U.S. patent application number 12/367661 was filed with the patent office on 2009-08-13 for template pillar formation.
This patent application is currently assigned to MOLECULAR IMPRINTS, INC.. Invention is credited to Gary F. Doyle, Dwayne L. LaBrake, Michael N. Miller, Douglas J. Resnick, Gerard M. Schmid.
Application Number | 20090200266 12/367661 |
Document ID | / |
Family ID | 40938007 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090200266 |
Kind Code |
A1 |
Doyle; Gary F. ; et
al. |
August 13, 2009 |
Template Pillar Formation
Abstract
Materials for forming an imprint lithography template may be
etched at different rates based on physical properties of the
layers. Additionally, reflectance of the materials may be monitored
to provide substantially uniform erosion of the materials.
Inventors: |
Doyle; Gary F.; (Round Rock,
TX) ; Schmid; Gerard M.; (Austin, TX) ;
Miller; Michael N.; (Austin, TX) ; Resnick; Douglas
J.; (Austin, TX) ; LaBrake; Dwayne L.; (Cedar
Park, TX) |
Correspondence
Address: |
MOLECULAR IMPRINTS
PO BOX 81536
AUSTIN
TX
78708-1536
US
|
Assignee: |
MOLECULAR IMPRINTS, INC.
Austin
TX
|
Family ID: |
40938007 |
Appl. No.: |
12/367661 |
Filed: |
February 9, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61027150 |
Feb 8, 2008 |
|
|
|
Current U.S.
Class: |
216/60 |
Current CPC
Class: |
B82Y 40/00 20130101;
G03F 1/26 20130101; B82Y 10/00 20130101; G03F 7/0002 20130101 |
Class at
Publication: |
216/60 |
International
Class: |
G01L 21/30 20060101
G01L021/30 |
Claims
1. A method comprising: identifying a first physical property of a
first material to determine a first estimated erosion rate of the
first material, the first material having a first reflectance;
identifying a second physical property of a second material to
determine a second estimated erosion rate of the second material,
the first material disposed on the second material; selecting a
process pressure for a reactive ion etching process for etching the
first material and the second material; adjusting the process
pressure during the reactive ion etching process based on the first
estimated erosion rate and the second estimated erosion rate; and,
monitoring a reflectance of the second material to provide
substantially uniform erosion of the second material.
2. The method of claim 1, further comprising: selecting a RF power
for the reactive ion etching process; and, adjusting the RF power
during the reactive ion etching process based on the first
estimated erosion rate and the second estimated erosion rate.
3. The method of claim 1, further comprising: selecting a gas flow
rate for the reactive ion etching process; and, adjusting the gas
flow rate during the reactive ion etching process based on the
first estimated erosion rate and the second estimated erosion
rate.
4. The method of claim 1, wherein the first physical property is a
thickness of the first material.
5. The method of claim 1, wherein the second physical property is a
thickness of the second material.
6. The method of claim 1, wherein the erosion rate of the first
material is less than the erosion rate of the second material.
7. The method of claim 1, wherein the first material is a hard mask
layer.
8. The method of claim 7, wherein the second material is a
conducting layer.
9. The method of claim 8, further comprising: identifying a third
physical property of a third material to evaluate a depth for
pattern transfer, the second material disposed on the third
material; and, monitoring the reflectance of the second material
and a reflectance of the third material to determine a targeted
etch time for etching the third material based on the evaluated
depth for pattern transfer.
10. The method of claim 9, wherein the third physical property is a
thickness of the third material.
11. The method of claim 9, wherein the third material is a
substrate layer.
12. The method of claim 9, wherein etching of the third material
provides an imprint lithography template.
13. A method comprising: identifying a first erosion rate of a
first material; identifying a second erosion rate of a second
material, the first material disposed on the second material;
identifying a third erosion rate of a third material, the second
material disposed on the third material; etching the first material
and the second material using a reactive ion etching process;
adjusting pressure and gas flow rate of the reactive ion etching
process based on the first erosion rate and the second erosion
rate; and, monitoring reflectance of the second material and the
third material to provide substantially uniform erosion of the
second material and the third material resulting in an imprint
lithography template.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. .sctn.
119(e)(1) of U.S. Provisional No. 61/027,150, filed on Feb. 8,
2008, which is hereby incorporated by reference herein.
BACKGROUND INFORMATION
[0002] Nano-fabrication includes the fabrication of very small
structures that have features on the order of 100 nanometers or
smaller. One application in which nano-fabrication has had a
sizeable impact is in the processing of integrated circuits. The
semiconductor processing industry continues to strive for larger
production yields while increasing the circuits per unit area
formed on a substrate, therefore nano-fabrication becomes
increasingly important. Nano-fabrication provides greater process
control while allowing continued reduction of the minimum feature
dimensions of the structures formed. Other areas of development in
which nano-fabrication has been employed include biotechnology,
optical technology, mechanical systems, and the like.
[0003] An exemplary nano-fabrication technique in use today is
commonly referred to as imprint lithography. Exemplary imprint
lithography processes are described in detail in numerous
publications, such as U.S. Patent Publication No. 2004/0065976,
U.S. Patent Publication No. 2004/0065252, and U.S. Pat. No.
6,936,194, all of which are hereby incorporated by reference
herein.
[0004] An imprint lithography technique disclosed in each of the
aforementioned U.S. patent publications and patent includes
formation of a relief pattern in a formable (polymerizable) layer
and transferring a pattern corresponding to the relief pattern into
an underlying substrate. The substrate may be coupled to a motion
stage to obtain a desired positioning to facilitate the patterning
process. The patterning process uses a template spaced apart from
the substrate and a formable liquid applied between the template
and the substrate. The formable liquid is solidified to form a
rigid layer that has a pattern conforming to a shape of the surface
of the template that contacts the formable liquid. After
solidification, the template is separated from the rigid layer such
that the template and the substrate are spaced apart. The substrate
and the solidified layer are then subjected to additional processes
to transfer a relief image into the substrate that corresponds to
the pattern in the solidified layer.
BRIEF DESCRIPTION OF DRAWINGS
[0005] So that the present invention may be understood in more
detail, a description of embodiments of the invention is provided
with reference to the embodiments illustrated in the appended
drawings. It is to be noted, however, that the appended drawings
illustrate only typical embodiments of the invention, and are
therefore not to be considered limiting of the scope.
[0006] FIG. 1 illustrates a simplified side view of a lithographic
system in accordance with an embodiment of the present
invention.
[0007] FIG. 2 illustrates a simplified side view of the substrate
shown in FIG. 1 having a patterned layer positioned thereon.
[0008] FIGS. 3-12 illustrate an exemplary method of forming an
imprint lithography template.
[0009] FIG. 13 illustrates a flow chart of an exemplary method for
etching a first material while substantially maintaining a second
material.
[0010] FIGS. 14A and 14B illustrate exemplary graphs showing
variation of reflectance intensity as an RIE etch process proceeds
through layers of material.
DETAILED DESCRIPTION
[0011] Referring to the figures, and particularly to FIG. 1,
illustrated therein is a lithographic system 10 used to form a
relief pattern on substrate 12. Substrate 12 may be coupled to
substrate chuck 14. As illustrated, substrate chuck 14 is a vacuum
chuck. Substrate chuck 14, however, may be any chuck including, but
not limited to, vacuum, pin-type, groove-type, electrostatic,
electromagnetic, and/or the like. Exemplary chucks are described in
U.S. Pat. No. 6,873,087, which is hereby incorporated by reference
herein.
[0012] Substrate 12 and substrate chuck 14 may be further supported
by stage 16. Stage 16 may provide motion along the x, y, and z
axes. Stage 16, substrate 12, and substrate chuck 14 may also be
positioned on a base (not shown).
[0013] Spaced-apart from substrate 12 is template 18. Template 18
may include mesa 20 extending therefrom towards substrate 12, mesa
20 having a patterning surface 22 thereon. Further, mesa 20 may be
referred to as mold 20. Alternatively, template 18 may be formed
without mesa 20.
[0014] Template 18 and/or mold 20 may be formed from such materials
including, but not limited to, fused-silica, quartz, silicon,
organic polymers, siloxane polymers, borosilicate glass,
fluorocarbon polymers, metal, hardened sapphire, and/or the like.
As illustrated, patterning surface 22 comprises features defined by
a plurality of spaced-apart recesses 24 and/or protrusions 26,
though embodiments of the present invention are not limited to such
configurations. Patterning surface 22 may define any original
pattern that forms the basis of a pattern to be formed on substrate
12.
[0015] Template 18 may be coupled to chuck 28. Chuck 28 may be
configured as, but not limited to, vacuum, pin-type, groove-type,
electrostatic, electromagnetic, and/or other similar chuck types.
Exemplary chucks are further described in U.S. Pat. No. 6,873,087,
which is hereby incorporated by reference herein. Further, chuck 28
may be coupled to imprint head 30 such that chuck 28 and/or imprint
head 30 may be configured to facilitate movement of template
18.
[0016] System 10 may further comprise fluid dispense system 32.
Fluid dispense system 32 may be used to deposit polymerizable
material 34 on substrate 12. Polymerizable material 34 may be
positioned upon substrate 12 using techniques such as drop
dispense, spin-coating, dip coating, chemical vapor deposition
(CVD), physical vapor deposition (PVD), thin film deposition, thick
film deposition, and/or the like. For example, polymerizable
material 34 may be positioned upon substrate 12 using techniques
such as those described in U.S. Patent Publication No. 2005/0270312
and U.S. Patent Publication No. 2005/0106321, both of which are
hereby incorporated by reference herein. Polymerizable material 34
may be disposed upon substrate 12 before and/or after a desired
volume is defined between mold 20 and substrate 12 depending on
design considerations. Polymerizable material 34 may comprise a
monomer mixture as described in U.S. Pat. No. 7,157,036 and U.S.
Patent Publication No. 2005/0187339, both of which are hereby
incorporated by reference herein.
[0017] Referring to FIGS. 1 and 2, system 10 may further comprise
energy source 38 coupled to direct energy 40 along path 42. Imprint
head 30 and stage 16 may be configured to position template 18 and
substrate 12 in superimposition with path 42. System 10 may be
regulated by processor 54 in communication with stage 16, imprint
head 30, fluid dispense system 32, and/or source 38, and may
operate on a computer readable program stored in memory 56.
[0018] Either imprint head 30, stage 16, or both vary a distance
between mold 20 and substrate 12 to define a desired volume
therebetween that is filled by polymerizable material 34. For
example, imprint head 30 may apply a force to template 18 such that
mold 20 contacts polymerizable material 34. After the desired
volume is filled with polymerizable material 34, source 38 produces
energy 40, e.g., ultraviolet radiation, causing polymerizable
material 34 to solidify and/or cross-link conforming to a shape of
surface 44 of substrate 12 and patterning surface 22, defining
patterned layer 46 on substrate 12. Patterned layer 46 may comprise
a residual layer 48 and a plurality of features shown as
protrusions 50 and recessions 52, with protrusions 50 having a
thickness t.sub.1 and residual layer having a thickness
t.sub.2.
[0019] The above-mentioned system and process may be further
employed in imprint lithography processes and systems referred to
in U.S. Pat. No. 6,932,934, U.S. Patent Publication No.
2004/0124566, U.S. Patent Publication No. 2004/0188381, and U.S.
Patent Publication No. 2004/0211754, all of which are hereby
incorporated by reference herein.
[0020] FIGS. 3-12 illustrate an exemplary method of forming imprint
lithography template 18 for use in system 10. Generally, template
18 may be formed by disposing a conducting layer 62 on a substrate
layer 60. A resist layer 64 may be disposed over conducting layer
62 and patterned (e.g., electron-beam lithography). A hard mask
layer 66 may then be disposed over resist layer 64A. Additionally,
a planarizing layer 68 may be disposed over resist layer 64 and/or
hard mask layer 66 to provide a substantially planar top surface.
Plasma etching processes may then be used to transfer the pattern
into substrate layer 60.
[0021] Referring to FIG. 3, conducting layer 62 may be disposed on
substrate layer 60. Substrate layer 60 may be formed of materials
including, but not limited to quartz, silicon, organic polymers,
siloxane polymers, borosilicate glass, fluorocarbon polymers,
metal, hardened sapphire, and/or the like. Generally, substrate
layer 60 may be formed with a high quality optical surface with low
roughness and/or defects. For example, substrate layer 60 may be
formed having a 20/10 scratch/dig ratio. Substrate layer 60 may
have a thickness t.sub.3. Thickness t.sub.3 of substrate layer 60
may be substantially uniform. The magnitude of thickness t.sub.3
may be between approximately 0.1 to 10 mm. A lesser magnitude of
thickness t.sub.3 of substrate layer 60 may provide for substrate
layer 60 and/or template 18 to be capable of flexing and/or
deforming during the imprinting process. For example, thickness
t.sub.3 may be approximately 1 mm.
[0022] Conducting layer 62 may be disposed on substrate layer 60
and is generally capable of being etched by a plasma etching
process. Conducting layer 62 may have a thickness t.sub.4.
Thickness t.sub.4 may be between approximately 1 to 10 nm. For
example, conducting layer 62 may have a thickness t.sub.4 of 5 nm.
Conducting layer 62 may be formed of materials including, but not
limited to, tantalum, tantalum nitride, tantalum silicide,
tungsten, tungsten nitride, silicon carbide, amorphous silicon,
chromium, chromium nitride, molybdenum, molybdenum silicide,
titanium, titanium nitride, and/or the like.
[0023] Referring to FIG. 4, resist layer 64 may be disposed on
substrate layer 60 and/or conducting layer 62. Resist layer 64 may
have a thickness t.sub.5. Thickness t.sub.5 may be between
approximately 5 to 150 nm. For example, resist layer 64 may have a
thickness t.sub.5 of 45 nm. Thickness t.sub.5 may be selected to
obtain a desired patterning resolution. For example, the magnitude
of thickness t.sub.5 of resist layer 64 may be approximately 100 nm
in circumstances that may be suitable for patterning structures
with lateral dimensions of 50 nm. Alternatively, the magnitude of
thickness t.sub.5 of resist layer 64 may be approximately 50 nm in
circumstances that may be suitable for patterning structures with
lateral dimensions of 25 nm.
[0024] Resist layer 64 may be formed of materials including, but
not limited to, imprint resist material, novolac-type photoresists,
acrylate photoresists, epoxy photoresists, bilayer resist
materials, and/or the like. Generally, resist layer 64 may be
formed of positive-tone electron beam resist such as, for example,
ZEP520A manufactured by Zeon Corporation, with an office located in
Tokyo, Japan, or 950k MW PMMA electron beam resist, and/or the
like.
[0025] Resist layer 64 may be patterned to provide one or more
features 70. For example, resist layer 64 may be exposed in an
electron beam lithography tool to pattern features 70. An exemplary
electron beam lithography tool is the VB6HR, manufactured by Vistec
Lithography, Inc., with an office located in Watervliet, N.Y. The
exposure pattern may consist of 25 nm diameter dots on a pitch of
50 nm. Resist layer 64 may be developed to obtain optimal
resolution and/or process window. After development, un-exposed
regions of resist layer 64 form features 70.
[0026] In one example, using ZEP520A, resist layer 64 may be
developed and features 70 formed by immersing resist layer 64 in
amyl acetate at a temperature between approximately -15 to 25
degrees Celsius for approximately 5 to 90 seconds.
[0027] In another example, using PMMA, resist layer 64 may be
developed and features 70 formed by immersing resist layer 64 in a
mixture of isopropyl alcohol and water at a temperature between
approximately -15 to 25 degrees Celsius for approximately 5 to 90
seconds. It should be noted that ultrasonic agitation (e.g.,
approximately 30 to 50 kHz) may be used during development.
[0028] Referring to FIGS. 5A and 5B, hard mask layer 66 may be
disposed on resist layer 64 by processes including, but not limited
to, sputtering, evaporation, and the like. For example, thermal
evaporation and e-beam evaporation may be used. Hard mask layer may
be disposed on portions of resist layer 64 as illustrated in FIG.
5A or disposed on the entire resist layer 64 as illustrated in FIG.
5B.
[0029] Hard mask layer 66 may be formed of materials including, but
not limited to, chromium, chromium nitride, nickel, platinum,
vanadium, and/or the like. Hard mask layer 66 may have a thickness
t.sub.6. Thickness t.sub.6 may be between approximately 1-20 nm.
For example, hard mask layer 66 may have a thickness t.sub.6 of
approximately 5 nm.
[0030] Referring to FIG. 6, planarizing layer 68 may be disposed on
resist layer 64 and/or hard mask layer 66 to provide for a
substantially planar top surface. Planarizing layer 68 may be
disposed by processes including, but not limited to, spin-coating,
evaporation, sputtering, chemical vapor deposition (CVD), and the
like. Alternatively, planarizing layer 68 may be disposed in an
imprint step such that a planar topography may be molded from an
unpatterned surface of template 18. Imprint techniques may provide
for planar surfaces with minimal dependence on pattern density of
underlying features 70.
[0031] Materials used to form planarizing layer 68 are generally
selected to provide little or no significant alterations to resist
layer 66 and/or features 70 of resist layer 66. Planarizing layer
68 may be formed of materials including, but not limited to,
organic imprint resist material, silicon-containing imprint resist
material, spin-on dielectric materials, silsesquioxane materials,
sol-gel materials, siloxane materials, bilayer resist materials,
and/or the like. Planarizing layer 68 may have a thickness t.sub.7.
Thickness t.sub.7 may be between approximately 20 to 200 nm or
other suitable range in order to provide for a substantially planar
top surface. For example, planarizing layer 68 may have a thickness
t.sub.7 of approximately 100 nm.
[0032] Referring to FIG. 7, planarizing layer 68 may be etched
until planarizing layer 68 is substantially removed in un-patterned
regions. Etching may be performed in plasma containing oxygen,
argon, and/or fluorocarbon.
[0033] Referring to FIG. 8, hard mask layer 66 may be plasma etched
until hard mask layer 66 is substantially removed in un-patterned
regions. In one example, hard mask layer 66 may be etched in plasma
containing chlorine and/or oxygen. It should be noted that the
etching of planarizing layer 68 and the etching of hard mask layer
66 may be performed in a single step process.
[0034] Etching of hard mask layer 66 and/or planarizing layer 68
may be monitored. For example, etching of hard mask layer 66 and/or
planarizing layer 68 may be monitored by a reflectance probe (e.g.,
laser reflectance probe). The reflectance probe may measure
reflectance loss as hard mask layer 66 and/or planarizing layer 68
are removed.
[0035] Referring to FIGS. 9A-C, resist layer 64 may be removed. For
example, resist layer 64 may be removed by dissolution in a solvent
as illustrated in FIG. 9A. Additionally, as shown in FIGS. 9B and
9C, removal of resist layer 64 may result in removal of planarizing
layer 68.
[0036] Exemplary solvents for dissolution of resist layer 64
include, but are not limited to, dichloromethane,
diemthylacetamide, N-methylpyrrolidone, and the like. In one
example, resist layer 64 is removed using a plasma etch. For
example, resist layer 64 may be removed in plasma containing oxygen
and/or argon.
[0037] Plasma etching of fused silica, silicon dioxide, and
refractory metals is generally an ion-enhanced process. As such,
the process may provide for etching of the surface of such
materials to provide surface chemical reactions that may result in
the removal of these materials. Generally, plasma conditions that
produce this effect may involve high RF power and/or lower process
chamber pressure. These conditions may result in unwanted erosion
or a higher rate of erosion of materials than may be needed. For
example, in certain circumstances, hard mask layer 66 may have a
thickness t.sub.6 substantially less than 15 nm. Application of
high RF power and/or lower pressure may substantially erode hard
mask layer 66 and may result in deformation during pattern transfer
(e.g., pattern critical dimension consistencies and/or poor profile
control).
[0038] FIG. 13 illustrates a flow chart of a method 80 for etching
conducting layer 62 (e.g., tantalum) while substantially
maintaining hard mask layer 66 (e.g., chromium). For example,
method 80 may reduce erosion rate of hard mask layer 66 (e.g.,
<1 nm/min) while maintaining a suitable erosion rate for
conducting layer 62 (e.g., >1 nm/min). In a step 82, physical
properties of hard mask layer 66 may be identified for
determination of an estimated erosion rate for hard mask layer 66.
For example, thickness t.sub.6 of hard mask layer 66 may be
identified to determine the estimated erosion rate for hard mask
layer 66. In a step 84, physical properties of conducting layer 62
may be identified for determination of an estimated erosion rate
for conducting layer 62. For example, thickness t.sub.4 may be
identified for determination of the estimated erosion rate for
conducting layer 62. In a step 86, physical properties of substrate
layer 60 (e.g. quartz) may be identified for evaluation of depth
desired for pattern transfer (e.g., approximately 10-100 nm). In a
step 88, RF power, process pressure, and/or gas flow ratio (e.g.,
CF.sub.4/helium gas flow ratio) within a commercially available
reactive ion etch (RIE) plasma processing system may be selected.
In a step 90, RF power, process pressure, and/or gas flow ratio may
be adjusted based on the estimated erosion rate for hard mask layer
66 and/or conducting layer 62. In a step 92, etch rate of
conducting layer 62 may be monitored by a reflectance probe to
provide substantially consistent results in patterning of substrate
layer 60.
[0039] The reflectance probe may be any apparatus that provides
information regarding surface reflectance of a material over time.
For example, reflectance probe may be a laser source that is
integrated into a video camera and/or reflectance sensor module.
The etch rate of conducting layer 62 may be monitored by the
reflectance probe to provide a surface reflectance graph. Exemplary
reflectance graphs 120 are illustrated in FIGS. 14A and 14B. Graphs
120 provide the surface reflectance of at least two materials over
time. Section A illustrates the surface reflectance of a first
material (e.g., conducting layer 62) at the beginning of the etch
process. Section B illustrates surface reflectance of the first
material as the etch process continues. Section C illustrates
surface reflectance of a second material (e.g., substrate layer 60)
once the first material is removed from the area being monitored.
Surface reflectance between the first material and the second
material may differ substantially or minimally. Additionally, the
surface reflectance of the first material may be more than the
surface reflectance of the second material (as shown in FIG. 14A)
or less than the surface reflectance of the second material (as
shown in FIG. 14B). Additionally, a targeted etch time for
substrate layer 62 may be determined based on surface reflectance
between Section B and Section C of graph 120. For example, between
samples, thickness t.sub.4 of conducting layer 62 may vary. A
standardized etch rate for substrate layer 62 with multiple
conducting layers 62 may result in inconsistent etch depth within
substrate layer 62. As such, a targeted etch time may be developed
for substrate layer 62 having a starting point at the transition of
Section B and Section C of graph 120. The targeted etch time may
remove thickness of conducting layer 62 in standardizing the
pattern depth in substrate layer 62.
[0040] The above identified method for etching conducting layer 62
while substantially maintaining hard mask layer 66 and monitoring
etching of two or more materials may be used in additional
processes such as those described in U.S. Ser. No. 11/856,862 and
U.S. Ser. No. 11/943,907, both of which are hereby incorporated by
reference herein.
[0041] Referring to FIG. 10, hard mask layer 66 may be used as an
etch mask to create topography in underlying substrate layer 60.
Substrate layer 60 may be etched using a fluorocarbon plasma etch
process. Etch time may be determined by graph 120 of FIG. 14A, as
described in further detail herein.
[0042] Referring to FIG. 11, cleaning process may be performed to
remove residual resist layer 64, planarizing layer 68, and/or
conducting layer 64. For example, substrate layer 60 may be
immersed in a piranha solution (e.g., H.sub.2SO.sub.4 and
H.sub.2O.sub.2). Hard mask layer 66 may be removed using an aqueous
solution containing ceric ammonium nitride. Conducting layer 64 may
be removed using a vapor containing xenon difluoride.
* * * * *