U.S. patent application number 12/061010 was filed with the patent office on 2008-10-09 for release layer for imprinted photocationically cured films.
This patent application is currently assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Robert D. Allen, Mark W. Hart, Frances Houle, Hiroshi Ito.
Application Number | 20080248213 12/061010 |
Document ID | / |
Family ID | 39794865 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080248213 |
Kind Code |
A1 |
Allen; Robert D. ; et
al. |
October 9, 2008 |
RELEASE LAYER FOR IMPRINTED PHOTOCATIONICALLY CURED FILMS
Abstract
An imprint process comprising coating a selected surface of a
micropatterned template with a release composition having a basic
reactive moiety; wherein the template is transparent to UV
radiation; imprinting the template onto a photocationically curable
composition; curing the UV curable composition to form an imprinted
composition, wherein the release composition having a basic
reactive moiety is effective to locally inhibit curing of the
composition at an interface between the template and the imprinted
composition; and releasing the template from the imprinted
composition.
Inventors: |
Allen; Robert D.; (San Jose,
CA) ; Hart; Mark W.; (San Jose, CA) ; Houle;
Frances; (Fremont, CA) ; Ito; Hiroshi; (San
Jose, CA) |
Correspondence
Address: |
CANTOR COLBURN, LLP - IBM ARC DIVISION
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
INTERNATIONAL BUSINESS MACHINES
CORPORATION
Armonk
NY
|
Family ID: |
39794865 |
Appl. No.: |
12/061010 |
Filed: |
April 2, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11694117 |
Mar 30, 2007 |
|
|
|
12061010 |
|
|
|
|
Current U.S.
Class: |
427/515 |
Current CPC
Class: |
B82Y 40/00 20130101;
G03F 7/0002 20130101; B82Y 10/00 20130101; Y10S 977/887
20130101 |
Class at
Publication: |
427/515 |
International
Class: |
C08J 7/18 20060101
C08J007/18 |
Claims
1. A step and flash imprint process comprising: coating a selected
surface of a micropatterned template with a release composition
having a basic reactive moiety; imprinting the template onto a
photocationically curable composition; curing the photocationically
curable composition to form an imprinted composition, wherein the
release composition having the basic reactive moiety is effective
to locally inhibit curing of the composition at an interface
between the template and the imprinted composition; and releasing
the template from the imprinted composition.
2. The process of claim 1, wherein the photocationically curable
composition comprises at least one polymerizable group selected
from a group consisting of epoxides, oxetanes, vinyl ethers, and
mixtures thereof.
3. The process of claim 1, wherein the release composition having
the basic reactive moiety is
.gamma.-aminopropyltriethylsiloxane.
4. The process of claim 1, wherein the release composition having
the basic reactive moiety is .gamma.-aminopropyltriethylsiloxane
and the photocationically curable composition is a vinyl ether.
5. A step and flash imprint process comprising: coating a selected
surface of a micropatterned template with
.gamma.-aminopropyltriethylsiloxane; wherein the template is
transparent to UV radiation; imprinting the template onto a UV
curable vinyl ether photoresist composition; curing the UV curable
vinyl ether photoresist to form a cured vinyl ether composition,
wherein the .gamma.-aminopropyltriethylsiloxane is effective to
locally inhibit curing of the composition at an interface between
the template and the cured vinyl ether composition; and releasing
the template from the UV curable composition.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S. Ser.
No. 11/694,117 filed Mar. 30, 2007, the contents of which are
incorporated by reference herein in their entirety.
TRADEMARKS
[0002] IBM.RTM. is a registered trademark of International Business
Machines Corporation, Armonk, N.Y., U.S.A. Other names used herein
may be registered trademarks, trademarks or product names of
International Business Machines Corporation or other companies.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention relates to release layers for templates used
in imprint lithography, and more particularly, to release layers
and the use thereof for release of templates used in step and flash
imprinting processes of photocationic curable films.
[0005] 2. Description of Background
[0006] Imprint lithography has emerged in various forms as a
potential alternative to conventional photolithography because of
its ability to print smaller features at low cost. Step and flash
imprint lithography (SFIL) is a variant of imprint lithography that
is amenable to the resolution and overlay requirements necessary
for the fabrication of advanced semiconductor devices. In SFIL, a
low-viscosity photosensitive molding material is molded between a
mechanically rigid template having a relief pattern and a substrate
and then is exposed to actinic radiation. The resulting hardened
layer, having a three dimensional pattern, can be used as an etch
mask to transfer the imprinted pattern into the substrate
below.
[0007] It is generally necessary to pre-coat the template with a
release agent to avoid sticking of the newly cured molding material
to the template. Fluorosilanes have been widely used as release
agents. The original assumption and impetus for using fluorosilanes
is that by providing a low energy surface adjacent to the cured
resist the adhesion energy will be minimized because the physical
and chemical attraction between the two surfaces will be minimized.
However, it has been found that that although the energy of the
release coating is low this coating is not inert. Single and
multiple cure passes are found to degrade the fluorosilane coating
by lowering its fluorine concentration.
[0008] Release coating failure of fluorosilanes is believed
attributable to chemical attack because of the proximity of free
radicals or acid, which drive the curing reaction of the
photosensitive molding material. This results not only in loss of
fluorine, but can lead to higher template adhesion due to chemical
bond formation of the template with the cured material. For
example, for one free radical cure formulation studied, the free
radical attack on the release layer lead to higher adhesion to the
template than if there were no release layer present.
[0009] In another example, cured vinyl ether resists exhibited
segregation of the ionic photoacid generator (PAG) to the surface
of the film as determined by angle-resolved x-ray photoemission.
The locally high concentration of PAG can be expected to ensure
maximum consumption of monomers during polymerization as well as
provide conditions for efficient attack of the release layer. As a
result, the fluorosilane release coatings can fail to provide a
benefit.
[0010] It is also noted that the adhesion energy of cured resists
to a fluorosilane-coated template varies significantly with resist
chemistry. For example, the acrylates tend to have lower adhesion
(<1-2 J/m.sup.2) than the vinyl ethers (>4-5 J/m.sup.2 and
often much higher).
[0011] Because it is generally desirable to reduce adhesion in
order to minimize the possibility of damaging the newly cured
resist layer during template removal, it would be advantageous to
have a release layer that reduces the extent of polymerization and
hence fracture toughness near the surface, thus facilitating crack
propagation at the resist-release interface during cure. A release
layer that would achieve this goal must not be itself attacked or
degraded during cure. There is no mechanism for the widely used
fluorosilane layer to achieve this goal.
[0012] Accordingly, there is a need in the art for improved release
layers for templates used in step and flash imprint lithography.
The release layers for templates must be thin, a few monolayers at
most, and very smooth to avoid interfering with pattern dimension
control.
SUMMARY OF THE INVENTION
[0013] The shortcomings of the prior art are overcome and
additional advantages are provided through the provision of a step
and flash imprint process comprising coating a selected surface of
a micropatterned template with a release composition having a basic
reactive moiety; wherein the template is transparent to UV
radiation; imprinting the template onto a photocationically curable
composition; curing the photocationically curable composition to
form an imprinted composition, wherein the release composition
having the basic reactive moiety is effective to locally inhibit
curing of the composition at an interface between the template and
the imprinted composition; and releasing the template from the
imprinted composition.
[0014] In another embodiment, a step and flash imprint process
comprises coating a selected surface of a micropatterned template
with .gamma.-aminopropyltriethylsiloxane; wherein the template is
transparent to UV radiation; imprinting the template onto a UV
curable vinyl ether photoresist composition; curing the UV curable
vinyl ether photoresist to form a cured vinyl ether composition,
wherein the .gamma.-aminopropyltriethylsiloxane is effective to
locally inhibit curing of the composition at an interface between
the template and the cured vinyl ether composition; and releasing
the template from the UV curable composition.
[0015] Additional features and advantages are realized through the
techniques of the present invention. Other embodiments and aspects
of the invention are described in detail herein and are considered
a part of the claimed invention. For a better understanding of the
invention with advantages and features, refer to the description
and to the drawings.
Technical Effects
[0016] As a result of the summarized invention, technically we have
achieved a solution that provides for effective release of a
template from a photocationic curable composition. The invention
utilizes a release agent having a reactive moiety that locally
inhibits curing at an interface between the template and the
curable composition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
objects, features, and advantages of the invention are apparent
from the following detailed description taken in conjunction with
the accompanying drawings in which:
[0018] FIG. 1 illustrates an exemplary imprint lithography
process;
[0019] FIG. 2 graphically illustrates fracture energies as a
function of crack lengths measured using a double cantilever beam
instrument; and
[0020] FIG. 3. graphically illustrates double cantilever beam
measurements of force as a function of displacement for the vinyl
ether resist-APTES interface.
[0021] The detailed description explains the preferred embodiments
of the invention, together with advantages and features, by way of
example with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0022] It has been found that a release composition having a basic
reactive moiety inhibits acid catalysis near the surface of the
imprintable medium provides for an improved release of templates
used for imprinting the imprintable medium. In one embodiment, the
imprintable medium comprises a photo-polymerizable monomer, which
may be a cationically polymerizable monomer. For ease of
understanding, specific reference will be made herein to vinyl
ether cationically polymerizable monomers and oligomers. However,
one of skill in the art will recognize that the release composition
having the basic reactive moiety can be used for other cationically
polymerizable imprintable mediums. For example, other suitable
cationically polymerizable monomers include monomers/oligomers
having at least one cationic polymerizable group such as an epoxide
group, an oxetane group, an ether group, a vinyl group,
combinations of the foregoing, and the like.
[0023] The release composition having the basic reactive moiety
functions to inhibit acid catalysis at an interface between the
template and the cured composition, which advantageously results in
improved release characteristics to the template. Suitable release
agents include, but are not limited to, amino functionalized
silanes, phosphinosilanes, and the like. In one embodiment, the
organic base release layer is .gamma.-aminopropyltriethylsiloxane
(APTES), the formula (I) of which is shown below:
##STR00001##
[0024] APTES is a well-known coupling agent generally used to
increase adhesion of polymer coatings to glass fibers. On glass,
APTES has a metastable conformation with the amino group hydrogen
bonded to surface OH groups. As such, it was surprising and
unexpected that APTES would provide improved release as compared to
other release agents such as the fluorosilane releasing agents
discussed in the background section above. The APTES release layer
can be applied to any suitable template by solution or vapor phase
processes to form an improved release layer of less than a 3
nanometers in thickness for imprintable vinyl ether curable
resists. The template can be composed of materials such as metals,
alloys, metal oxides, glass, quartz, combinations thereof and the
like. In one embodiment, the template is substantially transparent
to the radiation wavelength(s) employed to cure and polymerize the
resist.
[0025] Hereinafter, the terms "polymerizable," "polymerize",
"polymerizing" or "to polymerize" relate to any chemical process
that results in formation of a chain or polymer based on repeating
monomers or oligomers. Hereinafter, there terms "curable," "cure",
"curing" or "to cure" relate to polymerization to high molecular
weight with crosslinking.
[0026] The vinyl ether curable resists include monomers having at
least one vinyl ether having at least one vinyl ether group
(CR.sub.2.dbd.CRO--), wherein the at least one vinyl ether may be
represented by the following structures (II-VII):
C(R.sup.1)(R.sup.2).dbd.C(R.sup.3)OC.sub.n(R.sup.4)(R.sup.5)(D)(R.sup.6)-
(R.sup.7)(R.sup.8) (II)
C(R.sup.9)(R.sup.10).dbd.C(R.sup.11)OC.sub.o(R.sup.12)(R.sup.13)C.sub.p(-
R.sup.14)(R.sup.15)(E)(R.sup.16)(R.sup.17)(R.sup.18) (III)
C(R.sup.19)(R.sup.20).dbd.C(R.sup.21)OC.sub.q(R.sup.22)(R.sup.87)(F)(R.s-
up.23)(R.sup.24)C.sub.r(R.sup.25)(R.sup.26)OC(R.sup.27).dbd.C(R.sup.28)(R.-
sup.29) (IV)
##STR00002##
C(R.sup.60)(R.sup.61).dbd.C(R.sup.62)O[C(R.sup.63)(R.sup.64)C(R.sup.65)(R-
.sup.66)O].sub.sC(R.sup.67).dbd.C(R.sup.68)(R.sup.69) (VII)
[0027] Each D, E, F, G, J, and K may be independently at each
occurrence either a carbon or a silicon atom.
[0028] Each n, o, p, q, r, and s, (n-s) may be independently at
each occurrence represented by integers from 0 to 6, wherein a sum
of the integers (n-s) in any one of the vinyl ethers may be
.ltoreq.6.
[0029] Each R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6,
R.sup.7, R.sup.8, R.sup.9, R.sup.10, R.sup.11, R.sup.12, R.sup.13,
R.sup.14, R.sup.15, R.sup.16, R.sup.17, R.sup.18, R.sup.19,
R.sup.20, R.sup.21, R.sup.22, R.sup.23, R.sup.24, R.sup.25,
R.sup.26, R.sup.27, R.sup.28, R.sup.29, R.sup.30, R.sup.31,
R.sup.32, R.sup.33, R.sup.34, R.sup.35, R.sup.36, R.sup.37,
R.sup.38, R.sup.39, R.sup.40, R.sup.41, R.sup.42, R.sup.43,
R.sup.44, R.sup.45, R.sup.46, R.sup.47, R.sup.48, R.sup.49,
R.sup.50, R.sup.51, R.sup.52, R.sup.53, R.sup.54, R.sup.55,
R.sup.56, R.sup.57, R.sup.58, R.sup.59, R.sup.60, R.sup.61,
R.sup.62, R.sup.63, R.sup.64, R.sup.65, R.sup.66, R.sup.67,
R.sup.68, and R.sup.69 (R.sup.1-R.sup.69) may be independently at
each occurrence a hydrogen atom or a hydrocarbyl substituent with a
primary, a secondary or a tertiary carbon attachment point.
[0030] The hydrocarbyl substituent may be selected from the group
consisting of a linear alkyl or a linear alkoxy group having 1-6
carbon atoms, a branched alkyl or branched alkoxy group having 2-12
carbon atoms, a cycloalkyl, a bicycloalkyl, a cycloalkoxy or a
bicycloalkoxy group having 3-17 carbon atoms, a fluorinated linear
alkyl group having 2-12 carbon atoms, a fluorinated branched alkyl
group having 2-12 carbon atoms, a fluorinated cycloalkyl group
having 3-17 carbon atoms, an aryl group, an aralkyl group, an
alkaryl group, an alkenyl group, a cycloalkenyl group, a
dihydropyranyl group, a dihydrofuranyl group, an alkalkenyl group,
an alkenylalkyl group, an alkynyl group, an alkalkynyl group, an
alkynylalkyl group, a trifluoromethyl group, a trifluoroethyl
group, a trifluoropropyl group, a cyanopropyl group, a
tris-trialkylsilyl group, a tris-triarylsilyl group, a
tris-trialkarylsilyl group, a tris-triaralkylsilyl group, a
tris-trialkenylsilyl group, a tris-trifluoroalkyl group, a
tris-trialkynylsilyl group, a tris-trifluoromethylsilyl group, a
tris-trifluoroethylsilyl group, a tris-trifluoropropylsilyl group,
and a tris-cyanopropylsilyl group.
[0031] The alkyl substituents in the tris-trialkylsilyl group
include linear, branched, cyclic or bicyclic alkyl substituents
having 1 to 21 carbon atoms.
[0032] The aryl substituents in the tris-triarylsilyl group include
phenyl, naphthyl or phenanthryl.
[0033] The alkaryl substituents in the tris-trialkarylsilyl group
include tolyl.
[0034] The aralkyl substituents in the tris-triaralkylsilyl group
include benzyl.
[0035] The alkenyl substituents in the tris-trialkenylsilyl group
include vinyl.
[0036] The fluoroalkyl substituents in the tris-trifluoroalkyl
group include linear or branched fluorinated alkyl groups having
2-12 carbon atoms, or fluorinated cycloalkyl groups having 3-17
carbon atoms.
[0037] The alkynyl substituents in the tris-trialkynylsilyl group
include ethynyl groups.
[0038] The at least one vinyl ether (II) of the coating composition
may be CH.sub.2.dbd.CHOCH.sub.2Si(CH.sub.3).sub.3, wherein D is the
silicon atom, wherein n is 1, wherein R.sup.1, R.sup.2, R.sup.3,
R.sup.4 and R.sup.5 are H, and wherein R.sup.6, R.sup.7 and R.sup.8
are methyl groups.
[0039] Alternatively, the at least one vinyl ether (III) of the
coating composition may be
CH.sub.2.dbd.CHOCH.sub.2CH.sub.2Si(CH.sub.3).sub.3, wherein E is
the silicon atom, wherein o and p are 1, wherein R.sup.9, R.sup.10,
R.sup.11, R.sup.12, R.sup.13, R.sup.14 and R.sup.15 are H, and
wherein R.sup.16, R.sup.17 and R.sup.18 are methyl groups.
[0040] Alternatively, the at least one vinyl ether (IV) of the
coating composition may be
CH.sub.2.dbd.CHOCH.sub.2Si(CH.sub.3).sub.2CH.sub.2OCH.dbd.CH.sub.2,
wherein F is the silicon atom, wherein q and r are 1, wherein
R.sup.19, R.sup.20, R.sup.21, R.sup.22, R.sup.25, R.sup.26,
R.sup.27 R.sup.28 and R.sup.29 are H, and wherein R.sup.23 and
R.sup.24 are independently methyl groups or
CH.sub.2.dbd.CHOCH.sub.2C(CH.sub.3).sub.2CH.sub.2OCH.dbd.CH.sub.2,
wherein F is the carbon atom, wherein q and r are 1, wherein
R.sup.19, R.sup.20, R.sup.21, R.sup.22, R.sup.25, R.sup.26,
R.sup.27 R.sup.28 and R.sup.29 are H, and wherein R.sup.23 and
R.sup.24 are methyl groups.
[0041] Alternatively, the at least one vinyl ether (V) of the
coating composition may be
CH.sub.2.dbd.CHOCH.sub.2Si(CH.sub.3).sub.2OSi(CH.sub.3).sub.2CH.sub.2OCH.-
dbd.CH.sub.2, wherein G and J are the silicon atoms, wherein
R.sup.30, R.sup.31, R.sup.32, R.sup.28, R.sup.29, R.sup.34
R.sup.39, R.sup.40, R.sup.41, R.sup.42 and R.sup.43 are H, and
wherein R.sup.35, R.sup.36, R.sup.37 and R.sup.38 are methyl
groups.
[0042] Alternatively, the at least one vinyl ether (VI) of the
coating composition may be
CH.sub.2.dbd.CHOCH.sub.2CH.sub.2Si(CH.sub.3).sub.2CH.sub.2CH.sub.2OCH.dbd-
.CH.sub.2, wherein K is the silicon atom, wherein R.sup.44,
R.sup.45, R.sup.46, R.sup.47, R.sup.48, R.sup.49, R.sup.50,
R.sup.53, R.sup.54, R.sup.55, R.sup.56, R.sup.57, R.sup.58 and
R.sup.59 are H, wherein R.sup.51 and R.sup.52 are independently
methyl groups or
CH.sub.2.dbd.CHOCH.sub.2CH.sub.2C(CH.sub.3).sub.2CH.sub.2CH.sub.2OCH.dbd.-
CH.sub.2, wherein K is the carbon atom, wherein R.sup.44, R.sup.45,
R.sup.46, R.sup.47, R.sup.48, R.sup.49, R.sup.50, R.sup.53,
R.sup.54, R.sup.55, R.sup.56, R.sup.57, R.sup.58 and R.sup.59 are H
and wherein R.sup.51 and R.sup.52 are methyl groups.
[0043] Alternatively, the at least one vinyl ether (IV) of the
coating composition may be
CH(CH.sub.3).dbd.CHOCH.sub.2Si(CH.sub.3)(CH.sub.2OCH.dbd.CH(CH.sub.3))CH.-
sub.2OCH.dbd.CH(CH.sub.3), wherein F is the silicon atom, wherein q
and r are 1, wherein R.sup.19, R.sup.21, R.sup.22, R.sup.25,
R.sup.26, R.sup.27 and R.sup.28 are H, wherein R.sup.20, R.sup.23
and R.sup.29 are methyl, and wherein R.sup.24 is
--CH.sub.2OCH.dbd.CH(CH.sub.3).
[0044] Alternatively, the at least one vinyl ether (III) of the
coating composition may be
CH.sub.2.dbd.CHOCH.sub.2CH.sub.2Si(Si(CH.sub.3).sub.3).sub.3,
wherein E is the silicon atom, wherein o and p are 1, wherein
R.sup.9, R.sup.10, R.sup.11, R.sup.12, R.sup.13, R.sup.14 and
R.sup.15 are H, and wherein R.sup.16, R.sup.17 and R.sup.18 are
trimethylsilyl groups.
[0045] Alternatively, the at least one vinyl ether (IV) of the
coating composition may be
CH(CH.sub.3).dbd.CHOCH.sub.2C(CH.sub.3)(CH.sub.2OCH.dbd.CH(CH.sub.3))CH.s-
ub.2OCH.dbd.CH(CH.sub.3), wherein F is the carbon atom, wherein q
and r are 1, wherein R.sup.19, R.sup.21, R.sup.22, R.sup.25,
R.sup.26, R.sup.27 and R.sup.28 are H, wherein R.sup.20, R.sup.23
and R.sup.29 are methyl, and wherein R.sup.24 is
--CH.sub.2OCH.dbd.CH(CH.sub.3).
[0046] Alternatively, the at least one vinyl ether (II) of the
coating composition may be CH.sub.2.dbd.CHOCH.sub.2CF.sub.3,
wherein D is the carbon atom, wherein n is 1, wherein R.sup.1,
R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are H, and wherein R.sup.6,
R.sup.7 and R.sup.8 are fluorine groups.
[0047] Alternatively, the at least one vinyl ether (II) of the
coating composition may be dihydrofuran, wherein D is the carbon
atom, wherein n is 0, wherein R.sup.1 is methylene, wherein
R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are H, wherein R.sup.6 is
methylene, and wherein R.sup.7 and R.sup.8 are hydrogen atoms, or
dihydropyran, wherein D is the carbon atom, wherein n is 1, wherein
R.sup.1 is methylene, wherein R.sup.2, R.sup.3, R.sup.4 and R.sup.5
are H, wherein R.sup.6 is methylene, and wherein R.sup.7 and
R.sup.8 are hydrogen atoms.
[0048] Suitable epoxides and oxetanes are cyclic ethers having
three (one oxygen, two carbon atoms) and four atoms (one oxygen and
three carbon atoms), respectively. For example, aliphatic and
aromatic monofunctional and/or polyfunctional oxetane compounds can
be used. Specific non-limiting examples of the aliphatic or
aromatic oxetane monomers that can be used include
3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-phenoxymethyloxetane,
xylylene dioxetane, bis(3-ethyl-3-oxetanylmethyl)ether, and the
like. These monofunctional and/or polyfunctional oxetane compounds
can be used alone or as mixtures of two or more. Alicyclic epoxy
compounds can also be used such as for example,
3,4-epoxycyclohexylmethyl methacrylate and
3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate.
[0049] The coating composition may further include a radiation
sensitive photoacid generator (PAG). In certain embodiments of the
present invention, PAGs may be used in the coating composition.
These PAGs are compounds that generate an acid upon exposure to
radiation. In various embodiments, any suitable photoacid
generating agent may be used, so long as the selected photoacid
generator dissolves sufficiently in the coating composition, or in
the coating composition and an organic solvent, and the resulting
solution thereof may form a coating on a substrate by a dispensing
process, or spin coating, or the like. As is well known to those
skilled in the art after reading the present application, the
following illustrative classes of photoacid generators may be
employed in various embodiments of the present invention.
[0050] Any suitable photoacid generator can be used in the present
invention's stable viscosity coating composition. Typical photoacid
generators include, without limitation: (1) sulfonium salts, such
as triphenylsulfonium perfluoromethanesulfonate (triphenylsulfonium
triflate), triphenylsulfonium perfluorobutanesulfonate,
triphenylsulfonium perfluoropentanesulfonate, triphenylsulfonium
perfluorooctanesulfonate, triphenylsulfonium hexafluoroantimonate,
triphenylsulfonium hexafluoroarsenate, triphenylsulfonium
hexafluorophosphate, triphenylsulfonium bromide, triphenylsulfonium
chloride, triphenylsulfonium iodide,
2,4,6-trimethylphenyldiphenylsulfonium perfluorobutanesulfonate,
2,4,6-trimethylphenyldiphenylsulfonium benzenesulfonate,
tris(t-butylphenyl)sulfonium perfluorooctane sulfonate,
diphenylethylsulfonium chloride, and phenacyldimethylsulfonium
chloride; (2) halonium salts, particularly iodonium salts,
including diphenyliodonium
perfluoromethanesulfonate(diphenyliodonium triflate),
diphenyliodonium perfluorobutanesulfonate, diphenyliodonium
perfluoropentanesulfonate, diphenyliodonium
perfluorooctanesulfonate, diphenyliodonium hexafluoroantimonate,
diphenyliodonium hexafluoroarsenate, bis(t-butylphenyl)iodonium
triflate, and bis-(t-butylphenyl)-iodonium camphanylsulfonate; (3)
.alpha.,.alpha.'-bis-sulfonyl-diazomethanes such as
bis(p-toluenesulfonyl)diazomethane, methylsulfonyl
p-toluenesulfonyldiazomethane,
1-cyclohexylsulfonyl-1-(1,1-dimethylethylsulfonyl)diazomethane, and
bis(cyclohexylsulfonyl)diazomethane; (4) trifluoromethanesulfonate
esters of imides and hydroxyimides, e.g.,
.alpha.-(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarbo-
ximide (MDT); (5) nitrobenzyl sulfonate esters such as
2-nitrobenzyl p-toluenesulfonate, 2,6dinitrobenzyl
p-toluenesulfonate, and 2,4-dinitrobenzyl p-trifluoromethylbenzene
sulfonate; (6) sulfonyloxynaphthalimides such as
N-camphorsulfonyloxynaphthalimide and
N-pentafluorophenylsulfonyloxynaphthalimide; (7) pyrogallol
derivatives (e.g., trimesylate of pyrogallol); (8)
naphthoquinone-4-diazides; (9) alkyl disulfones; (10) s-triazine
derivatives; and (11) miscellaneous sulfonic acid generators
including t-butylphenyl-.alpha.-(ptoluenesulfonyloxy)-acetate,
t-butyl-.alpha.-(p-toluenesulfonyloxy)acetate, and
N-hydroxynaphthalimide dodecane sulfonate (DDSN), and benzoin
tosylate.
[0051] Additional suitable acid generators useful in conjunction
with the coating compositions and methods provided herein will be
known to those skilled in the art.
[0052] The PAG of the coating composition may include at least one
of the following structures (X-XII):
##STR00003##
[0053] FIG. 1 illustrates an exemplary step and flash imprint
process 10 for which the basic release component layer can be
utilized. The process first includes depositing the basic release
component layer 12 onto a rigid template 14 and applying a
photocationic polymerizable imprintable medium 16 e.g., a vinyl
ether monomer, onto a base substrate 18. The template 14 and the
substrate are then aligned and the gap between them decreased such
that the imprintable medium is imprinted with the features of the
template. The imprintable medium is then illuminated through the
backside of the template with activating radiation 20 to
photocationically cure the imprintable medium. The template is then
withdrawn leaving the now cured and imprinted medium with
relatively low aspect ratio, high-resolution features. The cured
and imprinted medium is then etched to form high aspect ratio high
resolution features. The use of the basic release component layer,
e.g., APTES, provides effective release of the template from the
cured and imprinted medium.
[0054] The following examples are presented for illustrative
purposes only, and are not intended to limit the scope of the
invention.
EXAMPLES
[0055] In this example, the efficacy of APTES for release was
tested using a double cantilever beam delamination instrument and
x-ray photoemission spectroscopy (XPS) for characterization of the
resist-template interface. The specimens for study comprised a
silicon substrate coated with an adhesion promoter (1 to 2 nm thick
film of o-(vinyloxybutyl)-n-(triethoxysilylpropyl)urethane), onto
which 4 to 6 microliters of liquid resist were dispensed prior to
being covered with an unpatterned UV-transparent quartz template.
The template material was pre-coated with either a very thin (1 to
2 monolayers) APTES release layer deposited from the gas phase, or
with a fluorosilane layer prepared using a commercially available
solution Cytonix FSD4500 (2 to 3 nm thick). The liquid resist was a
vinyl ether formulation composed of 1:1 diethyleneglycol divinyl
ether and dimethyl silane divinyl ether with CGI 1907 photoacid
generator (PAG) and 9-anthracene methanol sensitizer/stabilizer.
Following assembly the specimens were cured using 365 nm light with
a dose of approximately 80 mJ/cm.sup.2.
[0056] FIG. 2 graphically illustrates adhesion energies as a
function of crack lengths measured using a double cantilever beam
(DCB) instrument for both the fluorosilane and APTES release
layers. The average adhesion energy with a fluorosilane release
layer was 5.6 J/m.sup.2. Use of APTES instead reduced the average
adhesion energy to 2.1 J/m.sup.2.
[0057] In FIG. 3, the behavior of the resist during the DCB
measurement showed that it was considerably softened near the
surface relative to the resist cured adjacent to a fluorosilane
layer. The reduction of adhesion energy was unexpected because
APTES is normally used as an adhesion promoter, not a release
agent.
[0058] XPS studies of the newly separated interfaces were used to
determine whether the crack path followed the resist-template
interface or not. Confinement of the crack to the interface is
highly desirable to avoid damage to the cured resist or the
template during the imprinting process. Results for the APTES-vinyl
ether system are shown in Table 1 below, which provides elemental
concentrations for the APTES release layer. It is clear from the N
concentration data that the amine function was not removed during
cure, ensuring its presence for subsequent cure-release cycles.
TABLE-US-00001 TABLE 1 ATOMIC CONCENTRATION (%) APTES C1s N1s O1s
F1s Si2p Si side pt 1 66.7 0.2 26.6 3.5 3.0 glass side pt 4 18.0
1.1 53.8 4.0 23.1 glass side pt 1 17.7 2.0 49.7 8.4 22.1 unused pt
2 21.6 1.8 52.7 0.4 23.5 unused pt 3' 18.5 1.9 54.7 0.4 24.6
[0059] As referenced above, the term "APTES-Si side" refers to
analysis of the cured resist after separation; "APTES-glass side"
refers to analysis of the quartz side after separation; "APTES
unused" refers to analysis of a virgin layer; and "APTES layer"
refers to analysis on quartz.
[0060] It is not essential that the release layer be an amine, only
that it be a strong base. Other thin adsorbed layers that function
as bases such as phosphinosilanes can be used.
[0061] The flow diagrams depicted herein are just examples. There
may be many variations to these diagrams or the steps (or
operations) described therein without departing from the spirit of
the invention. For instance, the steps may be performed in a
differing order, or steps may be added, deleted or modified. All of
these variations are considered a part of the claimed
invention.
[0062] While the preferred embodiment to the invention has been
described, it will be understood that those skilled in the art,
both now and in the future, may make various improvements and
enhancements which fall within the scope of the claims which
follow. These claims should be construed to maintain the proper
protection for the invention first described.
* * * * *