[0007] Furthermore, soft-lithography and electrodeposition
techniques have not been combined into a single approach because
surfactant molecules which are chemisorbed to surfaces typically
form a layer only a few nanometers in height. Moreover, the
surfactant molecules do not consistently prevent electrodeposition,
and in many situations, the electrodeposition occurs without
selectivity in both the surfactant-covered regions and the
surfactant-free regions.
[0008] Accordingly, there is a need in the art for a method for
patterned electrodeposition of conductive material on a conductive
substrate in an efficient and cost-effective manner which overcomes
the disadvantages prevalent in the conventional methods.
SUMMARY OF THE INVENTION
[0009] The present invention relates to a method for depositing
patterned structures on a substrate using soft lithography (also
known as microcontact printing) and electrodeposition. According to
an embodiment of the present invention, the method provides for the
electrodeposition of a conductive material onto a conductive
substrate by bringing a stamp having a surfactant printed thereon
into contact with the substrate. After removing the stamp from
contact with the substrate, the surfactant is chemisorbed to the
substrate in patterns dictated by the relief of the stamp. Next,
the printed conductive substrate is immersed in a plating bath
wherein metal ions are dissolved. Metal ions are electrochemically
reduced to form metallic structures, or features, in the regions of
the substrate not covered with the chemisorbed surfactant.
Alternatively, metal ions are electrochemically reduced
preferentially in the regions of the substrate covered with the
chemisorbed surfactant to form metallic structures that are higher
in these regions of the substrate.
[0010] The method has several advantages over conventional methods
for producing patterned materials on substrates. First, methods
such as photolithography or electron-beam lithography are
considerably more costly and time consuming. Second,
electrodeposition has many advantages over other deposition
methods. It is low cost and can be used to deposit a wide range of
materials. Furthermore, electrodeposition is one of the only
methods for depositing materials in a pattern formed by surfactant
molecules on a substrate. Other methods that deposit material from
the vapor phase, such as sputter deposition or evaporation cannot
be used in conjunction with soft lithography since the depositing
atoms have sufficiently high energy that they will degrade or
remove the chemisorbed surfactant molecules from the substrate.
Thus the combination of soft lithography and electrodeposition
together provide a unique low cost, rapid method for producing
patterned structures.
[0011] According to further embodiments of the present invention,
the method may include multiple deposition and stamping steps to
create complex, multi-layered structures.
BRIEF DESCRIPTION OF THE FIGURES
[0012] FIG. 1 illustrates a fabrication of structure by
electrodeposition into surfactant-free regions of a patterned
substrate.
[0013] FIG. 2 illustrates another embodiment of the present
invention, in which complex topological structures can be created
by sequential application of the stamping and electrodeposition
processes.
[0014] FIG. 3 illustrates another embodiment of the present
invention wherein deposition occurs preferentially under the
surfactant layer.
[0015] FIG. 4 illustrates another embodiment of the present
invention, wherein two materials are deposited in a desired pattern
by sequential depositions using a single patterned surfactant layer
chemisorbed to a substrate by changing the composition of the
material to be deposited and/or by changing the deposition
conditions.
[0016] FIG. 5 illustrates an embodiment of the fabrication process
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention relates to a method for
electrodeposition of a conductive material, herein the "deposited
material", on a substrate. Conductive materials for use in the
present invention may include, e.g., gold, silver, platinum, cobalt
and bismuth. The method involves the use of a structure having a
patterned surface, herein referred to as a stamp, which includes a
patterned microscale or nanoscale surface. The patterned surface
comprises a solution which contains a surfactant material. Due to
the chemisorption of the surfactant material and the substrate, the
pattern of surfactant material as arranged on the stamp is
transferred to the substrate. The stamp is then removed from
contact from the substrate.
[0018] According to an embodiment of the present invention, the
deposited material is then electrodeposited onto the
surfactant-free regions of the substrate, to form features in the
pattern of the relief of the stamp. In this regard, the surfactant
layer serves as a resist, whereby the surfactant material binds to
the substrate to form a layer that prevents electrodeposition on
the one or more regions of the substrate covered by the surfactant
layer. According to an embodiment of the present invention, by
preventing electrodeposition of a material in a region of a
substrate, the surfactant material operates in the same way as a
conventional resist used in electron beam lithography or
photolithography. The ability of chemisorbed surfactant molecules
to serve as a resist depends on variables such as the molecular
structure of the surfactant, the substrate, the chemistry, and the
deposition potential or current, all of which are inter-related.
The molecule chemisorbs to the substrate to form a self-assembled
monolayer. The chemisorbed molecule functions as a molecular resist
over a limited range of deposition potentials and metal ion
concentrations. The range of deposition potentials and the
concentration of metal ions that are preferable are dependent on
the surfactant molecule and the substrate chosen. Thus under
suitable conditions, electrodeposition may be directed to occur
only in the surfactant-free regions, and not in the regions where
the surfactant is chemisorbed to the surface.
[0019] For example, molecules with sulfhydryl groups will chemisorb
to gold and silver surfaces. Alkanethiols
(CH.sub.3(CH.sub.2).sub.nSH) with chain lengths greater than about
12 will form ordered self-assembled monolayers that function as
resists for electrodeposition. For transition metals, such as
cobalt, deposition can be performed in 50 mM Co(II) solution at
-0.8 V (Ag/AgCl). The preceding examples are merely preferred
embodiments, and are not meant to limit the scope of the present
invention. One of skill in the art would recognize the relationship
between the variables of the surfactant molecules and substrate
chosen for use in the present invention.
[0020] According to an embodiment of the present invention, the
surfactant may also act to promote electrodeposition to occur
preferentially on the parts of the substrate covered by the
surfactant layer. In this embodiment, electrodeposition of the
deposited material occurs in both the surfactant-free regions and
the regions covered by the surfactant molecule. In such an
embodiment, the deposition rate is faster in regions covered by the
surfactant molecule.
Composition of the Stamp and Related Components
[0021] In preferred embodiments, the stamp is composed of an
elastomeric material, e.g., polydimethylsiloxane and
polyurethane.
[0022] In preferred embodiments, the solution is ink. In even more
preferred embodiments, the ink solution is an alkane thiol
R(CH.sub.2).sub.nSH solution, where R is selected from the group
consisting of hydrogen, hydroxy, branched chain or straight chain
alkyl, cycloalkyl, cycloalkenyl, heterocycle, aromatic ring, and
heteroaromatic ring, each of which may be optionally substituted,
and n=0-6. In other embodiments, the thiol solution can also be
dissolved in solvents such as hexane and chloroform.
[0023] In preferred embodiments, the surfactant material or
surfactant molecule is a conductive material composed of a
molecular structure which is adapted to chemisorb to the substrate
to form a self-assembled monolayer (SAM).
[0024] As described above, the selection of the surfactant and the
substrate is determined by the requirement that the surfactant must
chemisorb onto the substrate. Accordingly, a wide range of
different materials (i.e., different substrate/surfactant
combinations) may be used in accordance with the present invention.
For example, a surfactant material with a terminal sulfhydryl group
would be a suitable combination for a substrate composed of gold or
silver because sulfhydryl groups chemisorb to both gold and silver
substrates. Examples of other materials suitable for deposition
onto a gold or silver substrate that has been modified with a
surfactant molecule that is chemisorbed to the surface include, but
are not limited to gold, silver, copper, nickel, and cobalt. Other
exemplary substrate/surfactant molecule combinations include, but
are not limited to a surfactant molecule with an isocyanide group
that chemisorbs to platinum and palladium substrates; and a
surfactant molecule with a silane, carboxylic acid, phosphonic
acid, hydroxamic acid that chemisorbs to the thin native oxide on
many metals and alloys (e.g., transition metals and valve
metals).
[0025] In preferred embodiments, the surfactant has a saturated
alkane chain long enough to form strong intermolecular associations
that prevent ion penetration through the monolayer. The range of
potentials for which the surfactant behaves as a good resist is
dependent on several factors, such as the metal ion concentration,
the deposition potential, and the molecular structure of the
surfactant molecule. For a given surfactant molecule, breakdown is
minimized by depositing from solutions with low metal ion
concentrations and at more positive deposition potentials.
[0026] It is to be appreciated by one having ordinary skill in the
art that the substrate/surfactant combinations described herein are
exemplary in nature, and that the scope of the invention is not
limited to specific examples set forth herein.
[0027] An advantage of the process described herein is that
features can be deposited to heights much greater than the height
of the surfactant molecule chemisorbed to the substrate. Deposition
occurs in such a way that there is no lateral growth and the
features, i.e., the electrodeposited material of interest, maintain
the dimensions of the pattern even at heights above the height of
the surfactant layer on the substrate. This is an important
difference as compared to conventional electron beam lithography or
photolithography, wherein the resist is higher than the deposited
feature.
[0028] As shown in FIG. 1a, a stamp 10 having a patterned surface
15 including one or more features 16 is inked or coated with a
surfactant material 20. The stamp 10 is then brought into contact
and chemisorbs with a substrate 30, as shown in FIG. 1b. Upon
removing the stamp 10 from the substrate 30 (FIG. 1c) the
surfactant material is transferred to the substrate 30 in regions
where the stamp 10 contacts the surface of the substrate 30.
[0029] Next, electrodeposition is used to deposit a conductive
material (i.e., the deposited material) 40 onto the substrate, as
shown in FIG. 1d. In this embodiment, deposition occurs only in
regions of the substrate 30 where there are no chemisorbed
surfactant molecules. According to this embodiment, the surfactant
molecules act as a molecular resist directing deposition to occur
only in regions where there are no surfactant molecules. Note that
deposition of the deposited material 40 extends beyond the height
of the layer of surfactant molecules 20, which is typically less
than a few nanometers, with no lateral growth. Since there is no
lateral growth during deposition, the features (i.e., the deposited
material) 40, although much higher than the layer of surfactant
molecules 20, maintain the dimensions of the pattern of the
substrate with high fidelity.
EXAMPLE 1
Electrodeposition of Conductive Material
[0030] In a preferred embodiment, a molecule with a sulfhydryl
group at one end is used as the surfactant molecule. A stamp is
used to transfer a pattern of the surfactant molecule to a gold or
silver substrate. The patterned surfactant may be used to direct
deposition of a material to the surfactant-free regions. The
material is deposited at a potential positive to the reduction
potential for the chemisorbed surfactant molecule, that is, at a
potential positive to the potential where the surfactant molecule
is desorbed from the substrate. In certain embodiments of the
present invention, the deposited material is not applied to the
regions where the substrate is covered with the surfactant
molecule. The conditions under which deposition only occurs in the
surfactant-free regions of the substrate and where the material is
deposited with no lateral growth to heights greater than the height
of the surfactant layer are dependent on the molecular structure of
the surfactant molecule, the deposition potential or current, and
the composition of the solution used for deposition. For example,
silver from a solution containing 20 mM Ag(I) at -0.45 V (Ag/AgCl)
was deposited on a gold substrate with a patterned octadecanethiol
monolayer; copper from solution containing 100 mM Co(II) at -0.2 V
(Ag/AgCl) was deposited on a gold substrate with a patterned
octadecanethiol monolayer; and cobalt from solution containing 50
mM Co(II) at -0.8 V (Ag/AgCl) was deposited on a gold substrate
with a patterned octadecanethiol monolayer.
EXAMPLE 2
Sequential Stamping
[0031] As shown in FIG. 2a, a substrate 230 is stamped with a
surfactant material 220, using a stamp coated or inked with
surfactant molecules, thereby transferring surfactant molecules
that chemisorb onto the substrate 230 in regions where the stamp
contacts the surface of the substrate 230. A conductive material
240 is deposited by electrodeposition onto the substrate to create
features that grow vertically from the substrate with lateral
dimensions defined by the pattern, as shown in FIG. 2b. Thereafter,
the deposited material 240 obtained via the initial
electrodeposition is stamped with a second layer of surfactant 250
that chemisorbs to that material.
[0032] The stamp orientation and pattern are selected to place the
surfactant molecules in a pattern of interest on top of the layer
of deposited material 240. On removing the stamp (FIG. 2c) the
surfactant molecule is transferred to and chemisorbs only in
regions where the stamp is in contact with top of the features.
Subsequently, a second conductive material 260 is electrodeposited,
as shown in FIG. 2d. Advantageously, the electrochemical deposition
of the layer of the second deposited material 60 results in the
formation of vias between the features of the layer of the second
deposited material.
[0033] Deposition occurs only at the top of the first layer of
features where there are no chemisorbed surfactant molecules (i.e.,
the surfactant-free regions of the layer of the first deposited
material). Since there is no lateral growth during deposition, the
layer of the second layer of features grows vertically from the top
of the layer of the first deposited material in a pattern defined
by the surfactant distribution on those features with high
fidelity. One having ordinary skill in the art will appreciate that
the first deposited material 240 may be the same or different in
composition from the second deposited material 260. One having
ordinary skill in the art will further appreciate that the first
surfactant layer 220 may be composed of the same or different
material as the second surfactant layer 250. In addition, one
having ordinary skill in the art will appreciate that the above
sequential process may comprise additional stamping and depositing
steps to form any number of layers of features in any desired
pattern.
EXAMPLE 3
Preferential Deposition in the Regions where a Surfactant Molecule
is Chemisorbed to the Surface
[0034] According to the embodiment depicted in FIG. 3, a substrate
330 is stamped with a surfactant material 320, using, for example,
a stamp coated or inked with surfactant molecules, thereby causing
the surfactant molecules 320 to chemisorb onto the substrate 330 in
regions where the stamp made contact with the surface of the
substrate 330, as shown in FIG. 3a. Next, a conductive material 340
is deposited by electrodeposition onto the substrate, as shown in
FIG. 3b. In this embodiment, the material of interest is deposited
on both the regions of the surface covered with surfactant
molecules and on the regions that are not covered with surfactant
molecules. The rate of deposition in the regions covered by the
surfactant molecules is faster or higher than the rate of
deposition in the surfactant-free regions. As shown in FIG. 3b,
this preferential deposition results in the deposited features
growing vertically from the surface with lateral dimensions defined
by the patterned surface.
[0035] According to this embodiment of the present invention, the
ability of a chemisorbed surfactant to allow deposition to occur
preferentially on the regions covered by the surfactant depends on
the molecular structure of the surfactant, the deposition
chemistry, the solution chemistry, and/or the deposition potential
or current. Thus under suitable conditions, electrodeposition can
be directed to occur more rapidly in the regions where the
surfactant is chemisorbed to the substrate than in the
surfactant-free regions.
EXAMPLE 4
Sequential Use of Deposition in Surfactant-Free Regions and
Preferential Deposition in Regions Covered by the Surfactant
[0036] In the embodiment depicted in FIG. 4, conditions are
selected such that the chemisorbed surfactant 420 prevents
deposition of a first deposited material 440. According to this
exemplary method, the substrate 430 is stamped with surfactant
molecules 420, using, for example, a stamp coated or inked with
surfactant molecules 420. The surfactant molecules 420 chemisorb
onto the substrate in regions where the stamp made contact with the
surface of the substrate 430, as shown in FIG. 4a. A conductive
material 40 is deposited by electrodeposition onto the substrate
430 in the surfactant-free regions to create features that grow
vertically from the surface with lateral dimensions defined by the
patterned substrate, as illustrated in FIG. 4b.
[0037] Thereafter, conditions are selected such that the
chemisorbed surfactant 420 enhances the rate of deposition in the
regions covered by the surfactant of the deposited material 440.
For example, when the molecular resist is an alkanethiol,
deposition will occur in both surfactant covered regions as well as
surfactant-free regions, however the alkanethiol will stimulate an
increase in deposition rate in the surfactant covered regions.
[0038] Next, a second conductive material 450 is deposited by
electrodeposition onto the substrate 440 under conditions wherein
deposition is faster in the regions of the substrate 430 covered
with chemisorbed surfactant 420 than on top of the features of the
first deposited material 440, resulting in the patterned structure
illustrated in FIG. 4c.
[0039] As shown, the second deposited material 450 fills the spaces
between the features of the first deposited material 440, and is
also deposited at a slower rate on top of the original features of
the first deposited material 440. Accordingly, a two-component
patterned material is formed with feature lateral dimensions
defined by the surfactant distribution on those features with high
fidelity.
EXAMPLE 5
Stamping and Immersion to Create a Patterned Surfactant Layer on
the Surface of the Substrate
[0040] According to an embodiment of the present invention, a
patterned structure may be formed according to a process wherein a
surfactant resist is created by sequential stamping with a
surfactant ink, and immersed into a solution containing a second
surfactant ink. The first surfactant ink chemisorbs to the
substrate in patterns dictated by the stamp. Thereafter, the
printed substrate is immersed in a solution of the second
surfactant ink, which chemisorbs to the substrate in regions not
occupied by the first surfactant ink. According to this embodiment,
conditions may be selected such that the second surfactant is
chemisorbed to the surface of the substrate and prevents
electrodeposition. One having ordinary skill in the art will
appreciate that the surfactant ink is a solution which contains the
desired surfactant.
[0041] The fabrication process is illustrated in FIGS. 5a-5e. As
shown in FIG. 5a, a substrate 530 is stamped with molecules of the
first surfactant 510, thereby transferring surfactant molecules
that chemisorb onto the substrate in regions where the stamp is
contacted to the surface of the substrate 530. The printed
substrate is then immersed in a solution of the second surfactant
520, which forms a chemisorbed layer in regions of the surface not
covered by the first surfactant 510, as shown in FIG. 5b.
[0042] In one exemplary embodiment, the first surfactant 510 is
selected such that it does not prevent electrodeposition. In this
example, when a conductive material 540 is deposited by
electrodeposition onto the substrate in the regions covered with
the first surfactant 510, features grow vertically from the surface
with lateral dimensions defined by the patterned substrate, as
shown in FIG. 5c.
[0043] In another embodiment, the first surfactant 510 can be
removed from the surface of the substrate 530 by any suitable means
known to those having ordinary skill in the art, as shown in FIG.
5d. Next, as shown in FIG. 5e, electrodeposition onto the substrate
in the regions not covered with the first surfactant 510 creates
features that grow vertically from the surface with lateral
dimensions defined by the patterned substrate 530.
[0044] It is understood that the above-described embodiments are
illustrative of only a few of the many possible specific
embodiments, which can represent applications of the invention.
Numerous and varied other arrangements can be made by those skilled
in the art without departing from the spirit and scope of the
invention.
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