U.S. patent application number 14/048745 was filed with the patent office on 2014-02-06 for method for adhering materials together.
This patent application is currently assigned to Molecular Imprints, Inc.. The applicant listed for this patent is Molecular Imprints, Inc.. Invention is credited to Frank Y. Xu.
Application Number | 20140034229 14/048745 |
Document ID | / |
Family ID | 37968270 |
Filed Date | 2014-02-06 |
United States Patent
Application |
20140034229 |
Kind Code |
A1 |
Xu; Frank Y. |
February 6, 2014 |
Method for Adhering Materials Together
Abstract
The present invention provides a method for adhering a layer to
a substrate that features defining first and second interfaces by
having a composition present between the layer and the substrate
that forms covalent bonds to the layer and adheres to the substrate
employing one or more of covalent bonds, ionic bonds and Van der
Waals forces. In this manner, the strength of the adhering force of
the layer to the composition is assured to be stronger than the
adhering force of the layer to the composition formed from a
predetermined adhering mechanism, i.e., an adhering mechanism that
does not include covalent bonding.
Inventors: |
Xu; Frank Y.; (Round Rock,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Molecular Imprints, Inc. |
Austin |
TX |
US |
|
|
Assignee: |
Molecular Imprints, Inc.
Austin
TX
|
Family ID: |
37968270 |
Appl. No.: |
14/048745 |
Filed: |
October 8, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11187407 |
Jul 22, 2005 |
8557351 |
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14048745 |
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Current U.S.
Class: |
156/272.2 ;
156/60 |
Current CPC
Class: |
B81C 2201/0153 20130101;
B82Y 10/00 20130101; C09J 2301/416 20200801; C08L 59/00 20130101;
B81C 1/0046 20130101; Y10T 156/10 20150115; B82Y 40/00 20130101;
C09J 2451/00 20130101; G03F 7/0002 20130101; B32B 37/14 20130101;
C09J 5/00 20130101; B32B 38/06 20130101 |
Class at
Publication: |
156/272.2 ;
156/60 |
International
Class: |
B32B 37/14 20060101
B32B037/14 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] The United States government has a paid-up license in this
invention and the right in limited circumstance to require the
patent owner to license others on reasonable terms as provided by
the terms of 70NANB4H3012 awarded by National Institute of
Standards (NIST) ATP Award.
Claims
1. A method of adhering a layer to a substrate, said method
comprising: defining first and second interfaces by having a
composition present between said layer and said substrate, with
said first interface being defined between said layer and said
composition and said second interface being defined between said
substrate and said composition, with said first interface including
covalent bonds and said second interface including a mechanism
adhering said composition to said substrate.
2. The method as recited in claim 1 wherein said mechanism is
selected from a set of mechanisms including covalent bonds, ionic
bonds and Van der Waals forces.
3. The method as recited in claim 1 wherein said second interface
is formed by thermally curing said composition and said first
interface is formed by exposing said layer and said composition to
actinic energy.
4. The method as recited in claim 1 wherein defining further
includes solidifying said composition, defining a solidified
composition and forming said layer upon said solidified
composition.
5. The method as recited in claim 1 wherein defining further
includes locating, between said layer and said substrate, a
plurality of molecules, a subset of which includes an organic
backbone group and first and second functional groups with said
first functional group reacting with said layer to form said
covalent bonds and said second functional group reacting with said
substrate.
6. The method as recited in claim 1 wherein defining further
includes locating between said layer and said substrate a plurality
of molecules, a first subset of which is a cross-linker and a
second subset of which includes a backbone group and first and
second functional groups with said first functional group reacting
with said layer forming said covalent bonds and said second
functional group reacting with one of said substrate and said
cross-linker.
7. The method as recited in claim 6 wherein said backbone group
contains aromatic structures.
8. The method as recited in claim 1 wherein defining further
includes locating between said layer and said substrate a plurality
of molecules, a subset of which includes a backbone group and first
and second functional groups with said first functional group
consisting essentially of an acrylate functional group reacting
with said layer to form said covalent bonds.
9. The method as recited in claim 8 wherein said backbone group is
selected from a set of groups consisting essentially of aliphatic
and aromatic.
10. A method of adhering a layer to a substrate, said method
comprising: depositing a composition upon said substrate;
solidifying said composition forming a solidified composition; and
forming said layer upon said solidified composition, with a first
interface being defined between said layer and said solidified
composition and a second interface being defined between said
substrate and said composition, with said first interface including
covalent bonds and said second interface including a mechanism
adhering said composition to said substrate with said mechanism
being selected from a set of mechanisms bonds consisting
essentially of covalent bonds, ionic bonds and Van der Waals
forces.
11. The method as recited in claim 10 wherein said second interface
is formed by thermally curing said composition and said first
interface is formed by exposing said layer and said composition to
actinic energy.
12. The method as recited in claim 10 wherein depositing further
includes locating upon said substrate a plurality of molecules, a
subset of which includes an organic backbone group and first and
second functional groups, with said second functional group
reacting with said substrate, with forming further including
reacting said first functional group with said layer to form said
covalent bonds of said first interface.
13. The method as recited in claim 10 wherein depositing further
includes locating upon said substrate a plurality of molecules, a
first subset of which is a cross-linker and a second subset of
which includes a backbone group and first and second functional
groups with said second functional group reacting with one of said
substrate and said cross-linker, with forming further including
reacting said first functional group with said layer to form said
covalent bonds of said first interface.
14. The method as recited in claim 10 wherein depositing further
includes locating between said layer and said substrate a plurality
of molecules, a subset of which includes a backbone group and first
and second functional groups with said first functional group
consisting essentially of an acrylate functional group, with
forming further including reacting said first function group with
said layer to form said covalent bonds of said first interface.
15. The method as recited in claim 14 wherein said backbone group
is selected from a set of groups consisting essentially of
aliphatic and aromatic.
16. A method of adhering a layer to a substrate, said method
comprising: arranging said layer and said substrate so as to have a
composition disposed therebetween to create first and second
adhering forces, with said first adhering force being generated at
a first interface of said layer and said composition and said
second adhering force being disposed at a second interface of said
composition with said substrate, said first adhering force and
second adhering force being greater than the non-covalent bonded
first adhering force.
17. The method as recited in claim 16 wherein said first and second
adhering forces are greater than a separation force.
18. The method as recited in claim 16 wherein said first adhering
force is generated by covalently bonding said composition to said
layer and said second adhering force is generated by adhering said
composition to said substrate employing a mechanism selected from a
set of mechanisms including covalent bonds, ionic bonds and Van der
Waals forces.
19. The method as recited in claim 16 wherein said second interface
is formed by thermally curing said composition and said first
interface is formed by exposing said layer and said composition to
actinic energy.
20. The method as recited in claim 16 wherein defining further
includes solidifying said composition, defining a solidified
composition and forming said layer upon said solidified
composition.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. Ser. No.
11/187,407 filed Jul. 22, 2005; which in turn is a divisional of
U.S. Ser. No. 11/187,406 filed Jul. 22, 2005; both of which are
incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0003] The field of invention relates generally to nano-fabrication
of structures. More particularly, the present invention is directed
to a method for adhering differing materials together suitable for
use in imprint lithographic processes.
[0004] Nano-scale fabrication involves the fabrication of very
small structures, e.g., having features on the order of one
nanometer or more. A promising process for use in nano-scale
fabrication is known as imprint lithography. Exemplary imprint
lithography processes are described in detail in numerous
publications, such as U.S. Pat. No. 8,349,241; U.S. publication no.
2004/0065252; and U.S. Pat. No. 6,936,194; all of which are
assigned to the assignee of the present invention and incorporated
by reference herein.
[0005] Referring to FIG. 1, the basic concept behind imprint
lithography is forming a relief pattern on a substrate that may
function as, inter alia, an etching mask so that a pattern may be
formed into the substrate that corresponds to the relief pattern. A
system 10 employed to form the relief pattern includes a stage 11
upon which a substrate 12 is supported, and a template 14 having a
mold 16 with a patterning surface 18 thereon. Patterning surface 18
may be substantially smooth and/or planar, or may be patterned so
that one or more recesses are formed therein. Template 14 is
coupled to an imprint head 20 to facilitate movement of template
14. A fluid dispense system 22 is coupled to be selectively placed
in fluid communication with substrate 12 so as to deposit
polymerizable material 24 thereon. A source 26 of energy 28 is
coupled to direct energy 28 along a path 30. Imprint head 20 and
stage 11 are configured to arrange mold 16 and substrate 12,
respectively, to be in superimposition, and disposed in path 30.
Either imprint head 20, stage 11, or both vary a distance between
mold 16 and substrate 12 to define a desired volume therebetween
that is filled by polymerizable material 24.
[0006] Typically, polymerizable material 24 is disposed upon
substrate 12 before the desired volume is defined between mold 16
and substrate 12. However, polymerizable material 24 may fill the
volume after the desired volume has been obtained. After the
desired volume is filled with polymerizable material 24, source 26
produces energy 28, which causes polymerizable material 24 to
solidify and/or cross-link, forming polymeric material conforming
to the shape of the substrate surface 25 and mold surface 18.
Control of this process is regulated by processor 32 that is in
data communication with stage 11, imprint head 20, fluid dispense
system 22, and source 26, operating on a computer-readable program
stored in memory 34.
[0007] An important characteristic with accurately forming the
pattern in the polymerizable material is to reduce, if not prevent,
adhesion to the mold of the polymeric material, while ensuring
suitable adhesion to the substrate. This is referred to as
preferential release and adhesion properties. In this manner, the
pattern recorded in the polymeric material is not distorted during
separation of the mold. Prior art attempts to improve the release
characteristics employ a release layer on the surface of the mold.
The release layer is typically hydrophobic and/or has low surface
energy. The release layer adheres to the mold. Providing the
release layer improves release characteristics. This is seen by
minimization of distortions in the pattern recorded into the
polymeric material that are attributable to mold separation. This
type of release layer is referred to, for purposes of the present
discussion, as an a priori release layer, i.e., a release layer
that is solidified to the mold.
[0008] Another prior art attempt to improve release properties is
described by Bender et al. in "Multiple Imprinting in UV-based
Nanoimprint Lithography: Related Material Issues," Microeletronic
Engineering 61-62 (2002), pp. 407-413. Specifically, Bender et al.
employ a mold having an a priori release layer in conjunction with
a fluorine-treated UV curable material. To that end, a UV curable
layer is applied to a substrate by spin-coating a 200 cPs UV
curable fluid to form a UV curable layer. The UV curable layer is
enriched with fluorine groups to improve the release
properties.
[0009] A need exists, therefore, to improve the preferential
release and adhesion properties of a mold employed in imprint
lithography processes.
SUMMARY OF THE INVENTION
[0010] The present invention provides a method of adhering a layer
to a substrate that features defining first and second interfaces
by having a composition present between the layer and the substrate
that forms covalent bonds to the layer and adheres to the substrate
employing one or more of covalent bonds, ionic bonds and Van der
Waals forces. In this manner, the strength of the adhering force of
the layer to the composition is assured to be stronger than the
adhering force of the layer to the composition having a
predetermined adhering mechanism, i.e., an adhering mechanism that
does not include covalent bonding. These and other embodiments are
described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a simplified plan view of a lithographic system in
accordance with the prior art;
[0012] FIG. 2 is a simplified elevation view of a template and
imprinting material disposed on a substrate in accordance with the
present invention;
[0013] FIG. 3 is a simplified elevation view of the template and
substrate, shown in FIG. 2, with the imprinting material being
shown as patterned and solidified upon the layer;
[0014] FIG. 4 is a cross-sectional view of the template contacting
imprinting material demonstrating the formation of the weak
boundary lamella between solidified imprinting material and a
template;
[0015] FIG. 5 is a detailed view of the droplets of imprint
material, shown in FIG. 2, showing the bifurcation of the droplets
into surfactant-rich regions and surfactant-depleted regions;
[0016] FIG. 6 is a detailed view of a layer of imprinting material,
deposited employing spin-on techniques, showing the bifurcation of
the layer into surfactant-rich regions and surfactant-depleted
regions;
[0017] FIG. 7 is a cross-sectional view of the template contacting
solidified imprinting material, deposited as shown in either FIG. 5
or 6, formed on a substrate including a primer layer;
[0018] FIG. 8 is a plan view showing the chemical structure of a
component of a composition that may be employed to form the primer
layer shown in FIGS. 2, 3, and 7, in accordance with one embodiment
of the present invention;
[0019] FIG. 9 is a plan view showing the chemical structure of a
component of a composition that may be employed to form the primer
layer shown in FIGS. 2, 3, and 7, in accordance with a second
embodiment of the present invention;
[0020] FIG. 10 is a plan view showing the chemical structure of a
component of a composition that may be employed to form the primer
layer shown in FIGS. 2, 3, and 7, in accordance with a third
embodiment of the present invention; and
[0021] FIG. 11 is a plan view showing the chemical structure of a
component of a composition that may be employed to form the primer
layer shown in FIGS. 2, 3, and 7, in accordance with a fourth
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] Referring to FIGS. 1 and 2, a mold 36, in accordance with
the present invention, may be employed in system 10, and may define
a surface having a substantially smooth or planar profile (not
shown). Alternatively, mold 36 may include features defined by a
plurality of spaced-apart recessions 38 and protrusions 40. The
plurality of features defines an original pattern that forms the
basis of a pattern to be formed on a substrate 42. Substrate 42 may
comprise a bare wafer or a wafer with one or more layers disposed
thereon, one of which is shown as primer layer 45. To that end,
reduced is a distance "d" between mold 36 and substrate 42. In this
manner, the features on mold 36 may be imprinted into a conformable
region of substrate 42, such as an imprinting material disposed on
a portion of surface 44 that presents a substantially planar
profile. It should be understood that the imprinting material may
be deposited using any known technique, e.g., spin-coating, dip
coating and the like. In the present example, however, the
imprinting material is deposited as a plurality of spaced-apart
discrete droplets 46 on substrate 42. Imprinting material is formed
from a composition that may be selectively polymerized and
cross-linked to record the original pattern therein, defining a
recorded pattern.
[0023] Specifically, the pattern recorded in the imprinting
material is produced, in part, by interaction with mold 36, e.g.,
electrical interaction, magnetic interaction, thermal interaction,
mechanical interaction or the like. In the present example, mold 36
comes into mechanical contact with the imprinting material,
spreading droplets 36, so as to generate a contiguous formation 50
of the imprinting material over surface 44. In one embodiment,
distance "d" is reduced to allow sub-portions 52 of imprinting
material to ingress into and fill recessions 38. To facilitate
filling of recessions 38, before contact between mold 36 and
droplets 46, the atmosphere between mold 36 and droplets 46 is
saturated with helium or is completely evacuated or is a partially
evacuated atmosphere of helium.
[0024] The imprinting material is provided with the requisite
properties to completely fill recessions 38 while covering surface
44 with a contiguous formation of the imprinting material. In the
present embodiment, sub-portions 54 of imprinting material in
superimposition with protrusions 40 remain after the desired,
usually minimum, distance "d" has been reached. This action
provides formation 50 with sub-portions 52 having a thickness
t.sub.1, and sub-portions 54, having a thickness t.sub.2.
Thicknesses "t.sub.1" and "t.sub.2" may be any thickness desired,
dependent upon the application. Thereafter, formation 50 is
solidified by exposing the same to the appropriate curing agent,
e.g., actinic energy, such as broadband ultraviolet energy, thermal
energy or the like, depending upon the imprinting material. This
causes the imprinting material to polymerize and cross-link. The
entire process may occur at ambient temperatures and pressures, or
in an environmentally-controlled chamber with desired temperatures
and pressures. In this manner, formation 50 is solidified to
provide side 56 thereof with a shape conforming to a shape of a
surface 58 of mold 36.
[0025] Referring to FIGS. 1, 2 and 3, the characteristics of the
imprinting material are important to efficiently pattern substrate
42 in light of the unique patterning process employed. For example,
it is desired that the imprinting material have certain
characteristics to facilitate rapid and even filling of the
features of mold 36 so that all thicknesses t.sub.1 are
substantially uniform and all thicknesses t.sub.2 are substantially
uniform. To that end, it is desirable that the viscosity of the
imprinting material be established, based upon the deposition
process employed, to achieve the aforementioned characteristics. As
mentioned above, the imprinting material may be deposited on
substrate 42 employing various techniques. Were the imprinting
material deposited as a plurality of discrete and spaced-apart
droplets 46, it would be desirable that a composition from which
the imprinting material is formed have relatively low viscosity,
e.g., in a range of 0.5 to 20 centipoises (cPs). Considering that
the imprinting material is spread and patterned concurrently, with
the pattern being subsequently solidified into formation 50 by
exposure to radiation, it would be desired to have the composition
wet surface of substrate 42 and/or mold 36 and to avoid subsequent
pit or hole formation after polymerization. Were the imprinting
material deposited employing spin-coating techniques, it would be
desired to use higher viscosity materials, e.g., having a viscosity
greater than 10 cPs and typically, several hundred to several
thousand cPs, with the viscosity measurement being determined in
the absence of a solvent.
[0026] In addition to the aforementioned characteristics, referred
to as liquid phase characteristics, it is desirable that the
composition provide the imprinting material with certain solidified
phase characteristics. For example, after solidification of
formation 50, it is desirable that preferential adhesion and
release characteristics be demonstrated by the imprinting material.
Specifically, it is beneficial for the composition from which the
imprinting material is to be fabricated to provide formation 50
with preferential adhesion to substrate 42 and preferential release
of mold 36. In this fashion, reduced is the probability of
distortions in the recorded pattern resulting from the separation
of mold 36 therefrom due to, inter alia, tearing, stretching or
other structural degradation of formation 50.
[0027] The constituent components of the composition that form the
imprinting material to provide the aforementioned characteristics
may differ. This results from substrate 42 being formed from a
number of different materials. As a result, the chemical
composition of surface 44 varies dependent upon the material from
which substrate 42 is formed. For example, substrate 42 may be
formed from silicon, plastics, gallium arsenide, mercury telluride,
and composites thereof. As mentioned above, substrate 42 may
include one or more layers shown as primer layer 45, e.g.,
dielectric layer, metal layer, semiconductor layer, planarization
layer and the like, upon which formation 50 is generated. To that
end, primer layer 45 would be deposited upon a wafer 47 employing
any suitable technique, such as chemical vapor deposition,
spin-coating and the like. Additionally, primer layer 45 may be
formed from any suitable material, such as silicon, germanium and
the like. Additionally, mold 36 may be formed from several
materials, e.g., fused-silica, quartz, indium tin oxide,
diamond-like carbon, MoSi, sol-gels and the like.
[0028] It has been found that the composition from which formation
50 is generated may be fabricated from several different families
of bulk materials. For example, the composition may be fabricated
from vinyl ethers, methacrylates, epoxies, thiol-enes and
acrylates, just to name a few.
[0029] An exemplary bulk material from which to form formation 50
is as follows:
Bulk Imprinting Material
[0030] isobornyl acrylate [0031] n-hexyl acrylate [0032] ethylene
glycol diacrylate [0033]
2-hydroxy-2-methyl-1-phenyl-propan-1-one
[0034] The acrylate component, isobornyl acrylate (IBOA), has the
following structure:
##STR00001##
and comprises approximately 47% of bulk material by weight, but may
be present in a range of 20% to 80%, inclusive. As a result, the
mechanical properties of formation 50 are primarily attributable to
IBOA. An exemplary source for IBOA is Sartomer Company, Inc. of
Exton, Pa. available under the product name SR 506.
[0035] The component n-hexyl acrylate (n-HA) has the following
structure:
##STR00002##
and comprises approximately 25% of bulk material by weight, but may
be present in a range of 0% to 50%, inclusive. Also providing
flexibility to formation 50, n-HA is employed to reduce the
viscosity of the prior art bulk material so that bulk material, in
the liquid phase, has a viscosity in a range 2-9 Centipoises,
inclusive. An exemplary source for the n-HA component is the
Aldrich Chemical Company of Milwaukee, Wis.
[0036] A cross-linking component, ethylene glycol diacrylate, has
the following structure:
##STR00003##
and comprises approximately 25% of bulk material 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 n-HA and IBOA during polymerization of
the bulk material.
[0037] 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.RTM. 1173, and has the following structure:
##STR00004##
and comprises approximately 3% of the bulk material by weight, and
may be present in a range of 1% to 5%, inclusive. The actinic
energy to which the initiator is responsive is broadband
ultraviolet energy generated by a medium-pressure mercury lamp. In
this manner, the initiator facilitates cross-linking and
polymerization of the components of the bulk material.
[0038] It has been disclosed, however, in U.S. Pat. No. 7,307,118
that desirable preferential adhesion and release properties, as
discussed above, may be achieved by producing a weak boundary
layer, lamella 60, between mold 36, surface 58 and formation 50,
shown in FIGS. 3 and 4. Lamella 60 remains after solidification of
the imprinting material. As a result, the adhesion forced between
mold 36 and formation 50 are minimal. To that end, found beneficial
was employing a composition for the imprinting material that
includes one of several compositions, such as the BULK IMPRINTING
MATERIAL discussed above, along with a component that contains low
surface energy groups, referred to as a surfactant component and
fully described in U.S. Pat. No. 7,307,118, which is incorporated
by reference herein.
[0039] Referring to FIG. 5, after deposition of the imprinting
material, the surfactant component rises, after a period of time,
to the air liquid interface, providing droplets 146 of imprinting
material with a bifurcated concentration of materials. In a first
portion, droplets 146 include a higher concentration of the
surfactant component, referred to as a surfactant-component-rich
(SCR) sub-portion 136, than the second portion, referred to as a
surfactant-component-depleted (SCD) sub-portion 137. SCD
sub-portion 137 is positioned between surface 44 and SCR
sub-portion 136. SCR sub-portion 136 attenuates the adhesion forces
between mold 36 and the imprinting material, once the imprinting
material is solidified. Specifically, the surfactant component has
opposed ends. When the imprinting material is in the liquid phase,
i.e., polymerizable, one of the opposed ends has an affinity for
the bulk material included in the imprinting material. The
remaining end has a fluorine component.
[0040] Referring to FIGS. 4 and 5, as a result of the affinity for
the bulk material, the surfactant component is orientated so that
the fluorine component extends from an air-liquid interface defined
by the imprinting material and the surrounding ambient.
[0041] Upon solidification of the imprinting material, a first
portion of the imprinting material generates a lamella 60 and a
second portion of the imprinting material is solidified, i.e.,
polymeric material shown as formation 50. Lamella 60 is positioned
between formation 50 and mold 36. Lamella 60 results from the
presence and location of the fluorine components in the SCR
sub-portion 136. Lamella 60 prevents strong adhesion forces from
being developed between mold 36 and formation 50. Specifically,
formation 50 has first and second opposed sides 62 and 64. Side 62
adheres to mold 36 with a first adhesion force. Side 64 adheres to
substrate 42 with a second adhesion force. Lamella 60 results in
the first adhesion force being less than the second adhesion force.
As a result, mold 36 may be easily removed from formation 50 while
minimizing distortions and/or the force required to separate mold
36 therefrom. Although formation 50 is shown with side 62 being
patterned, it should be understood that side 62 may be smooth, if
not planar.
[0042] Furthermore, if desired, it is possible to generate lamella
60 so as to be disposed between formation 50 and substrate 42. This
may be achieved, for example, by applying imprinting material to
mold 36 and subsequently contacting substrate 42 with the
imprinting material on mold 36. In this manner, it can be said that
formation 50 will be disposed between lamella 60 and the body,
e.g., mold 36 or substrate 42, upon which the polymerizable
material is deposited. It should be understood that were the
imprinting material deposited employing spin-coating techniques,
similar bifurcated concentration of materials would occur, as shown
in FIG. 6 with respect to SCR sub-portion 236 and second and SCD
sub-portion 237. The time required for the bifurcation is dependent
upon several factors, including the size of molecules in the
composition and the viscosity of the composition. Only a few
seconds is needed to achieve the aforementioned bifurcation of
composition with viscosity below twenty cPs. Material with
viscosity in the hundreds of cPs, however, may require a few
seconds to several minutes.
[0043] It has been discovered, however, that lamella 60 may not be
uniform. Some regions of lamella 60 are thinner than others, and in
some extreme cases, lamella 60 may be absent in an extremely small
percentage of the template surface so that template 36 is in
contact with formation 50. As a result of the thinner regions of
lamella 60 and in the absence of lamella 60, distortion and/or
delamination of formation 50 from substrate 42 may occur.
Specifically, upon separation of mold 36, formation 50 is subjected
to a separation force F.sub.S. Separation force F.sub.S is
attributable to a pulling force F.sub.P on mold 36 and adhering
forces, e.g., Van der Waals forces, between formation 50 and mold
36 as reduced by lamella 60. Due to the presence of lamella 60
separation force F.sub.S typically has a magnitude that is less
than the magnitude of an adhering force F.sub.A between formation
50 and substrate 42. However, with the reduction, or absence, of
lamella 60, local separation force F.sub.S may approach the
magnitude of local adhering force F.sub.A. By local forces what is
meant are the forces present in a given region of lamella layer 60,
which in this example are the local forces proximate to a thin
region of lamella layer 60 or where lamella layer 60 is
substantially absent. This leads to distortion and/or delamination
of formation 50 from substrate 42.
[0044] Referring to FIG. 7, in the presence of primer layer 45, a
more complex situation exists due to the presence of two interfaces
66 and 68. At a first interface 66 a first adhering force F.sub.1
is present between primer layer 45 and formation 50. At a second
interface 68 a second adhering force, F.sub.2, is present between
primer layer 45 and wafer 47. It is desired that the separation
force F.sub.S have a magnitude that is less than either adhering
forces F.sub.1 and F.sub.2. However, due to variations in the
thickness, or absence, of lamella 60, as discussed above,
separation force F.sub.S may be similar or approach the magnitude
of one or both of adhering forces F.sub.1 and F.sub.2. This may
cause delamination of formation 50 from primer layer 45, primer
layer 45 from wafer 47 or both.
[0045] The present invention reduces, if not avoids, the
delamination problem mentioned above by forming primer layer 45
from a material that increases the probability that first F.sub.1
and second F.sub.2 adhering forces of the first and second
interface, respectively, are greater than the separation force
F.sub.S in view of lamella layer fluctuations. To that end, primer
layer 45 is formed from a composition that forms strong bonds at
interface 66, i.e., between primer layer 45 and formation 50, as
well as, i.e., between interface 66, primer layer 45 and wafer 47.
In the present example, adhesion between primer layer 45 and
formation 50 at first interface 66 is the result of covalent
bonding, i.e., covalent bonds between the composition from which
primer layer 45 is formed and the composition from which formation
50 is formed are present. Adhesion between primer layer 45 and
wafer 47 may be achieved through any one of various mechanisms.
These mechanisms may include covalent bonds formed between the
composition from which primer layer 45 is formed and the material
from which wafer 47 is formed. Alternatively, or in addition to,
the covalent bonds, ionic bonds may be formed between the
composition from which primer layer 45 is formed and the material
from which wafer 47 is formed. Alternatively, or in addition to,
the covalent bonds, and/or the ionic bonds or both, adhesion
between the composition from which primer layer 45 is formed and
the material from which wafer 47 is formed may be achieved
vis-a-vis Van der Waals forces.
[0046] This is achieved by forming primer layer 45 from a
composition that includes a multi-functional reactive compound,
i.e., a compound that contained two or more functional groups
generally represented as follows:
##STR00005##
In which R, R', R'' and R''' are linking groups and x, y, z are
averaged repeating numbers of the groups associated therewith.
These repeating units could be randomly distributed. The groups X
and X' denote the functional groups, with the understanding that
typically, the functional group X differs from functional group X'.
One of the functional groups X and X', for example X', is selected
to achieve cross-reaction with the material from which substrate 42
is formed to adhere thereto by forming a covalent bond therewith,
ionic bond therewith and/or Van der Waals forces.
[0047] One of the remaining functional groups X and X', for example
X, is selected to achieve cross-reaction with the material from
which formation 50 is formed to form a covalent bond therebetween.
The functionality of the X group is established so the
cross-reaction occurs during polymerization of formation 50. As a
result, the selection of functional group X depends upon the
characteristics of the material from which formation 50 is formed.
It is desired that functional group X react with the functional
groups of the composition from which formation 50 is formed. For
example, were formation 50 formed from acrylate monomers, X might
be comprised of acrylic, vinyl ether, and or alkoxyl functional
groups, and/or functional groups that could copolymerize with
acrylic groups in formation 50. As a result, X functional groups
cross-react in response to ultraviolet actinic energy.
[0048] Functional groups X' may also participate in the
cross-linking and polymerization reactions of primer layer 45.
Typically, X' functional groups facilitate polymerization and
cross-linking in response to an actinic energy that differs from
the actinic energy in response to which X functional groups
cross-react. The X' functional groups in the present example
facilitate cross-linking of molecules in primer layer 45 in
response to exposure to thermal energy. Typically, functional
groups X' are selected to facilitate cross-reaction with substrate
42 through three mechanisms: 1) direct reaction with material from
which substrate 42 is formed; 2) reaction with cross-linker
molecules with a linking functional group of the cross-linker
reacting with substrate 42; and 3) polymerization of and
cross-linking of primer layer 45 so that chains of molecules of
sufficient length may be developed to connect between formation 50
and substrate 42.
[0049] Referring to FIGS. 7 and 8, an exemplary multi-functional
reactive compound that may be employed to form primer layer 45 in
the presence of formation 50 being formed from BULK MATERIAL
includes a .beta.-carboxyethyl acrylate, available from UCB
Chemicals in Smyrna, Ga. under the product name .beta.-CEA.
.beta.-CEA is an aliphatic compound having the following
structure:
##STR00006##
The X' functional group 70 provides carboxylic functionality. The X
functional group 72 provides acrylate functionality. Functional
groups 70 and 72 are coupled to opposing ends of a backbone
component 74.
[0050] Referring to FIGS. 7 and 9, another multi-functional
reactive compound that may be employed to form primer layer 45 in
the presence of formation 50 being formed from BULK MATERIAL
includes an aromatic bis-phenyl compound available from UCB
Chemicals in Smyrna, Ga. under the product name Ebecryl 3605 that
has the following structure:
##STR00007##
The X' functional group 76 provides epoxy functionality. The X
functional group 78 provides acrylate functionality. Functional
groups 76 and 78 are coupled to opposing ends of a backbone
component 80.
[0051] Referring to FIGS. 7 and 10, another multi-functional
reactive compound that may be employed to form primer layer 45 in
the presence of formation 50 being formed from BULK MATERIAL
includes an aromatic compound available from Schenectady
International, Inc. in Schenectady, N.Y. under the product name
Isorad 501 that has the following structure:
##STR00008##
where x and y are integers indicating repeating units that are
randomly distributed. The X' functional group 82 provides
carboxylic functionality. The X functional group 84 provides
acrylate functionality. Functional groups 82 and 84 are coupled to
opposing ends of a backbone component 86.
[0052] Referring to FIGS. 7 and 11, in addition to cross-reaction
with formation 50, functional group X may generate radicals that
function to facilitate polymerization of the composition from which
formation 50 is formed during solidification of the same. As a
result, the functional group X would facilitate polymerization of
formation 50 upon exposure to actinic energy, e.g., broadband
ultraviolet energy. An exemplary multi-functional reactive compound
that includes these properties is a photoinitiator available from
Ciba Specialty Chemicals in Tarrytown, N.Y. under the tradename
Irgacure 2959 and has the following structure:
##STR00009##
The X' functional group 90 provides hydroxyl functionality. The X
functional group 92 provides initiator-type functionality.
Specifically, in response to exposure to broadband ultraviolet
energy, the functional group X undergoes alpha-cleavage to generate
benzoyl type of radicals. The radicals facilitate radical
polymerization of the composition from which formation 50 is
formed. Functional groups 90 and 92 are coupled to opposing ends of
a backbone component 94.
[0053] Several compositions were formed, including some of the
aforementioned multi-functional reactive compounds, to determine
the adhering strength of interfaces 66 and 68. An exemplary
composition including a multi-functional reactive compound is as
follows:
Composition 1
[0054] .beta.-CEA [0055] DUV30J-16 where DUV30J-16 comprises
approximately 100 grams of composition 1 and .beta.-CEA comprises
approximately 0.219 grams. DUV30J-16 is a bottom anti-reflective
coating, BARC, available from Brewer Science in Rolla, Mo.
containing 93% solvent, and 7% non-solvent reactive components.
DUV30J-16 contains phenolic resins, and its crosslinker can react
with the carboxylic functional group. It is believed that DUV30J-16
will not form covalent bonds with formation 50. In another
composition, .beta.-CEA was replaced by a cross-linking agent, a
catalyst and IsoRad 501. Both the cross-linking agent and catalyst
is sold by Cytec Industries, Inc. of West Patterson, N.J. The
cross-linking agent is sold under the product name Cymel 303ULF.
One of the main components of Cymel 303ULF is
hexamethoxymethyl-melamine (HMMM). The methoxyl functional groups
of HMMM can participate in many condensation reactions. The
catalyst is sold under the product name Cycat 4040 providing the
following composition:
Composition 2
[0055] [0056] DUV30J-16 [0057] Isorad 501 [0058] Cymel 303ULF
[0059] Cycat 4040 Approximately 100 grams of COMPOSITION 2
comprises DUV30J-16, 0.611 gram of COMPOSITION 2 comprises IsoRad
501, 0.175 gram of COMPOSITION 2 comprises Cymel 303ULF and 0.008
gram of COMPOSITION 2 comprises Cycat 4040.
[0060] Another composition that may be employed as the
multi-functional reactive compound omits DUV30J-16. The composition
is as follows:
Composition 3
[0061] IsoRad 501 [0062] Cymel 303ULF [0063] Cycat [0064] PM
Acetate Composition 3 includes approximately 77 grams of IsoRad
501, 22 grams of Cymel 303ULF and one gram of Cycat 4040. IsoRad
501, Cymel 303ULF and Cycat are combined. The combination of IsoRad
501, Cymel 303ULF and Cycat are then introduced into approximately
1900 grams of PM Acetate. PM Acetate is a product name of a solvent
consisting of 2-(1-Methoxy)propyl acetate sold by Eastman Chemical
Company of Kingsport, Tenn.
[0065] A fourth composition is identical to COMPOSITION 3,
excepting for the amount of the constituent components included.
For example, COMPOSITION 4 includes approximately 85.2 grams of
IsoRad 501, 13.8 grams of Cymel 303ULF and one gram of Cycat 4040.
IsoRad 501, Cymel 303ULF and Cycat are combined. The combination of
IsoRad 501, Cymel 303ULF and Cycat are then introduced into
approximately 1900 grams of PM Acetate.
[0066] A fifth composition is identical to COMPOSITION 3, excepting
for the amount of the constituent components included. For example,
COMPOSITION 5 includes approximately 81 grams of IsoRad 501, 18
grams of Cymel 303ULF and one gram of Cycat 4040. IsoRad 501, Cymel
303ULF and Cycat are combined. The combination of IsoRad 501, Cymel
303ULF and Cycat are then introduced into approximately 1900 grams
of PM Acetate.
[0067] Each of the five compositions discussed above with respect
to primer layer 45, COMPOSITIONs 1-5, are deposited upon substrate
42 employing spin-coating techniques wherein the substrate is
rotated at a velocity between 500 and 4,000 revolutions per minute
so as to provide a substantially smooth, if not planar layer with
uniform thickness. This is followed by exposing the compositions to
thermal actinic energy of 180.degree. C. (Celsius) for
approximately two minutes.
[0068] The five compositions described above, COMPOSITIONs 1-5,
were employed, along with IMPRINTING MATERIAL, to generate
comparative data of the strength of the adhesion forces of
interfaces 66 and 68 which was compared against baseline measuring
of a primer layer 45 formed entirely from DUV30J-16, which is not
known to form covalent bonds with formation 50 formed from
IMPRINTING MATERIAL. To that end, formation 50, formed from BULK
IMPRINTING MATERIAL, and primer layer 45, formed from COMPOSITIONS
1-5 and the base line COMPOSITION, were deposited and then
solidified between two glass slides (not shown). Each glass slide
(not shown) is approximately 1 mm thick, 75.times.25 mm in the
lateral dimension.
[0069] Before deposition of primer layer 45 and formation 50 the
glass slides (not shown) are cleaned. Specifically each glass slide
(not shown) is exposed to Piranha solution (H.sub.2SO.sub.4:
H.sub.2O.sub.2=2.5:1 by volume). The glass slides (not shown) are
subsequently rinsed with de-ionized water, sprayed with isopropyl
alcohol, and exposed to a stream of fluid for drying, e.g., a
stream of nitrogen gas. Thereafter, the glass slides (not shown)
are baked at 120.degree. C. (Celsius) for 2 hours.
[0070] Primer layer 45 is deposited onto each of the two glass
slides (not shown) employing spin-on techniques with a spin speed
up to 3000 rpm. Primer layer 45 is laid on the glass slides (not
shown) on hot plates at 180 C for 2 minutes. In other words, each
of COMPOSITIONs 1-5, as well as the baseline composition, are
solidified, i.e., polymerized and cross-linked, by exposure to
thermal energy. Formation is formed employing drop dispense
techniques mentioned above. Specifically, BULK IMPRINTING MATERIAL
is disposed as a plurality of droplets onto primer layer 45 on one
of the two glass slides. The BULK IMPRINTING MATERIAL is then
sandwiched between two primer layers 45 by having the primer layer
on the two glass slides (not shown) facing one another and
contacting BULK IMPRINTING MATERIAL. Typically, a longitudinal axis
of one of the two glass slides (not shown) extends orthogonally to
the longitudinal axis of the remaining glass slide (not shown). The
BULK IMPRINTING MATERIAL is solidified, i.e., polymerized, and
cross-linked by exposing the two glass slides (not shown) to
actinic energy, such as broad band ultraviolet wavelengths, using a
medium pressure mercury UV lamp for 40 seconds at 20 mW/cm2
intensity.
[0071] To measure the strength of the adhesion, a four-point
bending fixture (not shown) was adopted for the adhesion test and
technique, similar to that described in "Measurement of Adhesive
Force Between Mold and Photocurable Resin in Imprint Technology"
Japanese Journal of Applied Physics, Vol. 41 (2002) pp. 4194-4197.
The maximum force/load was taken as the adhesion value. The beam
distance of the top and bottom two points is 60 mm. The load was
applied at the speed of 0.5 mm per minute. Employing this test, it
was determined that delamination occurred at 6.1 pounds of force
when primer layer 45 was formed with the baseline composition. A
separation force of approximately 6.5 pounds was reached before
delamination occurred with primer layer 45 being formed from
COMPOSITION 1. A separation force of approximately 9.1 pounds was
reached before delamination occurred with primer layer 45 being
formed from COMPOSITION 2. When primer layer 45 was formed from
each of COMPOSITIONs 3, 4 or 5, one or both of the two glass slides
(not shown) failed (broke) before delamination occurred. As a
result, forces of up to 11 pounds were measured without
delamination being observed. As a result, it is observed that
COMPOSITIONs 3, 4 and 5 provide primer layer 45 with superior
operational characteristics in that it effectively prevents
delamination were lamella layer 60 to have undesirably thin regions
or be altogether absent.
[0072] 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 solvent PM Acetate is employed
primarily to dissolve the other constituent components of
COMPOSITIONs 3, 4 and 5. As a result, many common photo-resist
solvents may be employed in lieu of PM Acetate, such as Diethylene
Glycol Monoethyl Ether Acetate, Methyl Amyl Ketone or the like.
Further, the solid contents of COMPOSITIONs 3, 4 and 5, i.e.,
IsoRad 501, Cymel 303ULF and Cycat may comprise between 0.1% to 70%
of the composition, weight, and more preferably in a range of 0.5%
to 10% by weight, with the remaining quantity consisting of the
solvent. The solid component of each of COMPOSITIONs 3, 4, and 5
may comprise 50% to 99%, by weight of IsoRad 501, 1% to 50%, by
weight of Cymel 303ULF and 0% to 10% by weight of Cycat 4040. The
scope of the invention should not, therefore, be limited by the
above description, but instead should be determined with reference
to the appended claims along with their full scope of
equivalents.
* * * * *