U.S. patent application number 11/292402 was filed with the patent office on 2006-06-01 for methods of exposure for the purpose of thermal management for imprint lithography processes.
This patent application is currently assigned to Molecular Imprints, Inc.. Invention is credited to Byung-jin Choi, Sidlgata V. Sreenivasan.
Application Number | 20060115999 11/292402 |
Document ID | / |
Family ID | 36565833 |
Filed Date | 2006-06-01 |
United States Patent
Application |
20060115999 |
Kind Code |
A1 |
Sreenivasan; Sidlgata V. ;
et al. |
June 1, 2006 |
Methods of exposure for the purpose of thermal management for
imprint lithography processes
Abstract
The present invention is directed to a method that attenuates,
if not avoids, heating of a substrate undergoing imprint
lithography process and the deleterious effects associated
therewith. To that end, the present invention includes a method of
patterning a field of a substrate with a polymeric material that
solidifies in response to actinic energy in which a sub-portion of
the field is exposed sufficient to cure the polymeric material is
said sub-portion followed by a blanket exposure of all of the
polymeric material associated with the entire field to
cure/solidify the same.
Inventors: |
Sreenivasan; Sidlgata V.;
(Austin, TX) ; Choi; Byung-jin; (Austin,
TX) |
Correspondence
Address: |
MOLECULAR IMPRINTS, INC.;KENNETH C. BROOKS
PO BOX 81536
AUSTIN
TX
78708-1536
US
|
Assignee: |
Molecular Imprints, Inc.
|
Family ID: |
36565833 |
Appl. No.: |
11/292402 |
Filed: |
November 30, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60632125 |
Dec 1, 2004 |
|
|
|
Current U.S.
Class: |
438/780 ;
438/795 |
Current CPC
Class: |
G03F 7/0002 20130101;
B82Y 10/00 20130101; B82Y 40/00 20130101 |
Class at
Publication: |
438/780 ;
438/795 |
International
Class: |
H01L 21/31 20060101
H01L021/31; H01L 21/324 20060101 H01L021/324 |
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 other on reasonable terms as provided by
the terms of 70NANB4H3012 awarded by National Institute of
Standards (NIST) ATP Award.
Claims
1. A method of patterning a field of a substrate with a polymeric
material that solidifies in response to actinic energy: exposing a
sub-portion of said field to said actinic energy; and exposing all
of said field to said actinic radiation, whereby overlay
misalignment due to heating of said substrate by said actinic
radiation is reduced.
2. The method as recited in claim 1 wherein exposing all further
includes exposing, concurrently, all of said field to said actinic
radiation.
3. The method as recited in claim 1 wherein said substrate is a
semiconductor wafer and said field is coextensive with an entire
area of one side of said wafer.
4. The method as recited in claim 1 wherein said substrate is a
semiconductor wafer and said field is a sub-part of an entire area
of one side of said wafer.
5. The method as recited in claim 1 wherein exposing said
sub-portion further includes propagating a flux of said actinic
radiation along a path, with said flux having a cross-section that
is greater in dimensions than said sub-portion and further
including placing a spatial filter in said path to reduce said
flux, impinging upon said region, to dimensions commensurate with
said sub-portion.
6. The method as recited in claim 1 wherein exposing said
sub-portion further includes propagating a flux of said actinic
radiation along a path, with said flux having a cross-section that
is greater in dimensions than said sub-portion and further
including placing a spatial filter in said path to reduce said
flux, impinging upon said region, to dimensions commensurate with
said sub-portion, with exposing all of said field further including
removing said spatial filter from said path.
7. The method of claim 1 further including transferring thermal
energy, accumulating in said substrate, away from said substrate by
placing said substrate in thermal communication with a support.
8. A method of patterning a field of a substrate with a polymeric
material that solidifies in response to actinic energy: exposing a
first sub-portion of said field to said actinic energy; and
exposing a second sub-portion of said field to said actinic
radiation, with regions of said field associated with said first
sub-portion differing from the regions of said field associated
with said second-sub-portion to reduce overlay misalignment due to
heating of said substrate by said actinic radiation.
9. The method as recited in claim 8 further including establishing
said first and second sub-portions so that aggregate dimensions
thereof are coextensive with said field.
10. The method as recited in claim 8 wherein said substrate is a
semiconductor wafer and said field is coextensive with an entire
area of one side of said wafer.
11. The method as recited in claim 8 wherein said substrate is a
semiconductor wafer and said field is a sub-part of an entire area
of one side of said wafer.
12. The method as recited in claim 8 further including establishing
said first and second sub-portions so that aggregate dimensions
thereof are coextensive with said field, propagating a flux of said
actinic radiation along a path, with said flux having a
cross-section that is greater than said field, wherein exposing
said first sub-portion further includes placing a first spatial
filter in said path to reduce said flux, impinging upon said
region, to dimensions commensurate with said first sub-portion and
exposing said second sub-portion further includes placing a second
spatial filter in said path to reduce said flux, impinging upon
said region, to dimensions commensurate with said second
sub-portion.
13. The method as recited in claim 8 further including establishing
said first and second sub-portions so that aggregate dimensions
thereof are coextensive with said field, propagating a flux of said
actinic radiation along a path, with said flux having a
cross-section that is coextensive with said field, wherein exposing
said first sub-portion further includes placing a first spatial
filter in said path to reduce said flux, impinging upon said
region, to dimensions commensurate with said first sub-portion and
exposing said second sub-portion further includes placing a second
spatial filter in said path to reduce said flux, impinging upon
said region, to dimensions commensurate with said second
sub-portion.
14. The method of claim 8 further including transferring thermal
energy, accumulating in said substrate, away from said substrate by
placing said substrate in thermal communication with a support.
15. A method of patterning a field of a substrate with a polymeric
material that solidifies in response to actinic energy:
sequentially exposing a sub-portion of a plurality of sub-portions
of said field to said actinic energy until an entire area of said
field has been exposed to said actinic radiation, whereby overlay
misalignment due to heating of said substrate by said actinic
radiation is reduced.
16. The method as recited in claim 15 wherein each of said
plurality of sub-portions include a plurality of sub-regions, with
the sequentially exposing further including sequentially exposing
said plurality of sub-regions to said actinic radiation.
17. The method as recited in claim 15 wherein said plurality of
said sub-portions are exposed to actinic radiation
concurrently.
18. The method of claim 15 further including transferring thermal
energy, accumulating in said substrate, away from said substrate by
placing said substrate in thermal communication with a support.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Application No. 60/632,125, filed on Dec. 1, 2004, entitled
"Methods of Exposure for the Purpose of Thermal Management for
Imprint Lithography Processes," listing Sidlgata V. Sreenivasan and
Byung-Jin Choi as inventors, the entirety of which is incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0003] The field of the invention relates generally to
nano-fabrication of structures. More particularly, the present
invention is directed to a technique to achieve overlay alignment
of patterns formed during nano-scale fabrication.
[0004] Nano-fabrication involves the fabrication of very small
structures, e.g., having features on the order of nano-meters or
smaller. One area in which nano-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, nano-fabrication becomes increasingly
important. Nano-fabrication provides greater process control while
allowing increased reduction of the minimum feature dimension of
the structures formed. Other areas of development in which
nano-fabrication has been employed include biotechnology, optical
technology, mechanical systems and the like.
[0005] An exemplary nano-fabrication technique is commonly referred
to as imprint lithography. Exemplary imprint lithography processes
are described in detail in numerous publications, such as United
States patent application publication 2004/0065976 filed as U.S.
patent application Ser. No. 10/264,960, entitled, "Method and a
Mold to Arrange Features on a Substrate to Replicate Features
having Minimal Dimensional Variability"; United States patent
application publication 2004/0065252 filed as U.S. patent
application Ser. No. 10/264,926, entitled "Method of Forming a
Layer on a Substrate to Facilitate Fabrication of Metrology
Standards"; and U.S. Pat. No. 6,936,194, entitled "Functional
Patterning Material for Imprint Lithography Processes," all of
which are assigned to the assignee of the present invention.
[0006] The fundamental imprint lithography technique disclosed in
each of the aforementioned United States patent application
publications and United States patent includes formation of a
relief pattern in a polymerizable layer and transferring a pattern
corresponding to the relief pattern into an underlying substrate.
The substrate may be positioned upon a motion stage to obtain a
desired position to facilitate patterning thereof. To that end, a
template is employed spaced-apart from the substrate with a
formable liquid present between the template and the substrate. The
liquid is solidified to form 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 template is then
separated from the solidified layer such that the template and the
substrate are spaced-apart. The substrate and the solidified layer
are then subjected to processes to transfer, into the substrate, a
relief image that corresponds to the pattern in the solidified
layer.
[0007] A need exists, therefore, to provide improved alignment
techniques for imprint lithographic processes.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to a method that
attenuates, if not avoids, heating of a substrate undergoing
imprint lithography process and the deleterious effects associated
therewith. To that end, the present invention includes a method of
patterning a field of a substrate with a polymeric material that
solidifies in response to actinic energy in which a sub-portion of
the field is exposed sufficient to cure the polymeric material in
said sub-portion followed by a blanket exposure of all of the
polymeric material associated with the entire field to
cure/solidify the same. These and other embodiments are discussed
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a simplified plan view of an imprint lithography
system having a mold spaced-apart from a substrate;
[0010] FIG. 2 is a cross-sectional view of a patterned substrate
having a plurality of layers disposed thereon with a mold, shown in
FIG. 1, in superimposition therewith;
[0011] FIG. 3 is a simplified side view of a portion of the system
shown in FIG. 1, with the mold in contact with a polymeric layer on
the substrate;
[0012] FIG. 4 is a top-down view of a portion of the substrate
shown in FIG. 1, the substrate having a plurality of regions
associated therewith;
[0013] FIGS. 5 and 6 are side views of portions of the mold and the
polymeric layer, shown in FIG. 3, with a portion of the polymeric
layer solidified and/or cross-linked;
[0014] FIG. 7 is a top down view of a polymeric material positioned
on the substrate, shown in FIG. 1, with an outer region of the
polymeric material being solidified and/or cross-linked;
[0015] FIG. 8 is a top down view of a polymeric material positioned
on the substrate, shown in FIG. 1, with a grating region of the
polymeric material being solidified and/or cross-linked;
[0016] FIG. 9 is a top down view of a polymeric material positioned
on the substrate, shown in FIG. 1, with isolated regions of the
polymeric material being solidified and/or cross-linked; and
[0017] FIG. 10 is a top down view of a polymeric material
positioned on the substrate, shown in FIG. 1, with a scanning beam
exposing portions of the polymeric material.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Referring to FIG. 1, a system 8 to form a relief pattern on
a substrate 12 includes a stage 10 upon which substrate 12 is
supported and a template 14, having a mold 16 with a patterning
surface 18 thereon. In a further embodiment, substrate 12 may be
coupled to a substrate chuck (not shown), the substrate chuck (not
shown) being any chuck including, but not limited to, vacuum and
electromagnetic.
[0019] Template 14 and/or mold 16 may be formed from such materials
including but not limited to, fused-silica, quartz, silicon,
organic polymers, siloxane polymers, borosilicate glass,
fluorocarbon polymers, metal, and hardened sapphire. As shown,
patterning surface 18 comprises features defined by a plurality of
spaced-apart recesses 17 and protrusions 19. However, in a further
embodiment, patterning surface 18 may be substantially smooth
and/or planar. Patterning surface 18 may define an original pattern
that forms the basis of a pattern to be formed on substrate 12.
[0020] Template 14 may be coupled to an imprint head 20 to
facilitate movement of template 14, and therefore, mold 16. In a
further embodiment, template 14 may be coupled to a template chuck
(not shown), the template chuck (not shown) being any chuck
including, but not limited to, vacuum and electromagnetic. A fluid
dispense system 22 is coupled to be selectively placed in fluid
communication with substrate 12 so as to deposit polymeric material
24 thereon. It should be understood that polymeric material 24 may
be deposited using any known technique, e.g., drop dispense,
spin-coating, dip coating, chemical vapor deposition (CVD),
physical vapor deposition (PVD), and the like.
[0021] A source 26 of energy 28 is coupled to direct energy 28
along a path 30. Imprint head 20 and stage 10 are configured to
arrange mold 16 and substrate 12, respectively, to be in
superimposition and disposed in path 30. Either imprint head 20,
stage 10, or both vary a distance between mold 16 and substrate 12
to define a desired volume therebetween that is filled by polymeric
material 24.
[0022] Typically, polymeric material 24 is disposed upon substrate
12 before the desired volume is defined between mold 16 and
substrate 12. However, polymeric material 24 may fill the volume
after the desired volume has been obtained. After the desired
volume is filled with polymeric material 24, source 26 produces
energy 28, e.g., broadband ultraviolet radiation that causes
polymeric material 24 to solidify and/or cross-link conforming to
the shape of a surface 25 of substrate 12 and patterning surface
18. Control of this process is regulated by processor 32 that is in
data communication with stage 10, imprint head 20, fluid dispense
system 22, source 26, operating on a computer readable program
stored in memory 34.
[0023] To allow energy 28 to impinge upon polymeric material 24, it
is desired that mold 16 be substantially transparent to the
wavelength of energy 28 so that the same may propagate
therethrough. Additionally, to maximize a flux of energy 28
propagating through mold 16, energy 28 may have a sufficient
cross-section to cover the entire area of mold 16 with no
obstructions being present in path 30.
[0024] Referring to FIGS. 1 and 2, often a pattern generated by
mold 16 is disposed upon a substrate 112 in which a preexisting
pattern in present. To that end, a primer layer 36 is typically
deposited upon patterned features, shown as recesses 38 and
protrusions 40, formed into substrate 112 to provide a smooth, if
not planar, surface 42 upon which to form a patterned imprint layer
(not shown) from polymeric material 24 disposed upon surface 42. To
that end, mold 16 and substrate 112 include alignment marks, which
may include sub-portions of the patterned features. For example,
mold 16 may have alignment marks, referred to as mold alignment
marks, which are defined by features 44 and 46. Substrate 112 may
include alignment marks, referred to as substrate alignment marks,
which are defined by features 48 and 50.
[0025] To ensure proper alignment between the pattern on substrate
112 with the pattern generated by mold 16, it is desired to ensure
proper alignment between the mold and substrate alignment marks.
This has typically been achieved employing the aided eye, e.g., an
alignment system 53 selectively placed in optical communication
with both mold 16 and substrate 12, concurrently. Exemplary
alignment systems have included ocular microscopes or other imaging
systems. Alignment system 53 typically obtains information parallel
to path 30. Alignment is then achieved manually by an operator or
automatically using a vision system.
[0026] Referring to FIG. 1, as mentioned above, source 26 produces
energy 28 that causes polymeric material 24 to solidify and/or
cross-link conforming to the shape of surface 25 of substrate 12
and patterning surface 18. To that end, often it is desired to
complete solidification and/or cross-linking of polymeric material
24 prior to separation of mold 16 from polymeric material 24. A
time required to complete solidification and/or cross-linking of
polymeric material 24 may depend upon, inter alia, a magnitude of
energy 28 impinging upon polymeric material 24 and chemical and/or
optical properties of polymeric material 24 and/or substrate 12. To
that end, in the absence of any amplifying agents, i.e.,
chemically-amplified photoresist of optical lithography progresses,
the magnitude of energy 28 required to solidify and/or cross-link
polymeric material 24 may be substantially greater in imprint
lithography processes as compared to optical lithography processes.
As a result, during solidification and cross-linking of polymeric
material 24, energy 28 may impinge upon substrate 12, template 14,
and mold 16, and thus, heat substrate 12, template 14, and mold 16.
A substantially uniform magnitude of energy 28 may result in
substantially uniform heating of substrate 12, template 14, and
mold 16. However, a differential magnitude of energy 28 and/or a
differential CTE (coefficient of thermal expansion) associated with
substrate 12, template 14, and mold 16 may result in misalignment
between substrate 12 and mold 16 during solidification and/or
cross-linking of polymeric material 24, which may be undesirable.
To that end, a method to minimize, if not prevent, thermal effects
upon substrate 12, template 14, and mold 16 is described below.
[0027] Referring to FIG. 3, a portion of system 8 is shown. More
specifically, patterning surface 18 of mold 16 is shown in contact
with polymeric layer 24. Exposure of an entirety of surface 25 of
substrate 12 to energy 28 may increase a temperature thereof, and
thus, a linearly increase in size of substrate 12, which may be
undesirable. To that end, a portion of substrate 12 may be exposed
to energy 28, described below.
[0028] Referring to FIG. 4, a portion of substrate 12 is shown
having a plurality of regions a-p. As shown, substrate 12 comprises
sixteen regions; however, substrate 12 may comprise any number of
regions. To that end, to minimize, if not prevent, the
aforementioned linearly increase in size of substrate 12, a subset
of the regions a-p of substrate 12 may be exposed to energy 28,
shown in FIG. 1. More specifically, regions f, g, j, and k of
substrate 12 may be exposed to energy 28, with regions a-d, e, h,
i, and l-p of substrate 12 being substantially absent of exposure
to energy 28. As a result, region a-d, e, h, i, and l-p of
substrate 12 may minimize, if not prevent, region f, g, j, and k of
substrate 12 from linearly increasing in size, i.e., region a-d, e,
h, i, and l-p of substrate 12 may act as a physical constraint to
prevent region f, g, j, and k of substrate 12 from increasing in
size. Regions f, g, j, and k of substrate 12 may each be exposed to
energy 28 sequentially or concurrently.
[0029] To that end, after exposure of regions f, g, j, and k of
substrate 12 to energy 28, in a first embodiment, regions a-d, e,
h, i, and l-p of substrate 12 may be exposed to energy 28 to
solidify and/or cross-link the same. In a further embodiment, after
exposure of regions f, g, j, and k of substrate 12 to energy 28,
all regions (a-p) of substrate 12 may be exposed to energy 28,
i.e., a blanket exposure to complete solidification and/or
cross-linking of polymeric material 24.
[0030] Referring to FIG. 3, in a further embodiment, it may be
desired to expose a portion of substrate 12, and therefore,
polymeric material 24, to energy 28 such that a position between
substrate 12 and mold 16 prior to exposure to energy 28 is
substantially the same as a position between substrate 12 and mold
16 subsequent to exposure of energy 28. More specifically, an
interface between substrate 12 and mold 16 via polymeric material
24 may be maintained before and after exposure of substrate 12,
mold 16, and polymeric material 24 to energy 28. As a result, an
increase in size of substrate 12, template 14, and mold 16
resulting from thermal-induced scaling may be minimized, if not
prevented.
[0031] Referring to FIGS. 3, 5, and 6, in a first example of the
above-mentioned, an outer portion 62 of polymeric material 24 may
be exposed to energy 28 prior to inner portion 64 of polymeric
material 24, with outer portion 62 of polymeric material 24 being
solidified and/or cross-linked in response to energy 28. As a
result, outer portion 62 may maintain an interface between
substrate 12 and mold 18, and thus, minimize, if not prevent
substrate 12 from increasing in size, as desired. In a further
embodiment, after exposure of outer portion 62 of polymeric
material 24 to energy 28, inner portion 64 of polymeric material 24
may be subsequently exposed to energy 28 to solidify and/or
cross-link the same. In still a further embodiment, after exposure
of outer portion 62 of polymeric material 24 to energy 28, inner
and outer portions 62 and 64 of polymeric material 24 may be
exposed to energy 28, i.e., a blanket exposure to complete
solidification and/or cross-linking of polymeric material 24.
[0032] Referring to FIGS. 7-9, further examples are shown of
exposing desired regions of polymeric material 24 to minimize, if
not prevent, substrate 12 from increasing in size, as desired. FIG.
7 shows an outer region 66 being exposed to energy 28, shown in
FIG. 1, prior to inner region 68 being exposed to energy 28, shown
in FIG. 1. FIG. 8 shows a grating type exposure of polymeric
material 24, with region 70 being exposed to energy 28, shown in
FIG. 1, prior to regions 72 being exposed to energy 28, shown in
FIG. 1. FIG. 9 shows an isolated region exposure of polymeric
material 24, with regions 76 being exposed to energy 28, shown in
FIG. 1, prior to region 7 is exposed to energy 28, shown in FIG.
1.
[0033] Referring to FIG. 1, energy 28 may have a cross-sectional
area associated therewith that may be greater in dimension that a
desired region that is to be exposed to energy 28, i.e. a region
a-p of substrate 12, as shown in FIG. 4. To that end, to expose
desired regions of substrate 12 to energy 28, a mask (not shown)
may be positioned within path 30 such that energy 28 may propagate
therethrough and comprise dimensions commensurate with said desired
regions of substrate 12 to expose the same to energy 28. Further,
the mask (not shown) may be removed from path 30 such that
substantially all regions of substrate 12 are exposed to energy 28.
In a further embodiment, analogous to the above-mentioned, a first
mask (not shown) may be positioned within path 30 such that energy
28 may propagate therethrough to expose a first subset of substrate
12; and a second mask (not shown) may be positioned within path 30
such that energy 28 may propagate therethrough to expose a second
subset of substrate 12.
[0034] Furthermore, as described with respect to FIG. 4, a desired
subset of the plurality of regions a-p of substrate 12 may be
processed to minimize, if not prevent, linearly increasing a size
of substrate 12 [hereinafter small field]. However, the
above-mentioned methods may be applicable to imprinting of large
substrates, i.e., whole wafer imprinting or display substrate
imprinting [hereinafter large field]. More specifically, an overlay
error associated with large fields may be greater that that as
compared to an overlay error associated with small fields; however,
an error tolerance associated with the large fields may be
comparable or less than that associated with the small fields. In
an example of minimizing a size increase of substrate 12 employing
imprinting of large substrates, substrate 12 and polymeric material
24 may be exposed to energy 28, shown in FIG. 1, employing a
multi-ring type exposure to maintain a desired position between
substrate 12 and mold 16, similar to that as mentioned above with
respect to FIGS. 3, 5, and 6. Portions of substrate 12 not
previously exposed to energy 28, shown in FIG. 1, may be
subsequently exposed to energy 28 to complete solidification and/or
cross-linking of polymeric material 24.
[0035] In a further embodiment, energy 28 may comprise a scanning
beam, as shown in FIG. 10, such that desired regions of substrate
12 may be exposed to energy 28. As shown, region 78 of substrate 12
is exposed to energy 28 prior to region 80 of substrate 12 is
exposed to energy 28. In still a further embodiment, contact
between mold 16, shown in FIG. 1, and polymeric material 24 and a
path of the scanning beam may both travel across substrate 12 and
polymeric material 28 in substantially the same direction.
[0036] Referring to FIG. 1, in still a further embodiment, as
mentioned above substrate 12 may be coupled to a substrate chuck
(not shown). To that end, were the substrate chuck (not shown) able
to absorb energy 28, it may be desired to expose substrate 12 and
polymeric material 24 to energy 24 having a reduced magnitude for a
longer period of time as compared to the methods mentioned above.
As a result, a thermal variation of substrate 12 may be minimized,
if not prevented, as desired.
[0037] 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. Therefore, the scope of the invention should 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.
* * * * *