U.S. patent application number 10/948511 was filed with the patent office on 2006-03-23 for polymerization technique to attenuate oxygen inhibition of solidification of liquids and composition therefor.
This patent application is currently assigned to Molecular Imprints, Inc.. Invention is credited to Edward B. Fletcher, Pankaj B. Lad, Michael P. C. Watts, Frank Y. Xu.
Application Number | 20060062922 10/948511 |
Document ID | / |
Family ID | 36074353 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060062922 |
Kind Code |
A1 |
Xu; Frank Y. ; et
al. |
March 23, 2006 |
Polymerization technique to attenuate oxygen inhibition of
solidification of liquids and composition therefor
Abstract
The present invention includes a method of solidifying a
polymerizable liquid to form a film on a substrate that features
minimizing inhibition of the polymerization process by oxygen
contained in the atmosphere surrounding the polymerizable liquid.
To that end, the polymerizable liquid includes, inter alia, an
initiator that consumes oxygen that interacts with the
polymerizable liquid and generates additional free radicals to
facilitate the polymerization process.
Inventors: |
Xu; Frank Y.; (Round Rock,
TX) ; Fletcher; Edward B.; (Austin, TX) ; Lad;
Pankaj B.; (Austin, TX) ; Watts; Michael P. C.;
(Austin, TX) |
Correspondence
Address: |
MOLECULAR IMPRINTS, INC.;KENNETH C. BROOKS
PO BOX 81536
AUSTIN
TX
78708-1536
US
|
Assignee: |
Molecular Imprints, Inc.
Austin
TX
|
Family ID: |
36074353 |
Appl. No.: |
10/948511 |
Filed: |
September 23, 2004 |
Current U.S.
Class: |
427/372.2 |
Current CPC
Class: |
A61P 31/04 20180101;
B82Y 10/00 20130101; B82Y 40/00 20130101; G03F 7/0002 20130101 |
Class at
Publication: |
427/372.2 |
International
Class: |
B05D 3/02 20060101
B05D003/02 |
Claims
1. A method for solidifying a polymerizable liquid disposed in an
atmosphere and having a plurality of molecules, said method
comprising: creating a primary group of free radicals; forming a
secondary group of free radicals by interaction of molecules of
said atmosphere with a subset of the free radicals of said primary
group; and generating a tertiary group of free radicals by
interaction of said plurality of molecules with the free radicals
of said secondary group to link together a subset of molecules of
said plurality of molecules.
2. The method as recited in claim 1 wherein creating further
includes creating said primary group of free radicals by exposing
said polymerizable liquid to actinic radiation to initiate linking
together of an additional subset of said plurality of
molecules.
3. The method as recited in claim 1 further including combining an
amine group with a polymerizable composition, with generating
further including developing an alpha aminoalkyl radical capable of
initiating polymerization.
4. The method as recited in claim 1 further including combining a
morpholino group with a polymerizable composition, with generating
further including developing a morpholino radical capable of
initiating polymerization.
5. The method as recited in claim 1 further including combining an
amine group with a polymerizable composition, with generating
further including developing an alpha aminoalkyl radical capable of
initiating polymerization from said amine group, said amine group
being selected from a set of amine groups consisting essentially of
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
N-methyldiethanolamine and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone and
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.
6. The method as recited in claim 1 further including forming a
composition by combining isobornyl acrylate, n-hexyl acrylate and
ethylene glycol diacrylate with an amine group, with generating
further including developing an alpha aminoalkyl radical capable of
initiating polymerization from said amine group, said amine group
being selected from a set of amine groups consisting essentially of
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
N-methyldiethanolamine and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone and
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.
7. The method as recited in claim 1 further including forming a
composition by combining isobornyl acrylate, n-hexyl acrylate,
ethylene glycol diacrylate, a surfactant and an amine group, with
generating further including developing an alpha aminoalkyl radical
capable of initiating polymerization from said amine group, said
amine group being selected from a set of amine groups consisting
essentially of
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
N-methyldiethanolamine and 2-benzyl-2-dimethylamino-1-(4
morpholinophenyl)-1-butanone and
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.
8. A method for solidifying a polymerizable liquid disposed in an
oxygen-containing atmosphere and having a plurality of molecules,
said method comprising: disposing a volume of said liquid on a
substrate, said volume having a boundary defining a interface with
said atmosphere; and initiating polymerization of said molecules
while minimizing inhibition of polymerization of said molecules by
oxygen proximate to said boundary.
9. The method as recited in claim 8 initiating further includes
creating a plurality of groups of radicals to link said molecules
together, with a first subgroup of said plurality of radicals
forming peroxide radicals and a second subgroup of said plurality
of radicals being formed from a consumption reaction of said
peroxide radicals, with said second subgroup of radicals initiating
additional polymerization.
10. The method as recited in claim 8 initiating further includes
creating a plurality of groups of radicals to link said molecules
together, with a first subgroup of said plurality of radicals
forming oxygen radicals and a second subgroup of said plurality of
radicals including an oxygen scavenging radical to combine with
said oxygen radical before said oxygen radical combines with one of
said plurality of molecules.
11. The method as recited in claim 8 wherein initiating further
includes exposing said plurality of molecules to actinic
radiation.
12. The method as recited in claim 8 wherein initiating further
includes creating a primary group of free radicals by exposing said
polymerizable liquid to actinic radiation to initiate linking
together of said plurality of molecules and forming a secondary
group of free radicals by interaction of oxygen in said atmosphere
with a subset of the free radicals of said primary group; and
generating a tertiary group of free radicals by interaction of said
plurality of molecules with the free radicals of said secondary
group to link together additional molecules of said plurality of
molecules.
13. The method as recited in claim 8 further including combining an
amine group with a polymerizable composition, with initiating
further including developing an alpha aminoalkyl radical capable of
initiating polymerization.
14. The method as recited in claim 8 further including combining an
amine group with a polymerizable composition, with initiating
further including developing an alpha aminoalkyl radical capable of
initiating polymerization from said amine group, said amine group
being selected from a set of amine groups consisting essentially of
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
N-methyldiethanolamine,
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone and
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.
15. The method as recited in claim 14 wherein combining further
includes providing said polymerizable composition with a
surfactant.
16. A method for solidifying a polymerizable liquid disposed in an
oxygen-containing atmosphere and having a plurality of molecules
including photoinitiators and chemical initiators, said method
comprising: exposing said photoinitiators to actinic radiation to
create a plurality of radicals to initiate linking of said
plurality of molecules; and accelerating linking of said plurality
of molecules by creating additional radicals through combining said
photoinitiators with oxygen.
17. The method as recited in claim 16 wherein accelerating further
includes creating a plurality of groups of radicals to link said
molecules together, with a first subgroup of said plurality of
radicals forming oxygen radicals and a second subgroup of said
plurality of radicals including an oxygen scavenging radical to
combine with said oxygen radical.
18. The method as recited in claim 16 accelerating further includes
creating a plurality of groups of radicals to link said molecules
together, with a first subgroup of said plurality of radicals
forming oxygen radicals and a second subgroup of said plurality of
radicals including an oxygen scavenging radical to combine with
said oxygen radical before said oxygen radical combines with one of
said plurality of molecules.
19. The method as recited in claim 16 wherein accelerating further
includes creating a primary group of free radicals by exposing said
polymerizable liquid to actinic radiation to initiate linking
together of said plurality of molecules and forming a secondary
group of free radicals by interaction of oxygen in said atmosphere
with a subset of the free radicals of said primary group; and
generating a tertiary group of free radicals by interaction of said
plurality of molecules with the free radicals of said secondary
group to link together additional molecules of said plurality of
molecules.
20. The method as recited in claim 16 further including combining
an amine group with said plurality of molecules, with accelerating
further including developing an alpha aminoalkyl radical capable of
initiating polymerization.
21. The method as recited in claim 16 further including combining
an amine group with said plurality of molecules, with accelerating
further including developing an alpha aminoalkyl radical capable of
initiating polymerization from said amine group, said amine group
being selected from a set of amine groups consisting essentially of
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
N-methyldiethanolamine,
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone and
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.
22. The method as recited in claim 21 further including combining a
surfactant with said plurality of molecules.
23. A method of polymerizing a liquid, said method comprising:
combining isobornyl acrylate, n-hexyl acrylate, ethylene glycol
diacrylate and 2-hydroxy-2-methyl-1-phenyl-propan-1-one with an
oxygen scavenging initiator, defining a composition; and exposing
said composition to actinic radiation.
24. The method as recited in claim 23 wherein combining further
includes adding a surfactant.
25. The method as recited in claim 24 wherein combining further
includes generating said oxygen scavenging initiator by providing
an amine group, selected from a set of amine groups consisting
essentially of
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
N-methyldiethanolamine and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone and
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.
26. A composition having a plurality of molecules, said composition
comprising: a polymerizable composition including a photoinitiator
and an oxygen scavenging element to react with oxygen and
facilitate cross-linking of said plurality of molecules.
27. The composition as recited in claim 26 wherein said oxygen
scavenging element is an amine group selected from a set of amine
groups consisting essentially of
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
N-methyldiethanolamine and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone and
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.
28. The composition as recited in claim 26 wherein said
polymerizable composition further includes isobornyl acrylate
n-hexyl acrylate ethylene glycol diacrylate
2-hydroxy-2-methyl-1-phenyl-propan-1-one.
29. The composition as recited in claim 26 wherein said
polymerizable composition further includes isobornyl acrylate
n-hexyl acrylate ethylene glycol diacrylate
2-hydroxy-2-methyl-1-phenyl-propan-1-one, and
R.sub.1CH.sub.2CH.sub.2O(CH.sub.2CH.sub.2O).sub.XH.
30. A composition having a plurality of molecules, said composition
comprising: isobornyl acrylate n-hexyl acrylate ethylene glycol
diacrylate 2-hydroxy-2-methyl-1-phenyl-propan-1-one and an oxygen
scavenging element to react with oxygen and facilitate
cross-linking of said plurality of molecules.
31. The composition as recited in claim 30 wherein said oxygen
scavenging element is an amine group selected from a set of amine
groups consisting essentially of
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
N-methyldiethanolamine and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone and
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.
32. A composition having a plurality of molecules, said composition
comprising: isobornyl acrylate n-hexyl acrylate ethylene glycol
diacrylate 2-hydroxy-2-methyl-1-phenyl-propan-1-one,
R.sub.1CH.sub.2CH.sub.2O(CH.sub.2CH.sub.2O).sub.XH and an oxygen
scavenging element to react with oxygen and facilitate
cross-linking of said plurality of molecules.
33. The composition as recited in claim 31 wherein said oxygen
scavenging element is an amine group selected from a set of amine
groups consisting essentially of
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
N-methyldiethanolamine and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone and
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.
Description
BACKGROUND OF THE INVENTION
[0001] The field of invention relates generally to
micro-fabrication of structures. More particularly, the present
invention is directed to a polymerization technique suited for use
in imprint lithography.
[0002] Micro-fabrication involves the fabrication of very small
structures, e.g., having features on the order of micro-meters or
smaller. One area in which micro-fabrication has had a sizeable
impact is in the processing of integrated circuits. As the
semiconductor processing industry continues to strive for larger
production yields while increasing the circuits per unit area
formed on a substrate, micro-fabrication becomes increasingly
important. Micro-fabrication provides greater process control while
allowing increased reduction of the minimum feature dimension of
the structures formed. Other areas of development in which
micro-fabrication has been employed include biotechnology, optical
technology, mechanical systems and the like.
[0003] An exemplary micro-fabrication technique is commonly
referred to as imprint lithography and is described in detailed in
numerous publications, such as United States published patent
applications 2004/0065976 entitled METHOD AND A MOLD TO ARRANGE
FEATURES ON A SUBSTRATE TO REPLICATE FEATURES HAVING MINIMAL
DIMENSIONAL VARIABILITY, 2004/0065252, entitled METHOD OF FORMING A
LAYER ON A SUBSTRATE TO FACILITATE FABRICATION OF METROLOGY
STANDARDS, 2004/0046271, entitled METHOD AND A MOLD TO ARRANGE
FEATURES ON A SUBSTRATE TO REPLICATE FEATURES HAVING MINIMAL
DIMENSIONAL VARIABILITY, all of which are assigned to the assignee
of the present invention. The fundamental imprint lithography
technique as shown in each of the aforementioned published patent
applications includes formation of a relief pattern in a
polymerizable layer and transferring the relief image into an
underlying substrate forming a relief image in a structure. To that
end, a template is employed spaced-apart from a substrate, with a
formable liquid present between the template and the substrate. The
liquid is solidified forming a solidified layer that has a pattern
recorded therein that is conforming to a shape of the surface of
the template in contact with the liquid. The substrate and the
solidified layer are then subjected to processes to transfer, into
the substrate, a relief structure that corresponds to the pattern
in the solidified layer.
[0004] On manner in which the polymerizable liquid is located
between the template and the substrate is by depositing a plurality
of droplets of liquid on the substrate. Thereafter, contact is made
with the polymerizable liquid by the template to spread the
polyermizable liquid over the surface of the substrate and
subsequently record a pattern therein. It is highly desirable to
avoid trapping of gases, such as air, when the polymerizable liquid
spreads over the substrate.
[0005] It is desired, therefore, to provide a method for forming a
fluid layer on a substrate while minimizing the trapping of gases
therein.
SUMMARY OF THE INVENTION
[0006] The present invention includes a method of solidifying a
polymerizable liquid to form a film on a substrate that features
minimizing inhibition of the polymerization process by oxygen
contained in the atmosphere surrounding the polymerizable liquid.
To that end, the polyermizable liquid includes, inter alia, an
initiator or additive that consumes oxygen that interacts with the
polyermizable liquid and generates additional free radicals to
facilitate the polyermization process. Specifically, the method
includes creating a primary group of free radicals by exposing the
polymerizable liquid to actinic radiation to initiate linking
together of a plurality of molecules. A secondary group of free
radicals is generated by interaction of molecules of an atmosphere
surrounding the liquid by a subset of the free radicals of the
primary group. A tertiary group of free radicals is generated by
interaction of the plurality of molecules with the free radicals of
the secondary group to link together additional molecules of the
plurality of molecules. These and other embodiments are discussed
more fully below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a perspective view of a lithographic system in
accordance with the present invention;
[0008] FIG. 2 is a simplified elevation view of a lithographic
system, shown in FIG. 1, employed to create a patterned imprinting
layer in accordance with one embodiment of the present
invention;
[0009] FIG. 3 is a top down view of a region of the substrate,
shown in FIG. 2, upon which patterning occurs employing a pattern
of droplets of polymerizable fluid disposed thereon;
[0010] FIG. 4 is a simplified elevation view of an imprint device
spaced-apart from the patterned imprinting layer, shown in FIG. 1,
after patterning in accordance with the present invention;
[0011] FIG. 5 is a top down view of a region of the substrate,
shown in FIG. 4, showing an intermediate pattern formed by the
droplets of polymerizable fluid shown in FIG. 4, during
spreading;
[0012] FIG. 6 is a top down view of a layer, formed from a
polymerizable material, after being subjected to ultra-violet
radiation;
[0013] FIG. 7 is a cross-section view showing a primer layer that
may be employed in accordance with the present invention; and
[0014] FIG. 8 is a cross-section view showing a release layer
applied to a planarization mold.
DETAILED DESCRIPTION OF THE INVENTION
[0015] FIG. 1 depicts a lithographic system 10 in accordance with
one embodiment of the present invention that includes a pair of
spaced-apart bridge supports 12 having a bridge 14 and a stage
support 16 extending therebetween. Bridge 14 and stage support 16
are spaced-apart. Coupled to bridge 14 is an imprint head 18, which
extends from bridge 14 toward stage support 16. Disposed upon stage
support 16 to face imprint head 18 is a motion stage 20. Motion
stage 20 is configured to move with respect to stage support 16
along X and Y axes and may provide movement along the Z axis as
well. A radiation source 22 is coupled to system 10 to impinge
actinic radiation upon motion stage 20. As shown, radiation source
22 is coupled to bridge 14 and includes a power generator 23
connected to radiation source 22.
[0016] Referring to both FIGS. 1 and 2, connected to imprint head
18 is a template 24 having a mold 26 thereon, which may define a
smooth or planar surface of have a pattern formed therein. As
shown, mold 26 includes a pattern having a plurality of features
defined by a plurality of spaced-apart recesses 28 and projections
30. Projections 30 have a width W.sub.1, and recesses 28 have a
width W.sub.2, both of which are measured in a direction that
extends transversely to the Z axis. The plurality of features
defines an original pattern that forms the basis of a pattern to be
transferred into a substrate 32 positioned on motion stage 20. To
that end, imprint head 18 is adapted to move along the Z axis and
vary a distance "d" between mold 26 and substrate 32.
Alternatively, or in conjunction with imprint head 18, motion stage
20 may move template 24 along the Z-axis. In this manner, the
features on mold 26 may be imprinted into a flowable region of
substrate 32, discussed more fully below.
[0017] Radiation source 22 is located so that mold 26 is positioned
between radiation source 22 and substrate 32, with actinic
radiation generated by radiation source 22 propagating through mold
26. As a result, it is desired that mold 26 be fabricated from
material that is substantially transparent to the actinic
radiation. Exemplary materials from which mold 26 may be fabricated
include fused-silica, quartz, silicon, organic polymers, siloxane
polymers, borosilicate glass, fluorocarbon polymers, metal, and
combinations of the above dependent upon the actinic radiation
employed. An exemplary system is available under the trade name
IMPRIO 100.TM. from Molecular Imprints, Inc. having a place of
business at 1807-C Braker Lane, Suite 100, Austin, Tex. 78758. The
system description for the IMPRIO 100.TM. is available at
www.molecularimprints.com and is incorporated herein by
reference.
[0018] Referring to both FIGS. 2 and 3, a flowable region, such as
an imprinting layer 34, is formed on a portion of surface 36 that
presents a substantially smooth, if not planar, profile of a
surface facing mold 26. In one embodiment of the present
embodiment, the flowable region is deposited as a plurality of
spaced-apart discrete droplets 38 of imprinting material on
substrate 32. Specifically, droplets 38 are arranged on surface in
a pattern 100 that minimizes trapping of gases when the imprinting
material of droplets 38 merge to form a contiguous layer over
surface 36, shown more clearly in FIG. 4 as recorded pattern
134.
[0019] Referring to both FIGS. 2 and 4, the imprinting material may
be selectively polymerized and cross-linked to record an inverse of
the original pattern therein, defining a recorded pattern 134 that
is subsequently solidified as discussed below. The plurality of
features on mold 26 are shown as recesses 28 extending along a
direction parallel to projections 30 that provide a cross-section
of mold 26 with a shape of a battlement. However, recesses 28 and
projections 30 may correspond to virtually any feature desired and
may be as small as a few tenths of nanometers. Features such as
those that facilitate formation of integrated circuits.
[0020] Referring to both FIGS. 2 and 5, the recorded pattern 134 is
produced, in part, by interaction of the imprinting material with
mold 26, e.g., mechanical contact, electrical contact and the like.
In an exemplary embodiment, distance "d" is reduced to allow
imprinting layer 34 to come into mechanical contact with mold 26.
In response, the imprinting material in droplets 38 spreads forming
a series of intermediate patterns, one of which is shown as pattern
200, to form a contiguous formation of the imprinting material over
surface 36. In one embodiment, distance "d" is reduced to allow
sub-portions 46 of recorded pattern 134 to ingress into and fill
recesses 28. It may be desired to purge the volume, for example
with Helium gas flowed at 5 pounds per square inch (psi), defined
between mold 26 and both surface 36 and droplets 38 before contact
occurs. An exemplary purging technique is disclosed in U.S. patent
application Ser. No. 10/677,639 filed Oct. 2, 2003, entitled SINGLE
PHASE FLUID IMPRINT LITHOGRAPHY METHOD, which is incorporated by
reference herein.
[0021] In the present embodiment, sub-portions 48 of recorded
pattern 134 in superimposition with projections 30 remain after the
desired, usually minimum distance "d", has been reached, leaving
sub-portions 46 with a thickness t.sub.1, and sub-portions 48 with
a thickness, t.sub.2. Thickness t.sub.2 is referred to as a
residual thickness. Thicknesses "t.sub.1" and "t.sub.2" may be any
thickness desired, dependent upon the application. The total volume
contained in droplets 38 may be such so as to minimize, or avoid, a
quantity of the imprinting material from extending beyond the
region of surface 36 in superimposition with mold 26, while
obtaining desired thicknesses t.sub.1 and t.sub.2, i.e., through
capillary attraction of the imprinting material with mold 26 and
surface 36 and surface adhesion of the imprinting material.
[0022] Referring again to FIGS. 2 and 3, after a desired distance
"d" has been reached, radiation source 22 produces actinic
radiation that polymerizes and cross-links the imprinting material,
solidifying recorded pattern 134. The composition of imprinting
layer 34 transforms from a fluidic imprinting material to a
solidified material. This provides solidified imprinting layer 134
with a side having a shape that conforms to a shape of a surface 50
of mold 26, shown more clearly in FIG. 4. As a result, recorded
pattern 134 is formed having recessions 52 and protrusions 54.
After solidification of recorded pattern 134, distance "d" is
increased so that mold 26 and recorded pattern 134 are
spaced-apart. Typically, this process is repeated several times to
pattern different regions (not shown) of substrate 32, referred to
as a step and repeat process. An exemplary step and repeat process
is disclosed in published United States patent application No.
2004/0008334, filed Jul. 11, 2002 as application Ser. No.
10/194,414, entitled STEP AND REPEAT IMPRINT LITHOGRAPHY, which
assigned to assignee of the present invention and is incorporated
by reference.
[0023] The advantages of this patterning process are manifold. For
example, the thickness differential between protrusions 54 and
recessions 52 facilitates formation, in substrate 32, of a pattern
corresponding to the recorded pattern 134. Specifically, the
thickness differential between t.sub.1 and t.sub.2 of protrusions
54 and recession 52, respectively, results in a greater amount of
etch time being required before exposing regions of substrate 32 in
superimposition with protrusions 54 compared with the time required
for regions of substrate 32 in superimposition with recession 52
being exposed. For a given etching process, therefore, etching will
commence sooner in regions of substrate 32 in superimposition with
recessions 52 than regions in superimposition with protrusions 54.
This facilitates formation of a pattern in substrate corresponding
to recorded pattern 134. By properly selecting the imprinting
materials and etch chemistries, the relational dimensions between
the differing features of the pattern eventually transferred into
substrate 32 may be controlled as desired. To that end, it is
desired that the etch characteristics of recorded pattern 134, for
a given etch chemistry, be substantially uniform.
[0024] As a result, the characteristics of the imprinting material
are important to efficiently pattern substrate 32 in light of the
unique patterning process employed. As mentioned above, the
imprinting material is deposited on substrate 32 as a plurality of
discrete and spaced-apart droplets 38. The combined volume of
droplets 38 is such that the imprinting material is distributed
appropriately over an area of surface 36 where recorded pattern 134
is to be formed. In this fashion, the total volume of the
imprinting material in droplets 38 defines the distance "d", to be
obtained so that the total volume occupied by the imprinting
material in the gap defined between mold 26 and the portion of
substrate 32 in superimposition therewith once the desired distance
"d" is reached is substantially equal to the total volume of the
imprinting material in droplets 38. To facilitate the deposition
process, it is desired that the imprinting material provide rapid
and even spreading of the imprinting material in droplets 38 over
surface 36 so that all thicknesses t.sub.1 are substantially
uniform and all residual thicknesses t.sub.2 are substantially
uniform.
[0025] Referring to FIG. 6, a problem recognized by the present
invention involves varying evaporation characteristics of a
contiguous layer 300. Layer 300 was formed in the manner discussed
above, excepting that a planarization mold (not shown), i.e., a
non-patterned mold with a smooth surface was employed to spread
droplets 38. After spreading of droplets 38 the imprinting material
was exposed for approximately 700 ms to actinic radiation having a
wavelength of approximate 365 nm a flux of 77 mW/cm.sup.2 to
solidify the same. After solidification of layer 300, observed were
varying thicknesses over the area thereof. Specifically, regions
302 and 304 were found to be thinner than the remaining regions of
layer 300. As can be seen regions 304 have a substantially uniform
area compared to regions 302. Regions 302 have a first thickness
s.sub.1, proximate to regions 304, which becomes increasingly
larger reaching an apex proximate to an outer edge of layer 300
shown as s.sub.2. It is believed that regions 302 and 304 result
from partial polymerization attributable to the presence of oxygen
during the series of intermediate patterns that are generated as
the imprinting material in droplets 38 spreads. As shown, a
material-ambient boundary 202 is generated in intermediate pattern
200 material-ambient boundary 202 is formed as the imprinting
material spreads. The material-ambient boundary 202 persists until
adjacent volumes of imprinting material merges. As can be seen, the
imprinting material merges earlier in central regions of pattern
200 as compared to regions of pattern 200 disposed proximate to
boundary 204. It is believed that the reduction in polymerization
is directly related to the length of time of exposure to the
components of the ambient, such as oxygen, which is believed to
cause evaporation and inhibits polymerization. This provides a
rationale for the varying thickness of regions 302. The prior art
composition for the imprinting material used to form layer 300 is a
follows:
Prior Art Composition
isobornyl acrylate n-hexyl acrylate ethylene glycol diacrylate
2-hydroxy-2-methyl-1-phenyl-propan-1-one R.sub.1R.sub.2
[0026] with R.sub.1R.sub.2 being a surfactant. For purposes of this
invention a surfactant is defined as any molecule, one tail of
which is hydrophobic. Surfactants may be either
fluorine-containing, e.g., include a fluorine chain, or may not
include any fluorine in the surfactant molecule structure. In
surfactant R.sub.1R.sub.2, R.sub.1.dbd.F(CF.sub.2CF.sub.2).sub.y,
with y being in a range of 1 to 7, inclusive, and
R.sub.2.dbd.CH.sub.2CH.sub.2O(CH.sub.2CH.sub.2O).sub.XH, with X is
in a range of 0 to 15, inclusive. An exemplary surfactant is
available under the trade name ZONYL.RTM. FSO-100 from DUPONT.TM..
It was believed that during the polymerization reaction the PRIOR
ART COMPOSITION formed peroxide radicals proximate to the
material-gas boundaries. This slows the rate of, if not prevents,
polymerization of the imprinting material. As a result, for a given
polymerization process, film 300 is provided with varying degrees
of solidification over the volume thereof.
[0027] The present invention overcomes these drawbacks by including
in the composition, which forms the imprinting material, a
scavenger material that consumes molecules in the ambient that
would inhibit the curing process. Specifically, it was found that
by including an additive with the initiator, the inhibition of
polymerization at material-gas boundaries could be minimized. To
that end, included in the PRIOR ART COMPOSITION is an
amine-containing additive to provide the following composition:
Composition 1
isobornyl acrylate n-hexyl acrylate ethylene glycol diacrylate
2-hydroxy-2-methyl-1-phenyl-propan-1-one N-methyldiethanolamine
R.sub.1R.sub.2
[0028] The acrylate component isobornyl acrylate (IBOA) has the
following structure: ##STR1## and comprises approximately 55% of
COMPOSITION 1 by weight, but may be present in a range of 20% to
80%, inclusive. As a result, the mechanical properties of
solidified imprinting layer 134 are primarily attributable to IBOA.
The component n-hexyl acrylate (nHA) has the following structure:
##STR2## and comprises approximately 27% of COMPOSITION 1 by
weight, but may be present in a range of 0% to 50%, inclusive. Also
providing flexibility to solidified imprinting layer 134, nHA is
employed to reduce the viscosity of the prior art composition so
that COMPOSITION 1, in the liquid phase, has a viscosity in a range
2-9 Centipoises, inclusive. A cross-linking component, ethylene
glycol diacrylate, has the following structure: ##STR3## and
comprises approximately 15% of COMPOSITION 1 by weight, and may be
present in a range of 10% to 50%, inclusive. EGDA also contributes
to the modulus and stiffness buildup, as well as facilitates
cross-linking of nHA and IBOA during polymerization of COMPOSITION
1. An initiator component, 2-hydroxy-2-methyl-1-phenyl-propan-1-one
is available from Ciba Specialty Chemicals of Tarrytown, N.Y. under
the trade name DAROCUR 1173, has the following structure: ##STR4##
and comprises approximately 3% of COMPOSITION 1 by weight, and may
be present in a range of 1% to 5%, inclusive. The initiator is
responsive to a broad band of ultra-violet radiation generated by a
medium-pressure mercury lamp. In this manner, the initiator
facilitates cross-linking and polymerization of the components of
COMPOSITION 1. A surfactant component, R.sub.1R.sub.2, is as
described above with respect to the PRIOR ART COMPOSITION and has
the following general structure: ##STR5##
[0029] The surfactant component provides suitable wetting
properties of COMPOSITION 1 when in the liquid phase, as well as
desired release characteristics in the solid phase. An amine
component N-methyldiethanolamine has the following structure:
##STR6## and comprises approximately 0.5% to 4%, inclusive of
COMPOSITION 1 by weight. The amine component reduces, if not
prevents, the deleterious effects of the ambient on COMPOSITION 1.
Specifically, the following reactions occur during polymerization:
##STR7## where the initiator is
2-hydroxy-2-methyl-1-phenyl-propan-1-one, hv is the optical energy
generated by the ultraviolet radiation impinging upon the initiator
and R. is a primary group of free radicals generated by the
initiator in response to the radiation. The free primary group of
free radicals then interact with the IBOA and nHA acrylates, M, as
follows: ##STR8## where RM. is a radical chain also denoted as P.
and terminates into polymer chains as follows: P.+P..fwdarw.Polymer
(3)
[0030] In addition to reactions 1-3 above, additional reactions
occur proximate to boundary 202 where the ambient is present. An
exemplary reaction occurs between the radical initiator R. and
oxygen O.sub.2 as follows: R.+O.sub.2.fwdarw.RO.sub.2. (4) where
RO.sub.2. is a secondary group of radicals, i.e., peroxide
radicals. The peroxide radical is undesirable in that it
effectively consumes the radicals of the primary group R. reducing
the quantity of the same to facilitate the reaction of equation (2)
and peroxide radical itself and has a low probability of initiating
polymerization. This inhibits polymerization as defined by equation
(4). The amine group, DH, of COMPOSITION 1, however, reacts with
the secondary group of radicals RO.sub.2. to produce a tertiary
group of radicals D., as well as some residual molecules RO.sub.2H
as follows: RO.sub.2+DH.fwdarw.RO.sub.2H+D. (5)
[0031] In addition, the amine radical reacts with the acrylates M
to facilitate further polymerization thereof as follows:
D.+M.fwdarw.DM. (6)
[0032] Also, the amine group reacts with oxygen present in the
ambient to reduce the formation of the RO.sub.2. type of peroxide
radicals, as follows: D.+O.sub.2.fwdarw.DO.sub.2. (7)
[0033] Although the radical DO.sub.2. is undesirable, the same may
interact with other amine groups present in COMPOSITION 1 as
follows: DO.sub.2.+DH.fwdarw.DO.sub.2H+D. (8) that creates
additional radicals D. to further polymerization while reducing the
presence of oxygen in solidified imprinting layer by as much as
99%. It should be understood that the amine group may be included
in COMPOSITION 1 by replacing, or using in conjunction with the
2-hydroxy-2-methyl-1-phenyl-propan-1-one initiator, an
amine-containing initiator that may be included with the tertiary
amine component or in lieu thereof. Were the amine group employed
in lieu of the initiator, it is desirable that the amine group be
photo-active in generating radical upon UV exposure. To that end,
other compositions may include the following:
Composition 2
isobornyl acrylate n-hexyl acrylate ethylene glycol diacrylate
2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one
R.sub.1R.sub.2
where 2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one is
available from Ciba Specialty Chemicals Corporation of Tarrytown
N.Y. under the trade name IRGACURE.RTM. 907; and
Composition 3
isobornyl acrylate n-hexyl acrylate ethylene glycol diacrylate
2-Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone
R.sub.1R.sub.2
where 2-Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone is
available from Ciba Specialty Chemicals Corporation of Tarrytown,
N.Y. under the trade name IRGACURE.RTM. 369; and
Composition 4
isobornyl acrylate n-hexyl acrylate ethylene glycol diacrylate
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone
R.sub.1R.sub.2
where
2-(4-methyl-benzyl)-2-dimethylamino-1-(4-morpholinophenyl)-1-butan-
one is available from Ciba Specialty Chemicals Corporation of
Tarrytown, N.Y. under the trade name IRGACURE.RTM. 379.
[0034] Referring to FIGS. 2 and 7, it may be desirable to provide
substrate 32 with a smooth, if not planar, surface upon which to
form imprinting layer 34. To that end, substrate 32 may include a
primer layer 96. Primer layer 96 has proved beneficial when surface
36 of substrate 32 appears rough when compared to the features
dimensions to be formed in imprinting layer 34. Primer layer 96 may
also function, inter alia, to provide a standard interface with
imprinting layer 34, thereby reducing the need to customize each
process to the imprinting material from which substrate 32 is
formed. In addition, primer layer 96 may be formed from an organic
imprinting material with the same or different etch characteristics
as imprinting layer 34. As a result, primer layer 96 is fabricated
in such a manner so as to possess a continuous, smooth, relatively
defect-free surface that may exhibit excellent adhesion to
imprinting layer 34. An exemplary material to use to form primer
layer 96 is available from Brewer Science, Inc. of Rolla Mo. under
the trade name DUV30J-6. The primer layer 96 is typically provided
with a thickness to facilitate providing the desired surface
profile and without being opaque to optical sensing equipment
employed to detect patterns, such as alignment marks, on substrate
32 surface.
[0035] Referring to FIGS. 7 and 8, it has been found beneficial to
deposit a primer layer 196 when an imprinting layer 34 upon a
surface 136 of substrate 32 that has been previously patterned. To
that end, primer layer 196, as with primer layer 96, may be
deposited employing any known deposition method, including droplet
dispense techniques, spin-on techniques and the like. Furthermore,
to enhance the smoothness of the surface of either of primer layer
96 and 196 it may be desired to contact the same with a
planarization mold 80 having a substantially smooth, if not planar,
contact surface.
[0036] To reduce the probability that solidified primer layers 96
and 196 adhere to planarization mold 80 the same may be treated
with a low surface energy coating 98. Low surface energy coating 98
may be applied using any known process. For example, processing
techniques may include chemical vapor deposition method, physical
vapor deposition, atomic layer deposition or various other
techniques, brazing and the like. In a similar fashion a low
surface energy coating (not shown) may be applied to mold 26, shown
in FIG. 2.
[0037] In addition to the aforementioned surfactants and low
surface energy coatings, fluorinated additives may be employed to
improve release properties of the imprinting material. Fluorinated
additives, like surfactants, have a surface energy associated
therewith that is lower than a surface energy of the imprinting
material. An exemplary process by which to employ the
aforementioned fluorinated additive is discussed by Bender et al.
in MULTIPLE IMPRINTING IN UV-BASED NANOIMPRINT LITHOGRAPHY:RELATED
MATERIAL ISSUES, Microelectronic Engineering pp. 61-62 (2002). The
low surface energy of the additive provides the desired release
properties to reduce adherence of cross-linked and polymerized
imprinting material molds 26 and 80.
[0038] The embodiments of the present invention described above are
exemplary. Many changes and modifications may be made to the
disclosure recited above, while remaining within the scope of the
invention. For example, the ratio of the components of each of the
aforementioned COMPOSITIONs may be varied. The scope of the
invention should, therefore, not be limited by the above
description, but instead should be determined with reference to the
appended claims along with their full scope of equivalents.
* * * * *
References