U.S. patent application number 15/693942 was filed with the patent office on 2018-03-01 for heat actuated and projected lithography systems and methods.
The applicant listed for this patent is NORTHWESTERN UNIVERSITY. Invention is credited to Keith A. Brown, Daniel J. Eichelsdoerfer, Shu He, Xing Liao, Guoliang Liu, Chad A. Mirkin, Boris Rasin, Abrin L. Schmucke, Wooyoung Shim.
Application Number | 20180059550 15/693942 |
Document ID | / |
Family ID | 50627937 |
Filed Date | 2018-03-01 |
United States Patent
Application |
20180059550 |
Kind Code |
A1 |
Mirkin; Chad A. ; et
al. |
March 1, 2018 |
HEAT ACTUATED AND PROJECTED LITHOGRAPHY SYSTEMS AND METHODS
Abstract
In accordance with an embodiment of the disclosure, a tip array
can include an elastomeric tip substrate layer comprising a first
surface and an oppositely disposed second surface, the tip
substrate layer being formed from an elastomeric material; a
plurality of tips fixed to the first surface, the tips each
comprising a tip end disposed opposite the first surface, the tips
having a radius of curvature of less than about 1 micron; and an
array of heaters disposed on the second surface of the tip
substrate layer and configured such that when the tip substrate
layer is heated by a heater, a tip disposed in a location of a
heated portion of tip substrate layer is lowered relative to a tip
disposed in a location of an unheated portion of the tip substrate
layer.
Inventors: |
Mirkin; Chad A.; (Wilmette,
IL) ; Liao; Xing; (Evanston, IL) ; Brown;
Keith A.; (Newton, MA) ; Liu; Guoliang;
(Evanston, IL) ; Schmucke; Abrin L.; (Chicago,
IL) ; He; Shu; (Evanston, IL) ; Shim;
Wooyoung; (Skokie, IL) ; Eichelsdoerfer; Daniel
J.; (Evanston, IL) ; Rasin; Boris; (Evanston,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NORTHWESTERN UNIVERSITY |
Evanston |
IL |
US |
|
|
Family ID: |
50627937 |
Appl. No.: |
15/693942 |
Filed: |
September 1, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14439252 |
Apr 29, 2015 |
9766551 |
|
|
PCT/US13/64959 |
Oct 15, 2013 |
|
|
|
15693942 |
|
|
|
|
61719907 |
Oct 29, 2012 |
|
|
|
61719918 |
Oct 29, 2012 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 13/143 20130101;
B05D 3/06 20130101; G03F 7/20 20130101; G03F 7/70141 20130101; G03F
7/0002 20130101; G03F 7/70325 20130101; G03F 7/70383 20130101; G03F
7/7045 20130101; G03F 7/2049 20130101; B05D 1/26 20130101; B82Y
40/00 20130101; G03F 7/7035 20130101 |
International
Class: |
G03F 7/20 20060101
G03F007/20; B05D 1/26 20060101 B05D001/26; G03F 7/00 20060101
G03F007/00; G02B 13/14 20060101 G02B013/14; B05D 3/06 20060101
B05D003/06 |
Claims
1.-25. (canceled)
26. A method of aligning a tip array and pattern of radiation
projected from a projector, comprising: positioning a projector
comprising a digital micromirror device and a macro lens a distance
from a tip array, the distance being substantially equal to the
focal length of the macro lens; aligning the digital micromirror
device, the macro lens and a beam splitter using an optical
breadboard; displaying a first test pattern of radiation from the
projector and projecting the first test pattern onto the tip array,
wherein the first test pattern has first ratio of L/N, wherein L is
the number of mirrors disposed on an edge of an illuminated portion
of the test pattern and N is the number of tips disposed on an edge
of an illuminated portion of the test pattern; observing the
projected test pattern projected on a back surface of the tip
array; adjusting the position of the digital micromirror device to
center the first test pattern on the tips disposed in the irradiate
portion of the first test pattern; adjusting the position of the
beam splitter until the test pattern is in rough focus on the tip
array; adjusting the focal length of the macro lens until the test
pattern is in sharp focus; projecting a second test pattern of
radiation onto the tip array, wherein the second test pattern has a
second ratio of L/N that is smaller than the first ratio of L/N;
adjusting the size, orientation, and position of the second test
pattern such that the projected second test pattern substantially
matches the tips in the array until one tip of the tip array is in
the center of each irradiated portion of the second test
pattern.
27. The method of claim 26, wherein the first test pattern is in
the form of a checkerboard and sized such that at least a 5.times.5
array of tips is disposed in a single irradiated square of the
checkerboard.
28. The method of claim 26, comprising observing the projected test
pattern using a camera focused on the back surface of the tip
array.
29. The method of claim 26, wherein the second test pattern is in
the form of a checkerboard.
30. A tip array, comprising: an elastomeric tip substrate layer
comprising a first surface and an oppositely disposed second
surface, the tip substrate layer being formed from an elastomeric
material; a plurality of tips fixed to the first surface, the tips
each comprising a tip end disposed opposite the first surface, the
tips having a radius of curvature of less than about 1 micron; and
an array of heaters disposed on the second surface of the tip
substrate layer and configured such that when the tip substrate
layer is heated by a heater, a tip disposed in a location of a
heated portion of tip substrate layer is lowered relative to a tip
disposed in a location of an unheated portion of the tip substrate
layer.
31. The tip array of claim 30, wherein the tips are formed of an at
least translucent material, the tip array further comprising a
blocking layer coated on the tips and the first surface; and a
plurality of apertures defined in the blocking layer exposing the
tip ends of the plurality of tips.
32. The tip array of claim 30, wherein the tips are comprise an
elastomer.
33. The tip array of claim 30, wherein the elastomer of the one or
more tips and/or the elastomeric tip substrate layer comprises a
polymer, a cross-linked polymer, or a polymer gel.
34. The tip array of claim 30, wherein the elastomer of the one or
more tips and/or the elastomeric tip substrate layer comprises
polydimethylsiloxane (PDMS).
35. The tip array of claim 30, wherein the tips comprise a metal, a
metalloid (optionally silicon), a semi-conducting material, or a
combination thereof.
36. The tip array of claim 30, further comprising a rigid support
to which the tip substrate layer is attached, the heaters being
disposed between the rigid support and the tip substrate layer.
37. The tip array of claim 36, wherein the rigid support is a glass
slide.
38. The tip array of claim 30, wherein one or more of the tip
substrate layer, the rigid support, and the tips are
translucent.
39. The tip array of claim 30, wherein the heaters are electrically
activated heaters.
40. The tip array of claim 39, wherein the heaters are formed of
indium tin oxide, graphene, poly(3,4-ethylenedioxythiophene)
(PEDOT), gold, copper, platinum, and combinations thereof.
41. The tip array of claim 30, wherein the heaters are
photoconductive heaters.
42. The tip array of claim 41, wherein the photoconductive heaters
comprise amorphous hydrogenated silicon, zinc oxide, cadmium
selenide, or combinations thereof.
43. The tip array of claim 41, further comprising at least one
spatial light modulator disposed on at least one of the
photoconductive heaters.
44. The tip array of claim 43, wherein the at least one spatial
light modulator is dynamically controllable.
45. The tip array of claim 41, further comprising an array of
spatial light modulators disposed on the photoconductive
heaters.
46. The tip array of claim 30, wherein the tip array comprises
electrically activated heaters and photoconductive heaters.
47. The tip array of claim 30, wherein the heaters are at least
translucent.
48. The tip array of claim 47, wherein the heaters are
transparent.
49. The tip array of claim 30, wherein each heater of the array of
heaters is aligned with one tip of the tip array.
50. The tip array of claim 30, wherein each the heater is disposed
in a region of the tip substrate layer corresponding to a heating
zone comprising one or more tips, wherein upon activation of the
heater the one or more tips in the heating zone are lowered
relative to a tip disposed outside the heating zone.
51. The tip array of claim 30, further comprising a graphene film
coated on at least the tips of the tip array.
52. A method for selectively actuating one or more tips of the tip
array of claim 30, comprising selectively activating one or more
heaters to heat a portion of the elastomeric tip substrate layer to
selectively lower one or more tips disposed in the location of the
heated portion of the tip substrate layer relative to a tip
disposed in an unheated portion of the tip substrate layer.
53. The method of claim 52, further comprising contacting the
substrate with the tip array before selectively activating the one
or more heaters, wherein selecting activating the one or more
heaters selectively heats a portion of the tip substrate layer to
selectively lowers one or more tips into closer contact to print
larger feature sizes as compared to feature sizes printed by tips
disposed in an unheated portion of the tip substrate layer.
54. The method of claim 52 or 53, wherein each heater is disposed
in a heating zone comprising one or more tips and selectively
activating the heater in the heating zone selectively lowers the
one or more tips in the heating zone relative to a tip disposed
outside the heating zone.
55. The method of claim 52, wherein each heater is aligned with a
single tip and selectively activating the heater selectively lowers
only the tip which aligned with the activated heater.
56. A method of selectively applying a patterning composition to
one or more tips of the tips array of claim 30, comprising:
disposing the tip array adjacent to, but not in contact with one or
more patterning composition sources; and selectively activating one
or more heaters to heating a portion of the elastomeric tip
substrate layer to selectively lower one or more tips disposed in
the location of the heated portion of the elastomeric tip substrate
layer into contact with the one or more patterning composition
sources.
57. A method of selectively applying a patterning composition to
one or more tips of the tips array of claim 30, comprising:
selectively activating one or more heaters to heating a portion of
the elastomeric tip substrate layer to selectively lower one or
more tips disposed in the location of the heated portion of the
elastomeric tip substrate layer; disposing the tip array adjacent
to one or more patterning composition sources such that the
selectively lowered one or more tips are placed into contact with
the one or more patterning composition sources.
58. A method of selectively applying two different patterning
compositions to the tips of the tip array of 30, comprising:
disposing the tip array adjacent to, but not in contact with a
first patterning composition source; selectively heating a portion
of the elastomeric tip substrate layer to selectively lower a first
subset of one or more tips disposed in the location of the heated
portion of the elastomeric tip substrate layer into contact with
the first patterning composition source to apply the first
patterning composition to the first subset of one or more tips;
disposing the tip array adjacent to, but not in contact with a
second patterning composition source comprising a second patterning
composition; selectively heating a portion of the elastomeric tip
substrate layer to selectively lower a second subset of one or more
tips disposed in the location of the heated portion of the
elastomeric tip substrate layer into contact with the second
patterning composition source to apply the second patterning
composition to the second subset of one or more tips.
59. The method of claim 52, wherein the heaters are photoconductive
heaters and selectively heating a portion of the elastomeric tip
substrate layer comprises selectively irradiating one or more of
the photoconductive heaters.
60. The method of claim 59, comprising activating the one or more
heaters by irradiating the heaters with a pattern of radiation, the
pattern of radiation corresponding to the one or more heaters to be
activated.
61. The method of claim 52, wherein the heaters are photoconductive
heaters, the tip array comprises an array of spatial light
modulators disposed on the photoconductive heaters, and selectively
heating a portion of the elastomeric tip substrate layer comprises
irradiating the tip substrate layer and selectively actuating the
spatial light modulators to expose one or more of the
photoconductive heaters to the irradiation.
62. The method of claim 52, wherein the heaters comprise a first
subset of photoconductive heaters adapted to activate in response
to a first radiation, and a second subset of photoconductive
heaters adapted to activate in response to a second radiation, the
first and second radiations having different wavelengths, and
selectively activating one or more of the first subset of
photoconductive heaters comprises irradiating one or more of the
heaters with the first radiation and selectively activating one or
more of the second subset of photoconductive heaters comprises
irradiating one or more of the heaters with the second
radiation.
63. The method of claim 62, wherein selectively actuating one or
more heaters comprises irradiating all the heaters with the first
radiation, wherein only the first subset of photoconductive heaters
are activated to selectively lower one or more tips of the tip
array.
64. The method of claim 62, wherein selectively actuating one or
more heaters comprises irradiating all the heaters with the second
radiation, wherein only the second subset of photoconductive
heaters are activated to selectively lower one or more tips of the
tip array.
65. The method of claim 52, wherein the heaters are electric
heaters and selectively activating one or more heaters comprises
supplying a voltage to the one or more heaters.
66.-77. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Application Ser.
Nos. 61/719,907, filed Oct. 29, 2012, entitled "Heat Actuated and
Projected Lithography Systems and Methods" and 61/719,918, filed
Oct. 29, 2012, entitled "Heat Actuated and Projected Lithography
Systems and Methods", which are hereby incorporated by reference in
their entirety.
BACKGROUND
[0002] The demand for nanoscale components in integrated circuits,
medical diagnostics, and optoelectronics has generated much
interest in the development and study of various lithography
strategies. Conventional patterning methods, however, have failed
to satisfy the need for rapidly patterning of nanoscale features at
a low cost. The expense of patterning equipment grows dramatically
as the required resolution increases.
[0003] With conventional far-field optical lithography, lateral
feature resolution is diffraction-limited, as defined by the
Rayleigh or Abbe conditions, which in practical terms only allow
feature dimensions of approximately half the incident wavelength.
In order to overcome the diffraction limit, a number of lithography
approaches have been reported, including multi-photon induced
photoresist polymerization, zone-plate array lithography, and
phase-shift photolithography. Though these techniques are highly
parallel, they rely on non-standard optical instrumentation and
light sources not readily available to most researchers, or they
preclude arbitrary nanoscale pattern formation. In order to produce
complex patterns, established approaches including electron-beam
lithography, focused ion beam (FIB) lithography, and scanning probe
microscopy (SPM)-based techniques such as dip-pen nanolithography
(DPN) have been employed. Near-field scanning optical microscopy
(NSOM)-based techniques and scanning near-field photolithography
(SNP) are promising custom lithographic methods for sub-diffraction
limit patterning, but are inherently low throughput and restricted
to scan areas several hundred microns in length.
[0004] In order to generate sub-diffraction limit features, SNP
optics rely on the evanescent field of incident light passing
through an aperture, the intensity of which is strongly dependent
on the distance between this aperture and the surface. To control
precise aperture heights and lateral registry, SNP relies on
feedback systems used in piezo-controlled SPM instruments. Though
highly parallel two-dimensional (2D) silicon-based NSOM aperture
arrays have been fabricated, aligning a large area substrate
surface with near-field proximity to this hard, non-deformable
aperture array remains challenging. As a result, no successful
demonstrations of their use in homogeneous patterning have been
reported.
[0005] Beam pen lithography (BPL) is another desktop fabrication
technique, which uses light to write patterns, as opposed to
electrons and other particle-based techniques. Near-field apertures
in a BPL tip array offer a direct route to circumvent the
diffraction limit present in conventional photolithography.
However, BPL is limited in that all tips in the array act in
unison, making this technique only useful for generating replicas
of patterns, and the apertures are either constructed serially
using a focused ion beam or in parallel using a mechanical
stripping technique that yields large micron-sized pores.
SUMMARY
[0006] In accordance with an embodiment of the disclosure, a method
of patterning can include dividing an image into a set of frame
sections; determining a tip pattern for a respective portion of an
image to be patterned by each tip of the tip array in each frame
section of the set of frame sections; disposing the tip array in a
patterning position in a first location of the substrate
corresponding to a location of the substrate in which the first
frame section in the set of frame sections is to be patterned;
projecting a first pattern of radiation onto the tip array to
selectively irradiate one or more tips of the tip array and pattern
the substrate, wherein the first pattern of radiation corresponds
to a tip pattern for the first frame section; disposing the tip
array in a patterning position in a second location of the
substrate corresponding to a location of the substrate in which the
second frame section in the set of frame sections is to be
patterned; projecting a second pattern of radiation onto the tip
array to selectively irradiate tips of the tip array and pattern
the substrate, wherein the second pattern of radiation corresponds
to a tip pattern for the second frame section; and repeating the
disposing and projecting for each frame section in the set of frame
sections to pattern the image.
[0007] In accordance with another embodiment of the disclosure, a
method for patterning a substrate using projected radiation can
include (a) subdividing an image to be patterned into frame
sections, wherein each frame section corresponds to a portion of
the image to be patterned on a substrate by each pen of a tip array
in a patterning location; (b) receiving a set of data inputs, the
set of data inputs comprising a spatial size of the image, a center
location of the image, rotational offset of the image, a delay
time, an exposure time, and a safety time; (c) outputting an
instruction data set based the set of data inputs; (d) receiving
with a control system for the tip array the instruction data set
for directing movement of the tip array to a patterning location;
(e) disposing the tip array in a patterning position in a first
patterning location; (f) detecting a Z-piezo voltage, wherein a
threshold voltage corresponds to the tip array being in a
patterning position; (g) projecting onto the tip array a first
pattern of radiation after detecting the threshold voltage; the
first irradiation pattern selectively irradiate the tip array to
pattern a first portion of the image corresponding to a first
subset of the frames sections located in the first patterning
location; (h) maintaining projection of the first pattern of
radiation for an exposure time; (i) maintaining the tips in the
patterning position for a hold time equal to the exposure time, the
delay time, and the safety time to pattern the first portion of the
image on the substrate; (j) stopping projection of the first
pattern of radiation after the exposure time has lapsed; (k)
removing the tips from the patterning position after the hold time
has lapsed; (l) moving the tips to a second patterning location
once the tips are removed from the patterning position, the spatial
location of second patterning location being provided by the
instruction data set; and, (m) repeating steps (e)-(k) at the
second patterning location to pattern the substrate in a second
patterning location.
[0008] In accordance with an embodiment of the disclosure, a method
of aligning a tip array and pattern of radiation projected from a
projector can include positioning a projector comprising a digital
micromirror device and a macro lens a distance from a tip array,
the distance being substantially equal to the focal length of the
macro lens; aligning the digital micromirror device, the macro lens
and a beam splitter using an optical breadboard; displaying a first
test pattern of radiation from the projector and projecting the
first test pattern onto the tip array, wherein the first test
pattern has first ratio of L/N, wherein L is the number of mirrors
disposed on an edge of an illuminated portion of the test pattern
and N is the number of tips disposed on an edge of an illuminated
portion of the test pattern; observing the projected test pattern
projected on a back surface of the tip array; adjusting the
position of the digital micromirror device to center the first test
pattern on the tips disposed in the irradiate portion of the first
test pattern; adjusting the position of the beam splitter until the
test pattern is in rough focus on the tip array; adjusting the
focal length of the macro lens until the test pattern is in sharp
focus; projecting a second test pattern of radiation onto the tip
array, wherein the second test pattern has a second ratio of L/N
that is smaller than the first ratio of L/N; adjusting the size,
orientation, and position of the second test pattern such that the
projected second test pattern substantially matches the tips in the
array until one tip of the tip array is in the center of each
irradiated portion of the second test pattern.
[0009] In accordance with an embodiment of the disclosure, a system
for patterning a substrate using projected radiation, the system
including a tip array coupled to an actuator comprising a piezo
driver; a projector including a radiation source; a substrate
stage; a control module communicatively linked to the microscope
and the projector, the module including a processor for executing
instructions stored on a memory, the instructions to: (a) subdivide
an image to be patterned into square frame sections, wherein each
square frame section corresponds to a portion of the image to be
patterned on a substrate by each pen of a tip array in a patterning
location; (b) receive a set of data inputs, the set of data inputs
comprising a spatial size of the image, a center location of the
image, rotational offset of the image, a delay time, an exposure
time, and a safety time; (c) generate an instruction data set based
the set of data inputs, the instruction set for directing movement
of the tip array to a patterning location by the actuator; (d)
detect a threshold piezo voltage corresponding to the tip array
being in a patterning position; (e) cause the projector to: project
a first irradiation pattern onto the tip array after detecting the
threshold voltage, wherein the first irradiation pattern
corresponds to a first portion of the image and the first portion
of the image corresponds to a first subset of the frames sections
located in the first patterning location, maintain projection of
the first irradiation pattern for an exposure time, and stop
projection of the first pattern of radiation after the exposure
time has lapsed; (f) cause the actuator and/or substrate stage to:
maintain the tips in the patterning position for a hold time equal
to the exposure time, the delay time, and the safety time to
pattern the first portion of the image on the substrate, remove the
tips from the patterning position after the hold time has lapsed,
and move the tips to a second patterning location once the tips are
removed from the patterning position, the spatial location of
second patterning location being provided by the instruction data
set; and (h) repeat steps (e) and (f) at the second patterning
location to pattern the substrate in a second patterning
location.
[0010] In accordance with another embodiment of the disclosure, a
system for patterning a substrate using projected radiation can
include a micro tip array coupled to an actuator; a projector
including a radiation source; a substrate stage; a control module
communicatively linked to the actuator, optionally the substrate
stage, and the projector, the module including a processor for
executing instructions stored on a memory, the instructions to:
divide an image to be patterned into a set of frame sections;
determine a tip pattern for a respective portion of an image to be
patterned by each tip of the tip array in each frame section of the
set of frame sections; and for each frame section in the set of
frame sections, cause the actuator and/or the substrate stage to
dispose the tip array in a patterning position in a first location
of a substrate corresponding to a location of the substrate in
which the first frame section in the set of frame sections is to be
patterned; cause the projector to project a first pattern of
radiation onto the tip array to selectively irradiate one or more
tips of the tip array and pattern the substrate, wherein the first
pattern of radiation corresponds to a tip pattern for the first
frame section; cause the actuator and/or the substrate stage to
dispose the tip array in a patterning position in a second location
of the substrate corresponding to a location of the substrate in
which the second frame section in the set of frame sections is to
be patterned; and cause the projector to project a second pattern
of radiation onto the tip array to selectively irradiate tips of
the tip array and pattern the substrate, wherein the second pattern
of radiation corresponds to a tip pattern for the second frame
section.
[0011] In accordance with an embodiment of the disclosure, a tip
array can include an elastomeric tip substrate layer comprising a
first surface and an oppositely disposed second surface, the tip
substrate layer being formed from an elastomeric material; a
plurality of tips fixed to the first surface, the tips each
comprising a tip end disposed opposite the first surface, the tips
having a radius of curvature of less than about 1 micron; and an
array of heaters disposed on the second surface of the tip
substrate layer and configured such that when the tip substrate
layer is heated by a heater, a tip disposed in a location of a
heated portion of tip substrate layer is lowered relative to a tip
disposed in a location of an unheated portion of the tip substrate
layer.
[0012] In accordance with an embodiment of the disclosure, a method
of aligning a tip array and pattern of radiation projected from a
projector can include positioning a projector comprising a digital
micromirror device and a macro lens a distance from a tip array,
the distance being substantially equal to the focal length of the
macro lens; aligning the digital micromirror device, the macro lens
and a beam splitter using an optical breadboard; displaying a first
test pattern of radiation from the projector and projecting the
first test pattern onto the tip array, wherein the first test
pattern has first ratio of L/N, such that N number of tips is
disposed in an irradiated portion of the test pattern; observing
the projected test pattern projected on a back surface of the tip
array; adjusting the position of the digital micromirror device to
center the first test pattern on the tips disposed in the irradiate
portion of the first test pattern; adjusting the position of the
beam splitter until the test pattern is in rough focus on the tip
array; adjusting the focal length of the macro lens until the test
pattern is in sharp focus; projecting a second test pattern of
radiation onto the tip array, wherein the second test pattern has a
second ratio of L/N that is smaller than the first ratio of L/N;
adjusting the size, orientation, and position of the second test
pattern such that the projected second test pattern substantially
matches the tips in the array until one tip of the tip array is in
the center of each irradiated portion of the second test
pattern.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A is a high-level illustration of one embodiment of a
lithography system according to the disclosure herein;
[0014] FIG. 1B is a schematic illustration of a projected
lithography system using a beam pen tip array according to the
disclosure herein;
[0015] FIG. 2A is a user interface for computer-implemented
alignment of a lithography system according to the disclosure
herein;
[0016] FIGS. 2B-2D are flowcharts for methods to complete an
alignment process for a lithography system according to the
disclosure herein;
[0017] FIG. 2E is an optical image illustrating the checkerboard
alignment process in accordance with an embodiment of the
disclosure herein;
[0018] FIG. 3 is a user interface for controlling a lithography
process using the system of FIG. 1;
[0019] FIG. 4 is a flowchart for a method of completing a
lithography process according to the disclosure herein;
[0020] FIG. 5 is a high-level illustration of another embodiment of
a lithography system according to the disclosure herein;
[0021] FIG. 6 is a high-level illustration of still another
embodiment of a lithography system according to the disclosure
herein;
[0022] FIG. 7 is a user interface for controlling a lithography
process using the system of FIG. 5 or FIG. 6;
[0023] FIGS. 8A-8D are flowcharts for further methods to complete a
lithography process according to the disclosure herein;
[0024] FIG. 9 is a high-level block diagram of a computing system
according to the disclosure herein;
[0025] FIG. 10A is a schematic illustration of thermal actuation of
a tip array in accordance with an embodiment of the disclosure
herein;
[0026] FIG. 10B is a simulation of the heat profile in a PDMS and
glass substrate according to the disclosure herein;
[0027] FIG. 10C is an SEM image of a micro-heater array with a
close up of a single coil according to the disclosure herein;
[0028] FIG. 10D is an SEM image of a 4.times.4 tip array fabricated
on top of micro coil heaters according to the disclosure
herein;
[0029] FIG. 11 is a schematic illustration of a fabrication process
of a thermal actuation tip array in accordance with an embodiment
of the disclosure herein;
[0030] FIG. 12A is a thermal image of one heater in an array in an
"off" and an "on" state according to the disclosure herein;
[0031] FIG. 12B is a graph illustrating the measurement of the
actuation and extraction of a timescale .tau. and amplitude A
according to the disclosure herein;
[0032] FIG. 12C is a graph illustrating the linear relationship
observed between applied power and actuation amplitude according to
the disclosure herein;
[0033] FIG. 12D is a graph of an amplitude profile along the
surface of the PDMS according to the disclosure herein, showing
minimal crosstalk and fatigue;
[0034] FIG. 13A is a schematic of using multiple tips to write a
continuous pattern across a substrate according to the disclosure
herein;
[0035] FIG. 13B is a schematic of using several tips inked with
different inks having different colors to generate multiple
patterns on a substrate according to the disclosure herein, wherein
continuations of the unit cell patterns result in every spot on the
substrate being addressable by every color;
[0036] FIG. 14A is a schematic illustration of a patterning method
in accordance with an embodiment of the disclosure herein;
[0037] FIG. 14B is an SEM image of patterns achieved by 13 tips of
a 4.times.4 tip array writing MHA on gold followed by chemical
etching using a method of patterning with thermal actuation of the
tips of the tip array according to the disclosure herein, wherein
each box represents a patterned written by a single tip;
[0038] FIG. 15A is a schematic of an electrically addressable
heater scheme according to the disclosure herein, wherein when
electricity is allowed to flow by an external switch (here an NPN
transistor), it heats a resistive coil pattern;
[0039] FIG. 15B is a schematic of a photo-selected heater scheme
according to the disclosure herein, wherein when the
photoconductive discs are exposed to an irradiation source (e.g.,
light), electricity is allowed to flow which heats the
photoconductor and actuates the tip;
[0040] FIG. 16A is a schematic illustration of a Polymer Pen
Lithography set up;
[0041] FIG. 16B is a photograph of a 11 million tip array;
[0042] FIG. 16C is a scanning electron microscopy (SEM) image of
the polymer tip array of FIG. 16B;
[0043] FIG. 17 is a schematic illustration of a polymer tip array
fabrication;
[0044] FIG. 18 is a graph illustrating feature size as a function
of relative z-piezo extension, demonstrating the pressure
dependence of feature size when patterning with polymer pen or gel
pen or beam pen lithography;
[0045] FIG. 19 is a schematic illustration of a beam tip array and
a beam pen lithography method;
[0046] FIG. 20 is an SEM image of a beam pen tip array, with the
inset showing an aperture formed in a tip end;
[0047] FIGS. 21A and 21B are schematic illustrations of methods of
making a beam pen tip array;
[0048] FIG. 22A is a schematic illustration of a hard tip soft
spring lithography tip array;
[0049] FIG. 22B is a schematic illustration of a method of making a
hard tip soft spring lithography tip array;
[0050] FIGS. 23A is an SEM image of Si tip array after KOH etching
(40 wt %, 75.degree. C. for 65 min) with isopropyl alcohol, wherein
Si substrate attached directly to PDMS without SiO.sub.2
passivation layer resulted in Si tips falling from PDMS surface
during etching; the welling of PDMS in solution at relatively high
temperatures may cause the interfacial stress that weakens the
adhesion of Si to PDMS; employing a SiO.sub.2 passivation layer was
found to significantly improve the stability of Si pen on a surface
during etching;
[0051] FIG. 23B-23D show magnified images of different regions of
23a;
[0052] FIG. 23E-23I show fabricated Si tip arrays on
SiO.sub.2/PDMS/glass: E, Si wafer (2.times.2 cm) on a cured PDMS
surface on a glass slide before etching and F, an actual tip array
after etching in KOH. G, a SEM image of the Si tip array on
SiO.sub.2/PDMS/glass with 160 .mu.m in pitch that are uniform with
bottom width 30.+-.0.6 .mu.m corresponding to about 47.+-.0.9 .mu.m
in pen height; the pen height may vary up to 10% in optimized
condition, since the original wafer itself used as a starting
material in this experiment has a variation of 10% in thickness;
the inset shows the array in a large area that shows the
homogeneity of the tips; H, (311) planes were introduced during the
wet etching with <110> oriented masks on a (100) Si surface.
The measured surface intersection angles, .alpha..sub.1 and
.alpha..sub.2, as defined in this figure were 126.9.degree. and
143.1.degree. that correspond to the tip defining planes of (311);
rotation of the intersection of planes to <100>, .phi., was
18.4.degree., and also showed that the tip plane is (311); I, the
tip radius of curvature was 22.+-.3 nm.
[0053] FIGS. 24A and 24B are schematic illustrations of a hard tip
soft spring lithography tip array coated with a graphene film;
[0054] FIG. 25A is a schematic illustration of a method of coating
a graphene film on a tip array;
[0055] FIG. 25B is photographs of the method of FIG. 25a,
illustrating (left photograph) PMMA/graphene film floating on water
before coating, and (right photograph) submersion of the tip array
in the fluid at an angle to coat the tips with the PMMA/graphene
film;
[0056] FIG. 25C is a photograph of PMMA/graphene separated from the
Ni substrate by removing the Ni layer in an aqueous 1 M FeCl.sub.3
solution;
[0057] FIG. 26A is a schematic illustration of a method of making a
beam pen tip array tip array using a lift-off procedure, the inset
is an SEM image of an aperture formed by the method;
[0058] FIG. 26B is a schematic illustration of a method of making a
beam pen tip array using a dry and wet etching process, the inset
is an SEM image of an aperture formed by the method;
[0059] FIG. 27A is an SEM image of a dot pattern formed using
projected lithography according to the disclosure herein using a
beam pen tip array;
[0060] FIG. 27B is graph illustrating the relationship between
feature size and exposure time for a method of patterning using
projected lithography with a beam pen tip array according to the
disclosure herein;
[0061] FIG. 27C is an SEM image of a line pattern formed using
projected lithography using a beam pen tip array according to the
disclosure herein;
[0062] FIG. 28 is an SEM image of a pattern formed by projected
lithography according to the disclosure herein; the pattern was
formed using 10,000 coordinated tips addressing 10,000 points each
creating a cm.sup.2 image; the pattern includes mm-scale structures
composed of micron-scale images with 300 nm dots
[0063] FIG. 29A is an SEM image of a serpentine resistor formed by
projected lithography with a beam pen tip array according to the
disclosure herein;
[0064] FIG. 29B is an SEM image of resistors, planar capacitors,
inductors, and surface acoustic wave sensors formed by projected
lithography with a beam pen tip array according to the disclosure
herein;
[0065] FIG. 29C is a graph illustrating the sheet resistance of the
resistors of FIG. 29A;
[0066] FIGS. 30A and 30B are SEM image of dispersed semiconductor
nanowires electrically connected by leads that were formed by
projected lithography with a beam pen tip array according to the
disclosure herein;
[0067] FIG. 31 is an SEM image of a pattern formed by projected
lithography according to the disclosure herein; the pattern is the
phrase "Hello World" written in sixty-four languages with patterns
comprised of 1 .mu.m dots; and
[0068] FIG. 32 is a schematic illustration of conventional beam pen
lithography patterning.
DETAILED DESCRIPTION
[0069] Projected Lithography, for example projected beam pen
lithography (pBPL) or projected lithography using heat actuable tip
arrays, can allow for rapid patterning of sub-100 nm features in
arbitrary arrangements across a cm-scale surface. With pBPL, small
features are generated by directing light through small apertures
at the apexes of pyramidal tips of a beam pen tip array. With
projected lithography using heat actuable tips arrays, light can be
used to activate heaters disposed in proximity to tips to
selectively bring tips of the array into contact with a substrate
for patterning, or selective inking of the tips of the array prior
to patterning.
[0070] Projected lithography utilizes large tip arrays which can be
used to generate large scale, complete images comprising small
features by projecting a series of frames of the image onto the tip
array as it scans across the surface. For example, projected
lithography can advantageously allow for large-scale images to be
generated by raster scanning the tip array across a substrate and
projecting and rapidly changing the frames projected on the tip
array as it raster scans. This allows each point on the substrate
to be addressed by the tip array as it scans across the surface.
Patterning using projected lithography can also advantageously
allow for patterning with variable exposure times (e.g., in
grayscale) in which each pen is capable of writing different sized
features.
[0071] As compared to conventional BPL and other lithography
methods, projected lithography can allow for the patterning of a
macro-pattern comprised of micro-patterns without the need to mask
the entire tip array in the desired macro-pattern or manipulate the
tip array and/or the substrate in the desired micro-pattern. For
example, referring to FIG. 32, with conventional BPL a
macro-pattern in the shape of an "N" or a "U" can be formed with
micro-patterns of "U" by masking the tip array such that the tips
are arranged in the "N" or "U" macro-pattern are selectively
illuminated and then manipulating the tip array or the substrate in
the "U" micro-pattern shape to generate the macro-pattern. Such
masking and manipulation of the tip array can be difficult with
large macro-patterns and complex micro- or macro-patterns. In
contrast, projected lithography allows a base pattern comprising
both the macro- and the micro patterns to be subdivided into
patterning frames and the tips to be selectively illuminated with
an irradiation pattern corresponding to the patterning frame, to
pattern each frame of the base pattern while the tip array scans
across the substrate. For example, projected lithography can allow
for generation of complex patterns while the tip array performs a
simple raster scan across the substrate surface. Projection of the
irradiation patterns corresponding to patterning frames can be
rapidly changed as the tip array is scanned across the substrate to
generate large, complex patterns rapidly and without complex
manipulation of the tip array. This advantageously eliminates the
need to manipulate the tip array and/or the substrate in complex
patterns or perform complex masking of the tips in the form of the
complete image of the macro-pattern.
[0072] In one embodiment, a method for patterning using projected
lithography can include dividing an image into a set of frame
sections and determining a tip irradiation pattern for a respective
portion of an image to be patterned by selected tips of the tip
array in each frame section of the set of frame sections. The tip
array can be positioned in a patterning position in a first
location of the substrate corresponding to the location of the
substrate in which a first frame section in the set of frame
sections is to be patterned. The first frame section is patterned
by projecting a first pattern of radiation onto the tip array to
selectively irradiate one or more tips of the tip array and pattern
the substrate. The first pattern of radiation corresponds to a tip
irradiation pattern for the first frame section. The method can
further include disposing the tip array in a patterning position in
a second location of the substrate corresponding to a location of
the substrate in which the second frame section in the set of frame
sections is to be patterned. The second frame section can be
patterned by projecting a second pattern of radiation onto the tip
array to selectively irradiate tips of the tip array and pattern
the substrate, wherein the second pattern of radiation corresponds
to a tip irradiation pattern for the second frame section. The
positioning and projecting steps can be repeated for each frame
section in the set of frame sections. The tip array can be
positioned in the patterning location by moving the tip array and
holding the substrate still, moving the substrate and holding the
tip array still, or by moving both the tip array and the
substrate.
[0073] In one embodiment of the disclosure, a system for projected
lithography includes a tip array and a projector for projecting an
irradiation pattern onto the tip array to selectively illuminate
(e.g., irradiate) and/or actuate one or more tips of the tip array.
The projector can be communicatively coupled to a computer device
for manipulating the irradiation pattern projected onto the tip
array based on the spatial location of the tip array and the
portion of the image to patterned in that spatial location.
[0074] FIG. 1A illustrates an embodiment of projected lithography
and specifically pBPL. As shown in FIG. 1A, pBPL includes an array
of tips having near-field apertures that are each individually
addressed by a light source. For example, collimated light from a
light source, such as a UV light emitting diode (LED) can be
spatially modulated by micromirrors of a digital micromirror device
(DMD) and directed onto the back of the tip array in registry with
the tips. The light addressing each of the tips can be modulated by
tilting the mirrors in the DMD directed at that tip. Once the light
reaches the tip array, the mechanical compliance of the tips in the
array and the nanoscale size of the apertures in the array allow
the tip array to perform near-field lithography (for example, in
the embodiment illustrated in FIG. 1A) or to selectively actuate
the tips by activating heaters disposed on the tip array, as
described in detail below.
[0075] FIGS. 28 and 31 illustrate examples of complex patterns that
can be advantageously formed using projected lithography.
[0076] In accordance with embodiments of the disclosure, a tip
array having individual addressability of tips provided by
selectively and locally heating the tips of a tip array is
provided. The heat actuable tip arrays can be used alone or in
connection with the pBPL system described herein. As discussed in
detail below, the heat actuable tip arrays include tips disposed on
a common elastomeric tip substrate layer and can be selectively
actuated by selective heating of portions of the elastomeric tip
substrate layer in the region of the tip or tips to be actuated. As
illustrated in FIG. 10A, heating of the tip substrate layer
thermally expands the heated region of the tip substrate layer,
thereby lowering (in the orientation illustrated) the tip disposed
in the heated region relative to tips disposed in an unheated
region of the tip substrate layer. In one type of embodiment,
heaters are disposed on the common substrate layer to provide for
the selective actuation of the tips. In another, non-exclusive type
of embodiment, heaters are disposed on the backs of the tips to
provide for the selective actuation of the tips. Advantageously,
the heaters can be photo-activated heaters, for example, and can
optionally be activated in connection with the projected
lithography system described herein, although non-photo-activated
heaters are also contemplated.
[0077] In any of the patterning methods disclosed herein, it should
be understood that the tip arrays can be intentionally tilted
relative to the substrate, such as is described in International
Patent Publication No. WO 2011/071753.
Projected Lithography System
[0078] Projected pen lithography is a lithography system that may
include a tip array coupled with a projector, for example, a
digital micromirror device (DMD), to direct light to specific
locations on a surface with spatial high resolution. Various
embodiments of tip arrays may be used with projected lithography
including a beam pen lithography tip array and a heat actuated tip
array as described in detail below.
[0079] In a projected lithography system, a tip array may be
combined with a projection system to allow for rapid patterning of
sub-100 nm features in arbitrary arrangements across a large (e.g.,
cm-scale) surface. Some embodiments of projected lithography may
represent a significant advance in capabilities over conventional
tip-based lithography systems. For example, in projected
lithography systems, a projector may allow the substrate to be
patterned in any conceivable pattern, versus conventional
lithography in which typically copies of the same pattern are
written in parallel by all tips. Further, in embodiments in which
the tip array is a beam pen lithography tip array, the size of
features may be controlled through the intensity of light used in
pBPL. Thus, pBPL may allow for different tips in the array to
create different sized features.
[0080] FIG. 1A illustrates a system for projected lithography 100,
though any suitable lithography platform may be used in the systems
and methods described herein (e.g., a Park AFM platform such as a
XEP made by Park Systems Co., Suwon, Korea or platforms made by
NanoInk Inc., Skokie, Ill.). The system 100 may include any number
of computing devices and components that are communicatively
coupled via a network such as the Internet or other type of
networks (e.g., LAN, a MAN, a WAN, a mobile, a wired or wireless
network, a private network, or a virtual private network, etc.).
Each component of the system 100 may include a processor configured
to execute instructions of one or more instruction modules stored
in computer memory.
[0081] The system 100 may combine a tip array 102 on a
translational stage with a light projection system 104 to form a
platform for writing patterns on a surface 106. The tip array 102
may include millions of elastomeric pyramidal tips. It should be
understood herein that radiation sources other than light can be
used with the systems described herein. The use of the term "light"
should be understood to include any suitable wavelength of
radiation and any suitable radiation source unless specified
otherwise. Various types of tips arrays may be used, as described
in detail below. In one embodiment, the projected lithography
system includes a beam pen tip array, which includes tips having a
near field aperture for exposing a substrate with irradiation. The
projected radiation selectively activates the tips of the tip array
by passing through activated tips to expose the substrate. In
another embodiment, the projected lithography system includes a
heat actuated tip array. As discussed in detail below, such tip
arrays include a tip substrate layer having tips extending from a
first surface of the tip substrate layer and an array of heaters
disposed on a second surface opposite the first surface. The
heaters can be photoconductive heaters, which are activated upon
exposure to radiation. In such embodiments, the projected
lithography system projects a pattern of radiation onto the heaters
of the tip array to selectively activate irradiated heaters and
thereby heat the tip substrate layer in the region of the heater
and lower (as shown in the orientation of FIG. 10A) the tip in the
region of the heated tip substrate layer. Methods of patterning
using heat actuation of tips are described in detail below. The
projected lithography system described herein can be used as the
radiation source and control system for the selective activation of
the heaters.
[0082] Various hardware and software components may direct light to
the surface of the tip array 102 at predetermined times in
coordination with scanning, for example, raster scanning, of the
tip array with respect to a surface. The array 102 may include any
of the various embodiments for a tip array as herein described.
[0083] The projected lithography system 100 can utilize a modified
Park Systems XE-150 Scanning probe platform. The tip array 102 may
be magnetically mounted on a scanner head 108. The head 108 may
include a square frame with a 1.times.1 cm.sup.2 aperture to allow
optical addressing of each tip in the array 102. The scanner head
108 may be vertically (z-direction) positioned by a piezoelectric
driver on the head. Samples for lithography may be held on a vacuum
chuck on a stage 110 below the head which may be positioned in X
and Y dimensions with stepper motors for coarse positioning and
piezoelectric scanners for fine positioning. Additionally, the
sample may be rotated with stepper motors (roll and pitch) to level
the sample with respect to the beam tip array 102. A digital
micromirror device (DMD-DLP LightCommander-Logic PD) 112 can allow
the system 100 to project spatial patterns onto the tip array 102.
A collimated light source 114 (e.g., a collimated 440 mW 405 nm LED
light source such as a M405L2 made by Thor Labs USA) may be used in
conjunction with a digital light processing projector (DLP) with a
macro lens (e.g., AF Micro-Nikkor 200 mm f/4D IF-ED) 116 to focus
an image generated by the DMD 112 onto the surface of the beam tip
array 102. The image projected by the DMD 112 onto the surface of
the tip array 102 may be controlled by a first computer 118
including a processor 118a and memory 118b. In some embodiments,
the processor 118a executes instructions stored in the memory 118b.
For example, the instructions may include custom software written
in a technical computing language (e.g., MATLAB, The Mathworks
Inc.). Alignment between the projected image and the tip array 102
may be monitored by a camera 120 (e.g., a digital camera such as a
CCD camera like the PLB782 made by PixeLINK). This alignment may be
adjusted using an interface (e.g., a MATLAB interface executing on
the first computer 118). During printing, the motion of a scanning
probe microscope 122 (e.g., a Park XE-150) may be controlled by a
second computer 124 including a processor 124a and memory 124b that
stores scanning probe software instructions for execution using the
processor 124a. The state of the projector 116 may be controlled by
the first computer 118. To coordinate the actions of the first
computer 118 and the second computer 124, the first computer 118
may monitor the voltage supplied to the z-piezo through a data
acquisition module (DAQ) 126 (e.g., a NI-USB 6212). As described
herein, arbitrary patterns may be created by projecting a series of
images as the scanning probe instrument scans across the surface to
be patterned.
[0084] In another embodiment, the system 100 may include a Zeiss
microscope with a light source having a wavelength in a range of
about 360 nm to about 450 nm. Movement of the tip array 102 when
using the Zeiss microscope may be controlled, for example, by the
microscope stage 108.
[0085] In various embodiments, the projector 116 includes the DMD
112 and the macro lens 116a for focusing the irradiation pattern
emitted by the DMD 112 onto the tip array 102. The digital
micromirror device can include any commercially available device
having a suitable radiation source for the desired patterning.
Historically, photolithography has used ultraviolet light from
gas-discharge lamps using mercury, sometimes in combination with
noble gases such as xenon. These lamps produce light across a broad
spectrum with several strong peaks in the ultraviolet range. This
spectrum is filtered to select a single spectral line, for example
the "g-line" (436 nm) or "i-line" (365 nm). More recently,
lithography has moved to "deep ultraviolet," for example
wavelengths below 300 nm, which can be produced by excimer lasers.
Krypton fluoride produces a 248-nm spectral line, and argon
fluoride a 193-nm line. In principle, the type of radiation used
with the present apparatus and methods is not limited. One
practical consideration is compatibility with the tip array 102
materials chosen and the digital micromirror device. For example,
the radiation can be in the wavelength range of about 300 nm to
about 600 nm. For example, the radiation optionally can have a
minimum wavelength of about 300, 350, 400, 450, 500, 550, or 600
nm. For example, the radiation optionally can have a maximum
wavelength of about 300, 350, 400, 450, 500, 550, or 600 nm. In
some embodiments, the wavelength can be greater than 400 nm to
avoid damage to a digital micromirror device 112. For example, the
wavelength can be about 405 nm. An exemplary commercially available
digital micromirror device 102 is the DLP5500 (Texas instruments).
In various embodiments, the commercially provided light source can
be replaced with a collimated 440 mW 405 nm LED light source
(M405L2--Thor Labs USA). The digital micromirror device DLP550 chip
is a 0.55'' chip with 10.8 .mu.m pitch pixels with XGA resolutions
(1024/758 independent pixels).
[0086] Any commercially available lens having a suitable minimum
focal length, for example, of about one foot, can be used for the
macro lens 116a. Nikon f-mount lens, such as 105 mm f/2.8 G ED-IF
AF-S VR Micro-Nikkor Lens (Nikon), are exemplary commercially
available lenses suitable for use in pBPL. In various embodiments,
a macro lens 116a having an adjustable focal length is used. The
macro lens 116a can be used to selectively allow the light from
multiple mirrors of the digital micromirror device 112 to be
focused onto a single pen of the tip array, and thus adjust the
intensity. Selection of the focal length of the macro lens 116a in
combination with the distance between the tip array 102 and the
lens 116a can be used to tailor the number of mirrors that focus
light on a single pen. For example, the ratio of mirrors focusing
light onto a pen can be in a range of about 1:1 to about 100:1,
about 10:1 to about 90:1, about 20:1 to about 80:1, about 30:1 to
about 70:1, about 40:1 to about 60:1, about 50:1 to about 75:1, 1:1
to about 40:1, about 5:1 to about 35:1, about 10:1 to about 30:1,
and about 15:1 to about 25:1. Other suitable ratios include, for
example, about 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1,
45:1, 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, 80:1, 85:1, 90:1, 95:1,
and 100:1.
Methods of Patterning using Projected Lithography
[0087] While the system 100 illustrated in FIG. 1A may include one
or more instruction modules stored in the memory 118b for execution
by the processor 118a of the first computer 118, some or all of the
components and functions of the system 100 described herein may
also be incorporated on the second computer 124, the controller
104, the DAQ 126, etc. Further, any instruction module of the
system 100 may be implemented as a separate module or system.
[0088] The irradiation pattern projected by the projector 116 can
be controlled using the first computer 118 including computer
software executed by the processor 118a and stored in the memory
118b to interface with the control system of the lithography system
100. In some embodiments, the system 100 may execute instructions
for alignment and then execute a lithography printing process.
Hardware Alignment of the Projector and Tip Array
[0089] The projector and the tip array can be aligned by
positioning the projector, for example, a digital mirror device, a
suitable distance from the tip array. In various embodiments, the
distance is substantially equal to the focal length of a macro lens
of the projector.
[0090] The macro lens, the digital mirror device, and optionally a
beam splitter can be aligned in a generally parallel plane. For
example, alignment can be achieved using an optical breadboard in
which the holes of the optical breadboard are utilized to achieve
parallel alignment. A test pattern, for example, a pattern of dots,
can be projected from the projector (for example, the digital
mirror device) onto a back plane of the tip array. When a beam
splitter is used, a camera can be focused to observe the back plane
of the tip array through the beam splitter. The position of the
digital mirror device can then be adjusted to center the test
pattern on the tip array.
[0091] In embodiments utilizing a beam splitter, the position of
the beam splitter can be adjusted until a roughly focused
irradiation pattern is observed, for example, by a camera focused
on the beam splitter.
[0092] The focal length of the macro lens can then be adjusted
until the edge of the test pattern is sharp and clearly observed by
a camera, if used. In various embodiments, the focal length of the
macro lens can be adjusted to selectively adjust the number of
mirrors focusing irradiation on a single pen of the tip array. For
example, about 1 to about 50 mirrors can focus irradiation on a
single pen. Other examples of the number of mirrors that can focus
irradiation on a single pen include a range of about 2 to about 45,
about 4 to about 40, about 6 to about 35, about 8 to about 30,
about 10 to about 25, about 12 to about 20, and about 14 to about
18. For example, about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
48, 49, or 50 tips can focus irradiation onto a single pen.
[0093] The test pattern can then be checked for distortion across
the entire tip array to ensure that the focal plane of the macro
lens is parallel to the plane of the tip array.
[0094] FIG. 2A illustrates an alignment user interface 200 and FIG.
2B illustrates a block diagram of a method 250 for aligning the
system 100 for executing a lithography printing process. As
described below, the user interface 200 may facilitate execution of
other instructions stored in the memory 118b to complete the
alignment.
[0095] The method 250 may include one or more blocks, modules,
functions, or routines in the form of computer-executable
instructions that are stored in a tangible computer-readable medium
and executed using a processor (e.g., processor 118a) of a
computing device (e.g., the first computing device 118). The
methods may be included as part of any modules of a computing
environment for the lithography system 100, or as part of a module
that is external to such a system. For example, the methods may be
part of the second computer 124, the controller 104, an AFM 122, a
DAQ 126, or other system component. FIGS. 2a and 2b will be
described with reference to other figures for ease of explanation,
but the methods may of course be utilized with other objects and
user interfaces.
[0096] Alignment between the light projected from the projector 116
and the beam tip array 102 is necessary to achieve individual
addressability of each tip in the array. Since the DMD 112 is not
transparent and designed to redirect light at a specific angle of
incidence, it cannot be directly attached to the tip array 102. In
some embodiments, the DMD 112 may be positioned in a far field
projection mode where focusing optics reproduce an image directed
by the projector 116 on the surface of the DMD 112 on a distant
object. With a combination of optical and software adjustments, the
alignment process may ensure that the pattern generated by the DMD
is reproduced in focus and in the correct location of the beam tip
array 102.
[0097] With reference to FIG. 2B, at block 252, a light pattern
generated by the DMD may be focused on the plane of tip array 102
with minimum distortion. In one embodiment, a lens with a minimum
focal length of twelve inches (30.5 cm) may be employed to focus
the light from the DMD. At block 254, the light pattern may be
guided onto the scanning probe platform and reflected onto the beam
tip array by a beam splitter. Generally, the distance between lens
116a and tip array 102 should be identical to the focal length of
the lens 116a and the focal plane of the light pattern needs to be
parallel to the plane of tip array 102, otherwise only part of the
tip array 102 will be in focus. To accomplish this manual
adjustment, at block 256, the light pattern on the tip array 102
may be monitored by the camera 120.
[0098] FIG. 2C illustrates one method 275 for monitoring the light
pattern using the camera 120. At block 276, the DMD 112 may be
positioned a fixed distance from a head of the scanning probe
microscope 122. In some embodiments, the method 275 may position
the DMD ten inches (25.4 cm) from the scanning probe head. At block
278, the method 275 may align the center lens 116a, a beam
splitter, and a mirror 128. In some embodiments, block 278 may
include instructions to use a rectangular array of holes in the
optical breadboard of the microscope 122 as a starting point. At
block 278, the method may display a test pattern with the projector
116 and use the visible light to fine tune this alignment. At block
280, the method may fine tune the alignment by engaging the camera
120 to observe the back plane of tip array 102 through a beam
splitter. At block 282, the method 275 may focus the camera until a
clear image of the tips of the tip array is observed. At block 284,
the method may adjust the position of DMD 112 in both horizontal
and vertical direction to make sure the light pattern is centered
on the tip array 102. In some embodiments, the position of the DMD
may be adjusted with finely adjustable mechanical standings. At
block 286, the method may adjust the position of the beam splitter
until a roughly focused light pattern is observed by the camera and
at block 288, the method may adjust the focal length of the
projector lens until the edge of light pattern is sharp and clearly
observed by the camera. At block 289, the method may check the
distortion of light pattern across the whole beam array to make
sure the focal plane of lens is parallel to the plane of tip array.
If the pattern is out of focus, the method may repeat blocks
282-288 until the pattern is as crisp as possible.
Software Alignment of the Projected Image and the Tip Array
[0099] Referring to FIG. 2E, the projected image and coordination
of the software program controlling the projection of the
irradiation patterns can be aligned using a checkerboard
irradiation test pattern. A first test pattern can be projected
onto the tip array. For example, the first test pattern can be a
checkerboard pattern. The first test pattern has a large ratio of
L/N, such that each illuminated region of the test pattern contains
at least a 5.times.5 array of tips (FIG. 2E, left and center
images). N refers to the number of tips on an edge of the test
pattern and L is the number of mirrors on an edge of the test
pattern. The ratio L/N describes how many mirrors address each tip.
N2 is the total number of tips in the test pattern. For example, in
a checkerboard test pattern, N2 is the total number of tips in a
single illuminated square. L2 is the total number of mirrors in the
illuminated portion of the test pattern, for example an illuminated
square of a checkerboard test pattern. The arrangement of the tips
of the tip array in the test pattern is observed, for example,
using a camera focused on a beam splitter, to determine whether any
of the tips in the illuminated square region cross an edge of the
square region. If one or more tips cross the illuminated square
region, the test pattern is rotated until the tips are aligned
along the edge of the illuminated square region. Rotation of the
test pattern accounts for any rotation of the tip array. Once
rotational alignment of the first test pattern and the tips of the
tip array is achieved, a second test pattern, for example, a
checkerboard test pattern, is projected onto the tip array. The
second checkerboard test pattern has an increased N value such that
a single pen is in a single illuminated square of the second test
pattern (FIG. 2E, right image). For example, where the first test
pattern is selected such that each illuminated square of the test
pattern contains a 5.times.5 array of tips, the second test pattern
is selected to have a value of 5N, while maintaining the same L
value of the first test pattern. The second checkerboard pattern is
then observed on the tip array, for example using a camera through
a beam splitter, and the second test pattern is adjusted in the x
and y directions to center each pen in the illuminated square,
thereby aligning the projected pattern with the tip array. The
rotational and translational adjustments made to align the test
patterns are maintained within the software program, which utilizes
such values when projecting irradiation patterns for patterning a
substrate to ensure alignment of the projected irradiation pattern
and the tip array.
[0100] FIG. 2D illustrates a block diagram of a method 290 to
further align the system 100 for executing a lithography printing
process. While method 275 aligns the optical hardware 104 to the
tip array 102, there may still be no registry between the tips in
the array and the pixels in the DMD 112. Thus, the method 290
generally adjusts the parameters of the DMD 112. With reference to
FIG. 2A, a checker board pattern image 202 may be displayed on the
projector 116. The size, orientation, and position of the image 202
may be adjusted in software until the projected image matches the
tips in the array 102. For example, "X" 204 and "Y" 206 may
determine the center of the checker board; "Rotation" 208 may allow
for compensation if the beam tip array is slightly rotated, "L" 210
may include the edge length of the board counted as mirrors in the
DMD while "N" 212 may include the edge length of the board in tips
on the tip array. "L/N" may give the period of the checker board,
and also dictates how many mirrors direct light to each pen.
Mirrors in the DMD are grouped in this way by the method 290 to
achieve one to one correspondence with the BPL tips. To tune this
alignment, the method 290 may monitor the image 202 projected on
the surface of the beam tip array 102.
[0101] At block 291, the rotational mismatch is the first parameter
to be tuned. A large value of L/N may be selected so that more than
5.times.5 tips are located in one square. By checking across the
tip array 102, the method 290 may determine if any row or column of
tips crosses the edge of square. If they do, the rotational angle
needs to be adjusted. A value of the Rotation 208 may be changed to
ensure the light pattern is finally in the same rotational angle of
the tip array. At block 292, the method may adjust the L value 210
and the N value 212 to approach a coarse value of L and N.
[0102] In some embodiments, the values are adjusted to have
5.times.5 tips in each square. At block 293, the method may adjust
the X value 204 and the Y value 206 to center the tips in the
squares. At block 294, the N value 212 may be changed to the number
reflecting the number of tips in each square. In some embodiments,
the method adjusts the N value to five. At block 295, the method
may further adjust X and Y values slightly to make sure each pen is
in the center of each square. At block 296, the method may check
all the tips across the whole array to see if any mismatches still
exist. If mismatches still exist, then the method 290 may return to
block 291. If not, then the alignment process may end. At the
completion of the method 290, the optical path is aligned and the
correspondence between mirrors in the DMD and tips in the tip array
is saved in the system (e.g., memory 118b, 124b). With reference to
FIG. 3, instructions stored in the memory 118b may cause the
processor 118a to display a user interface 300 on the first
computer 118. As described below, the user interface 300 may
facilitate execution of other module instructions to complete the
lithography process using the system 100.
[0103] FIG. 4 is a flow diagram of example a method 400 for
completing a lithography process using the system 100. The method
may include one or more blocks, modules, functions, or routines in
the form of computer-executable instructions that are stored in a
tangible computer-readable medium (e.g., memory 118b) and executed
using a processor (e.g., processor 118a) of a computing device
(e.g., the first computing device 118). The method may be included
as part of any modules of a computing environment for the
lithography system 100, or as part of a module that is external to
such a system. FIG. 4 will be described with reference to other
figures for ease of explanation, but the method 400 may of course
be utilized with other objects and user interfaces.
[0104] At block 402, a module stored in the memory 118b may cause
the processor 118a to subdivide a selected image 302 to be
patterned on substrate into geometric sections (also referred to
herein as "frames"). The geometric sections can have substantially
the same size and shape as the tip array 102. For example, where
the tip array has tips generally arranged in a rectangle or square,
the frame section can be correspondingly shaped in a rectangle or a
square. Other frame section shapes, including, hexagonal and
triangular, can be used where the tips are arranged in such shapes
on the tip array. The image 302 can be divided into any suitable
number of geometric sections such that each pixel of the image is
addressed by a tip of the array 102 in a geometric section. The
geometric sections can optionally overlap such that pixels having
spacing of less than the tip pitch, and thus not addressable by a
tip in a first geometric section, can be addressed by a tip in a
second, overlapping geometric section.
[0105] Once the image is divided into the geometric sections, block
404 may cause the processor 118a to execute an instruction stored
in the memory 118b to determine a tip pattern for each geometric
section. The tip pattern corresponds to the portion of the image
302 to be patterned by the tips of the tip array in a given
geometric section. Determination of the tip pattern can include
determining which tips will be selectively illuminated to pattern
the portion of the image 302 in the geometric shape and optionally
the intensity of the radiation that will be supplied to each tip
that is selectively illuminated. For example, within a given tip
pattern radiation directed to one or more tips can be selectively
modulated during patterning to allow for patterning in with
variable intensity (e.g. "grayscale" 304), whereby tips of the tip
array are capable of patterning different sized features in a
single printing operation.
[0106] At block 406, the method 400 may generate an instruction
file for the tip array system 100. The instruction file may include
further instructions to control movement of the tip array across
the substrate to each geometric section. The instruction file can
further dictate to the tip array system the allotted time for each
patterning operation in given geometric section, as well as the
travel time of the tip array between geometric sections. For
example, the user interface 300 may receive a desired patterning or
exposure time 306, a safety time 308 to ensure patterning is
complete and the tip array is no longer illuminated before the tip
array is moved to the next geometric section. The safety time 308
may avoid patterning contamination during movement of the tip
array. In embodiments, the safety time 308 can be zero, if no delay
is needed. Additionally, the interface 300 may receive a delay time
310, which may ensure that the tip array is in position for
patterning prior to illumination of the tip array. For example, the
instruction file may include instructions to cause the system 100
to maintain a tip array in a given geometric section for a time
equal to the sum of the delay time 310, the patterning or exposure
time 306, and the safety time 308. By generating the instruction
file for instruction movement of the tip array 102, the location of
the tip array is known and predictable such that a given pattern of
radiation can be generated by the projector 116 to selectively
illuminate the tip array in a given tip pattern for a given
geometric section.
[0107] In one exemplary patterning operation, at block 408, the
system 100 can manipulate the tip array 100 to a first geometric
section and lower the tip array into a patterning position. For
example, block 408 may cause the tip array to be lowered adjacent
to the substrate, but not contacting the substrate or can be
contacting the substrate at a selected degree of pressure,
depending on the desired feature size. At block 410, the method may
detect a z-piezo voltage of the tip array 102. The z-piezo voltage
may indicate a vertical position of the tip array 102 relative to
the substrate 106. Once a threshold voltage is detected, block 412
may cause the system 100 to wait a set delay time 310 before, at
block 414, causing the projector 116 to project the a first pattern
of radiation to selectively illuminate the tip array 102 and expose
the substrate 106 in a first tip pattern corresponding to the
portion of the image to be patterned in the first geometric
section. The threshold voltage is indicative of the tip array being
in the patterning position. Selective illumination of the tip array
102 results in exposure of the substrate in the first tip pattern.
After lapse of a set exposure or patterning time, at block 416, the
method 400 may cause the projector 116 to cease projection of any
radiation into the tip array. At block 418, the method 400 may
cause the tip array to be maintained in the first geometric section
for a set safety time 308 before, at block 420, determining if
other sections require patterning. If so, then the method 400 may
return to block 408 and cause the array 102 to be lifted away from
the substrate and moved to a second geometric section. Once at the
second geometric section, the tip array is again lowered into a
patterning position, generating a threshold voltage for detection
by the program. Once the threshold voltage is again detected, the
program instructs the projector to project a second pattern of
radiation to selectively illumination the tip array and expose the
substrate in a second tip pattern corresponding to the portion of
the image to be patterned in the second geometric section. This
process can be repeated until each geometric section has been
addressed by the tip array and the method 400 ends. As the person
of ordinary skill in the art will appreciate, if patterning is
performed without the array touching the substrate, then the
raising and lowering of the array may be unnecessary, and the
method can omit such steps.
[0108] In some embodiments, the system 100 may include
thermally-actuated tip array. With reference to FIG. 5, a system
500 may include a power amp 502 to provide a voltage to heaters at
the tip array 504. For example, projecting the a pattern of
radiation (as described above in FIGS. 1-4 and the accompanying
text) may selectively expose the heaters to such radiation to
selectively activate the exposed heaters to locally heat a heating
zone of the tip substrate layer and lower (as pictured) one or more
tips disposed in the heating zone into contact or closer contact
with the substrate, as further described below.
[0109] The pattern of radiation projected by the projector can
include selective illumination of the tips of the tip array, as
well as selection of the dose of radiation illuminating each tip.
For example, the projector 116 can include a digital micromirror
device 112, in which one or more mirrors selectively illuminate a
tip and such mirrors can be actuated at a given rate or duty cycle
to control the dose of the radiation illuminating a given tip. Such
control can allow for the patterning in "grayscale" in which
different tips are capable of patterning different feature sizes in
a single patterning operation and with the tip array being oriented
level with respect to the substrate. In various embodiments, the
instruction file can further include instructions for tilting the
tip array for generation of varying features sizes in given
geometric section by patterning with the tilted array.
Thermal Actuation of Tips of the Tip Arrays
[0110] In various embodiments of the disclosure, a tip array having
a plurality of tips disposed on a common elastomeric tip substrate
layer can be selectively actuated by selective heating portions of
the elastomeric tip substrate layer in the region of the tip or
tips to be actuated. As illustrated in FIG. 10A, heating of the tip
substrate layer thermally expands the heated region of the tip
substrate layer, thereby lowering (in the orientation pictured) the
tip disposed in the heated region relative to tips disposed in an
unheated region of the tip substrate layer. Individual actuation
can advantageously allow the tip arrays to print continuous
patterns over cm-scales, print independent patterns with different
patterning compositions, and/or use different dwell times and
extensions for different tips to print different size features with
different tips of the tip array. Individual actuation can also
allow for simple and rapid selective inking of tips of a tip array
with one or more patterning compositions.
[0111] In accordance with an embodiment of the disclosure, the tip
arrays generally include an array of heaters disposed on a second
surface of the tip substrate layer opposite the first surface
having the tips. The one or more heaters of the array can be
selectively activated to locally heat a region of the tip substrate
layer and lower the tip or tips located in the heated region as
compared to the tips located in a region of the tip substrate layer
that remains unheated. For example, the method of selectively
actuating a tip array using heat can include leveling the tip array
relative to the substrate. Optical and force feedback leveling
methods can be used as is known in the art. In an embodiment, the
tips of the tip array can be held a distance above the substrate,
for example, a few micrometers away from the substrate. The
activation of the heater can then be used to selectively bring each
tip or a region of tips into contact with the substrate. In another
embodiment, the tips of the tip array can be placed into contact
with the substrate. Activation of one or more heaters can be used
to selectively bring each tip or a region of tips into closer
contact with the substrate, thereby forming pattern features of
different sizes by relying on the force dependent nature of feature
size when patterning with the various tips.
[0112] The tip array generally includes a tip substrate layer
comprising a first surface and an oppositely disposed second
surface. A variety of tip array systems including polymer pen tip
arrays, beam pen tip arrays, hard tip soft spring arrays (also
referred to herein as silicon pen tip arrays), a graphene coated
tip arrays are described in detail below. Each of these tip arrays
can be modified to include a heater disposed on the tip substrate
layer to achieve thermal actuation of the tips in accordance with
embodiments of the disclosure. In each of the various types of tip
arrays, for purposes of thermal actuation the tip substrate layer
is formed of an elastomeric material capable of thermally expanding
when heated. The tip substrate layer can be selected to have a high
coefficient of thermal expansion, for example, about 10.sup.-4 per
degree Kelvin, which allows a tip to be actuated a significant
distance upon localized heating of the tip substrate layer. PDMS
has a coefficient of thermal expansion of about 3.times.10.sup.-4
per degree Kelvin. Additionally, the small volume of material in
the locally heated region of the substrate layer allows the
material to be rapidly heated and cooled. The tip substrate layer
can also be an elastomeric material having a low thermal
conductivity, such as PDMS. Using low thermal conductivity
materials can allow the heat generated by the heater to be
localized in the tip substrate layer. Additionally, by virtue of
the elastomeric nature of the materials, once the heat dissipates
from the material, the thermally expanded material will recover,
returning to its original non-expanded form, thereby raising the
selectively actuated tip.
[0113] The tip array further includes a plurality of tips fixed to
the first surface of the tip substrate layer and having a tip end
disposed opposite the first surface of the tip substrate layer. A
detailed description of the tips of various suitable tip arrays is
provided below.
[0114] One or more heaters are disposed on the second surface of
the tip substrate layer. For example, the heaters can be disposed
on a support layer, and between the support layer and the tip
substrate layer. In one embodiment, the tip array includes a
plurality of heaters such that a single heater is disposed above
each tip of the tip array. For example, FIG. 10C illustrates an
embodiment in which a single heater corresponds to each single tip
of the tip array. In another embodiment, the tip array can include
one or more heaters disposed in a zone of the tip substrate layer
corresponding to a heating zone that includes a subset of the tips
of the tips array. Any suitable number of tips can be included in
the subset of tips. In such an arrangement, activation of a heater
can result in the actuation of the subset of tips of the tip
array.
[0115] In an embodiment, the heater in a zone can be adapted to
heat the zone in a gradient fashion such that regions of the tip
substrate layer in the zone disposed nearest the heater exhibit
increased thermal expansion as compared to regions of the tip
substrate in the zone disposed away from the heater. This, in turn,
can result in a gradient of lowering of the tips disposed in the
zone. A tip array can be divided into any suitable number of zones
having any number of tips in each zone. The zones can each include
the same or a different number of tips depending on the
application.
[0116] Actuation of the heaters can be controlled, for example, by
wiring each heater directly to an electronic switch. For example, a
distinct wire can be connected to the heater of each tip or each
heating zone and an electrical control can be used to activate the
heaters selectively. The heaters can be formed of indium tin oxide
(ITO), graphene, poly(3,4-ethylenedioxythiophene) (PEDOT), gold,
copper, platinum, and combinations thereof.
[0117] As described in detail below, a control system can be used
to control actuation of the tips. In another embodiment, active
memory elements can be fabricated on the same substrate as the tip
array. Using such a memory system, the state of the entire array
can be loaded using fewer wires by dividing the signal in time. In
some embodiments, the tip array need not remain translucent
allowing for increased flexibility in heater material and the
application of such memory systems. In such embodiments, the tip
array can be leveled by force feedback leveling as known in the
art.
[0118] Alternatively, the heaters can be made out of a
photoconductive material that can be activated by irradiating the
heater with an irradiation source, for example, visible and/or UV
light. Photoconductive materials experience a dramatic change in
electrical conductivity in response to irradiation. For example,
the irradiation can cause the electrical conductivity of the heater
to increase, thereby allowing the heater to heat. A voltage can be
applied across the photoconductive heaters, which act as a
radiation-controlled electrical switch that only allows the current
will only flow if irradiation is applied. In this way, the
irradiation can be used to select which heater is activated while
the power for heating is supplied electrically using only two wires
for a much simpler array design. Any suitable photoconductive
material can be used. If optical leveling is utilized, the
photoconductive material is preferably translucent, and more
preferably transparent. Suitable materials include, for example,
amorphous hydrogenated silicon, zinc oxide, graphene, CdS, CdSe,
ZnS, ZnSe, PbS, SnS, Bi.sub.2S.sub.3, Bi.sub.2Se.sub.3,
Sb.sub.2S.sub.3, CuS, CuSe. Each of these materials can achieve a
ratio of illuminated to dark conductivity, for example, of over
10.sup.2.
[0119] In one embodiment, the heat actuation tip array can include
multiple photoconductive heaters, the heaters being activated at
different wavelengths. The heaters can be selectively activated by
controlling various irradiation sources having wavelengths for
selectively activating only certain heaters. This can
advantageously be used to allow for general irradiation of a tip
array with an irradiation having a wavelength for only a subset of
the heaters, thereby allowing for selective actuation without
selective irradiation. In other embodiments, the tip array can be
selectively actuated by selectively irradiating photoconductive
heaters. For example, the tip arrays can further include an array
of spatial light modulators disposed on the tip substrate layer to
selectively expose a heater to allow for selective irradiation of
the heaters. The spatial light modulators can be, for example,
dynamically controllable. In another embodiment, as described in
detail below, the heat actuation tip arrays can be used in
connection with the projected lithography system and irradiation
images can be projected onto the heaters of the tip array to active
the heaters and selectively actuate the tips. In one embodiment,
tip array is a beam pen tip array that includes an array of heaters
for selectively actuating the beam pen tips. In such embodiments,
the wavelength for activating the heaters and for patterning (i.e.,
exposure of the substrate) can be the same or can be different
wavelengths. For example, in one embodiment, the beam pen tip array
can be placed in a patterning position not in contact with the
substrate. A radiation source for patterning can be focused on the
tip array and an radiation source for activating the heaters can be
used in connection with the projected lithography and projected
onto the heaters in patterns of radiation for selectively actuation
the tips to be in contact or near-field contact with the tip array,
thereby activating the tip to expose the substrate. In the
patterning position, the tips are disposed at a distance at which
exposure does not occur, despite the tips being illuminated. Thus,
it is upon selective actuation of the tips by the activation of a
heater that the tips are activated for patterning.
[0120] FIG. 15 illustrates a comparison of the heaters using the
direct wire (FIG. 15A) and the photoconductive (FIG. 15B)
embodiments. While the electrical actuation scheme incorporates a
coil heater that is switched on an off by a transistor, in the
photo-active scheme, incident irradiation increases the electrical
conductivity of a photoconductive disc which functions both as the
heater and as the switch.
[0121] Any suitable heaters can be used. For example, the heaters
can be resistive heaters or photoconductive heaters. In various
embodiments the heaters are substantially transparent. By providing
substantially transparent heaters, the tip arrays can be optically
leveled as is known the art. Optical leveling is described, for
example, in U.S. Patent Application Publication No. 2011/0132220,
the entire disclosure of which is incorporated herein by reference.
In alternative embodiments, the heaters are opaque. In such
embodiments, the tip arrays can be leveled using force feedback
leveling, as is known in the art. Force feedback leveling is
described, for example, in U.S. Patent Application Publication No.
2011/0165329.
[0122] An example of a printed pattern is shown in FIG. 14. Here,
the pattern was formed by inking the tips in a solution of
16-mercaptohexadecanoic acid (MHA) in ethanol. The tips were then
used to generate a pattern corresponding to a region of the
periodic table of the elements. MHA transfers to the gold surface,
forming a self-assembled monolayer which protects patterned regions
from a chemical etch that is selective for gold. Final patterns
were visualized by scanning electron microscopy. In the 4.times.4
actuation scheme presented here, each probe was actuated in series,
meaning there is never a time when two tips are simultaneously
lowered into contact with the substrate. Selectively lowering only
one tip at a time can be used mitigate crosstalk between tips. In
alternative embodiments, multiple tips can be selectively lowered
at the same time.
[0123] Mitigating crosstalk or interference with selection of the
tips can be achieved by examining the heat profile of the heaters
and dividing the tip array in to sub-grids accordingly.
Interference can be mitigated by only simultaneously activating
sub-grid regions that do not have overlapping heat profiles. For
example, based on the characterization of thermal actuation
presented in FIG. 12D, this can be achieved conservatively by
dividing up the array into 9 sub-grids that are all addressed in
sequence. This presents a good compromise between throughput and
protection against crosstalk.
[0124] In accordance with embodiments of the disclosure, a tip
array having an array of heaters can be manufactured by defining
the heaters on a substrate, coating the substrate with an
elastomeric material layer, defining tip masks that are aligned to
the heaters on the substrate, and etching the tip masks to form the
tips. In an embodiment in which the tip array is a silicon tip
array, the method can include defining heaters on a substrate,
coating the substrate with an elastomeric material and a thin
silicon wafer, defining tip masks in the silicon wafer that are
aligned with the heaters on the substrate, and etching the tip
masks to form the silicon tip arrays having heaters disposed on the
tip substrate layer.
[0125] Heaters can be fabricated, for example of indium tin oxide
(ITO) by etching an ITO coated glass slide. ITO is transparent and
conductive. 25.times.25 mm.sup.2 glass slides coated with 8 to 12
.OMEGA./sq are commercially available from Sigma Aldrich. The
coated slides can be cleaned, for example, by rinsing in acetone,
DI water, and isopropanol. The samples can be dried, for example,
under nitrogen, and then coated with a photoresist material. For
example, a positive tone photoresist material such as SHIPLEY1805
can be used and can be spin coated at 4000 rpm for 40 seconds and
then baked for 1 min at 115.degree. C. Any suitable positive or
negative tone photoresist can be used and any suitable coating
method can be used as is known in the art. Samples can be aligned
in a mask aligner and then exposed for a sufficient time, for
example 2 seconds, and optionally post-exposure baked for about 1
minute at 115.degree. C. Patterns can then be developed in a
suitable developer, for example MF-24A (Shipley) for a suitable
time, for example, about 60 seconds and then rinsed and dried.
Rinsing can be done using DI water and drying can be done using
nitrogen.
[0126] The heater material can be etched using any suitable etching
method. For example, ITO can be etched using reactive ion etching.
For example, samples can be mounted on a 4'' wafer and loaded into
a deep reactive ion etch apparatus such as a DRIE-STS Lpx Pegasus.
The samples can be etched under 200 sccm of Argon that is held at 5
mTorr using 2500 W RF power and 40 W delivered to the platen. Under
these conditions, the etch rate of ITO is approximately 1 .ANG./s.
The completion of the etch can be verified using a multimeter to
measure the background resistance and the resistance of the
devices. To remove the residual resist, the samples can be soaked
in a suitable remover or cleaning solution, such as Remover PG
(Microchem). Heating can optionally be used to facilitate resist
removal. For example, removal can be done by soaking in a suitable
remover or cleaning solution at an elevated temperature, for
example, 80.degree. C. FIG. 10C is a scanning electron microscopy
image of a heater fabricated by the foregoing process, which
illustrates a 4.times.4 array of coil heaters and associated bus
lines.
[0127] Once heaters are formed, the fabrication of the tip arrays
can be generally in accordance with known methods of forming the
various tip arrays, but using the substrate having the heaters
thereon as the support layer onto which the tip array is
formed.
[0128] FIG. 13A illustrates an embodiment in which heat actuation
of a tip array is used to generate a continuous pattern across the
entire substrate. In accordance with an embodiment, heat actuation
of tip arrays can be used to pattern multiple patterns such that
each patterning region of the substrate is addressable by the tips.
For example, the tips can be inked with different patterning
compositions (also referred to herein as "inks") such that each
region of the substrate can be addressed by each ink. Referring to
FIG. 13B, for example, a tip array can be scanned such that each
region of the substrate can be accessed by not only the closest
tip, but also by the neighboring tips of the tip array. The image
of FIG. 13B was generated using a tip array having tips with a 150
.mu.m pitch and a piezoelectric scan range of 400 .mu.m was used.
Different inks can be applied to different tips, then repeating
patterns of up to nine (in this example) different inks can be
applied such that each region can still be addressed by a tip with
each ink. In FIG. 13B, four tips of different colors were used to
write overlapping patterns. This technique can be of particular use
when patterning biomolecules with orthogonal chemistries for
combinatorial screening or diagnostics is important.
[0129] In order to ink the tips independently, a Perkin Elmer
Piezoarray microarraying system can be used. This equipment can
print droplets as small as 333 pL, which corresponds to a width of
about 7 .mu.m, and pattern them with micrometer-scale accuracy and
registration. Using this instrument, multiple varieties of ink can
be directly deposited on the tip in a regular repeating fashion to
create a multiplexed multi-ink patterning system.
[0130] In an alternative embodiment, the tip array can be
independently inked by selectively actuating the tips using the
heat actuation system into contact with one or more ink sources to
thereby dip-coat the tips with the selected inks.
[0131] In yet another embodiment, an inking well can be formed
using the master used to form the tip array. An ink or multiple
inks can be inserted into the wells of the tips to ink the tips
with a single ink or selectively ink the tips with multiple
different inks. Any other suitable inking methods can also be
used.
[0132] FIG. 6 illustrates one example of a thermally-activated
lithography system 600. With reference to FIG. 6, one embodiment of
a thermally-activated lithography system 600 may include a control
computer 604 including a processor 604a and memory 604b
communicatively coupled to an atomic force microscopy (AFM)
controller 606. The controller 606 may be communicatively coupled
to an atomic force microscope (AFM) 608 such as, for example, the
XE-150 AFM produced by Park Systems of Santa Clara, Calif. The AFM
may include a tip array 602 (e.g., a hard-tip array) including a
plurality of tips for implementing the various lithography
processes described herein, in place of a traditional AFM probe.
The system 600 may include other components to receive data from
the AFM 508 or send data to the AFM 608 to execute lithography
operations. For example, the system 600 may include an actuation
computer 610 with a processor 610a and memory 610b in communication
with a data acquisition component (DAQ) 612 to receive feedback
data from the AFM 608 or send printing commands to the AFM 608.
[0133] The system 600 may include any number of computing devices
and components that are communicatively coupled via a network such
as the Internet or other type of networks (e.g., LAN, a MAN, a WAN,
a mobile, a wired or wireless network, a private network, or a
virtual private network, etc.). Each component of the system 600
may include a processor (e.g., 604a, 610a) configured to execute
instructions of one or more instruction modules stored in computer
memory (604b, 610b). For example, the actuation computer 610 memory
610b may store one or more modules including instructions for
execution by the processor 610a during operation of the system 600,
as herein described. In some embodiments, the modules may include
instructions that, upon execution, cause the processor 610a to
generate an instruction set to complete a lithography process as
herein described. For simplicity, the actuation computer 610 is
illustrated with a single processor 610a to execute various modules
stored in the memory 610b, as described herein. The actuation
computer 610 in other embodiments may include additional processing
units (not shown).
[0134] The instruction module stored within the memory 610b may
include instructions that, when executed by a processor (e.g.,
processor 610a) generate the instruction set for the AFM 608 as
well as instructions for a tip array 602 to complete a lithography
action. In one embodiment, the memory 610c includes instructions to
break an image of a desired pattern into regions corresponding to a
tip array 602 of the AFM 608; receive a plurality of patterning
parameters; generate a patterning file; load the patterning file;
and cause the system 600 to generate a lithography image. Of
course, the memory 610b may include any number of additional
instructions to generate an instruction set and complete a
lithography process, as described herein.
Method for Electrical Control of Heat Actuated Tip Arrays
[0135] With reference to FIG. 7, the memory 710b may also include
instructions to display a user interface 700 on the module
actuation computer 710. As described below, the user interface 700
may facilitate execution of other instructions to complete the
lithography process.
[0136] FIGS. 8A to 8D are flow diagrams of example methods for
completing a lithography process. The methods may include one or
more blocks, modules, functions, or routines in the form of
computer-executable instructions that are stored in a tangible
computer-readable medium and executed using a processor (e.g.,
processor 604a, 610a) of a computing device. The methods may be
included as part of any modules of a computing environment for the
lithography system 600, or as part of a module that is external to
such a system. For example, the methods may be part of the
actuation computer 610, the control computer 604, the controller
606, an AFM 608, a data acquisition component 612, or other system
component. FIGS. 8a-d will be described with reference to other
figures for ease of explanation, but the methods may of course be
utilized with other objects and user interfaces.
[0137] With reference to the figures, a method 800 (FIG. 8A) may
generate an instruction set for the various lithography processes
as described herein. At block 802, the method 800 may execute
instruction to load an image 702 (FIG. 7) corresponding to the
desired lithography pattern into the memory 610b. In some
embodiments, block 802 may include instructions to both load the
image 702 into the memory 610b and display the image 702 in the
user interface 700. For example, the method 800 may execute
instructions of block 802 in response to receiving an indication
that a user has selected an image file name 704 and a button 706
for uploading and storing the image 702.
[0138] At block 804, the method 800 may execute an instruction to
deconstruct the image 702 for patterning on a substrate by the
lithography system 600. In some embodiments, instructions of block
804 may break the image 702 into regions corresponding to one or
more tips of the tip array 602. The geometric regions may have
substantially the same size and shape as the tip array. The image
may be divided into any suitable number of geometric regions such
that each pixel of the image is addressed by a tip of the array in
a geometric section. The geometric sections can optionally overlap
such that pixels having spacing of less than the tip pitch and thus
not addressable by a tip in a first geometric section may be
addressed by a tip in a second, overlapping geometric section. For
example, an image can be pixelated into a black and white
500,000.times.500,000 square grid. The pixelated image can then be
deconstructed into non-overlapping frames 1000.times.1000 pixels in
size, for imaging by a 1,000,000-tip array having 1000.times.1000
tips in a square pattern. Thus, the image would be deconstructed
into 250,000 frames in a 500.times.500 square grid. Parameters
defining the regions may be stored in the memory as a list or
regions that may be used in the lithography patterning process. For
example, block 804 may include instructions to divide the image 702
into a grid of sixteen areas each corresponding to a tip within the
tip array 602, where the array 602 includes a four by four array of
tips. Parameters describing these sixteen areas may then be stored
as a list within the memory 610a.
[0139] At block 806, the method 800 may execute instructions to
receive patterning parameters 708. Generally, the patterning
parameters 708 prepare the image 702 and system 600 for a
lithography process. The parameters 708 may include a width of the
lithography pattern determined by block 804, as written by each
tip, a location of this pattern in the lateral and vertical
dimensions, and an angular offset. The angular offset may be
applied to the image 702 to rotate the pattern of the lithography
process. In some embodiments, the angular offset parameter corrects
for any angular offset between the tip array 602 and the XY
piezoelectric stage. Other received patterning parameters may
include a dwell time for each tip at a point of the image 702, a
travel time or transit time between subsequent points in the image
702, a delay time, and a safety time. For example, a delay time may
indicate a time period between when the DAQ 612 detects that the
z-piezo of the AMF is extended and commencing writing. The safety
time may describe an extra time period to ensure patterning is
complete before the tip array 602 is moved to the next geometric
section, thereby avoiding patterning contamination during movement
of the tip array. Additionally, as illustrated by the parameters
708, an extension height, lift height, and speed of the z-piezo may
be received as well as a trigger voltage. The method 800 may use
the trigger voltage to determine when the z-piezo is in an extended
or lifted configuration.
[0140] At block 808, the method 800 may execute instructions to
generate a patterning file. The patterning file may ensure that the
location of the tip array is known and predictable such that a
given pattern may be generated so that particular tips of the array
106a may be activated to address a writing action. In some
embodiments, the method 800 may execute the instructions of block
808 in response to receiving a command from the user interface 700
(e.g., a user selection of the "Update" or "Generate Pattern"
button). By generating the patterning file for instruction movement
of the tip array, the location of the tip array is known and
predictable such that a given pattern can be generated in a given
tip pattern for a given geometric section of the image.
[0141] With reference to FIG. 8B, a method 820 for generating a
patterning file may include a plurality of instructions that are
stored in a memory 610b and executed by a processor 610a. At block
822, the method 820 may execute instructions to analyze the
uploaded image 702 to calculate a number of pixels in width and
height that the tip array 602 needs to address. At block 824, the
method 820 may execute instructions to determine how many tips
within the tip array 602 will write at each location. In some
embodiments, block 824 includes instructions to step through each
of the locations or points that were determined at block 804 and
evaluate each point individually. In other embodiments, block 824
may include instructions to evaluate more than one point at a time
to determine how many tips will write at that point. At block 826,
the method 820 may execute instructions to modify the list of
regions that was determined at block 804. For example, where block
824 determines that no tips will write at a particular point within
the list, then the processor 610a may execute instructions of 826
to remove those location from the list. At block 828, the method
820 may execute instructions to assign a residence time for
locations at which tips will write. In some embodiments, the
residence time may equal:
T.sub.residence=((T.sub.delay+T.sub.dwell).times.#active
tips)+T.sub.safety Equation 1:
[0142] Returning to FIG. 8A, block 810 may execute instructions to
display a pattern of points 710 within the user interface 700. The
pattern 710 may include those points that the tip array 602 will
write. In some embodiments, the pattern 710 may include a region of
the image as determined at block 804. At block 812, the method 800
may execute instructions to write the instruction set for the
lithography system 600 using the parameters and other data of the
methods 800 and 820 and store the set in the memory 610b. In some
embodiments, the instruction set includes a .ppl file for the AFM
608, although the system 600 may use other types of file formats.
At block 814, the method 800 may execute instructions to load the
instruction set into a memory (i.e., memory 610b or a memory of the
AFM 608). At block 816, the method 800 may execute instructions to
write the image 702 beginning with a pattern 710. In some
embodiments, the method 700 begins the writing process in response
to receiving a command from the user interface indicating selection
of a "write" button 712 or other user-initiated command. In other
embodiments, the write process begins automatically upon generating
the instruction set or other action.
[0143] With reference to FIG. 8C, a method 840 may include
instructions to write the image 702 on a substrate. At block 842,
the system 600 may execute instructions to move to a first location
or "patterning position" with the z-piezo of the array 602 lifted.
For example, the tip array may be lowered to be adjacent to the
substrate, but not contacting the substrate or can be contacting
the substrate depending on the desired feature size. Once at the
first location, block 844 may execute instructions to lower the
z-piezo to a descended position over the substrate. At block 846,
the method 840 may execute instructions to monitor the threshold
voltage (i.e., the z-piezo voltage) to determine if the z-piezo is
extended. For example, the z-piezo is indicative of the vertical
position of the tip array relative to the substrate. In some
embodiments, the method 840 instructs the DAQ 612 to monitor the
z-piezo voltage and determine, at block 848, whether the z-piezo
has exceeded a trigger voltage (i.e., one of the parameters entered
at block 806). The threshold or z-piezo voltage is indicative of
the tip array being in the patterning position. If, at block 848,
the method 840 determines that the trigger voltage is exceeded
(and, thus, the z-piezo is extended), then the method 840 may
activate one or more tips of the array 602 to begin a
projecting/writing process for a first region of the image 702. The
activated tips may continue the projecting/writing process for the
duration of the dwell time. In some embodiments, the method may
load a next geometric region for the lithography process if the
dwell time exceeds a threshold amount (e.g., 1.45 seconds).
Further, block 850 may include instructions to wait a period of
time (e.g., the wait time) before lifting the z-piezo away from the
substrate and moving to a second geometric region of the image
702.
[0144] With reference to FIG. 8D, each tip of the array 602 may be
activated one at a time. At block 862, the method 860 may execute
instructions to set a voltage to high for a particular tip
corresponding to the region 710. For example, the method 860 may
instruct the system 600 to set a voltage to "high" for a tip which,
at block 864, switches a transistor (i.e., an NPN transistor) to
allow current to pass though a heater for the selected tip within
the array 602. This voltage may be set to "high" for a variable
amount of time corresponding to one of the parameters entered at
block 806 (e.g., a dwell time). At the expiration of the dwell
time, the high voltage for the tip may be set to zero at block 866.
At block 868, the method 860 may determine if another tip at the
region 710 should write and, if so, proceed to block 362. If there
are no more tips for the writing process at the region 710, then
the method 860 may end. Returning to FIG. 8C, following writing the
entire region 710, the method 840 may execute instructions to
determine if the image 702 includes another region at block 852. If
the image 702 includes another region 710, then block 852 may cause
the method 840 to execute instructions to lift the z-piezo of the
array and travel to the next region. If the image 702 does not
include another region 710, then block 852 may cause the method 840
to return to method 300 and end.
Computing System for Implementing the Methods
[0145] FIG. 9 is a high-level block diagram of an example computing
environment for a lithography system to execute the methods as
herein described. The computing device 901 may include any of the
computing devices described herein (e.g., a desktop or laptop
computer, a tablet computer, a Wi-Fi-enabled device or other
personal computing device capable of wireless or wired
communication), a thin client, or other known type of computing
device. As will be recognized by one skilled in the art, in light
of the disclosure and teachings herein, other types of computing
devices can be used that have different architectures. Processor
systems similar or identical to the example lithography systems
100, 500, and 600 may be used to implement and execute the example
system of FIG. 1, the example methods, the user interfaces, and the
like. Although the example systems are described as including a
plurality of peripherals, interfaces, chips, memories, etc., one or
more of those elements may be omitted from other example processor
systems used to implement and execute the example systems. Also,
other components may be added.
[0146] As shown in FIG. 9, the computing device 901 of this
embodiment includes a processor 902 that is coupled to an
interconnection bus 904. The processor 902 includes a register set
or register space 906, which is depicted in FIG. 9 as being
entirely on-chip, but which could alternatively be located entirely
or partially off-chip and directly coupled to the processor 902 via
dedicated electrical connections and/or via the interconnection bus
904. The processor 902 may be any suitable processor, processing
unit or microprocessor. Although not shown in FIG. 9, the computing
device 901 may be a multi-processor device and, thus, may include
one or more additional processors that are identical or similar to
the processor 902 and that are communicatively coupled to the
interconnection bus 904.
[0147] The processor 902 of FIG. 9 is coupled to a chipset 908,
which includes a memory controller 910 and a peripheral
input/output (I/O) controller 912. As is well known, a chipset
typically provides I/O and memory management functions as well as a
plurality of general purpose and/or special purpose registers,
timers, etc. that are accessible or used by one or more processors
coupled to the chipset 908. The memory controller 910 performs
functions that enable the processor 902 (or processors if there are
multiple processors) to access a system memory 914 and a mass
storage memory 916.
[0148] The system memory 914 may include any desired type of
volatile and/or non-volatile memory such as, for example, static
random access memory (SRAM), dynamic random access memory (DRAM),
flash memory, read-only memory (ROM), etc. The mass storage memory
916 may include any desired type of mass storage device. For
example, if the computing device 901 is used to implement a module
918 having an application programming interface (API) 919
(including functions and instructions as described by the methods
of FIGS. 2b-d, 4, 8a-d), and user interfaces (UI) 200, 300, and 700
to receive user input, the mass storage memory 916 may include a
hard disk drive, an optical drive, a tape storage device, a
solid-state memory (e.g., a flash memory, a RAM memory, etc.), a
magnetic memory (e.g., a hard drive), or any other memory suitable
for mass storage. In one embodiment, non-transitory program
functions, modules and routines (e.g., an application 918, an API
920, and the user interfaces, etc.) are stored in mass storage
memory 916, loaded into system memory 914, and executed by a
processor 902 or can be provided from computer program products
that are stored in tangible computer-readable storage mediums (e.g.
RAM, hard disk, optical/magnetic media, etc.). Mass storage 916 may
also include a cache memory 921 storing application data, user
profile data, and timestamp data corresponding to the application
data, and other data for use by the application 918.
[0149] The peripheral I/O controller 910 performs functions that
enable the processor 902 to communicate with peripheral
input/output (I/O) devices 922 and 924, a network interface 926,
via a peripheral I/O bus 928. The I/O devices 922 and 924 may be
any desired type of I/O device such as, for example, a keyboard, a
display (e.g., a liquid crystal display (LCD), a cathode ray tube
(CRT) display, etc.), a navigation device (e.g., a mouse, a
trackball, a capacitive touch pad, a joystick, etc.), etc. The I/O
devices 922 and 924 may be used with the application 918 to provide
an instruction set and the user interfaces as described in relation
to the figures. The local network transceiver 928 may include
support for Wi-Fi network, Bluetooth, Infrared, cellular, or other
wireless data transmission protocols. In other embodiments, one
element may simultaneously support each of the various wireless
protocols employed by the computing device 901. For example, a
software-defined radio may be able to support multiple protocols
via downloadable instructions. In operation, the computing device
901 may be able to periodically poll for visible wireless network
transmitters (both cellular and local network) on a periodic basis.
Such polling may be possible even while normal wireless traffic is
being supported on the computing device 901. The network interface
926 may be, for example, an Ethernet device, an asynchronous
transfer mode (ATM) device, an 802.11 wireless interface device, a
DSL modem, a cable modem, a cellular modem, etc., that enables the
systems 100, 500, and 600 to communicate with another computer
system having at least the elements described in relation to the
systems.
[0150] While the memory controller 912 and the I/O controller 910
are depicted in FIG. 9 as separate functional blocks within the
chipset 908, the functions performed by these blocks may be
integrated within a single integrated circuit or may be implemented
using two or more separate integrated circuits. The systems 100,
500, and 600 may also implement the user interfaces and instruction
sets on remote computing devices 930 and 932. The remote computing
devices 930 and 932 may communicate with the computing device 901
over a network link 934. For example, the computing device 901 may
receive location data created by an application executing on a
remote computing device 930, 932. In some embodiments, the module
918 including the user interfaces may be retrieved by the computing
device 901 from a cloud computing server 936 via the Internet 938.
When using the cloud computing server 936, the module 918 may be
programmatically linked with the computing device 901. The module
918 may be a Java.RTM. applet executing within a Java.RTM. Virtual
Machine (JVM) environment resident in the computing device 901 or
the remote computing devices 930, 932. The module 918 may also be a
"plug-in" adapted to execute in a web-browser located on the
computing devices 901, 930, and 932. In some embodiments, the
module 918 may communicate with back end components via the
Internet or other type of network.
Tip Arrays
Polymer Pen and Gel Pen Tip Arrays
[0151] Polymer Pen Lithography is a direct-write method that
delivers collections of molecules in a positive printing mode.
Polymer Pen Lithography utilizes elastomeric tips without
cantilevers as the ink delivery tool. The tips are preferably made
of polydimethylsiloxane, PDMS or agarose gel. As used herein, "Gel
Polymer Pen Lithography" and "Gel Pen Lithography" refer to Polymer
Pen Lithography utilizing elastomeric gel polymer tips. Reference
to Polymer Pen Lithography or polymer pen tip arrays herein should
be understood to include Gel Pen Lithography and Gel Pen tip
arrays. As used herein, references to polymers, polymer pens, and
polymer pen tip arrays include gel polymer types, unless indicated
otherwise in context.
[0152] A preferred polymer pen tip array (FIG. 16) contains
thousands of tips, preferably having a pyramidal shape, which can
be made with a master prepared by conventional photolithography and
subsequent wet chemical etching (FIGS. 16a and 17). The tips
preferably are connected by a common substrate which includes a
thin polymer backing layer (50-100 .mu.m thick), which preferably
is adhered to a rigid support (e.g., a glass, silicon, quartz,
ceramic, polymer, or any combination thereof), e.g. prior to or via
curing of the polymer. The rigid support is preferably highly rigid
and has a highly planar surface upon which to mount the array
(e.g., silica glass, quartz, and the like). The rigid support and
thin backing layer significantly improve the uniformity of the
polymer pen tip array over large areas, such as three inch wafer
surface (FIG. 16B), and make possible the leveling and uniform,
controlled use of the array. When the sharp tips of the polymer pen
tips are brought in contact with a substrate, ink is delivered at
the points of contact (FIGS. 16a and 17). Gel pen lithography is a
direct-write method that delivers collections of molecules in a
positive printing mode. A gel polymer can be selected (e.g. a
polysaccharide gel, e.g. agarose gel) such that the ink solution is
absorbed into the gel matrix of a gel tip array.
[0153] The amount of light reflected from the internal surfaces of
the tips increases significantly when the tips make contact with
the substrate. Therefore, a translucent or transparent elastomer
polymer tip array allows one to visually determine when all of the
tips are in contact with an underlying substrate, permitting one to
address the otherwise daunting task of leveling the array in an
experimentally straightforward manner. Thus, preferably one or more
of the array tips, backing layer, and rigid support are at least
translucent, and preferably transparent.
[0154] Polymer pen or gel pen lithography can be performed, for
example, with an Nscriptor.TM. system (NanoInk Inc., Ill.).
[0155] Referring to FIG. 17, an embodiment of a tip array 10
includes a tip substrate layer 12 and a plurality of tips 14 fixed
to the tip substrate layer 12. The tip substrate layer 12 and the
plurality of tips 14 are formed of a polymer and one or both can be
formed of a transparent polymer. The tip substrate layer 12 and the
tips 14 can be formed of the same polymer or can be formed of
different polymers.
[0156] The tip substrate layer 12 can have any suitable thickness,
for example in a range of about 50 .mu.m to about 5 mm, about 50
.mu.m to about 100 .mu.m, or about 1 mm to about 5 mm. For example,
the tip substrate layer 12 can have a minimum thickness of about
50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000,
4000, or 5000 .mu.m. For example, the tip substrate layer 12 can
have a maximum thickness of about 50, 100, 200, 300, 400, 500, 600,
700, 800, 900, 1000, 2000, 3000, 4000, or 5000 .mu.m. The thickness
of the tip substrate layer can be decreased as the rigidity of the
polymer used to form the tip substrate layer increases. For
example, for a gel polymer (e.g., agarose), the tip substrate layer
can have a thickness in a range of about 1 mm to about 5 mm. For
other, more rigid, polymers (e.g., PDMS) the tip substrate layer
can have a thickness in a range of about 50 .mu.m to about 100
.mu.m, for example. The combined thickness of the tip substrate
layer 12 and the tips 14 can be in range of about 50 .mu.m to about
5 mm. For example, for a gel polymer (e.g., agarose), the combined
thickness can be up to about 5 mm. For example, for other polymers
(e.g., PDMS) the combined thickness can be less than about 200
.mu.m, preferably less than about 150 .mu.m, or more preferably
about 100 .mu.m.
[0157] The tip substrate layer 12 can be attached to a transparent
rigid support, for example, formed from glass, silicon, quartz,
ceramic, polymer, or any combination thereof. The rigid support is
preferably highly rigid and has a highly planar surface upon which
to mount the tip array 10.
[0158] The tip arrays are non-cantilevered and comprise tips 14
which can be designed to have any shape or spacing (pitch) between
them, as needed. The shape of each tip can be the same or different
from other tips 14 of the array, and preferably the tips 14 have a
common shape. Contemplated tip shapes include spheroid,
hemispheroid, toroid, polyhedron, cone, cylinder, and pyramid
(trigonal or square). The tips 14 have a base portion fixed to the
tip substrate layer 12. The base portion preferably is larger than
the tip end portion. The base portion can have an edge length in a
range of about 1 .mu.m to about 50 .mu.m, or about 5 .mu.m to about
50 .mu.m. For example, the minimum edge length can be about 1, 2,
3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 22,
24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, or 50 .mu.m.
For example, the maximum edge length can be about 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 26,
28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, or 50 .mu.M.
[0159] A preferred tip array 10 contains thousands of tips 14,
preferably having a pyramidal shape. The substrate-contacting (tip
end) portions of the tips 14 each can have a diameter in a range of
about 50 nm to about 1 .mu.m before coating with the graphene film.
For example, the minimum diameter can be about 50, 55, 60, 65, 70,
75, 80, 85, 90, 95, 100, 150, 200, 250, 300, 350, 400, 450, 500,
550, 600, 650, 700, 750, 800, 850, 900, 950, or 1000 nm. For
example, the minimum diameter can be about 50, 55, 60, 65, 70, 75,
80, 85, 90, 95, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550,
600, 650, 700, 750, 800, 850, 900, 950, or 1000 nm. The
substrate-contacting portions of the tips 14 are preferably sharp,
so that each is suitable for forming submicron patterns, e.g., less
than about 500 nm. The sharpness of the tip is measured by its
radius of curvature. The tips 14 can have a radius of curvature
before coating with the graphene film, for example, of below about
1 .mu.m, and can be less than about 0.9 .mu.m, less than about 0.8
.mu.m, less than about 0.7 .mu.m, less than about 0.6 .mu.m, less
than about 0.5 .mu.m, less than about 0.4 .mu.m, less than about
0.3 .mu.m, less than about 0.2 .mu.m, less than about 0.1 .mu.m,
less than about 90 nm, less than about 80 nm, less than about 70
nm, less than about 60 nm, or less than about 50 nm.
[0160] The tip-to-tip spacing between adjacent tips 14 (tip pitch)
can be in a range of about 1 .mu.m to about over 10 mm, or about 20
.mu.m to about 1 mm. For example, the minimum tip-to-tip spacing
can be about 1 .mu.m, 2 .mu.m, 3 .mu.m, 4 .mu.m, 5 .mu.m, 6 .mu.m,
7 .mu.m, 8 .mu.m, 9 .mu.m, 10 .mu.m, 15 .mu.m, 20 .mu.m, 25 .mu.m,
30 .mu.m, 35 .mu.m, 40 .mu.m, 45 .mu.m, 50 .mu.m, 55 .mu.m, 60
.mu.m, 65 .mu.m, 70 .mu.m, 75 .mu.m, 80 .mu.m, 85 .mu.m, 90 .mu.m,
95 .mu.m, 100 .mu.m, 200 .mu.m, 300 m, 400 .mu.m, 500 .mu.m, 600
.mu.m, 700 .mu.m, 800 .mu.m, 900 .mu.m, 1 mm, 2 mm, 3 mm, 4 mm, 5
mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm. For example, the maximum
tip-to-tip spacing can be about 1 .mu.m, 2 .mu.m, 3 .mu.m, 4 .mu.m,
5 .mu.m, 6 .mu.m, 7 .mu.m, 8 .mu.m, 9 .mu.m, 10 .mu.m, 15 .mu.m, 20
.mu.m, 25 .mu.m, 30 .mu.m, 35 .mu.m, 40 .mu.m, 45 .mu.m, 50 .mu.m,
55 .mu.m, 60 .mu.m, 65 .mu.m, 70 .mu.m, 75 .mu.m, 80 .mu.m, 85
.mu.m, 90 .mu.m, 95 .mu.m, 100 .mu.m, 200 .mu.m, 300 m, 400 .mu.m,
500 .mu.m, 600 .mu.m, 700 .mu.m, 800 .mu.m, 900 .mu.m, 1 mm, 2 mm,
3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm.
[0161] The tips 14 of the tip array 10 can be designed to have any
desired thickness, for example in a range of about 50 nm to about
50 .mu.m, about 50 nm to about 1 .mu.m, about 10 .mu.m to about 50
.mu.m, about 50 nm to about 500 nm, about 50 nm to about 400 nm,
about 50 nm to about 300 nm, about 50 nm to about 200 nm, or about
50 nm to about 100 nm. For example, the minimum thickness can be
about 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm,
400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 .mu.m, 5 .mu.m,
10 .mu.m, 15 .mu.m, 20 .mu.m, 25 .mu.m, 30 .mu.m, 35 .mu.m, 40
.mu.m, 45 .mu.m, or 50 .mu.m. For example, the maximum thickness
can be about 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300
nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 .mu.m, 5
.mu.m, 10 .mu.m, 15 .mu.m, 20 .mu.m, 25 .mu.m, 30 .mu.m, 35 .mu.m,
40 .mu.m, 45 .mu.m, or 50 .mu.m. The thickness of the tip array 10
can be decreased as the rigidity of the polymer used to form the
tip substrate layer increases. For example, for a gel polymer
(e.g., agarose), the tip array 10 can have a thickness in a range
of about 10 .mu.m to about 50 .mu.m. For other polymers (e.g.,
PDMS), for example, the tip array 10 can have a thickness of about
50 nm to about 1 .mu.m. As used herein, the thickness of the tip
array 10 refers to the distance from the tip end to the base end of
a tip. The tips 14 can be arranged randomly or in a regular
periodic pattern (e.g., in columns and rows, in a circular pattern,
or the like).
[0162] Polymeric materials suitable for use in the tip array 10 can
have linear or branched backbones, and can be crosslinked or
non-crosslinked, depending upon the particular polymer and the
degree of compressibility desired for the tip. Cross-linkers refer
to multi-functional monomers capable of forming two or more
covalent bonds between polymer molecules. Non-limiting examples of
cross-linkers include such as trimethylolpropane trimethacrylate
(TMPTMA), divinylbenzene, di-epoxies, tri-epoxies, tetra-epoxies,
di-vinyl ethers, tri-vinyl ethers, tetra-vinyl ethers, and
combinations thereof.
[0163] Thermoplastic or thermosetting polymers can be used, as can
crosslinked elastomers. In general, the polymers can be porous
and/or amorphous. A variety of elastomeric polymeric materials are
contemplated, including polymers of the general classes of silicone
polymers and epoxy polymers. Polymers having low glass transition
temperatures such as, for example, below 25.degree. C. or more
preferably below -50.degree. C., can be used. Diglycidyl ethers of
bisphenol A can be used, in addition to compounds based on aromatic
amine, triazine, and cycloaliphatic backbones. Another example
includes Novolac polymers. Other contemplated elastomeric polymers
include methylchlorosilanes, ethylchlorosilanes, and
phenylchlorosilanes, polydimethylsiloxane (PDMS). Other materials
include polyethylene, polystyrene, polybutadiene, polyurethane,
polyisoprene, polyacrylic rubber, fluorosilicone rubber, and
fluoroelastomers.
[0164] Further examples of suitable polymers that may be used to
form a tip can be found in U.S. Pat. No. 5,776,748; U.S. Pat. No.
6,596,346; and U.S. Pat. No. 6,500,549, each of which is hereby
incorporated by reference in its entirety. Other suitable polymers
include those disclosed by He et al., Langmuir 2003, 19, 6982-6986;
Donzel et al., Adv. Mater. 2001, 13, 1164-1167; and Martin et al.,
Langmuir, 1998, 14-15, 3791-3795. Hydrophobic polymers such as
polydimethylsiloxane can be modified either chemically or
physically by, for example, exposure to a solution of a strong
oxidizer or to an oxygen plasma.
[0165] The polymer of the tip array 10 can be a polymer gel. The
gel polymer can comprise any suitable gel, including hydrogels and
organogels. For example, the polymer gel can be a silicon hydrogel,
a branched polysaccharide gel, an unbranched polysaccharide gel, a
polyacrylamide gel, a polyethylene oxide gel, a cross-linked
polyethylene oxide gel, a
poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (polyAMPS) gel,
a polyvinylpyrrolidone gel, a cross-linked polyvinylpyrrolidone
gel, a methylcellulose gel, a hyaluronan gel, and combinations
thereof. For example, the polymer gel can be an agarose gel. By
weight, gels are mostly liquid, for example the gel can be greater
than 95% liquid, yet behave like a solid due to the presence of a
cross-linked network within the liquid.
[0166] The material used to form the tip array 10 has a suitable
compression modulus and surface hardness to prevent collapse of the
tip during contact with the surface, but too high a modulus and too
great a surface hardness can lead to a brittle material that cannot
adapt and conform to a substrate surface during exposure. As
disclosed in Schmid, et al., Macromolecules, 33:3042 (2000), vinyl
and hydrosilane prepolymers can be tailored to provide polymers of
different modulus and surface hardness. Thus, in another type of
embodiment, the polymer can be a mixture of vinyl and hydrosilane
prepolymers, wherein the weight ratio of vinyl prepolymer to
hydrosilane crosslinker is about 5:1 to about 20:1, about 7:1 to
about 15:1, or about 8:1 to about 12:1.
[0167] The material used to form the tip array 10 can have a
surface hardness of about 0.2% to about 3.5% of glass, as measured
by resistance of a surface to penetration by a hard sphere with a
diameter of 1 mm, compared to the resistance of a glass surface (as
described in Schmid, et al., Macromolecules, 33:3042 (2000) at p
3044). The surface hardness optionally can be about 0.3% to about
3.3%, about 0.4% to about 3.2%, about 0.5% to about 3.0%, or about
0.7% to about 2.7% of glass. The polymers of the tip array 10 can
have a compression modulus of about 10 MPa to about 300 MPa. The
tip array 10 preferably comprises a compressible polymer which is
Hookean under pressures of about 10 MPa to about 300 MPa. The
linear relationship between pressure exerted on the tip array 10
and the feature size allows for control of the near field and
feature size using the disclosed methods and tip arrays.
[0168] A Polymer Pen Lithography tip array can comprise a polymer
that has adsorption and/or absorption properties for the patterning
composition, such that the tip array acts as its own patterning
composition reservoir. For example, PDMS is known to adsorb
patterning inks. See e.g., U.S. Patent Publication No 2004/22962,
Zhang et al., Nano Lett. 4, 1649 (2004), and Wang et al., Langmuir
19, 8951 (2003).
[0169] Polymer Pen Lithography tip arrays can be made with a master
prepared by conventional photolithography and subsequent wet
chemical etching. The mold can be engineered to contain as many
tips arrayed in any fashion desired. The tips of the tip array can
be any number desired, and contemplated numbers of tips 14 include
about 1000 tips 14 to about 15 million tips, or greater. The number
of tips 14 of the tip array 10 can be greater than about 1 million,
greater than about 2 million, greater than about 3 million, greater
than about 4 million, greater than 5 million tips 14, greater than
6 million, greater than 7 million, greater than 8 million, greater
than 9 million, greater than 10 million, greater than 11 million,
greater than 12 million, greater than 13 million, greater than 14
million, or greater than 15 million tips.
[0170] Polymer Pen Lithography exhibits both time- and
pressure-dependent ink transport. Polymer Pen Lithography probes
having a graphene film coated thereon also exhibit both time- and
pressure-dependent ink transport. This property of Polymer Pen
Lithography, which is a result of the diffusive characteristics of
the ink and the small size of the delivery tips, allows one to
pattern sub-micron features with high precision and reproducibility
(variation of feature size is less than 10% under the same
experimental conditions). The pressure dependence of Polymer Pen
Lithography derives from the compressible nature of the elastomer
pyramid array and is not inhibited by the graphene film. Indeed,
the microscopic, preferably pyramidal, tips can be made to deform
with successively increasing amounts of applied pressure, which can
be controlled by simply extending the piezo in the vertical
direction (z-piezo). The controlled deformation can be used as an
adjustable variable, allowing one to control tip-substrate contact
area and resulting feature size. Within the pressure range allowed
by z-piezo extension of about 5 to about 25 .mu.m, one can observe
a near linear relationship between piezo extension and feature size
at a fixed contact time of 1 s (FIG. 18). Interestingly, at the
point of initial contact and up to a relative extension 0.5 .mu.m,
the sizes of the MHA dots do not significantly differ and are both
about 500 nm, indicating that the backing elastomer layer, which
connects all of the pyramids, deforms before the pyramid-shaped
tips do. This type of buffering is fortuitous and essential for
leveling because it provides extra tolerance in bringing all of the
tips in contact with the surface without tip deformation and
significantly changing the intended feature size. When the z-piezo
extends 1 .mu.m or more, the tips exhibit a significant and
controllable deformation (FIG. 3). With the pressure dependency of
Polymer Pen Lithography, one does not have to rely on the
time-consuming, meniscus-mediated ink diffusion process to generate
large features. Indeed, one can generate either nanometer or
micrometer sized features in only one printing cycle by simply
adjusting the degree of tip deformation.
[0171] Polymer Pen Lithography allows for the combinatorial
patterning of molecule-based and solid-state features with dynamic
control over features size, spacing, and shape. The maskless nature
of Polymer Pen Lithography allows one to arbitrarily make many
types of structures without the hurdle of designing a new master
via a throughput-impeded serial process. In addition, Polymer Pen
Lithography can be used with sub-100 nm resolution with the
registration capabilities of a closed-loop scanner.
Beam Pen Lithography
[0172] The tips 14 of a Beam Pen Lithography tip array can be used
to both channel the radiation to a surface in a massively parallel
scanning probe lithographic process and to control one or more
parameters such as the distance between the tip and the substrate,
and the degree of tip deformation. Control of such parameters can
allow one to take advantage of near-field effects. In one
embodiment, the tips 14 are elastomeric and reversibly deformable,
which can allow the tip array 10 to be brought in contact with the
substrate without damage to the substrate or the tip array 10. This
contact can ensure the generation of near-field effects.
[0173] Referring to FIGS. 4, an embodiment of a Beam Pen
Lithography tip array 10 includes a tip substrate layer 12 and a
plurality of tips 14 fixed to the tip substrate layer 12. The tip
substrate layer 12 and the plurality of tips 14 are formed of a
transparent polymer. The tip substrate layer 12 and the tips 14 can
be formed of the same polymer or can be formed of different
polymers. Details regarding the tips and tip arrays, including, for
example, the tip and tip substrate dimensions, shape, spacing,
materials, and number of tips, are provided above.
[0174] A Beam Pen Lithograph tip array 10 further includes a
blocking layer 16 coated on the sidewalls of the tips 14 and on the
portions of the tip substrate layer 12 between adjacent tips 14.
Referring to FIG. 19, an aperture 18 is defined in the blocking
layer 16 at the tip end (e.g., the photosensitive layer-contacting
end of each of the tips 14), such that the transparent polymer tip
end is exposed through the aperture 18. The tips 14 are formed from
a material which is at least translucent to the wavelength of
radiation intended for use in patterning, e.g. in a range of 300 nm
to 600 nm, and preferably the tips 14 are transparent to such
light. Each tip can have a blocking layer 16 disposed thereon, with
an aperture 18 defined in the blocking layer 16 and exposing the
tip end. The blocking layer 16 serves as a radiation blocking layer
16, channeling the radiation through the material of the tip and
out the exposed tip end.
[0175] The blocking layer 16 on the polymer tip sidewalls serves as
a radiation blocking layer 16, allowing the radiation illuminated
on a surface of the substrate layer opposite the surface to which
the tips 14 are fixed to be emitted only through the tip end
exposed by the aperture 18 defined in the blocking layer 16. The
exposure of a substrate pre-coated with a resist layer 20 with the
radiation channeled through the tip ends 18 of the tip array 10 can
allow for the formation of a single dot per tip for each exposure.
The blocking layer 16 can be formed of any material suitable for
blocking (e.g., reflecting) a type of radiation used in the
lithography process. For example, the blocking layer 16 can be a
metal, such as gold, when used with UV light. Other suitable
blocking layers include, but are not limited to, gold, chromium,
titanium, silver, copper, nickel, silicon, aluminum, opaque organic
molecules and polymers, and combinations thereof. The blocking
layer 16 can have any suitable thickness, for example in a range of
about 40 nm to about 500 nm. For example, the minimum thickness can
be about 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 150,
200, 250, 300, 350, 400, 450, or 500 nm. For example, the maximum
thickness can be about 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90,
95, 100, 150, 200, 250, 300, 350, 400, 450, or 500 nm.
[0176] The pressure dependence exhibited by polymer pen lithography
tip arrays and described above is similarly exhibited by beam pen
lithography tip arrays. As noted above, the graphene film does not
inhibit or otherwise adversely affect the pressure dependent
properties of beam pen lithography.
[0177] As described above, the tip portion of the tip arrays can be
made with a master prepared by conventional photolithography and
subsequent wet chemical etching. The mold can be engineered to
contain as many tips 14 arrayed in any fashion desired. The tips of
the tip array can be any number desired, and contemplated numbers
of tips 14 include about 1000 tips 14 to about 15 million tips, or
greater. The number of tips 14 of the tip array 10 can be greater
than about 1 million, greater than about 2 million, greater than
about 3 million, greater than about 4 million, greater than 5
million tips 14, greater than 6 million, greater than 7 million,
greater than 8 million, greater than 9 million, greater than 10
million, greater than 11 million, greater than 12 million, greater
than 13 million, greater than 14 million, or greater than 15
million tips.
[0178] Optionally, the tips 14 can be cleaned, for example, using
oxygen plasma, prior to coating with the blocking layer 16. The
blocking layer 16 can be disposed on the tips 14 by any suitable
process, including coating, for example, spin-coating, the tips 14
with the blocking layer 16
[0179] An aperture 18 in the blocking layer 16 can be formed by any
suitable method, including, for example, focused ion beam (FIB)
methods, dry and wet chemical etchings, or using a lift-off method.
The lift-off method can be a dry lift off method. Referring to FIG.
6A, one suitable approach includes applying an adhesive 22, such as
poly(methyl methacrylate) (PMMA) on top of the blocking layer 16 of
the tip array 10, and removing a portion of the adhesive 22
material disposed at the substrate contacting end of the tips 14 by
contacting the tip array 10 to a clean and flat surface, for
example a glass surface. The tips 14 can then be immersed in an
etching solution to remove the exposed portion of the blocking
layer 16 to form the aperture 18 and expose the material of the
tip, e.g. the transparent polymer. The remaining adhesive 22
material protects the covered surfaces of the blocking layer 16
from being etched during the etching step. The adhesive can be, for
example, PMMA, poly(ethylene glycol) (PEG), polyacrylonitrile, and
combinations thereof.
[0180] Referring to FIGS. 21B and 26, alternatively, a simple
contact approach can be used in which a tip array 10 having the
blocking layer 16 is brought in contact with a glass slide or other
surface coated with an adhesive 22 material, such as PMMA. Other
suitable adhesive 22 materials include, for example, PMMA, PEG,
polyacrylonitrile, and combinations thereof. Upon removal of the
pen tip from surface coated with the adhesive 22 material, the
adhesive 22 material removes the contacted portion of the blocking
layer 16, thereby defining an aperture 18 and exposing the tip
material, e.g. the transparent polymer.
[0181] In either of the above described aperture 18 forming
methods, the size of the aperture 18 formed can be controlled by
applying different external forces on the backside of the BPL tip
array 10. As a result of the flexibility of elastomeric tips 14,
the application of force on the backside of the BPL tip array 10
can be used to control the contact area between the tips 14 and
adhesive 22 material surface. The contact force optionally can be
in a range of about 0.002 N to about 0.2N for a 1 cm.sup.2 tip
array.
[0182] Referring to FIG. 26, in an embodiment, the aperture is
formed by coating the tip array having the blocking layer with a
polymer layer, such as a layer of PMMA. The tip array can be
repeatedly coated with the polymer layer to ensure complete
coverage of the tips. The polymer layer can be coated on the
blocking layer, for example, using spin coating or any other
suitable coating methods, as is well known in the art. Reactive ion
etching can then be used to etch the polymer layer and expose the
apexes of the tips. The reactive ion etching process can be
monitored, for example, using optical microscopy to ensure that
etching is stopped when only the apexes are exposed or to ensure
the desired amount of etching be done to form a selected aperture
size. The size of the aperture can be controlled by controlling the
etching of the polymer layer to expose more or less of the apex of
the tip. The blocking layer exposed through the etched portion of
the polymer layer can then be etched using any known etching
process, for example, a chemical etching process, and using the
remaining polymer layer as an etch mask. The exposed blocking layer
can be etched to expose the underlying polymer layer of the tips
and thereby form the aperture. The polymer layer can be removed
using any suitable methods. For example, the polymer layer can be
removed by rinsing with acetone.
[0183] Any of the above-described approaches can be utilized when
forming a blocking layer on a tip having a graphene film coated
thereon.
[0184] The BPL tip array 10 can include pyramidal tips 14, with
each pyramid-shaped tip being covered by a gold blocking layer 16
having a small aperture 18 defined in the blocking layer 16 at the
very end of the tip. The size of the aperture 18 does not
significantly change from tip to tip. For example, the size of the
aperture 18 can vary less than about 10% from tip to tip. The size
of the aperture 18 can be tailored over the 200 nm to 1 to 10 .mu.m
ranges, for example, by controlling contact force. For example, the
aperture 18 can have a diameter in a range of about 5 nm to about 5
.mu.m, about 30 nm to about 500 nm, or about 200 nm to about 5
.mu.m. For example, the minimum aperture 18 diameter can be about
5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,
90, 95, 100, 200, 300, 400, 500, 600, 700, 800, 900 1000, 1500,
2000, 2500, 3000, 3500, 4000, 4500, or 5000 nm. For example, the
maximum aperture 18 diameter can be about 5, 10, 15, 20, 25, 30,
35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 200, 300,
400, 500, 600, 700, 800, 900 1000, 1500, 2000, 2500, 3000, 3500,
4000, 4500, or 5000 nm.
[0185] A PDMS array of pyramid-shape tips 14 can be fabricated by
known methods. (17, 20). For example, each pyramid tip can have a
square base with a several tens of .mu.m edge length and can come
to a tip that has tip diameter of about 100 nm. The entire array,
including tips 14, can then be cleaned, for example, by oxygen
plasma and covered with a blocking layer 16 (e.g. gold), by a
thermal evaporation method, for example. The coating can include,
for example, a layer of gold that is about 80 nm thick with an
about 5 nm thick Ti adhesion layer. The tip array 10 is then
brought in contact with a glass slide coated with PMMA, an adhesive
22 material, which subsequently removes the Au/Ti layer from the
PDMS tips 14 and exposes the underlying transparent PDMS.
[0186] In one class of embodiments, the graphene film is coated on
the tips prior to forming the blocking layer. In such embodiments,
the graphene film is transparent and therefore can remain on the
tip end without inhibiting the photolithography performance of the
beam tip array. In another class of embodiments, the blocking layer
is formed on the tips and the graphene film is coated on the
blocking layer. In such embodiments, the aperture can be formed
prior to forming the graphene film and the graphene film can be
coated over the blocking layer and the aperture.
Hard Tip Soft Spring Lithography
[0187] Referring to FIGS. 22A and 22B, Hard tip soft spring
lithography is a massively parallel, hybrid tip-based molecular
printing method. When silicon is used for the tip material, Hard
tip soft spring lithography is also referred to as Silicon Pen
Lithography. The method and apparatus employs an array of tips,
e.g. Si tips, mounted onto a backing layer to create patterns of
molecules on surfaces with features as small as 30 nm in diameter
over large area. While the tips described herein are described in
the context of silicon or silicon-containing tips, the tips can
also comprise a metal, metalloid, a semi-conducing material, and/or
combinations thereof. For example, silicon nitride AFM probes,
metal carbide coated AFM probes, plasma treated AFM probes,
silanized AFM probes, diamond AFM probes, gallium containing
materials (e.g., gallium nitride, gallium sulfide, gallium
arsenide), and other semi-conducting materials are known in the
art. The tips can have an average radius of curvature of, e.g.,
down to 22 nm or even less. Hard tip soft spring lithography tips
arrays demonstrate time-dependent feature size that is analogous to
DPN, but there is no relation between the force and the feature
size, which is distinct from polymer pen lithography. Hard tip soft
spring lithography tips can write features as small as 34 nm, and
can transfer energy to the surface to form a pattern.
[0188] The tip arrays disclosed herein comprise a plurality of tips
(e.g., silicon or silicon-containing) fixed to an elastomeric
backing layer. The backing layer can be at least translucent, or
preferably substantially transparent. The backing layer can have
any suitable thickness, for example in a range of about 50 .mu.m to
about 1000 .mu.m, about 50 .mu.m to about 500 .mu.m, about 50 .mu.m
to about 250 .mu.m, or about 50 .mu.m to about 200 .mu.m, or about
50 .mu.m to about 100 .mu.m.
[0189] The elastomeric backing layer comprises an elastomeric
polymeric material. Polymeric materials suitable for use in the
backing layer can have linear or branched backbones, and can be
crosslinked or non-crosslinked. Cross-linkers refer to
multi-functional monomers capable of forming two or more covalent
bonds between polymer molecules. Non-limiting examples of
cross-linkers include such as trimethylolpropane trimethacrylate
(TMPTMA), divinylbenzene, di-epoxies, tri-epoxies, tetra-epoxies,
di-vinyl ethers, tri-vinyl ethers, tetra-vinyl ethers, and
combinations thereof.
[0190] Thermoplastic or thermosetting polymers can be used, as can
crosslinked elastomers. In general, the polymers can be porous
and/or amorphous. A variety of elastomeric polymeric materials are
contemplated, including polymers of the general classes of silicone
polymers and epoxy polymers. Polymers having low glass transition
temperatures such as, for example, below 25.degree. C. or more
preferably below -50.degree. C., can be used. Diglycidyl ethers of
bisphenol A can be used, in addition to compounds based on aromatic
amine, triazine, and cycloaliphatic backbones. Another example
includes Novolac polymers. Other contemplated elastomeric polymers
include methylchlorosilanes, ethylchlorosilanes, and
phenylchlorosilanes, polydimethylsiloxane (PDMS). Other materials
include polyethylene, polystyrene, polybutadiene, polyurethane,
polyisoprene, polyacrylic rubber, fluorosilicone rubber, and
fluoroelastomers.
[0191] Further examples of suitable polymers that may be used in
the backing layer can be found in U.S. Pat. No. 5,776,748; U.S.
Pat. No. 6,596,346; and U.S. Pat. No. 6,500,549, each of which is
hereby incorporated by reference in its entirety. Other suitable
polymers include those disclosed by He et al., Langmuir 2003, 19,
6982-6986; Donzel et al., Adv. Mater. 2001, 13, 1164-1167; and
Martin et al., Langmuir, 1998, 14-15, 3791-3795. Hydrophobic
polymers such as polydimethylsiloxane can be modified either
chemically or physically by, for example, exposure to a solution of
a strong oxidizer or to an oxygen plasma. In some cases, the
elastomeric polymer is a mixture of vinyl and hydrosilane
prepolymers, where the weight ratio of vinyl prepolymer to
hydrosilane crosslinker is about 5:1 to about 20:1, about 7:1 to
about 15:1, or about 8:1 to about 12:1.
[0192] The tips of the tip array can be any number desired, and
contemplated numbers of tips include about 100 tips to about 15
million tips, or greater. The number of tips of the tip array can
be greater than about 1 million, greater than about 2 million,
greater than about 3 million, greater than about 4 million, greater
than 5 million tips, greater than 6 million, greater than 7
million, greater than 8 million, greater than 9 million, greater
than 10 million, greater than 11 million, greater than 12 million,
greater than 13 million, greater than 14 million, or greater than
15 million tips.
[0193] The tip array comprising tips and backing layer can have any
suitable thickness, for example in a range of about 50 .mu.m to
about 5 mm, about 50 .mu.m to about 100 .mu.m, or about 1 mm to
about 5 mm. For example, the tip array can have a minimum thickness
of about 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000,
2000, 3000, 4000, or 5000 .mu.m. For example, the backing layer can
have a maximum thickness of about 50, 100, 200, 300, 400, 500, 600,
700, 800, 900, 1000, 2000, 3000, 4000, or 5000 .mu.m.
[0194] The tip array can be attached to a rigid support. The rigid
support, when present, is disposed opposite the tips of the tip
array and parallel to the backing layer. In some cases, the rigid
support is at least translucent, or is substantially transparent.
In some cases, the backing layer and rigid support together are at
least translucent or are substantially transparent. Non-limiting
examples of rigid supports include formed from glass, silicon,
quartz, ceramic, polymer, or any combination thereof. The rigid
support is preferably highly rigid and has a highly planar surface
upon which to mount the tip array. The combined thickness of the
tip array and optional rigid support can be of any desired
thickness, for example in range of about 50 .mu.m to about 5 mm.
The combined thickness can be less than about 5 mm, less than 1 mm,
less than about 750 .mu.m, or less than about 500 .mu.m, for
example.
[0195] The tip arrays are non-cantilevered and comprise tips (e.g.
silicon or silicon-containing) which can be designed to have any
shape or spacing (pitch) between them, as needed. The shape of each
tip can be the same or different from other tips of the array, and
preferably the tips have a common shape. Contemplated tip shapes
include spheroid, hemispheroid, toroid, polyhedron, cone, cylinder,
and pyramid (e.g., trigonal or square or octagonal). The tips can
be arranged randomly or preferably in a regular periodic pattern
(e.g., in columns and rows, in a circular pattern, or the
like).
[0196] The tips have a base portion fixed to the backing layer. The
base portion preferably is larger than the tip end portion. The
base portion of the tips can have diameter of any suitable
dimension, for example in a range of about 1 .mu.m to about 50
.mu.m, or about 5 .mu.m to about 50 .mu.m, or less than 100 .mu.m,
or less than 50 .mu.m. For example, the minimum diameter of the
base of the tips can be about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
12, 13, 14, 15, 16, 17, 18, 19, 20 22, 24, 26, 28, 30, 32, 34, 36,
38, 40, 42, 44, 46, 48, or 50 .mu.m. For example, the maximum
diameter of the base of the tips can be about 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 26, 28,
30, 32, 34, 36, 38, 40, 42, 44, 46, 48, or 50 .mu.m.
[0197] A preferred shape of the tips is pyramidal, more preferably
octagonal pyramidal. The substrate-contacting (tip end) portions of
the tips each can have a radius of curvature of any suitable
dimension, for example in a range of about 5 nm to about 1 .mu.m.
For example, the minimum radius of curvature can be about 5, 10,
15, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 55,
60, 65, 70, 75, 80, 85, 90, 95, 100, 150, 200, 250, 300, 350, 400,
450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, or 1000 nm.
The substrate-contacting portions of the tips are preferably sharp,
so that each is suitable for forming submicron patterns, e.g., a
radius of curvature of less than about 500 nm, less than 100 nm,
less than 50 nm, or less than 25 nm.
[0198] The tip-to-tip spacing between adjacent tips (tip pitch) can
be of any desired dimension, for example in a range of about 1
.mu.m to about over 10 mm, or about 20 .mu.m to about 1 mm. For
example, the minimum tip-to-tip spacing can be about 1 .mu.m, 2
.mu.m, 3 .mu.m, 4 .mu.m, 5 .mu.m, 6 .mu.m, 7 .mu.m, 8 .mu.m, 9
.mu.m, 10 .mu.m, 15 .mu.m, 20 .mu.m, 25 .mu.m, 30 .mu.m, 35 .mu.m,
40 .mu.m, 45 .mu.m, 50 .mu.m, 55 .mu.m, 60 .mu.m, 65 .mu.m, 70
.mu.m, 75 .mu.m, 80 .mu.m, 85 .mu.m, 90 .mu.m, 95 .mu.m, 100 .mu.m,
200 .mu.m, 300 m, 400 .mu.m, 500 .mu.m, 600 .mu.m, 700 .mu.m, 800
.mu.m, 900 .mu.m, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9
mm, or 10 mm. For example, the maximum tip-to-tip spacing can be
about 1 .mu.m, 2 .mu.m, 3 .mu.m, 4 .mu.m, 5 .mu.m, 6 .mu.m, 7
.mu.m, 8 .mu.m, 9 .mu.m, 10 .mu.m, 15 .mu.m, 20 .mu.m, 25 .mu.m, 30
.mu.m, 35 .mu.m, 40 .mu.m, 45 .mu.m, 50 .mu.m, 55 .mu.m, 60 .mu.m,
65 .mu.m, 70 .mu.m, 75 .mu.m, 80 .mu.m, 85 .mu.m, 90 .mu.m, 95
.mu.m, 100 .mu.m, 200 .mu.m, 300 m, 400 .mu.m, 500 .mu.m, 600
.mu.m, 700 .mu.m, 800 .mu.m, 900 .mu.m, 1 mm, 2 mm, 3 mm, 4 mm, 5
mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm.
[0199] The tips of the tip array can be designed to have any
desired height, for example in a range of about 50 nm to less than
100 .mu.m, about 50 nm to about 90 .mu.m, about 50 nm to about 80
.mu.m, about 50 nm to about 70 .mu.m, about 50 nm to about 60
.mu.m, about 10 .mu.m to about 50 .mu.m, about 50 nm to about 40
.mu.m, about 50 nm to about 30 .mu.m, about 50 nm to about 20
.mu.m, about 50 nm to about 500 nm, about 50 nm to about 400 nm,
about 50 nm to about 300 nm, about 50 nm to about 200 nm, or about
50 nm to about 100 nm. For example, the minimum height can be about
50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm,
500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 .mu.m, 5 .mu.m, 10 .mu.m,
15 .mu.m, 20 .mu.m, 25 .mu.m, 30 .mu.m, 35 .mu.m, 40 .mu.m, 45
.mu.m, or 50 .mu.m. For example, the maximum height can be about 50
nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500
nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 .mu.m, 5 .mu.m, 10 .mu.m, 15
.mu.m, 20 .mu.m, 25 .mu.m, 30 .mu.m, 35 .mu.m, 40 .mu.m, 45 .mu.m,
or 100 .mu.m.
[0200] The tip array can optionally include an adhesion-enhancing
layer between the tips and the backing layer. This layer can
increase the stability of the tip-backing layer adhesion and/or
increase the facility with which the tips and backing layer are
adhered. The adhesion-enhancing layer can be disposed over the
entire elastomeric backing layer, or optionally only in selected
regions (e.g. between each tip and the elastomeric backing layer).
One non-limiting example of an adhesion-enhancing layer is a
silicon dioxide layer. Other examples include epoxy resins or other
adhesive materials.
[0201] The tip array can optionally include a coating disposed on
the exposed surfaces of the tips and further optionally also over
the surfaces of the backing layer adjacent to the tips. This
coating can comprise a conductive material (e.g., a material
capable of conducting electrical energy), for example. Non-limiting
examples of a conductive coating include gold, silver, titanium,
nickel, copper, conductive metals, conductive metal alloys, or
combinations thereof.
[0202] The Si tips, prepared by a self-sharpening wet etching
protocol, can have a radius of curvature of about 22 nm, thereby
enabling the easy preparation of sub-50 nm features in a pattern.
Because the tip arrays can be prepared on a glass slide, these
arrays can be easily mounted onto the piezoelectric actuators of a
conventional AFM, which provides the precise tip positioning and
registration that are hallmarks of scanning probe lithographies.
Both the elastomer and glass onto which the arrays are mounted can
be selected to be transparent, which enables the compression of the
elastomer that occurs when the tips touch the surface of a
substrate to be observed visually, thereby enabling a
straightforward, optical method for leveling the plane of the tip
array with respect to the substrate surface, when desired.
[0203] The preferred tip-array fabrication protocol described
herein involves two major steps, photolithography and a
self-sharpening etching step (22b). Importantly, no micromachining
steps are required, thereby reducing significantly the
manufacturing costs to about $10 for a 1.times.1 cm tip array,
whereas a single, cantilever-bound AFM probe costs about $40.
Depending on the intended use, the pitch of a tip array can be
deliberately set between 100 and 200 .mu.m, corresponding to tip
densities of 10,000/cm2 and 2,500/cm2, respectively, and the
density can be as high as 111,110/cm2 (9,007,700 tips in a 4-inch
wafer) with a pitch of 30 .mu.m, for example.
[0204] The method can include the steps of providing a substrate
wafer (e.g., silicon) from which the tips will be formed; adhering
an elastomeric backing layer to the wafer to form a structure; and
etching the wafer material to form tips attached to the backing
layer. Preferably, a mask pattern is formed over the wafer prior to
etching, to form pre-tip regions.
[0205] As an example, to make the tip arrays, a Si wafer (e.g.,
1.times.1 cm piece of a 50 .mu.m-thick (100)), optionally with a
layer of silicon dioxide (SiO2) (e.g., 1 .mu.m thick) on each side
of the wafer, was placed onto uncured elastomer. The top layer of
SiO2 can serve as an etching mask material, while the SiO2 layer of
the wafer in contact with the backing layer can increase adhesion
between the two surfaces, so that the tips do not fall off a
certain PDMS elastomeric backing material once the wafer has been
etched (FIG. 23). Following an optional curing of elastomer of the
backing layer, an array of square SiO2 masks over silicon (e.g.,
pre-tip regions) are prepared from the top SiO2 layer along the
<110> axis of the wafer by conventional photolithography and
a subsequent buffered hydrofluoric acid (HF) etch. The tips are
prepared by etching the Si of the pre-tip regions and Si between
pre-tip regions in an etching solution, e.g., 40% (w/v) aqueous
potassium hydroxide (KOH) solution that etches the (311) and the
(100) planes of the wafer at rates of 88 and 50 .mu.m/hr,
respectively. In one preferred embodiment, during the etching, the
Si wafer is embedded in the elastomer or backing layer (e.g., PDMS)
so that the sides of the wafer are not exposed to the etching
solution, thereby protecting the (110) crystal face exposed on the
sides that would etch faster than the (100) face on the surface. In
other embodiments, the sides of the wafer can be protected from
etchant by any other suitable methods and materials, as would be
recognized by the skilled artisan. The sidewall etching rate,
Rw/cos .theta. (.theta. is a slope of sidewall), must exceed the
surface etching rate, Rf in order to form sharp Si tips. Thus the
anisotropy ratio .eta..sub.c and the condition for self-sharpening
points is expressed as .eta.=R.sub.f/R.sub.w.ltoreq.1/cos
.theta.=.eta..sub.c, which indicates that faster etching rate for
sidewall than that of floor is required to form a sharp tip. For
(311) sidewall and (100) floor, the experimental
.eta.=R.sub.(100)/R.sub.(311) was measured as 0.56 in 40 wt % KOH
at 70.degree. C., while theoretical .eta..sub.c is 3.33. This
parameter can be changed to altering the weight % of the KOH and/or
the temperature at which the etching occurs. Other etching
solutions that etch silicon anisotropically include
ethylenediamine/pyrocathecol/water and tretramethylammonium
hydroxide.
[0206] Analysis of the resulting tip arrays reveals that this
fabrication protocol does indeed achieve massively parallel Si tip
arrays with tip radii of about 22 nm (FIG. 23E-23I). The massively
parallel Si tip array is immobilized onto a glass slide (FIG. 23E),
which is a rigid support for the arrays, allows handling of the
fragile tip array without damage, and is a platform for mounting
the arrays onto the AFM. In a preferred embodiment, the elastomeric
backing and rigid support together are transparent (FIG. 23F),
which enables the visual leveling alignment of the tips onto a
surface. A scanning electron microscope (SEM) image of the tips
with 160 .mu.m in pitch shows that the tips are remarkably uniform
with bottom width 30.+-.0.6 .mu.m, corresponding to a tip height of
47.+-.0.9 .mu.m, and that they adhere well to the elastomer surface
(FIG. 23G). It was found by SEM that the surface intersection
angles, .alpha.1, .alpha.2, and the rotation of the intersection of
the planes to the <100> plane of the wafer, .phi., are 127.2,
143.3, and 18.3.degree. (FIG. 23H), respectively, which
demonstrates that the sidewall of the tips is (311) plane because
the value of angles correspond perfectly to theoretical value of
those for (311) of 126.9, 143.1, and 18.4.degree., respectively.
Importantly, the Si tip radius of the arrays is found to be 22.+-.3
nm (FIG. 23I), demonstrating that self-sharpening has been achieved
under the etching conditions of 40% KOH in H2O. The tip radius can
be reduced to 5 nm by changing the etching conditions, e.g.,
changing the KOH concentration and solution temperature during
etching. This etching protocol, with a SiO2 etching mask and
homogeneous KOH etching provides a tip yield >99%. Since the
wafer used in this experiment has a thickness variation of 10%
(50.+-.5 .mu.m, NOVA Electronic Materials Ltd., Tex.), the tip
height can vary up to 10%.
[0207] In one exemplary embodiment, Hard tip soft spring
lithography (HSL) tip arrays were formed using Si wafers (NOVA
Electronic Materials; resistivity 1-10 .OMEGA.cm, (100)
orientation, 50.+-.5 .mu.m thick) with a 10,000-.ANG. (.+-.5%) SiO2
layer on each side were used for fabricating the tip arrays. The
wafers were cleaned in acetone and ethanol, and then rinsed with
water before use. In preparing the elastomer base, PDMS and a
curing agent (Sylgard 184 Silicone) were mixed in a 20:1 ratio
(W/W), and then degassed under vacuum (10-3 torr) for 30 minutes.
Oxygen-plasma-treated (30 W at a pressure of 100 mTorr) wafers were
then placed on drop-coated PDMS on clean glass slides, followed by
curing at 75.degree. C. for 1 h. Before curing, the bubbles that
can form at the interface between the wafer and the uncured PDMS
must be removed with additional degassing. To create HSL arrays, an
array of squares must be defined on the surface of the silicon
wafer to act as etch masks. These squares must be between 120 and
140 .mu.m on edge (depending on the thickness of the silicon wafer)
and the edges of the squares and aligned along the Si layers
<110> direction. This array of squares is created by
photolithography then transferred into the silica layer to form a
hard mask for wet etching. The photolithography proceeds by
treating with oxygen plasma for 1 minute at 30 W, then spin coating
photoresist (Shipley; S1805 positive photoresist) at 500 r.p.m. for
10 s followed by 4,000 r.p.m. for 60 s onto the wafer/PDMS/glass
slide. After spin-coating, the photoresist was baked at 105.degree.
C. for 90 s due to the thermal insulation of the PDMS layer (on a
conventional substrate this photoresist is usually baked for only
60 s). The photoresist/wafer/PDMS/glass slide was exposed (UV light
source) through a photomask defining the etch mask and subsequently
developed (15 s, Shipley; Micoposit MF-319 Developer and washed
with water). The sample edge was passivated with PDMS to prevent
etching in from the sides. The exposed SiO2 was selectively etched
in isotropic buffered hydrofluoric acid (Transene, 9% HF, BUFFER-HF
Improved) etchant for 9 min in a polystyrene petri dish and then
washed with water. To remove the photoresist, the wafer was cleaned
in acetone, ethanol, and subsequently dried with flowing nitrogen.
The wafer was then cleaned with oxygen plasma (1 min at 30 W at a
pressure of 100 mTorr). Oxygen plasma cleaning prior to Si etching
was found to improve the uniformity of the tips. Samples were
immediately transferred into 40 wt % KOH (333 g KOH in 500 ml DI
water) (KOH from Sigma-Aldrich; 99.99% metal basis, semiconductor
grade, product no. 306568) at 75.degree. C. and held in the centre
of the etchant in a Teflon holder. The solution was continuously
stirred to reduce the effect of micro-masking by hydrogen bubbles
generated by the reaction at the Si surface. After 60-65 min, the
sample was removed from the etchant, was rinsed in water, rinsed in
ethanol, and then dried in air. As the etching rate of Si(100) in
40 wt % KOH at 75.degree. C. is .about.50 .mu.mh-1, the minimum
required thickness of SiO2 was found to be 250 nm for an
experimentally viable fabrication procedure, which motivated our
choice for a 1 .mu.m thick SiO2 layer.
Method of Coating the Tip Array with Graphene
[0208] Referring to FIG. 25A, in one embodiment of the disclosure,
a micro probe having at least one tip is coated with a graphene
film by immersing the at least one tip in a fluid in which a
graphene film is floating on a surface thereof. The at least one
tip can be immersed beneath the floating graphene film and then the
graphene film can be brought into contact with the tip to thereby
coat the tip. For example, the fluid can be evaporated to lower the
graphene film into contact with the at least one tip.
Alternatively, the at least one tip can be raised into contact with
the graphene film. In various embodiments in which the micro probe
includes a plurality of tips, all or a subset of tips can be
immersed in the fluid to coat the immersed tips and immersed
portions of the first side of the tip substrate layer with the
graphene.
[0209] Optionally, prior to coating the tips can be cleaned or
pre-treated. In one embodiment, the tips are oxygen plasma
treated.
[0210] The fluid can comprise water and a surfactant to lower the
surface tension of water. It has been advantageously found that a
tenting phenomenon in which the graphene film tents over and does
not conform to the at least one tip can be avoided when the surface
tension of the fluid (such as water) is reduced. When coating in
water having no surfactant a significant tenting phenomenon is
observed, such that the graphene layer covers across the tip ends
and does not conform to the tips. By comparison, when a surfactant
is added to the fluid to reduce the surface tension of the fluid,
the tenting phenomenon is eliminated. Any suitable surfactant that
is compatible and non-destructive to graphene and the tip material,
and optionally a backing support layer (e.g. polymethylmethacrylate
(PMMA)), can be provided with the fluid for floating graphene film.
In one embodiment for use with water, the surfactant is
ethanol.
[0211] When immersed in the fluid, the tip or tip array can be
angled relative to the surface of the fluid (and, thus, the
floating graphene film), as measured from a plane parallel to the
base of the tip. It has advantageously been determined that tilting
the tip or tip array improves conformance of the graphene film to
the tip or tip array. Referring to FIGS. 25A and 25B, tilting was
advantageously found to maximize the coating coverage. Furthermore,
in embodiments in which a tip array having a plurality of tips is
coated, tilting of the tip array can allow for row by row coating
of the tips with the graphene film as the graphene film is brought
into contact with the tip array. The angling of the tip array also
guides the graphene film across the tip array as the successive
rows are coated. The degree of tiling can be dependent upon by the
tip-to-tip distances, tip bottom diameter, and the tip height (also
referred to herein as tip thickness), and suitable degrees can be
determined through routine experimentation. For example, the tip or
tip array can be tilted at least about 10.degree. from the base of
the tip, at least about 18.degree., at least about 20.degree., at
least about 30.degree., or at least about 40.degree. relative to
the surface of the fluid. The angle optionally can be in a range of
about 10.degree. to about 80.degree., about 20.degree. to about
70.degree., about 15.degree. to about 60.degree., about 30.degree.
to about 60.degree., about 40.degree. to about 80.degree., about
20.degree. to about 40.degree., about 10.degree. to about
30.degree., about 15.degree. to about 45.degree., or about
25.degree. to about 35.degree.. Other suitable tilting angles
include, about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,
23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,
40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 52, 54, 56, 58, 60, 62,
64, 66, 68, 70, 72, 74, 76, 78, or 80.degree..
[0212] The graphene film can include one or more layers of graphene
as noted above. As used herein "graphene" refers to graphene as
well as chemically- and electrochemically-modified graphene (e.g.
covalent or non-covalent modifications). The graphene film can
further include a support or backing layer when provided in the
fluid. For example, the support layer can be PMMA. In embodiments
in which the graphene film is provided with a support layer, the
support layer can be washed away after the graphene film is coated
on the at least one tip. For example, when PMMA is used a support
layer, acetone can be used to remove the PMMA layer after the tip
is coated.
[0213] The graphene film provided in the fluid optionally can be
larger in size than the tip or tip array to be coated. The portion
of the graphene sheet extending beyond the tip or the tip array in
such an arrangement can be coated on a glass slide or cantilever
supporting the tip or tip array. Such excess coating can
advantageously be used as electrical contact points to electrically
connect the graphene film and thereby the tip or tip array to a
voltage source. This, in turn, can allow for a simple means of
providing electro- or thermal-patterning functionality to the
tips.
[0214] As proof of concept, hard tip soft spring lithography tip
arrays were conformally coated with a multilayer film of graphene
20. In a typical experiment, 1.times.1 cm2 HSL tip arrays with
4,490 tips and a tip-to-tip pitch of 150 .mu.m were fabricated as
described in paragraph 128 above. Large-area graphene films grown
by chemical vapor deposition (CVD) on Ni films (Graphene
Laboratories Inc.) were used, and a thin poly(methylmethacrylate)
(PMMA) 22 (70 nm) layer was spin coated on the graphene, acting as
a supporting layer for the graphene upon the separation of the
graphene from the Ni film. The PMMA/graphene was separated from the
Ni film by etching away the Ni with a 1M FeCl3 solution, and the
PMMA/graphene was washed in DI water.
[0215] Following etching of the Ni film, the separated
PMMA/graphene film was transferred onto a HSL tip array (1.times.1
cm2) having silicon tips that had been pre-treated with oxygen
plasma. The transfer took place while the PMMA/graphene layer was
floating on a mixture of water and ethanol (1:2 V/V). The HSL tip
array was submerged in the liquid and held at an angle of
.about.40.degree. with respect to the surface. The solvent was then
allowed to evaporate, which caused the PMMA/graphene to fall onto
the tip array and coat it conformally.
[0216] Tilting the array during the solvent evaporation process
significantly improved the coverage of graphene onto the tip array
(FIG. 25B), while utilizing a mixture of the water and ethanol
reduced the surface tension and improved the conformal coating
(FIG. 13B). Subsequent washing with acetone was used to remove the
PMMA. The graphene-coated, glass-supported tip arrays remained
transparent, which allowed for optical leveling of the tips with
respect to a surface.
[0217] Low flexural rigidity also leads to surface wrinkles when a
layer experiences small compressive strain during the coating of a
flat surface. On further compression that can arise from coating an
uneven surface, the wrinkles become unstable and new morphologies
emerge, namely folds. Folds are observed between tips. This
repetitive fold formation between the tips finally generates a
network of folds that completely connect tip to tip, thus
indicating complete coverage of even PMMA/graphene. Once the PMMA
layer is removed, the flexural rigidity decreases and the graphene
experiences more mechanical sagging to the surface. Indeed, as the
network of folds formed by PMMA/graphene can be clearly seen, the
graphene fold network can only be imaged by AFM and is not clearly
observable under an optical microscope. This excellent flexibility
of graphene, which allows it to conform to the surface, leads to
ultra-strong adhesion to the tip surface, owing to the graphene's
interaction with the surface being more liquid-like than
solid-like. Furthermore, the folds make the graphene layers more
stable and resistant to mechanical stretching by making the layers
more expandable, thus more coherently coupling the graphene to the
tips during writing.
Beam Pent Lithography Patterning
[0218] In accordance with embodiments of the disclosure, projected
lithography can be used in connection with a beam pen tip array.
Referring again to FIG. 19, beam pen lithography generally includes
bringing a transparent polymer tip array in contact with a
photosensitive layer, for example, for example SHIPLEY1805
(MicroChem Inc.) photoresist material, followed by exposure (e.g.
irradiation) of the top surface (the substrate layer) of the tip
array 10 with a radiation source. The projected lithography system
controls the exposure as described above. As a result of the
blocking layer 16 blocking the radiation (e.g., by reflection), the
radiation is transmitted through the transparent polymer and out
the portion of the transparent polymer exposed by the aperture 18
(i.e., the tip end). Historically, photolithography has used
ultraviolet light from gas-discharge lamps using mercury, sometimes
in combination with noble gases such as xenon. These lamps produce
light across a broad spectrum with several strong peaks in the
ultraviolet range. This spectrum is filtered to select a single
spectral line, for example the "g-line" (436 nm) or "i-line" (365
nm). More recently, lithography has moved to "deep ultraviolet,"
for example wavelengths below 300 nm, which can be produced by
excimer lasers. Krypton fluoride produces a 248-nm spectral line,
and argon fluoride a 193-nm line. The type of radiation used with
the present apparatus and methods is not limited. One practical
consideration is compatibility with the tip array materials.
Radiation in the wavelength range of about 300 nm to about 600 nm
is preferred, optionally 380 nm to 420 nm, for example about 365
nm, about 400 nm, or about 436 nm. For example, the radiation
optionally can have a minimum wavelength of about 300, 350, 400,
450, 500, 550, or 600 nm. For example, the radiation optionally can
have a maximum wavelength of about 300, 350, 400, 450, 500, 550, or
600 nm.
[0219] The photosensitive layer 20 can be exposed by the radiation
transmitted through the polymer tip for any suitable time, for
example in a range of about 1 second to about 1 minute. For
example, the minimum exposure time can be about 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 20, 30, 40, 50, or 60 seconds. For example, the
maximum exposure time can be about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
20, 30, 40, 50, or 60 seconds.
[0220] The tip array 10 and/or the substrate can be moved during
patterning to form the desired indicia. For example, in one
embodiment, the tip array 10 is moved while the substrate is held
stationary. In another embodiment, the tip array 10 is held
stationary while the substrate is moved. In yet another embodiment,
both the tip array 10 and the substrate are moved.
[0221] The method can further include developing the photosensitive
layer 20, for example by any suitable process known in the art. For
example, when a resist layer is used, the exposed resist layer can
be developed for by exposed for about 30 seconds in MF319 (Rohm
& Haas Electronic Materials LLC). The resist layer can be a
positive resist or a negative resist. If a positive resist layer is
used, developing of the resist layer 20 removes the exposed portion
of the resist layer. If a negative resist layer is used, developing
of the resist layer removes the unexposed portion of the resist
layer.
[0222] Optionally, the method can further include depositing a
patterning layer on the substrate surface after exposure followed
by lift off of the resist layer to thereby form the patterning
layer into the indicia printed on the resist layer by BPL. The
patterning layer can be a metal, for example, and can be deposited,
for example, by thermal evaporation. The resist lift off can be
performed using, for example, acetone. For example, the patterns
formed by pBPL can be developed for one minute in MF24A (MicroChem
Inc., USA). The patterning layer can then be evaporated onto the
sample. For example, the patterning layer can be 5 nm of Cr and 15
nm of Au. With such patterning compositions, an overnight lift-off
procedure can be performed, for example, in Remover PG (MicroChem
Inc., USA) to form the final patterns.
[0223] Another factor contributing to BPL resolution is the tip
aperture 18 size, which controls the area of the resist which is
exposed to light from the tip. Referring to FIG. 4A, with a near UV
light or halogen light source and conventional photolithography
conditions, dot sizes close to and below the light diffraction
limit, of about 200 nm. Without intending to be bound by any
particular theory, it is believed that this small feature size may
be attributed to near-field effects at the point-of-contact between
the tip and surface. Even though the aperture 18 used to create a
small, for example 200 nm dots can be 500 nm, the contact area is
much smaller, acting like a light pipe. Further optimization of the
photolithography conditions can include, for example, using deep-UV
illumination, thinner resist layers, and high resolution resist
materials, which may improve BPL resolution down to the sub-100 nm
range.
[0224] The features that can be patterned range from sub-100 nm to
1 mm in size or greater, and can be controlled by altering the
exposure time and/or the contacting pressure of the tip array
10.
[0225] The BPL tip arrays can exhibit pressure dependence which
results from the compressible nature of the polymer used to form
the tip array 10. Indeed, the microscopic, preferably pyramidal,
tips 14 can be made to deform with successively increasing amounts
of applied pressure, which can be controlled by simply extending
the piezo in the vertical direction (z-piezo). The controlled
deformation of the tip array 10 can be used as an adjustable
variable, allowing one to control tip-substrate contact area and
resulting feature size. The pressure of the contact can be
controlled by the z-piezo of a piezo scanner. The more pressure (or
force) exerted on the tip array 10, the larger the feature size.
Thus, any combination of contacting time and contacting
force/pressure can provide a means for the formation of a feature
size from about 30 nm to about 1 mm or greater. Within the pressure
range allowed by z-piezo extension of about 5 to about 25 .mu.m,
one can observe a near linear relationship between piezo extension
and feature size at a fixed contact time of 1 s. The substrate
layer of the tip arrays can deform before deformation of the tips
14 occurs, which can offer a buffering provides extra tolerance in
bringing all of the tips 14 in contact with the surface without tip
deformation and significantly changing the intended feature size.
The contacting pressure of the tip array 10 can be about 10 MPa to
about 300 MPa.
[0226] At very low contact pressures, such as pressures of about
0.01 to about 0.1 g/cm2 for the preferred materials described
herein, the feature size of the resulting indicia is independent of
the contacting pressure, which allows for one to level the tip
array 10 on the substrate surface without changing the feature size
of the indicia. Such low pressures are achievable by 0.5 .mu.m or
less extensions of the z-piezo of a piezo scanner to which a tip
array 10 is mounted, and pressures of about 0.01 g/cm2 to about 0.1
g/cm2 can be applied by z-piezo extensions of less than 0.5 .mu.m.
This "buffering" pressure range allows one to manipulate the tip
array 10, substrate, or both to make initial contact between tips
14 and substrate surface without compressing the tips 14, and then
using the degree of compression of tips 14 (observed by changes in
reflection of light off the inside surfaces of the tips 14) to
achieve a uniform degree of contact between tips 14 and substrate
surface. This leveling ability is important, as non-uniform contact
of the tips 14 of the tip array 10 can lead to non-uniform indicia.
Given the large number of tips 14 of the tip array 10 (e.g., 11
million in an example provided herein) and their small size, as a
practical matter it may be difficult or impossible to know
definitively if all of the tips 14 are in contact with the surface.
For example, a defect in a tip or the substrate surface, or an
irregularity in a substrate surface, may result in a single tip not
making contact while all other tips 14 are in uniform contact.
Thus, the disclosed methods provide for at least substantially all
of the tips 14 to be in contact with the substrate surface (e.g.,
to the extent detectable). For example, at least 90%, at least 95%,
at least 96%, at least 97%, at least 98%, or at least 99% of the
tips 14 will be in contact with the substrate surface.
[0227] The leveling of the tip array 10 and substrate surface with
respect to one another can be assisted by the transparent, or at
least translucent nature of the tip array 10 and tip substrate
layer 12, which allow for detection of a change in reflection of
light that is directed from the top of the tip array 10 (i.e.,
behind the base of the tips 14 and common substrate) through to the
substrate surface. The intensity of light reflected from the tips
14 of the tip array 10 increases upon contact with the substrate
surface (e.g., the internal surfaces of the tip array 10 reflect
light differently upon contact). By observing the change in
reflection of light at each tip, the tip array 10 and/or the
substrate surface can be adjusted to effect contact of
substantially all or all of the tips 14 of the tip array 10 to the
substrate surface. Thus, the tip array 10 and common substrate
preferably are translucent or transparent to allow for observing
the change in light reflection of the tips 14 upon contact with the
substrate surface. Likewise, any rigid backing material to which
the tip array 10 is mounted is also preferably at least transparent
or translucent.
[0228] The contacting time for the tips 14 can be from about 0.001
seconds to about 60 seconds. For example, the minimum contact time
can be about 0.001, 0.01, 0.1, 1, 10, 20, 30, 40, 50, or 60
seconds. For example, the maximum contact time can be about 0.001,
0.01, 0.1, 1, 10, 20, 30, 40, 50, or 60 seconds. The contacting
force can be controlled by altering the z-piezo of the piezo
scanner or by other means that allow for controlled application of
force across the tip array 10.
[0229] The substrate surface can be contacted with a tip array 10 a
plurality of times, wherein the tip array 10, the substrate surface
or both move to allow for different portions of the substrate
surface to be contacted. The time and pressure of each contacting
step can be the same or different, depending upon the desired
pattern. The shape of the indicia or patterns has no practical
limitation, and can include dots, lines (e.g., straight or curved,
formed from individual dots or continuously), a preselected
pattern, or any combination thereof.
[0230] The indicia resulting from the disclosed methods have a high
degree of sameness, and thus are uniform or substantially uniform
in size, and preferably also in shape. The individual indicia
feature size (e.g., a dot or line width) is highly uniform, for
example within a tolerance of about 5%, or about 1%, or about 0.5%.
The tolerance can be about 0.9%, about 0.8%, about 0.7%, about
0.6%, about 0.4%, about 0.3%, about 0.2%, or about 0.1%.
Non-uniformity of feature size and/or shape can lead to roughness
of indicia that can be undesirable for sub-micron type
patterning.
[0231] The feature size can be about 10 nm to about 1 mm, about 10
nm to about 500 .mu.m, about 10 nm to about 100 .mu.m, about 50 nm
to about 100 .mu.m, about 50 nm to about 50 .mu.m, about 50 nm to
about 10 .mu.m, about 50 nm to about 5 .mu.m, or about 50 nm to
about 1 .mu.m. Features sizes can be less than 1 .mu.m, less than
about 900 nm, less than about 800 nm, less than about 700 nm, less
than about 600 nm, less than about 500 nm, less than about 400 nm,
less than about 300 nm, less than about 200 nm, less than about 100
nm, or less than about 90 nm.
Patterning Compositions
[0232] For ink-based patterning, patterning compositions suitable
for use in the disclosed methods include both homogeneous and
heterogeneous compositions, the latter referring to a composition
having more than one component, for example combinations of any one
or more of the components described herein. The patterning
composition is coated on the tip array. The term "coating," as used
herein when referring to the patterning composition, refers both to
coating of the tip array as well adsorption and absorption by the
tip array of the patterning composition. Upon coating of the tip
array with the patterning composition, the patterning composition
can be patterned on a substrate surface using the tip array.
[0233] Patterning compositions can be liquids, solids, semi-solids,
and the like. Patterning compositions suitable for use include, but
are not limited to, molecular solutions, polymer solutions, pastes,
gels, creams, glues, resins, epoxies, adhesives, metal films,
particulates, solders, etchants, and combinations thereof.
[0234] Patterning compositions can include materials such as, but
not limited to, monolayer-forming species, thin film-forming
species, oils, colloids, metals, metal complexes, metal oxides,
ceramics, organic species (e.g., moieties comprising a
carbon-carbon bond, such as small molecules, polymers, polymer
precursors, proteins, antibodies, and the like), polymers (e.g.,
both non-biological polymers and biological polymers such as single
and double stranded DNA, RNA, and the like), polymer precursors,
dendrimers, nanoparticles, and combinations thereof. In some
embodiments, one or more components of a patterning composition
includes a functional group suitable for associating with a
substrate, for example, by forming a chemical bond, by an ionic
interaction, by a Van der Waals interaction, by an electrostatic
interaction, by magnetism, by adhesion, and combinations
thereof.
[0235] The composition can be formulated to control its viscosity,
via routine methods without undue experimentation. Parameters that
can control ink viscosity include, but are not limited to, solvent
composition, solvent concentration, thickener composition,
thickener concentration, particles size of a component, the
molecular weight of a polymeric component, the degree of
cross-linking of a polymeric component, the free volume (i.e.,
porosity) of a component, the swellability of a component, ionic
interactions between ink components (e.g., solvent-thickener
interactions), and combinations thereof.
[0236] In some embodiments, the patterning composition comprises an
additive, such as a solvent, a thickening agent, an ionic species
(e.g., a cation, an anion, a zwitterion, etc.), a carrier matrix
(e.g., polyethylene glycol or agarose), the concentration of which
can be selected to adjust one or more of the viscosity, the
dielectric constant, the conductivity, the tonicity, the density,
and the like.
[0237] Suitable thickening agents include, but are not limited to,
metal salts of carboxyalkylcellulose derivatives (e.g., sodium
carboxymethylcellulose), alkylcellulose derivatives (e.g.,
methylcellulose and ethylcellulose), partially oxidized
alkylcellulose derivatives (e.g., hydroxyethylcellulose,
hydroxypropylcellulose and hydroxypropylmethylcellulose), starches,
polyacrylamide gels, homopolymers of poly-N-vinylpyrrolidone,
poly(alkyl ethers) (e.g., polyethylene oxide, polyethylene glycol,
and polypropylene oxide), agar, agarose, xanthan gums, gelatin,
dendrimers, colloidal silicon dioxide, lipids (e.g., fats, oils,
steroids, waxes, glycerides of fatty acids, such as oleic,
linoleic, linolenic, and arachidonic acid, and lipid bilayers such
as from phosphocholine) and combinations thereof. In some
embodiments, a thickener is present in a concentration of about
0.5% to about 25%, about 1% to about 20%, or about 5% to about 15%
by weight of a patterning composition.
[0238] Suitable solvents for a patterning composition include, but
are not limited to, water, C1-C8 alcohols (e.g., methanol, ethanol,
propanol and butanol), C6-C12 straight chain, branched and cyclic
hydrocarbons (e.g., hexane and cyclohexane), C6-C14 aryl and
aralkyl hydrocarbons (e.g., benzene and toluene), C3-C10 alkyl
ketones (e.g., acetone), C3-C10 esters (e.g., ethyl acetate),
C4-C10 alkyl ethers, and combinations thereof. In some embodiments,
a solvent is present in a concentration of about 1% to about 99%,
about 5% to about 95%, about 10% to about 90%, about 15% to about
95%, about 25% to about 95%, about 50% to about 95%, or about 75%
to about 95% by weight of a patterning composition.
[0239] Patterning compositions can comprise an etchant. As used
herein, an "etchant" refers to a component that can react with a
surface to remove a portion of the surface. Thus, an etchant is
used to form a subtractive feature by reacting with a surface and
forming at least one of a volatile and/or soluble material that can
be removed from the substrate, or a residue, particulate, or
fragment that can be removed from the substrate by, for example, a
rinsing or cleaning method. In some embodiments, an etchant is
present in a concentration of about 0.5% to about 95%, about 1% to
about 90%, about 2% to about 85%, about 0.5% to about 10%, or about
1% to about 10% by weight of the patterning composition.
[0240] Etchants suitable for use in the methods disclosed herein
include, but are not limited to, an acidic etchant, a basic
etchant, a fluoride-based etchant, and combinations thereof. Acidic
etchants suitable for use with the present invention include, but
are not limited to, sulfuric acid, trifluoromethanesulfonic acid,
fluorosulfonic acid, trifluoroacetic acid, hydrofluoric acid,
hydrochloric acid, carborane acid, and combinations thereof. Basic
etchants suitable for use with the present invention include, but
are not limited to, sodium hydroxide, potassium hydroxide, ammonium
hydroxide, tetraalkylammonium hydroxide ammonia, ethanolamine,
ethylenediamine, and combinations thereof. Fluoride-based etchants
suitable for use with the present invention include, but are not
limited to, ammonium fluoride, lithium fluoride, sodium fluoride,
potassium fluoride, rubidium fluoride, cesium fluoride, francium
fluoride, antimony fluoride, calcium fluoride, ammonium
tetrafluoroborate, potassium tetrafluoroborate, and combinations
thereof.
[0241] The patterning composition can include a reactive component.
As used herein, a "reactive component" refers to a compound or
species that has a chemical interaction with a substrate. In some
embodiments, a reactive component in the ink penetrates or diffuses
into the substrate. In some embodiments, a reactive component
transforms, binds, or promotes binding to exposed functional groups
on the surface of the substrate. Reactive components can include,
but are not limited to, ions, free radicals, metals, acids, bases,
metal salts, organic reagents, and combinations thereof. Reactive
components further include, without limitation, monolayer-forming
species such as thiols, hydroxides, amines, silanols, siloxanes,
and the like, and other monolayer-forming species known to a person
or ordinary skill in the art. The reactive component can be present
in a concentration of about 0.001% to about 100%, about 0.001% to
about 50%, about 0.001% to about 25%, about 0.001% to about 10%,
about 0.001% to about 5%, about 0.001% to about 2%, about 0.001% to
about 1%, about 0.001% to about 0.5%, about 0.001% to about 0.05%,
about 0.01% to about 10%, about 0.01% to about 5%, about 0.01% to
about 2%, about 0.01% to about 1%, about 10% to about 100%, about
50% to about 99%, about 70% to about 95%, about 80% to about 99%,
about 0.001%, about 0.005%, about 0.01%, about 0.1%, about 0.5%,
about 1%, about 2%, or about 5% weight of the patterning
composition.
[0242] The patterning composition can comprise a conductive and/or
semi-conductive component. As used herein, a "conductive component"
refers to a compound or species that can transfer or move
electrical charge. Conductive and semi-conductive components
include, but are not limited to, a metal, a nanoparticle, a
polymer, a cream solder, a resin, and combinations thereof. In some
embodiments, a conductive component is present in a concentration
of about 1% to about 100%, about 1% to about 10%, about 5% to about
100%, about 25% to about 100%, about 50% to about 100%, about 75%
to about 99%, about 2%, about 5%, about 90%, about 95% by weight of
the patterning composition.
[0243] Metals suitable for use in a patterning composition include,
but are not limited to, a transition metal, aluminum, silicon,
phosphorous, gallium, germanium, indium, tin, antimony, lead,
bismuth, alloys thereof, and combinations thereof.
[0244] The patterning composition can comprise a semi-conductive
polymer. Semi-conductive polymers suitable for use with the present
invention include, but are not limited to, a polyaniline, a
poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), a
polypyrrole, an arylene vinylene polymer, a polyphenylenevinylene,
a polyacetylene, a polythiophene, a polyimidazole, and combinations
thereof.
[0245] The patterning composition can include an insulating
component. As used herein, an "insulating component" refers to a
compound or species that is resistant to the movement or transfer
of electrical charge. In some embodiments, an insulating component
has a dielectric constant of about 1.5 to about 8 about 1.7 to
about 5, about 1.8 to about 4, about 1.9 to about 3, about 2 to
about 2.7, about 2.1 to about 2.5, about 8 to about 90, about 15 to
about 85, about 20 to about 80, about 25 to about 75, or about 30
to about 70. Insulating components suitable for use in the methods
disclosed herein include, but are not limited to, a polymer, a
metal oxide, a metal carbide, a metal nitride, monomeric precursors
thereof, particles thereof, and combinations thereof. Suitable
polymers include, but are not limited to, a polydimethylsiloxane, a
silsesquioxane, a polyethylene, a polypropylene, a polyimide, and
combinations thereof. In some embodiments, for example, an
insulating component is present in a concentration of about 1% to
about 95%, about 1% to about 80%, about 1% to about 50%, about 1%
to about 20%, about 1% to about 10%, about 20% to about 95%, about
20% to about 90%, about 40% to about 80%, about 1%, about 5%, about
10%, about 90%, or about 95% by weight of the patterning
composition.
[0246] The patterning composition can include a masking component.
As used herein, a "masking component" refers to a compound or
species that upon reacting forms a surface feature resistant to a
species capable of reacting with the surrounding surface. Masking
components suitable for use with the present invention include
materials commonly employed in traditional photolithography methods
as "resists" (e.g., photoresists, chemical resists, self-assembled
monolayers, etc.). Masking components suitable for use in the
disclosed methods include, but are not limited to, a polymer such
as a polyvinylpyrollidone, poly(epichlorohydrin-co-ethyleneoxide),
a polystyrene, a poly(styrene-co-butadiene), a
poly(4-vinylpyridine-co-styrene), an amine terminated
poly(styrene-co-butadiene), a poly(acrylonitrile-co-butadiene), a
styrene-butadiene-styrene block copolymer, a
styrene-ethylene-butylene block linear copolymer, a
polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene, a
poly(styrene-co-maleic anhydride), a
polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-mal-
eic anhydride, a polystyrene-block-polyisoprene-block-polystyrene,
a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene,
a polynorbornene, a dicarboxy terminated
poly(acrylonitrile-co-butadiene-co-acrylic acid), a dicarboxy
terminated poly(acrylonitrile-co-butadiene), a polyethyleneimine, a
poly(carbonate urethane), a
poly(acrylonitrile-co-butadiene-co-styrene), a poly(vinylchloride),
a poly(acrylic acid), a poly(methylmethacrylate), a poly(methyl
methacrylate-co-methacrylic acid), a polyisoprene, a
poly(1,4-butylene terephthalate), a polypropylene, a poly(vinyl
alcohol), a poly(1,4-phenylene sulfide), a polylimonene, a
poly(vinylalcohol-co-ethylene), a
poly[N,N'-(1,3-phenylene)isophthalamide], a poly(1,4-phenylene
ether-ether-sulfone), a poly(ethyleneoxide), a poly[butylene
terephthalate-co-poly(alkylene glycol) terephthalate], a
poly(ethylene glycol) diacrylate, a poly(4-vinylpyridine), a
poly(DL-lactide), a poly(3,3',4,4'-benzophenonetetracarboxylic
dianhydride-co-4,4'-oxydianiline/1,3-phenylenediamine), an agarose,
a polyvinylidene fluoride homopolymer, a styrene butadiene
copolymer, a phenolic resin, a ketone resin, a
4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxane, a salt thereof,
and combinations thereof. In some embodiments, a masking component
is present in a concentration of about 1% to about 10%, about 1% to
about 5%, or about 2% by weight of the patterning composition.
[0247] The patterning composition can include a conductive
component and a reactive component. For example, a reactive
component can promote at least one of: penetration of a conductive
component into a surface, reaction between the conductive component
and a surface, adhesion between a conductive feature and a surface,
promoting electrical contact between a conductive feature and a
surface, and combinations thereof. Surface features formed by
reacting this patterning composition include conductive features
selected from the group consisting of: additive non-penetrating,
additive penetrating, subtractive penetrating, and conformal
penetrating surface features.
[0248] The patterning composition can comprise an etchant and a
conductive component, for example, suitable for producing a
subtractive surface feature having a conductive feature inset
therein.
[0249] The patterning composition can comprise an insulating
component and a reactive component. For example, a reactive
component can promote at least one of: penetration of an insulating
component into a surface, reaction between the insulating component
and a surface, adhesion between an insulating feature and a
surface, promoting electrical contact between an insulating feature
and a surface, and combinations thereof. Surface features formed by
reacting this patterning composition include insulating features
selected from the group consisting of: additive non-penetrating,
additive penetrating, subtractive penetrating, and conformal
penetrating surface features.
[0250] The patterning composition can comprise an etchant and an
insulating component, for example, suitable for producing a
subtractive surface feature having an insulating feature inset
therein.
[0251] The patterning composition can comprise a conductive
component and a masking component, for example, suitable for
producing electrically conductive masking features on a
surface.
[0252] Other contemplated components of a patterning composition
suitable for use with the disclosed methods include thiols,
1,9-nonanedithiol solution, silane, silazanes, alkynes cystamine,
N-Fmoc protected amino thiols, biomolecules, DNA, proteins,
antibodies, collagen, peptides, biotin, and carbon nanotubes.
[0253] For a description of patterning compounds and patterning
compositions, and their preparation and use, see Xia and
Whitesides, Angew. Chem. Int. Ed., 37, 550-575 (1998) and
references cited therein; Bishop et al., Curr. Opinion Colloid
& Interface Sci., 1, 127-136 (1996); Calvert, J. Vac. Sci.
Technol. B, 11, 2155-2163 (1993); Ulman, Chem. Rev., 96:1533 (1996)
(alkanethiols on gold); Dubois et al., Annu. Rev. Phys. Chem.,
43:437 (1992) (alkanethiols on gold); Ulman, An Introduction to
Ultrathin Organic Films: From Langmuir-Blodgett to Self-Assembly
(Academic, Boston, 1991) (alkanethiols on gold); Whitesides,
Proceedings of the Robert A. Welch Foundation 39th Conference On
Chemical Research Nanophase Chemistry, Houston, Tex., pages 109-121
(1995) (alkanethiols attached to gold); Mucic et al. Chem. Commun.
555-557 (1996) (describes a method of attaching 3' thiol DNA to
gold surfaces); U.S. Pat. No. 5,472,881 (binding of
oligonucleotide-phosphorothiolates to gold surfaces); Burwell,
Chemical Technology, 4, 370-377 (1974) and Matteucci and Caruthers,
J. Am. Chem. Soc., 103, 3185-3191 (1981) (binding of
oligonucleotides-alkylsiloxanes to silica and glass surfaces);
Grabar et al., Anal. Chem., 67, 735-743 (binding of
aminoalkylsiloxanes and for similar binding of
mercaptoalkylsiloxanes); Nuzzo et al., J. Am. Chem. Soc., 109, 2358
(1987) (disulfides on gold); Allara and Nuzzo, Langmuir, 1, 45
(1985) (carboxylic acids on aluminum); Allara and Tompkins, J.
Colloid Interfate Sci., 49, 410-421 (1974) (carboxylic acids on
copper); Iler, The Chemistry Of Silica, Chapter 6, (Wiley 1979)
(carboxylic acids on silica); Timmons and Zisman, J. Phys. Chem.,
69, 984-990 (1965) (carboxylic acids on platinum); Soriaga and
Hubbard, J. Am. Chem. Soc., 104, 3937 (1982) (aromatic ring
compounds on platinum); Hubbard, Acc. Chem. Res., 13, 177 (1980)
(sulfolanes, sulfoxides and other functionalized solvents on
platinum); Hickman et al., J. Am. Chem. Soc., 111, 7271 (1989)
(isonitriles on platinum); Maoz and Sagiv, Langmuir, 3, 1045 (1987)
(silanes on silica); Maoz and Sagiv, Langmuir, 3, 1034 (1987)
(silanes on silica); Wasserman et al., Langmuir, 5, 1074 (1989)
(silanes on silica); Eltekova and Eltekov, Langmuir, 3,951 (1987)
(aromatic carboxylic acids, aldehydes, alcohols and methoxy groups
on titanium dioxide and silica); and Lec et al., J. Phys. Chem.,
92, 2597 (1988) (rigid phosphates on metals); Lo et al., J. Am.
Chem. Soc., 118, 11295-11296 (1996) (attachment of pyrroles to
superconductors); Chen et al., J. Am. Chem. Soc., 117, 6374-5
(1995) (attachment of amines and thiols to superconductors); Chen
et al., Langmuir, 12, 2622-2624 (1996) (attachment of thiols to
superconductors); McDevitt et al., U.S. Pat. No. 5,846,909
(attachment of amines and thiols to superconductors); Xu et al.,
Langmuir, 14, 6505-6511 (1998) (attachment of amines to
superconductors); Mirkin et al., Adv. Mater. (Weinheim, Ger.), 9,
167-173 (1997) (attachment of amines to superconductors); Hovis et
al., J. Phys. Chem. B, 102, 6873-6879 (1998) (attachment of olefins
and dienes to silicon); Hovis et al., Surf. Sci., 402-404, 1-7
(1998) (attachment of olefins and dienes to silicon); Hovis et al.,
J. Phys. Chem. B, 101, 9581-9585 (1997) (attachment of olefins and
dienes to silicon); Hamers et al., J. Phys. Chem. B, 101, 1489-1492
(1997) (attachment of olefins and dienes to silicon); Hamers et
al., U.S. Pat. No. 5,908,692 (attachment of olefins and dienes to
silicon); Ellison et al., J. Phys. Chem. B, 103, 6243-6251 (1999)
(attachment of isothiocyanates to silicon); Ellison et al., J.
Phys. Chem. B, 102, 8510-8518 (1998) (attachment of azoalkanes to
silicon); Ohno et al., Mol. Cryst. Liq. Cryst. Sci. Technol., Sect.
A, 295, 487-490 (1997) (attachment of thiols to GaAs); Reuter et
al., Mater. Res. Soc. Symp. Proc., 380, 119-24 (1995) (attachment
of thiols to GaAs); Bain, Adv. Mater. (Weinheim, Fed. Repub. Ger.),
4, 591-4 (1992) (attachment of thiols to GaAs); Sheen et al., J.
Am. Chem. Soc., 114, 1514-15 (1992) (attachment of thiols to GaAs);
Nakagawa et al., Jpn. J. Appl. Phys., Part 1, 30, 3759-62 (1991)
(attachment of thiols to GaAs); Lunt et al., J. Appl. Phys., 70,
7449-67 (1991) (attachment of thiols to GaAs); Lunt et al., J. Vac.
Sci. Technol., B, 9, 2333-6 (1991) (attachment of thiols to GaAs);
Yamamoto et al., Langmuir ACS ASAP, web release number Ia990467r
(attachment of thiols to InP); Gu et al., J. Phys. Chem. B, 102,
9015-9028 (1998) (attachment of thiols to InP); Menzel et al., Adv.
Mater. (Weinheim, Ger.), 11, 131-134 (1999) (attachment of
disulfides to gold); Yonezawa et al., Chem. Mater., 11, 33-35
(1999) (attachment of disulfides to gold); Porter et al., Langmuir,
14, 7378-7386 (1998) (attachment of disulfides to gold); Son et
al., J. Phys. Chem., 98, 8488-93 (1994) (attachment of nitriles to
gold and silver); Steiner et al., Langmuir, 8, 2771-7 (1992)
(attachment of nitriles to gold and copper); Solomun et al., J.
Phys. Chem., 95, 10041-9 (1991) (attachment of nitriles to gold);
Solomun et al., Ber. Bunsen-Ges. Phys. Chem., 95, 95-8 (1991)
(attachment of nitriles to gold); Henderson et al., Inorg. Chim.
Acta, 242, 115-24 (1996) (attachment of isonitriles to gold); Huc
et al., J. Phys. Chem. B, 103, 10489-10495 (1999) (attachment of
isonitriles to gold); Hickman et al., Langmuir, 8, 357-9 (1992)
(attachment of isonitriles to platinum); Steiner et al., Langmuir,
8, 90-4 (1992) (attachment of amines and phospines to gold and
attachment of amines to copper); Mayya et al., J. Phys. Chem. B,
101, 9790-9793 (1997) (attachment of amines to gold and silver);
Chen et al., Langmuir, 15, 1075-1082 (1999) (attachment of
carboxylates to gold); Tao, J. Am. Chem. Soc., 115, 4350-4358
(1993) (attachment of carboxylates to copper and silver); Laibinis
et al., J. Am. Chem. Soc., 114, 1990-5 (1992) (attachment of thiols
to silver and copper); Laibinis et al., Langmuir, 7, 3167-73 (1991)
(attachment of thiols to silver); Fenter et al., Langmuir, 7,
2013-16 (1991) (attachment of thiols to silver); Chang et al., Am.
Chem. Soc., 116, 6792-805 (1994) (attachment of thiols to silver);
Li et al., J. Phys. Chem., 98, 11751-5 (1994) (attachment of thiols
to silver); Li et al., Report, 24 pp (1994) (attachment of thiols
to silver); Tarlov et al., U.S. Pat. No. 5,942,397 (attachment of
thiols to silver and copper); Waldeck, et al., PCT application
WO/99/48682 (attachment of thiols to silver and copper); Gui et
al., Langmuir, 7, 955-63 (1991) (attachment of thiols to silver);
Walczak et al., J. Am. Chem. Soc., 113, 2370-8 (1991) (attachment
of thiols to silver); Sangiorgi et al., Gazz. Chim. Ital., 111,
99-102 (1981) (attachment of amines to copper); Magallon et al.,
Book of Abstracts, 215th ACS National Meeting, Dallas, Mar. 29-Apr.
2, 1998, COLL-048 (attachment of amines to copper); Patil et al.,
Langmuir, 14, 2707-2711 (1998) (attachment of amines to silver);
Sastry et al., J. Phys. Chem. B, 101, 4954-4958 (1997) (attachment
of amines to silver); Bansal et al., J. Phys. Chem. B. 102,
4058-4060 (1998) (attachment of alkyl lithium to silicon); Bansal
et al., J. Phys. Chem. B, 102, 1067-1070 (1998) (attachment of
alkyl lithium to silicon); Chidsey, Book of Abstracts, 214th ACS
National Meeting, Las Vegas, Nev., Sep. 7-11, 1997, I&EC-027
(attachment of alkyl lithium to silicon); Song, J. H., Thesis,
University of California at San Diego (1998) (attachment of alkyl
lithium to silicon dioxide); Meyer et al., J. Am. Chem. Soc., 110,
4914-18 (1988) (attachment of amines to semiconductors); Brazdil et
al. J. Phys. Chem., 85, 1005-14 (1981) (attachment of amines to
semiconductors); James et al., Langmuir, 14, 741-744 (1998)
(attachment of proteins and peptides to glass); Bernard et al.,
Langmuir, 14, 2225-2229 (1998) (attachment of proteins to glass,
polystyrene, gold, silver and silicon wafers); Pereira et al., J.
Mater. Chem., 10, 259 (2000) (attachment of silazanes to SiO2);
Pereira et al., J. Mater. Chem., 10, 259 (2000) (attachment of
silazanes to SiO2); Dammel, Diazonaphthoquinone Based Resists (1st
ed., SPIE Optical Engineering Press, Bellingham, Wash., 1993)
(attachment of silazanes to SiO2); Anwander et al., J. Phys. Chem.
B, 104, 3532 (2000) (attachment of silazanes to SiO2); Slavov et
al., J. Phys. Chem., 104, 983 (2000) (attachment of silazanes to
SiO2).
[0254] For a description of patterning compounds and patterning
compositions, and their preparation and use, see Xia and
Whitesides, Angew. Chem. Int. Ed., 37, 550-575 (1998) and
references cited therein; Bishop et al., Curr. Opinion Colloid
& Interface Sci., 1, 127-136 (1996); Calvert, J. Vac. Sci.
Technol. B, 11, 2155-2163 (1993); Ulman, Chem. Rev., 96:1533 (1996)
(alkanethiols on gold); Dubois et al., Annu. Rev. Phys. Chem.,
43:437 (1992) (alkanethiols on gold); Ulman, An Introduction to
Ultrathin Organic Films: From Langmuir-Blodgett to Self-Assembly
(Academic, Boston, 1991) (alkanethiols on gold); Whitesides,
Proceedings of the Robert A. Welch Foundation 39th Conference On
Chemical Research Nanophase Chemistry, Houston, Tex., pages 109-121
(1995) (alkanethiols attached to gold); Mucic et al. Chem. Commun.
555-557 (1996) (describes a method of attaching 3' thiol DNA to
gold surfaces); U.S. Pat. No. 5,472,881 (binding of
oligonucleotide-phosphorothiolates to gold surfaces); Burwell,
Chemical Technology, 4, 370-377 (1974) and Matteucci and Caruthers,
J. Am. Chem. Soc., 103, 3185-3191 (1981) (binding of
oligonucleotides-alkylsiloxanes to silica and glass surfaces);
Grabar et al., Anal. Chem., 67, 735-743 (binding of
aminoalkylsiloxanes and for similar binding of
mercaptoalkylsiloxanes); Nuzzo et al., J. Am. Chem. Soc., 109, 2358
(1987) (disulfides on gold); Allara and Nuzzo, Langmuir, 1, 45
(1985) (carboxylic acids on aluminum); Allara and Tompkins, J.
Colloid Interfate Sci., 49, 410-421 (1974) (carboxylic acids on
copper); Iler, The Chemistry Of Silica, Chapter 6, (Wiley 1979)
(carboxylic acids on silica); Timmons and Zisman, J. Phys. Chem.,
69, 984-990 (1965) (carboxylic acids on platinum); Soriaga and
Hubbard, J. Am. Chem. Soc., 104, 3937 (1982) (aromatic ring
compounds on platinum); Hubbard, Acc. Chem. Res., 13, 177 (1980)
(sulfolanes, sulfoxides and other functionalized solvents on
platinum); Hickman et al., J. Am. Chem. Soc., 111, 7271 (1989)
(isonitriles on platinum); Maoz and Sagiv, Langmuir, 3, 1045 (1987)
(silanes on silica); Maoz and Sagiv, Langmuir, 3, 1034 (1987)
(silanes on silica); Wasserman et al., Langmuir, 5, 1074 (1989)
(silanes on silica); Eltekova and Eltekov, Langmuir, 3,951 (1987)
(aromatic carboxylic acids, aldehydes, alcohols and methoxy groups
on titanium dioxide and silica); and Lec et al., J. Phys. Chem.,
92, 2597 (1988) (rigid phosphates on metals); Lo et al., J. Am.
Chem. Soc., 118, 11295-11296 (1996) (attachment of pyrroles to
superconductors); Chen et al., J. Am. Chem. Soc., 117, 6374-5
(1995) (attachment of amines and thiols to superconductors); Chen
et al., Langmuir, 12, 2622-2624 (1996) (attachment of thiols to
superconductors); McDevitt et al., U.S. Pat. No. 5,846,909
(attachment of amines and thiols to superconductors); Xu et al.,
Langmuir, 14, 6505-6511 (1998) (attachment of amines to
superconductors); Mirkin et al., Adv. Mater. (Weinheim, Ger.), 9,
167-173 (1997) (attachment of amines to superconductors); Hovis et
al., J. Phys. Chem. B, 102, 6873-6879 (1998) (attachment of olefins
and dienes to silicon); Hovis et al., Surf. Sci., 402-404, 1-7
(1998) (attachment of olefins and dienes to silicon); Hovis et al.,
J. Phys. Chem. B, 101, 9581-9585 (1997) (attachment of olefins and
dienes to silicon); Hamers et al., J. Phys. Chem. B, 101, 1489-1492
(1997) (attachment of olefins and dienes to silicon); Hamers et
al., U.S. Pat. No. 5,908,692 (attachment of olefins and dienes to
silicon); Ellison et al., J. Phys. Chem. B, 103, 6243-6251 (1999)
(attachment of isothiocyanates to silicon); Ellison et al., J.
Phys. Chem. B, 102, 8510-8518 (1998) (attachment of azoalkanes to
silicon); Ohno et al., Mol. Cryst. Liq. Cryst. Sci. Technol., Sect.
A, 295, 487-490 (1997) (attachment of thiols to GaAs); Reuter et
al., Mater. Res. Soc. Symp. Proc., 380, 119-24 (1995) (attachment
of thiols to GaAs); Bain, Adv. Mater. (Weinheim, Fed. Repub. Ger.),
4, 591-4 (1992) (attachment of thiols to GaAs); Sheen et al., J.
Am. Chem. Soc., 114, 1514-15 (1992) (attachment of thiols to GaAs);
Nakagawa et al., Jpn. J. Appl. Phys., Part 1, 30, 3759-62 (1991)
(attachment of thiols to GaAs); Lunt et al., J. Appl. Phys., 70,
7449-67 (1991) (attachment of thiols to GaAs); Lunt et al., J. Vac.
Sci. Technol., B, 9, 2333-6 (1991) (attachment of thiols to GaAs);
Yamamoto et al., Langmuir ACS ASAP, web release number Ia990467r
(attachment of thiols to InP); Gu et al., J. Phys. Chem. B, 102,
9015-9028 (1998) (attachment of thiols to InP); Menzel et al., Adv.
Mater. (Weinheim, Ger.), 11, 131-134 (1999) (attachment of
disulfides to gold); Yonezawa et al., Chem. Mater., 11, 33-35
(1999) (attachment of disulfides to gold); Porter et al., Langmuir,
14, 7378-7386 (1998) (attachment of disulfides to gold); Son et
al., J. Phys. Chem., 98, 8488-93 (1994) (attachment of nitriles to
gold and silver); Steiner et al., Langmuir, 8, 2771-7 (1992)
(attachment of nitriles to gold and copper); Solomun et al., J.
Phys. Chem., 95, 10041-9 (1991) (attachment of nitriles to gold);
Solomun et al., Ber. Bunsen-Ges. Phys. Chem., 95, 95-8 (1991)
(attachment of nitriles to gold); Henderson et al., Inorg. Chim.
Acta, 242, 115-24 (1996) (attachment of isonitriles to gold); Huc
et al., J. Phys. Chem. B, 103, 10489-10495 (1999) (attachment of
isonitriles to gold); Hickman et al., Langmuir, 8, 357-9 (1992)
(attachment of isonitriles to platinum); Steiner et al., Langmuir,
8, 90-4 (1992) (attachment of amines and phospines to gold and
attachment of amines to copper); Mayya et al., J. Phys. Chem. B,
101, 9790-9793 (1997) (attachment of amines to gold and silver);
Chen et al., Langmuir, 15, 1075-1082 (1999) (attachment of
carboxylates to gold); Tao, J. Am. Chem. Soc., 115, 4350-4358
(1993) (attachment of carboxylates to copper and silver); Laibinis
et al., J. Am. Chem. Soc., 114, 1990-5 (1992) (attachment of thiols
to silver and copper); Laibinis et al., Langmuir, 7, 3167-73 (1991)
(attachment of thiols to silver); Fenter et al., Langmuir, 7,
2013-16 (1991) (attachment of thiols to silver); Chang et al., Am.
Chem. Soc., 116, 6792-805 (1994) (attachment of thiols to silver);
Li et al., J. Phys. Chem., 98, 11751-5 (1994) (attachment of thiols
to silver); Li et al., Report, 24 pp (1994) (attachment of thiols
to silver); Tarlov et al., U.S. Pat. No. 5,942,397 (attachment of
thiols to silver and copper); Waldeck, et al., PCT application
WO/99/48682 (attachment of thiols to silver and copper); Gui et
al., Langmuir, 7, 955-63 (1991) (attachment of thiols to silver);
Walczak et al., J. Am. Chem. Soc., 113, 2370-8 (1991) (attachment
of thiols to silver); Sangiorgi et al., Gazz. Chim. Ital., 111,
99-102 (1981) (attachment of amines to copper); Magallon et al.,
Book of Abstracts, 215th ACS National Meeting, Dallas, Mar. 29-Apr.
2, 1998, COLL-048 (attachment of amines to copper); Patil et al.,
Langmuir, 14, 2707-2711 (1998) (attachment of amines to silver);
Sastry et al., J. Phys. Chem. B, 101, 4954-4958 (1997) (attachment
of amines to silver); Bansal et al., J. Phys. Chem. B. 102,
4058-4060 (1998) (attachment of alkyl lithium to silicon); Bansal
et al., J. Phys. Chem. B, 102, 1067-1070 (1998) (attachment of
alkyl lithium to silicon); Chidsey, Book of Abstracts, 214th ACS
National Meeting, Las Vegas, Nev., Sep. 7-11, 1997, I&EC-027
(attachment of alkyl lithium to silicon); Song, J. H., Thesis,
University of California at San Diego (1998) (attachment of alkyl
lithium to silicon dioxide); Meyer et al., J. Am. Chem. Soc., 110,
4914-18 (1988) (attachment of amines to semiconductors); Brazdil et
al. J. Phys. Chem., 85, 1005-14 (1981) (attachment of amines to
semiconductors); James et al., Langmuir, 14, 741-744 (1998)
(attachment of proteins and peptides to glass); Bernard et al.,
Langmuir, 14, 2225-2229 (1998) (attachment of proteins to glass,
polystyrene, gold, silver and silicon wafers); Pereira et al., J.
Mater. Chem., 10, 259 (2000) (attachment of silazanes to SiO2);
Pereira et al., J. Mater. Chem., 10, 259 (2000) (attachment of
silazanes to SiO2); Dammel, Diazonaphthoquinone Based Resists (1st
ed., SPIE Optical Engineering Press, Bellingham, Wash., 1993)
(attachment of silazanes to SiO2); Anwander et al., J. Phys. Chem.
B, 104, 3532 (2000) (attachment of silazanes to SiO2); Slavov et
al., J. Phys. Chem., 104, 983 (2000) (attachment of silazanes to
SiO2).
Substrates to be Patterned
[0255] Any suitable substrates can be patterned, depending on the
patterning methods used. For example, for beam pen lithography any
photosensitive substrate or substrate layer can be patterned. For
electrochemical deposition and suitable electro-sensitive substrate
or substrate layer can be used. For thermal deposition, a thermal
sensitive substrate can be used or a thermal sensitive ink
composition can be deposited on any substrate.
[0256] Substrates can include, but are not limited to, metals,
alloys, composites, crystalline materials, amorphous materials,
conductors, semiconductors, optics, fibers, inorganic materials,
glasses, ceramics (e.g., metal oxides, metal nitrides, metal
silicides, and combinations thereof), zeolites, polymers, plastics,
organic materials, minerals, biomaterials, living tissue, bone,
films thereof, thin films thereof, laminates thereof, foils
thereof, composites thereof, and combinations thereof. A substrate
can comprise a semiconductor such as, but not limited to:
crystalline silicon, polycrystalline silicon, amorphous silicon,
p-doped silicon, n-doped silicon, silicon oxide, silicon germanium,
germanium, gallium arsenide, gallium arsenide phosphide, indium tin
oxide, and combinations thereof. A substrate can comprise a glass
such as, but not limited to, undoped silica glass (SiO2),
fluorinated silica glass, borosilicate glass, borophosphorosilicate
glass, organosilicate glass, porous organosilicate glass, and
combinations thereof. The substrate can be a non-planar substrate,
such as pyrolytic carbon, reinforced carbon-carbon composite, a
carbon phenolic resin, and the like, and combinations thereof. A
substrate can comprise a ceramic such as, but not limited to,
silicon carbide, hydrogenated silicon carbide, silicon nitride,
silicon carbonitride, silicon oxynitride, silicon oxycarbide,
high-temperature reusable surface insulation, fibrous refractory
composite insulation tiles, toughened unipiece fibrous insulation,
low-temperature reusable surface insulation, advanced reusable
surface insulation, and combinations thereof. A substrate can
comprise a flexible material, such as, but not limited to: a
plastic, a metal, a composite thereof, a laminate thereof, a thin
film thereof, a foil thereof, and combinations thereof.
[0257] The substrate can comprise a compressible material. The
compressible material can be layered on top of a substrate as
described herein. Examples of compressible materials include, but
are not limited to, polymers, metals (e.g., soft metals), foils,
films, or the like. Non-limiting examples of a compressible layer
include polymethylmethacrylate (PMMA), polydimethylsiloxane (PDMS),
nitrocellulose, and combinations thereof.
[0258] The substrate can comprise a material that can be desorbed
upon application of electrical energy. Non-limiting examples of
such a material include 16-mercaptohexadecanoic acid (MHA) and
octadecanethiol (ODT), alkane thiols, and phosphonic acids.
Surfaces to be Patterned by pBPL
[0259] The surfaces to pattern by BPL can include any suitable
substrate, such as those described above which is photosensitive or
includes a photosensitive layer. For example, the photosensitive
substrate or photosensitive layer 20 can be a resist layer. The
resist layer can be any known resist material, for example
SHIPLEY1805 (MicroChem Inc.). Other suitable resist materials
include, but are not limited to, Shipley1813 (MicroChem Inc.),
Shipley1830 (MicroChem Inc.), PHOTORESIST AZ1518 (MicroChemicals,
Germany), PHOTORESIST AZ5214 (MicroChemicals, Germany), SU-8, and
combinations thereof. Other examples of photosensitive materials
include, but are not limited to, liquid crystals and metals. For
examples, the substrate can include metal salts that can be reduced
when exposed to the radiation. Substrates suitable for use in
methods disclosed herein include, but are not limited to, metals,
alloys, composites, crystalline materials, amorphous materials,
conductors, semiconductors, optics, fibers, inorganic materials,
glasses, ceramics (e.g., metal oxides, metal nitrides, metal
silicides, and combinations thereof), zeolites, polymers, plastics,
organic materials, minerals, biomaterials, living tissue, bone, and
laminates and combinations thereof. The substrate can be in the
form of films, thin films, foils, and combinations thereof. A
substrate can comprise a semiconductor including, but not limited
to one or more of: crystalline silicon, polycrystalline silicon,
amorphous silicon, p-doped silicon, n-doped silicon, silicon oxide,
silicon germanium, germanium, gallium arsenide, gallium arsenide
phosphide, indium tin oxide, graphene, and combinations thereof. A
substrate can comprise a glass including, but not limited to, one
or more of undoped silica glass (SiO2), fluorinated silica glass,
borosilicate glass, borophosphorosilicate glass, organosilicate
glass, porous organosilicate glass, and combinations thereof. The
substrate can be a non-planar substrate, including, but not limited
to, one or more of pyrolytic carbon, reinforced carbon-carbon
composite, a carbon phenolic resin, and combinations thereof. A
substrate can comprise a ceramic including, but not limited to, one
or more of silicon carbide, hydrogenated silicon carbide, silicon
nitride, silicon carbonitride, silicon oxynitride, silicon
oxycarbide, high-temperature reusable surface insulation, fibrous
refractory composite insulation tiles, toughened unipiece fibrous
insulation, low-temperature reusable surface insulation, advanced
reusable surface insulation, and combinations thereof. A substrate
can comprise a flexible material, including, but not limited to one
or more of: a plastic, a metal, a composite thereof, a laminate
thereof, a thin film thereof, a foil thereof, and combinations
thereof.
[0260] The photosensitive substrate or the photosensitive layer 20
can have any suitable thickness, for example in a range of about
100 nm to about 5000 nm. For example, the minimum photosensitive
substrate or photosensitive layer 20 thickness can be about 100,
150, 200, 250, 300, 350, 400, 450 or 500, 550, 600, 650, 700, 750,
800, 850, 900, 950, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500,
or 5000 nm. For example, the maximum photosensitive substrate or
photosensitive layer 20 thickness can be about 100, 150, 200, 250,
300, 350, 400, 450 or 500, 550, 600, 650, 700, 750, 800, 850, 900,
950, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, or 5000 nm.
The diameter of the indicia formed by the tip array 10 can be
modulated by modifying the resist material used and/or the
thickness of the photosensitive substrate or photosensitive layer
20. For example, under the same radiation conditions, a thicker
photosensitive layer can result in indicia having larger diameters.
At constant photosensitive layer thickness, an increase in
radiation intensity can result in indicia having larger
diameters.
[0261] In one embodiment a substrate is spin-coated with a layer of
positive-tone photoresist (for example, SHIPLEY1805). The
photoresist can be applied by pre-diluting with propylene glycol
mononmethyl ether acetate at a ratio selected based on the desired
thickness of the resist layer. For example, if a 40 nm thick
photoresist layer is desired, the photoresist can be diluted with
the acetate in a ratio of 1:4. If a 150 nm thick photoresist layer
is desired the dilution ratio can be, for example, 1:1. The
photoresist coated substrate can be soft-baked, for example, on a
hot plate at 115.degree. C. for about one minute. To improve the
performance of the resist for lift-off processing, a layer of
lift-off resist can optionally be applied. For example LOR 3A
lift-off resist (available from MicroChem Corp) can be used. The
lift-off resist can be spin coated onto the photoresist for example
at 4000 rpm for one minute and can then be baked, for example at
180.degree. C. for about five minutes.
EXAMPLES
Examples 1
Formation of BPL Tip Array
[0262] BPL tip arrays were fabricated starting from a PPL tip array
in accordance with known methods. See Huo et al., Science 2008,
321, 1658-60. Hard PDMS composed of 3.4 g of vinyl-compound-rich
prepolymer (VDT-731, Gelest) and 1.0 g of hydrosilane-rich
crosslinker (HMS-301) was poured onto a Si master and followed by
curing at 80.degree. C. for 24 hours. After peeling the PPL tip
array off the Si master, it was exposed to air plasma at 200 mb and
60 W for 1 min. Next, a 5 nm layer of Ti followed by a 100 nm layer
of Au was evaporated on the tip array at 0.25 .ANG./s to make the
entire tip array opaque. In order to open apertures in the apex of
the pyramidal tips PMMA (950c 7, MicroChem Inc., USA) was
spin-coated onto the metal-coated tip array at 1000 rpm for 1 min
and baked at 150.degree. C. for 5 minutes. The PMMA coating was
repeated an additional 1 to 3 times to ensure complete coverage.
Reactive ion etching was then employed to homogeneously etch the
PMMA until the apexes of the tips were exposed. The array was
observed in an optical microscope every minute in order to stop the
etch precisely when only the apexes were exposed. Typically,
etching with 25 W for 5 minutes in 100 mTorr O.sub.2 was
sufficient. The gold at the apex of each pen was removed through
soaking in a selective chemical etch, using the remaining portion
of the PMMA as an etch mask. The chemical etch was performed for
about 50 seconds, leaving an aperture at the tip of each tip in the
array. Finally, rinsing in acetone was used to remove the remaining
PMMA. FIG. 26B provides a schematic illustration of the aperture
formation process. Apertures having a diameter of about 100 nm were
formed in the apexes of the tips.
Example 2
Patterning with pBPL without Tip Array Movement
[0263] A BPL tip array was mounted on a scanning probe lithography
platform and leveled with respect to a photoresist-coated Si wafer
utilizing an optical leveling procedure. To expose a region of the
resist, the tips were brought into contact with the resist surface
and UV light with a wavelength .lamda. of about 405 nm was shined
on the back side of the tip array and held for a specific exposure
time. While sub-.lamda. sized apertures of the tip arrays blocked
the propagating light, evanescent light extended into the
photoresist with an intensity that decayed exponentially with depth
into the resist surface.
[0264] To optimize the exposure time, a dose-test was performed in
which the tip array wrote a series of dots (FIG. 27A) with exposure
times between 2 and 4 seconds. In this experiment, the exposure
times were modulated by controlling the mirrors to print in
"grayscale," which modulated the duty cycle of each mirror. This
provided a simple way to adjust the exposure dose received by each
pixel patterned. At an exposure dose of 2 seconds, the patterned
features had a diameter of 122.+-.12 nn, which is substantially
smaller than .lamda./2. At longer exposure times, larger features
were patterned (FIG. 27A).
[0265] In contrast to pattern dots with the tips held still, moving
the tips linearly across the sample while in contact with the
sample allows one to pattern lines. Gold lines with widths of about
375 nm, about 750 nm, about 1.125 .mu.m, and about 1.5 .mu.m were
patterned by scanning the tip array at 4, 2, 1, and 0.5 .mu.m/s,
respectively. The structures written by the tips were visualized by
scanning electron microscopy after being coated with 5 nm of Cr and
25 nm of Au and subjected to solvent lift off to remove the
remaining photoresist.
Example 3
Patterning by pBPL with Raster Scanning of the Tip Array
[0266] To generate a large scale image, the tip array was raster
scanned across a sample while a DMD displayed images extracted from
a master image. To achieve registry between the projected image and
the tips, an alignment procedure as described above was used.
[0267] Once good alignment was achieved, the large scale pattern
was written while the actions of the DMD and the scanning probe
system were controlled by the software program as described
above.
[0268] Referring to FIG. 28, a tip array having 10,000 tips
addressing 10,000 points each creating a cm.sup.2 image. The
features had a diameter of about 300 nm. This demonstrates the high
quality control of light from macroscale to nanoscale achievable
with embodiments of the disclosure. This ability corresponds to a
four order magnitude increase in data transfer rate as compared to
conventional BPL. Fabrication of this pattern would not be possible
using conventional optical techniques, and instead would include
the significantly more costly and complicated electron beam
lithography (EBL) process.
Example 4
Generation of Circuit Patterns using pBPL
[0269] The utility of pBPL was evaluated by patterning functional
circuits. Arrays of serpentine resistors with varying lengths were
patterned. FIG. 29A illustrates representative SEM images of the
resistors. All resistors required the coordination of multiple tips
with the smallest lines requiring three tips and the largest lines
requesting fifteen tips. The largest lines were continuous wires
having a length of 4 mm and a width of 2 .mu.m. Current-voltage
characterization of sixty-one devices revealed that all measured
devices had Ohmic character with resistances that depended linearly
on the line length (FIG. 29B).
[0270] The sheet resistance of the resistance of resistors can be
computed by combining the slope of the linear fit in FIG. 29C to
find r=0.32 .OMEGA./square, in agreement with the expected value of
about 0.4 .OMEGA./square for a 50 nm thick gold film.
[0271] In addition to resistors, planar capacitors, inductors, and
surface acoustic wave sensors (SAWS) were also patterned,
demonstrating a full pallet of passive circuit elements that can be
patterned using embodiments of the disclosure (FIG. 29B). The
capacitor illustrated in FIG. 29C was patterned using fifty-seven
tips, the inductor was patterned using fifty-one tips, and the SAWS
was patterned using 101 tips.
[0272] FIG. 30A illustrates electrical wire connections generated
using pBPL. To evaluate the potential of pBPL to generate patterns
in registry with existing structures, semiconductor nanowires were
dispersed on a substrate and electrically connected by leads
generated by pBPL (FIG. 30B). An array consisting of 729 tips
(27.times.27) and alignment markers was used to pattern connections
to sixty wires that had been located by optical microscopy.
Patterning of this type, which is traditionally done by EBL,
demonstrates the ability of pBPL to rapidly pattern in a mask-free
fashion with registry to an existing pattern. Once the patterns
were written, 59/60 of the wires were successfully connected and
after the lift-off of the photoresist, 40/60 working devices were
obtained. The electrical transport of the nanowire structure
demonstrated clear semiconducting behavior.
Example 5
Method of Making a Heat Actuation Tip Array
[0273] FIG. 11 provides a schematic illustration of a method of
making a heat actuation tip array, the tip array being a silicon
pen tip array. Heaters were fabricated by etching an indium tin
oxide (ITO) coated glass slide. ITO was chosen as an electrode
material because it is transparent and a conductor. 25.times.25
mm.sup.2 glass slides coated in 8 to 12 .OMEGA./sq ITO were
purchased from Sigma Aldrich and cleaned chemically by rinsing in
acetone, DI water, and isopropanol. They were then dried under
nitrogen. The slides were spin coated with a positive tone
photoresist (S1805-Shipley) at 4000 rpm for 40 s and baked on a hot
plate for 1 minute at 115.degree. C. Samples were then aligned in a
mask aligner and exposed for 2 s and post-exposure baked for 1
minute at 115.degree. C. Patterns were then developed in MF-24A
(Shipley) for 60 s then rinsed in DI water and dried under
nitrogen. In order to make the patterned photoresist a better mask
for etching, samples were hard baked for 4 hours at 80.degree.
C.
[0274] To etch the ITO, a reactive ion etch was utilized. Samples
were mounted on 4 inch (10 cm) wafers with photoresist and loaded
into a deep reactive ion etch (DRIE-STS LpX Pegasus). The samples
were etched under 200 sccm of Argon that was held at 5 mTorr using
2500 W RF power and 40 W delivered to the platen. Under these
conditions, the etch rate of ITO was found to be approximately 1
.ANG./s. The completion of the etch was verified by using a
multimeter to measure the background resistance and resistance of
the devices. To remove the residual resist, samples were soaked
overnight in Remover PG (Microchem) on an 80.degree. C. hot plate.
Samples were visualized in a scanning electron microscope (FIG.
10C) to reveal the ITO coils and bus lines. In this figure, a
4.times.4 array of coil heaters is present.
[0275] Next, the slides were coated with PDMS placed on a Si wafer.
Si wafers (NOVA Electronic Materials; resistivity 1-10 .OMEGA.cm,
(100) orientation, 50.+-.5 .mu.m thick) with a 10,000 .ANG.
(.+-.5%) SiO.sub.2 layer on each side were used for fabricating the
tip arrays. The wafers were cleaned in acetone, ethanol, then
rinsed with water before use. In preparing the elastomer base, PDMS
and a curing agent (Sylgard 184 Silicone) were mixed in a 10:1
ratio (w/w), and then degassed under vacuum (10-3 Ton) for 30 min.
Uncured PDMS was spin-coated at 1,000 rpm for 30 s with a ramping
speed of 1,000 rpm/s, followed by curing at 75.degree. C. for 10
min. The average thickness was determined by profilometry (Veeco,
Dektak 150) to be 88.5.+-.1.3 .mu.m. To increase the adhesion
between the cured PDMS and Si wafers, epoxy (DAP Dow Corning,
Silicone Rubber Aquarium Sealant) was used by spin-coating it onto
the cured PDMS. The epoxy was diluted with heptane (0.2 g epoxy and
2 mL heptane) to decrease the viscosity of the epoxy and, as a
result, homogeneous film thickness less than 1 .mu.m were obtained.
Oxygen-plasma-treated (60 W at a pressure of 100 mTorr) wafers were
then placed on spin-coated epoxy/PDMS on clean glass slides,
followed by curing at 75.degree. C. for 1 h.
[0276] Photolithography was used to define square masks for the tip
etching procedure. These squares were be between 120 .mu.m and 140
.mu.m (depending on the thickness of the silicon wafer) and the
edges of the squares must be aligned along the Si layers
<110> direction. First, samples were treated in oxygen plasma
for 1 min at .about.100 mTorr at 30 W. This step can enhance
adhesion of the resist. Samples were then spin-coated with
photoresist (S1805--Shipley) at 4000 rpm for 40 s and baked on a
hot plate for 1 minute at 115.degree. C. Samples were then aligned
using a mask aligner. In contrast to previous HSL work, where the
tip masks are aligned to be parallel to the edge of the silicon
wafer, here the tip masks were aligned to predefined alignment
markers on the ITO surface below. This alignment ensured that each
tip rested above a heater. Samples were exposed for 2 s and
post-exposure baked for 1 minute at 115.degree. C. Patterns were
developed in MF-24A for 60 s then rinsed in DI water and dried
under nitrogen.
[0277] An anisotropic wet etch was used to define the tips. The
edge of the Si wafer chip was passivated with PDMS to prevent
etching in from the sides. Exposed SiO.sub.2 was then selectively
etched in isotropic buffered hydrofluoric acid (Transene, 9% HF,
BUFFER-HF Improved) for 9 min in a polystyrene petri dish and
washed with water. To remove the photoresist, the wafer was cleaned
in acetone, ethanol, and subsequently dried with flowing nitrogen.
The wafer was then cleaned with oxygen plasma (1 min at 30 W at a
pressure of 100 mTorr). O.sub.2 plasma cleaning prior to Si etching
was found to improve the uniformity of the tips. Samples were
immediately transferred into 40 wt % KOH (333 g KOH in 500 mL DI
water) (KOH from Sigma-Aldrich; 99.99% metal basis, semiconductor
grade, product no. 306568) at 75.degree. C. and held in the center
of the etchant in a Teflon holder. The solution was continuously
stirred to reduce the effect of micro-masking by hydrogen bubbles
generated by the reaction at the Si surface. After 60-65 min, the
sample was removed from the etchant, rinsed in water, ethanol, and
then dried in air. As the etching rate of Si (100) in 40 wt % KOH
at 75.degree. C. is about 50 .mu.m/h, the minimum thickness of
SiO.sub.2 can be about 250 nm for an experimentally viable
fabrication procedure. In view of this, a 1 .mu.m thick SiO.sub.2
layer was selected.
Example 6
Characterization of Thermal Actuation
[0278] Thermal actuation was characterized with atomic force
microscopy (AFM), resistance measurements, and thermal imaging. For
characterization purposes, samples were used that consisted of the
heater coil array and PDMS coating layer, but no tip array. When no
power was applied to the heaters, thermal imaging revealed the
structure of the coils and leads as slight differences in
temperature (FIG. 12A--top). When 28 mW was applied to the top left
heater for 1 s, a temperature plume was visible, centered on the
selected heater (FIG. 12A--bottom). A maximum temperature increase
of about 35.degree. C. was observed in this case. The thermal
actuation of the PDMS can be directly measured with AFM by scanning
in contact mode (Dimension Icon-Bruker) using a contact mode probe
(PPP-CONT-NanoWorld AG) in a small (100.times.100 nm.sup.2) region
on the PDMS above the heater. Scans were taken with a resolution of
4096 points and 10 lines at 0.1 Hz. The deflection set point was 1
V and the integral and proportional gain were 5 and 10
respectively. At the same time, the heater was driven with a 0.5 Hz
square wave at a set power P. The height recorded by the AFM was a
square wave with damping given by the finite heating time of the
PDMS (FIG. 12B). Each rise and fall of the height was fit to the
sum of two exponentials and was characterized by a total amplitude
A and a rise time .tau. defined to be the time required to reach
63% (equivalent to the time constant of an exponential function).
.tau. was found to only depend on the thickness of the PDMS film
and equaled about 20 ms for a 40 .mu.m thick PDMS film and 40 ms
for a 90 .mu.m thick PDMS film. Both of these times are adequately
fast for a molecular patterning. The amplitude A was found to
depend linearly on the applied power P (FIG. 12C). The constant of
proportionality a increases with smaller heaters and increases with
thicker PDMS films. a was found to be between 87 nm/mW and 120
nm/mW.
[0279] AFM was also used to evaluate the importance of crosstalk
between tips and fatigue with continued use. FIG. 12D shows the
amplitude of driving recorded at different locations along the
surface of the PDMS when the heater at the origin was driven with
28 mW for 50 ms. The red trace was the initial measurement and it
was apparent that since the amplitude at 150 .mu.m was only 20% its
peak value, crosstalk between tips will not be an issue. It is
worth noting that crosstalk was a considerably larger issue if the
power was left on longer, reaching about 40% at 1 s. By restricting
the on time, it was possible to mitigate crosstalk. Fatigue was
also not an issue as after cycling for 12 hours (23,000 on/off
cycles) the amplitude vs. position curve was barely different (FIG.
12D black line). This characterization shows that thermal actuation
is powerful and fast enough to perform actuated SPL and that
crosstalk and fatigue are not major concerns.
[0280] The foregoing describes and exemplifies the invention but is
not intended to limit the invention defined by the claims which
follow. All of the methods disclosed and claimed herein can be made
and executed without undue experimentation in light of the present
disclosure. While the materials and methods of this invention have
been described in terms of specific embodiments, it will be
apparent to those of skill in the art that variations may be
applied to the materials and/or methods and in the steps or in the
sequence of steps of the methods described herein without departing
from the concept, spirit and scope of the invention. More
specifically, it will be apparent that certain agents which are
both chemically and physiologically related may be substituted for
the agents described herein while the same or similar results would
be achieved.
[0281] All patents, publications and references cited herein are
hereby fully incorporated by reference. In case of conflict between
the present disclosure and incorporated patents, publications and
references, the present disclosure should control.
[0282] The following additional considerations apply to the
foregoing discussion. Throughout this specification, plural
instances may implement methods, instructions, functions,
components, operations, or structures described as a single
instance. Although individual methods and instructions are
illustrated and described as separate operations, one or more of
the methods and instructions may be performed concurrently, and
nothing requires that the operations be performed in the order
illustrated. Structures and functionality presented as separate
components in example configurations may be implemented as a
combined structure or component. Similarly, structures and
functionality presented as a single component may be implemented as
separate components. These and other variations, modifications,
additions, and improvements fall within the scope of the subject
matter herein.
[0283] For example, the various component of the system 100 may
communicate through any combination of a LAN, a MAN, a WAN, a
mobile, a wired or wireless network, a private network, or a
virtual private network. Moreover, while only one actuation
computer is illustrated in FIG. 1 to simplify and clarify the
description, it is understood that any number of computers or
display devices are supported and can be in communication with the
system 100.
[0284] Additionally, certain embodiments are described herein as
including logic or a number of methods, instructions, modules, etc.
Methods and modules may constitute either software modules (e.g.,
non-transitory code stored on a tangible machine-readable storage
medium) or hardware modules. A hardware module is a tangible unit
capable of performing certain operations and may be configured or
arranged in a certain manner. In example embodiments, one or more
computer systems (e.g., a standalone, client or server computer
system) or one or more hardware modules of a computer system (e.g.,
a processor or a group of processors) may be configured by software
(e.g., an application or application portion) as a hardware module
that operates to perform certain operations as described
herein.
[0285] In various embodiments, a hardware module may be implemented
mechanically or electronically. For example, a hardware module may
comprise dedicated circuitry or logic that is permanently
configured (e.g., as a special-purpose processor, such as a field
programmable gate array (FPGA) or an application-specific
integrated circuit (ASIC)) to perform certain functions. A hardware
module may also comprise programmable logic or circuitry (e.g., as
encompassed within a general-purpose processor or other
programmable processor) that is temporarily configured by software
to perform certain operations. It will be appreciated that the
decision to implement a hardware module mechanically, in dedicated
and permanently configured circuitry, or in temporarily configured
circuitry (e.g., configured by software) may be driven by cost and
time considerations.
[0286] Accordingly, the term hardware should be understood to
encompass a tangible entity, be that an entity that is physically
constructed, permanently configured (e.g., hardwired), or
temporarily configured (e.g., programmed) to operate in a certain
manner or to perform certain operations described herein.
Considering embodiments in which hardware modules are temporarily
configured (e.g., programmed), each of the hardware modules need
not be configured or instantiated at any one instance in time. For
example, where the hardware modules comprise a general-purpose
processor configured using software, the general-purpose processor
may be configured as respective different hardware modules at
different times. Software may accordingly configure a processor,
for example, to constitute a particular hardware module at one
instance of time and to constitute a different hardware module at a
different instance of time.
[0287] Hardware and software modules can provide information to,
and receive information from, other hardware and/or software
modules. Accordingly, the described hardware modules may be
regarded as being communicatively coupled. Where multiple of such
hardware or software modules exist contemporaneously,
communications may be achieved through signal transmission (e.g.,
over appropriate circuits and buses) that connect the hardware or
software modules. In embodiments in which multiple hardware modules
or software are configured or instantiated at different times,
communications between such hardware or software modules may be
achieved, for example, through the storage and retrieval of
information in memory structures to which the multiple hardware or
software modules have access. For example, one hardware or software
module may perform an operation and store the output of that
operation in a memory device to which it is communicatively
coupled. A further hardware or software module may then, at a later
time, access the memory device to retrieve and process the stored
output. Hardware and software modules may also initiate
communications with input or output devices, and can operate on a
resource (e.g., a collection of information).
[0288] The various operations of example functions and methods
described herein may be performed, at least partially, by one or
more processors that are temporarily configured (e.g., by software)
or permanently configured to perform the relevant operations.
Whether temporarily or permanently configured, such processors may
constitute processor-implemented modules that operate to perform
one or more operations or functions. The modules referred to herein
may, in some example embodiments, comprise processor-implemented
modules.
[0289] Similarly, the methods and instructions described herein may
be at least partially processor-implemented. For example, at least
some of the instructions of a method may be performed by one or
processors or processor-implemented hardware modules. The
performance of certain of the instructions may be distributed among
the one or more processors, not only residing within a single
machine, but deployed across a number of machines. In some example
embodiments, the processor or processors may be located in a single
location (e.g., within a laboratory environment, a factory
environment or as a server farm), while in other embodiments the
processors may be distributed across a number of locations.
[0290] The one or more processors may also operate to support
performance of the relevant operations in a "cloud computing"
environment or as a "software as a service" (SaaS). For example, at
least some of the functions may be performed by a group of
computers (as examples of machines including processors), these
operations being accessible via a network (e.g., the Internet) and
via one or more appropriate interfaces (e.g., application program
interfaces (APIs).
[0291] The performance of certain of the operations may be
distributed among the one or more processors, not only residing
within a single machine, but deployed across a number of machines.
In some example embodiments, the one or more processors or
processor-implemented modules may be located in a single geographic
location (e.g., within a lab environment, etc.). In other example
embodiments, the one or more processors or processor-implemented
modules may be distributed across a number of geographic
locations.
[0292] Some portions of this specification are presented in terms
of algorithms or symbolic representations of operations on data and
data structures stored as bits or binary digital signals within a
machine memory (e.g., a computer memory). These algorithms or
symbolic representations are examples of techniques used by those
of ordinary skill in the data processing arts to convey the
substance of their work to others skilled in the art. As used
herein, a "method" or an "instruction" or an "algorithm" or a
"routine" is a self-consistent sequence of operations or similar
processing leading to a desired result. In this context, methods,
instructions, algorithms, routines and operations involve physical
manipulation of physical quantities. Typically, but not
necessarily, such quantities may take the form of electrical,
magnetic, or optical signals capable of being stored, accessed,
transferred, combined, compared, or otherwise manipulated by a
machine. It is convenient at times, principally for reasons of
common usage, to refer to such signals using words such as "data,"
"content," "bits," "values," "elements," "symbols," "characters,"
"terms," "numbers," "numerals," or the like. These words, however,
are merely convenient labels and are to be associated with
appropriate physical quantities.
[0293] Unless specifically stated otherwise, discussions herein
using words such as "processing," "computing," "calculating,"
"determining," "presenting," "displaying," or the like may refer to
actions or processes of a machine (e.g., a computer) that
manipulates or transforms data represented as physical (e.g.,
electronic, magnetic, or optical) quantities within one or more
memories (e.g., volatile memory, non-volatile memory, or a
combination thereof), registers, or other machine components that
receive, store, transmit, or display information.
[0294] As used herein any reference to "some embodiments" or "one
embodiment" or "an embodiment" means that a particular element,
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment. The
appearances of the phrase "in one embodiment" in various places in
the specification are not necessarily all referring to the same
embodiment.
[0295] Some embodiments may be described using the expression
"coupled" and "connected" along with their derivatives. For
example, some embodiments may be described using the term "coupled"
to indicate that two or more elements are in direct physical or
electrical contact. The term "coupled," however, may also mean that
two or more elements are not in direct contact with each other, but
yet still co-operate or interact with each other. The embodiments
are not limited in this context.
[0296] As used herein, the terms "comprises," "comprising,"
"includes," "including," "has," "having" or any other variation
thereof, are intended to cover a non-exclusive inclusion. For
example, a function, process, method, article, or apparatus that
comprises a list
* * * * *