U.S. patent application number 15/223714 was filed with the patent office on 2016-12-15 for line pattern collapse mitigation through gap-fill material application.
The applicant listed for this patent is Tokyo Electron Limited. Invention is credited to Ian J. BROWN, Joshua S. HOOGE, Benjamen M. RATHSACK, Steven SCHEER, Mark H. SOMERVELL.
Application Number | 20160363868 15/223714 |
Document ID | / |
Family ID | 44476235 |
Filed Date | 2016-12-15 |
United States Patent
Application |
20160363868 |
Kind Code |
A1 |
SOMERVELL; Mark H. ; et
al. |
December 15, 2016 |
LINE PATTERN COLLAPSE MITIGATION THROUGH GAP-FILL MATERIAL
APPLICATION
Abstract
Disclosed is a method and apparatus for mitigation of
photoresist line pattern collapse in a photolithography process by
applying a gap-fill material treatment after the post-development
line pattern rinse step. The gap-fill material dries into a solid
layer filling the inter-line spaces of the line pattern, thereby
preventing line pattern collapse due to capillary forces during the
post-rinse line pattern drying step. Once dried, the gap-fill
material is depolymerized, volatilized, and removed from the line
pattern by heating, illumination with ultraviolet light, by
application of a catalyst chemistry, or by plasma etching.
Inventors: |
SOMERVELL; Mark H.; (Austin,
TX) ; RATHSACK; Benjamen M.; (Austin, TX) ;
BROWN; Ian J.; (Austin, TX) ; SCHEER; Steven;
(Houston, TX) ; HOOGE; Joshua S.; (Austin,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tokyo Electron Limited |
Tokyo |
|
JP |
|
|
Family ID: |
44476235 |
Appl. No.: |
15/223714 |
Filed: |
July 29, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14323664 |
Jul 3, 2014 |
9454081 |
|
|
15223714 |
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13031112 |
Feb 18, 2011 |
8795952 |
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14323664 |
|
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61306512 |
Feb 21, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03F 7/2024 20130101;
G03F 7/405 20130101; G03F 7/0384 20130101; G03F 7/38 20130101; G03F
7/038 20130101; G03F 7/40 20130101; G03F 7/30 20130101 |
International
Class: |
G03F 7/40 20060101
G03F007/40 |
Claims
1. A chemical composition of a gap-fill treatment liquid
comprising: at least one polymer compound from the group consisting
of poly(phthalaldehyde), poly(succinaldehyde), poly(allyl alcohol),
poly(glyoxylic acid), poly(methyl glyoxylic acid), a polymeric salt
of poly(methyl glyoxylic acid), poly(ethyl glyoxylic acid), a
polymeric salt of poly(ethyl glyoxylic acid), poly(methyl
glyoxylate), and poly(ethyl glyoxylate), wherein the gap-fill
treatment liquid depolymerizes into volatile compounds on exposure
to at least one depolymerizing agent from the group consisting of
heat, electromagnetic radiation, and a catalyst.
2. The chemical composition of claim 1, wherein the electromagnetic
radiation comprises infrared radiation.
3. The chemical composition of claim 1, wherein the electromagnetic
radiation comprises visible light radiation.
4. The chemical composition of claim 1, wherein the electromagnetic
radiation comprises ultraviolet radiation.
5. The chemical composition of claim 1, wherein the catalyst
comprises an acid.
6. The chemical composition of claim 1, wherein the exposure of the
gap-fill treatment liquid to heat comprises heating the gap-fill
treatment liquid to a temperature between 30.degree. C. and
200.degree. C.
7. The chemical composition of claim 1, wherein the exposure of the
gap-fill treatment liquid to heat comprises heating the gap-fill
treatment liquid to a temperature between 50.degree. C. and
150.degree. C.
8. The chemical composition of claim 1, wherein the gap-fill
treatment liquid comprises a solvent.
9. The chemical composition of claim 8, wherein the solvent
comprises water.
10. The chemical composition of claim 8, wherein the solvent
comprises an alcohol.
11. The chemical composition of claim 1, wherein the polymeric salt
of poly(methyl glyoxylic acid) is an ammonium salt of poly(methyl
glyoxylic acid).
12. The chemical composition of claim 1, wherein the polymeric salt
of poly(methyl glyoxylic acid) is a sodium salt of poly(methyl
glyoxylic acid).
13. The chemical composition of claim 1, wherein the polymeric salt
of poly(ethyl glyoxylic acid) is an ammonium salt of poly(ethyl
glyoxylic acid).
14. The chemical composition of claim 1, wherein the polymeric salt
of poly(ethyl glyoxylic acid) is a sodium salt of poly(ethyl
glyoxylic acid).
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims the benefit
of priority from co-pending U.S. patent application Ser. No.
14/323,664, entitled "LINE PATTERN COLLAPSE MITIGATION THROUGH
GAP-FILL MATERIAL APPLICATION" (Ref. No. CT-095CON), filed on Jul.
3, 2014, which is a continuation of and claims the benefit of
priority from U.S. Patent Application No. 13/031,112, entitled
"LINE PATTERN COLLAPSE MITIGATION THROUGH GAP-FILL MATERIAL
APPLICATION" (Ref. No. CT-095), filed on Feb. 18, 2011, now U.S.
Pat. No. 8,795,952, which is a non-provisional of and claims the
benefit of priority to U.S. Provisional Patent Application No.
61/306,512, entitled "LINE PATTERN COLLAPSE MITIGATION THROUGH
GAP-FILL MATERIAL APPLICATION" (Ref. No. CT-095PRO), filed on Feb.
21, 2010, all of which applications are herein incorporated by
reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and apparatus for
mitigation of photoresist line pattern collapse in a
photolithography process by applying a gap-fill material treatment
after the post-development line pattern rinse step, and subsequent
removal thereof to expose the line pattern.
[0004] 2. Description of Related Art
[0005] Photolithography processes for manufacturing semiconductor
devices, liquid crystal displays (LCDs), and photovoltaics
generally coat a layer of radiation-sensitive material, such as
photoresist, on a substrate, expose the radiation-sensitive
material coating to light to impart a latent image line pattern,
and develop the exposed radiation-sensitive material coating to
transform the latent image line pattern into a final image line
pattern having masked and unmasked areas. Such a series of
processing stages is typically carried out in a coating/developing
system.
[0006] Feature sizes of semiconductor device circuits have been
scaled to less than 0.1 micron. Typically, the pattern wiring that
interconnects individual device circuits is formed with sub-micron
line widths. In the post-development phase of a photolithography
process, once a photoresist line pattern has been already formed, a
deionized water rinse step is used to remove the developer from and
clean the developed line pattern. Following the rinse step, the
photoresist line pattern and substrate are dried so the substrate
can be transported to the next processing tool for the next
processing step. During the drying step, capillary forces arise at
the interfaces between the deionized water or other rinse liquid,
ambient air, and the photoresist material. The tighter the
photoresist line pattern (i.e. the smaller the line pattern pitch),
the larger the capillary forces become, and in some cases these
forces can overcome the mechanical strength of the photoresist line
pattern itself, leading to line pattern collapse. Once collapsed,
the photoresist line pattern does not anymore represent an exact
image of the image line pattern applied to the photoresist during
the exposure step, leading to lower device yields, etc.
[0007] A number of ways have been used to mitigate line pattern
collapse generally involving reducing the surface tension of the
rinse liquid in contact with the photoresist. For example, a
surfactant can be added to the rinse liquid (e.g. deionized water)
to reduce the surface tension, and hence capillary forces acting
upon the photoresist line pattern during the drying step. Another
approach involves adding a reactive additive to the rinse liquid
(e.g. deionized water), to react with the polymeric photoresist
material, with the effect of modifying the surface energy of the
photoresist and hence lowering the contact angle (i.e. wetting
angle) and capillary forces. However, these methods may have
limitations. For example, surfactants compatible with the
photolithography process and materials can only reduce the surface
tension a certain amount, and a larger reduction may be necessary
to overcome the increase of capillary forces due to photoresist
line pattern pitch reduction in newer generations of semiconductor
devices. Therefore, there exists a need for a method of mitigating
photoresist line pattern collapse without the above shortcomings,
and which will be effective for next generations of
semiconductor.
SUMMARY OF THE INVENTION
[0008] The present invention relates to a method and apparatus for
mitigation of photoresist line pattern collapse in a
photolithography process by applying a gap-fill material treatment
after the post-development line pattern rinse step, and subsequent
removal thereof to expose the line pattern.
[0009] According to an embodiment, a method of patterning a
substrate is provided, comprising: forming a layer of
radiation-sensitive material on the substrate; performing a
patterned exposure of the layer of radiation-sensitive material;
performing a post-exposure bake of the layer of radiation-sensitive
material; developing the layer of radiation-sensitive material to
form a radiation sensitive material pattern; rinsing the
radiation-sensitive material pattern with a rinse liquid;
dispensing gap-fill treatment liquid on the radiation-sensitive
material pattern to displace the rinse liquid; and spinning the
substrate to remove excess gap-fill treatment liquid and allow the
remaining gap-fill treatment liquid to dry, thereby forming a
gap-fill material layer which prevents collapse of the
radiation-sensitive material pattern. These steps are followed by
removing the gap-fill material layer from the radiation-sensitive
material pattern.
[0010] According to further embodiments of the invention, the
gap-fill material is depolymerized, volatilized, and removed from
the line pattern by heating, illumination with electromagnetic
(e.g. ultraviolet light or laser) radiation, by application of a
catalyst chemistry, by plasma etching, or a combination of two or
more thereof.
[0011] According to yet further embodiments of the invention, the
gap-fill treatment liquid can comprise a polymer compound that
depolymerizes into volatile compounds on exposure to at least one
depolymerizing agent from the group consisting of heat,
electromagnetic radiation, a catalyst, or a plasma in an etch
processing tool.
[0012] According to yet further embodiments of the invention, the
gap-fill treatment liquid can comprise at least one polymer
compound from the group consisting of poly(vinyl alcohol),
poly(acrylamide), poly(phthalaldehyde), poly(succinaldehyde),
poly(allyl alcohol), poly(glyoxylic acid), poly(methyl glyoxylic
acid), poly(ethyl glyoxylic acid), poly(methyl glyoxylate),
poly(ethyl glyoxylate), and poly(aspartic acid). Furthermore, the
gap-fill treatment liquid can comprise at least one polymer salt of
the poly(methyl glyoxylic acid) and/or poly(ethyl glyoxylic acid),
such as ammonium and sodium polymer salts thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] A more complete appreciation of the invention and many of
the attendant advantages thereof will become readily apparent with
reference to the following detailed description, particularly when
considered in conjunction with the accompanying drawings, in
which:
[0014] FIG. 1 is a plan view showing the general structure of a
coating/developing system used to process substrates in accordance
with an embodiment of the invention.
[0015] FIG. 2 is a front view of the coating/developing system in
FIG. 1.
[0016] FIG. 3 is a rear view of the coating/developing system in
FIG. 1.
[0017] FIG. 4 is schematic of an embodiment of a method for
mitigation of photoresist line pattern collapse by the application
of gap-fill material.
[0018] FIG. 5 is a flowchart of an embodiment of a method for
mitigation of photoresist line pattern collapse by the application
of gap-fill material.
[0019] FIG. 6 shows a table of polymer compounds useful as gap-fill
materials for photoresist line pattern collapse mitigation.
[0020] FIG. 7 is schematic of an exemplary embodiment of a
developing device capable of performing, in part, the method
outlined in the flowchart of FIG. 5.
[0021] FIG. 8 is a schematic of an exemplary embodiment of a
heating device in accordance with an embodiment of the
invention.
[0022] FIG. 9 is a schematic of an exemplary embodiment of an
illumination device in accordance with an embodiment of the
invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0023] In the following description, in order to facilitate a
thorough understanding of the invention and for purposes of
explanation and not limitation, specific details are set forth,
such as particular geometries of a lithography, coater/developer,
and gap-fill treatment system, and descriptions of various
components and processes. However, it should be understood that the
invention may be practiced in other embodiments that depart from
these specific details.
[0024] In the description to follow, the terms radiation-sensitive
material and photoresist may be used interchangeably, photoresist
being only one of many suitable radiation-sensitive materials for
use in photolithography. Similarly, hereinafter the term substrate,
which represents the workpiece being processed, may be used
interchangeably with terms such as semiconductor wafer, LCD panel,
photovoltaic device panel, etc., the processing of all of which
falls within the scope of the claimed invention.
[0025] An exemplary coating/developing system 100, as shown in FIG.
1, may be constituted to integrally connect a cassette station 102,
which transports a cassette typically holding 25 substrates, such
as semiconductor wafers 104, for example, into the
coating/developing system 100 from outside and which transports a
wafer 104 to the cassette 106; an inspection station 108, which
performs a predetermined inspection on the wafer 104; a processing
station 110 with a plurality of types of processing devices
disposed in stages to perform predetermined processes in a layered
manner in the photolithography step; and an interface unit 112,
provided adjacent to the processing station 110, for delivering the
wafer 104 to an exposure device (not shown).
[0026] A cassette support stand 114 is provided at the cassette
station 102; the cassette support stand 114 may freely carry a
plurality of cassettes 106 in a row in the X direction (vertically,
in FIG. 1). The cassette station 102 is provided with a wafer
transporter 116 able to move on the transport path 118 in the X
direction. The wafer transporter 116 may also move freely in the
wafer array direction (Z direction; perpendicular) of the wafers
104 housed in the cassette 106 and can selectively access the wafer
104 vertically arrayed in the cassette 106. The wafer transporter
116 may rotate around an axis (8 direction) in the particular
direction, and may also access the inspection station's transfer
unit 120.
[0027] Disposed at the cassette station 102 side of inspection
station 108 is the transfer unit 120 for transferring the wafer 104
from the cassette station 102. A carrying unit 122 for carrying the
wafer 104 may be provided in the transfer unit 120. A wafer
transporter 124 able to move on a transport path 126 in the X
direction may be provided at the positive X direction side (upward
in FIG. 1) of the inspection station 108. The wafer transporter 124
also may move vertically and rotate freely in the 8 direction, and
may also access the transfer unit 120 and each processing device in
a processing device group 130 at the processing station 110
side.
[0028] A processing station 110 adjacent to the inspection station
108 is provided with a plurality of processing devices disposed in
stages, such as five processing device groups 128-132. The first
processing device group 128 and the second processing device group
129 are disposed in sequence from the inspection station 108 side,
at the negative X direction side (downward in FIG. 1) of the
processing station 110. The third processing device group 130,
fourth processing device group 131, and fifth processing device
group 132 are disposed in sequence from the inspection station 108
side, at the positive X direction side (upward in FIG. 1) of the
processing station 110. A first transport device 134 is provided
between the third processing device group 130 and the fourth
processing device group 131. The first transport device 134 may
transport the wafer 104 to access each device in the first
processing device group 128, third processing device group 130, and
fourth processing device group 131. A second transport device 136
transports the wafer 104 and selectively accesses the second
processing device group 129, fourth processing device group 131,
and fifth processing device group, 132.
[0029] With further reference to FIG. 2, the first processing
device group 128 stacks liquid processing devices that supply a
predetermined liquid spin-on material to the wafer 104 and process
it. Devices such as spin coating devices 140, 141, and 142, which
may apply a photoresist solution to the wafer 104 and form a
photoresist film, and bottom coating devices 143 and 144, which
form an anti-reflection film that prevents light reflection during
exposure processing, may be arranged in five levels in sequence
from the bottom. The second processing device group 129 stacks
liquid processing devices such as developing devices 150-154, which
supply developer (i.e. developer liquid) to the wafer 104 and
develop it, in five levels in sequence from the bottom. Also,
terminal chambers 160 and 161 are provided at the lowest stages of
the first processing device group 128 and the second processing
device group 129 in order to supply processing liquids to the
liquid processing devices in the processing device groups 128 and
129.
[0030] Also, as shown in FIG. 3, for example, the third processing
device group 130 stacks temperature regulation device 170,
transition device 171 for transfer of the wafer 104, high precision
temperature regulation devices 172-174, which regulate the
temperature of the wafer 104 under high precision temperature
management, and high temperature heating devices 175-178, which
heat the wafer 104 to high temperature, in nine levels in sequence
from the bottom.
[0031] The fourth processing device group 131 stacks a high
precision temperature regulation device 180, pre-baking devices
181-184 for heating the wafer 104 after photoresist coating
processing, and post-baking devices 185-189, which heat the wafer
104 after developing, in ten levels in sequence from the bottom.
Each of the pre-baking devices 181-184 and post-baking devices
185-189 includes at least one hot plate wafer holder (not shown)
for elevating the temperature of the wafer 104 and the layer on the
wafer 104.
[0032] The fifth processing device group 132 stacks a plurality of
heating devices that heat the wafer W, such as high precision
temperature regulation devices 190-193, and post-exposure baking
devices 194-199 in ten levels in sequence from the bottom.
[0033] A plurality of processing devices may be disposed at the
positive X direction side of the first transport device 134 as
shown in FIG. 1. Adhesion devices 200 and 202 for making the wafer
104 hydrophobic and heating devices 204 and 206 for heating the
wafer 104 are stacked in four levels in sequence from the bottom,
as shown in FIG. 5, for example. A peripheral exposure device 208
for selectively exposing only the edge of the wafer 104 may be
disposed at the positive X direction side of the second transport
device 136 as shown in FIG. 1.
[0034] Provided in the interface unit 112 are a wafer transporter
210 that moves on a transport path 212 extending in the X direction
as shown in FIG. 1 and a buffer cassette 214. The wafer transporter
210 can move in the Z direction and can rotate in the 8 direction;
and can transport the wafer 104 and access the exposure device (not
shown) adjacent to the interface unit 112 and the buffer cassette
214 and the fifth processing device group 132.
[0035] FIG. 5 shows a flowchart of an exemplary embodiment of a
photolithography process 400 comprising steps for mitigating
collapse of photoresist line patterns. FIG. 4 depicts the same
process outlined in the flowchart of FIG. 5 starting with rinsing
step 450, and ending with the gap-fill layer removal step 480. In
step 410, the substrate (e.g. a semiconductor wafer, LCD panel, or
photovoltaic device panel) is coated with a layer of photoresist in
e.g. spin coating devices 140, 141, and 142, of coating/developing
system 100, of FIGS. 1-3. In step 420, the photoresist layer is
exposed to light to impart a latent image line pattern therein.
This step is performed in an exposure device (not shown in FIGS.
1-3). In step 430, the substrate is exposed to an elevated
temperature in a post-exposure bake step, which serves multiple
purposes in photoresist processing. First, the elevated temperature
of the bake drives the diffusion of the photoproducts (i.e.
photo-acid) in the photoresist. A small amount of diffusion may be
useful in minimizing the effects of standing waves, which are the
periodic variations in exposure dose throughout the depth of the
photoresist layer that result from interference of incident and
reflected radiation during exposure. Another main purpose of the
bake is to drive an acid-catalyzed reaction that alters polymer
solubility in many chemically amplified resists. Post-exposure bake
also plays a role in removing solvent from the substrate surface.
In step 440, the substrate is transferred to a developing device,
such as for example, one of developing devices 150-154 of
coating/developing system 100, of FIGS. 1-3. In the developing
device, developer (i.e. developer liquid) is dispensed onto the
substrate to activate the photoproducts in the photoresist, and
thereby develop portions of the photoresist, leaving a developed
photoresist line pattern on the substrate.
[0036] With further reference to the flowchart of FIG. 5, and the
schematic of FIG. 4, in step 450, excess developer is rinsed from
the developed photoresist line pattern 310, and the substrate 300
by dispensing rinse liquid 330, such as deionized water, from a
rinse liquid nozzle 320. The rinse liquid 330 may contain various
additives, such as surfactants to reduce the surface tension of the
rinse liquid 330, and to aid in displacing the developer. In step
460, in order to prevent photoresist line pattern 310 from
collapsing during the step of drying rinse liquid 330 from the
substrate, a gap-fill treatment liquid 350 is dispensed onto the
photoresist line pattern 310, and substrate 300, to fully displace
the rinse liquid 330. In step 470, excess gap-fill treatment liquid
350 is spun off the substrate 300 and photoresist line pattern 310,
typically by spinning (i.e. rotating) the substrate 300 within one
of the developing devices 150-154 of coating/developing system 100,
of FIGS. 1-3. Once excess gap-fill treatment liquid is removed, the
remaining amount is allowed to dry and form a solid gap-fill layer
360, which fills the inter-line spaces of the photoresist line
pattern 310, preventing collapse thereof during drying. Finally, in
step 480, the gap-fill material layer is removed from the substrate
300, thereby exposing the photoresist line pattern 310. The step
480 of removing the gap-fill layer 360 can be performed in a
multitude of ways, e.g. using a dry etch process in an etch tool,
or using a depolymerizing agent, such as heat, electromagnetic
radiation, or a chemical catalyst to cause depolymerization of the
gap-fill polymer material. During depolymerization, volatile
monomer compounds are formed and evolved from the surface of the
gap-fill layer material, and eventually the entire gap-fill layer
360 is removed from the photoresist line pattern 310. The process
of depolymerization will be discussed in greater detail later. It
is important to note that, unlike during conventional drying of
rinse liquid 330, the depolymerization, volatilization, and
evolution of the solidified gap-fill layer 360 during step 480 does
not give rise to capillary forces, and therefore the risk of
photoresist line pattern collapse is mitigated.
[0037] The gap-fill treatment liquid 350 and solidified gap-fill
layer material have to satisfy a number of requirements to be
suitable for use in the photolithography process 400. First, the
gap-fill treatment liquid 350 has to comprise a polymer that is
soluble in a solvent so it can be spun onto the substrate 300
inside the developing device, such as one of developing devices
150-154 of coating/developing system 100, of FIGS. 1-3. For
compatibility with the developer and rinse liquids used within the
same developing device, it is preferable that the polymer be
water-soluble (i.e. employ water as a solvent). However, it is also
possible to use a polymer which is not water-soluble, but utilizes
a solvent such as e.g. an alcohol, which is chemically compatible
with other liquids used in the developing device. The solvent is
evolved from the gap-fill treatment liquid 350 during the drying
step 470 to form the gap-fill layer 360. The gap-fill treatment
liquid also needs to be self-planarizing during the spin-off and
drying step 470, it has to have good pattern wetting and filling
properties so as to not leave voids between the photoresist pattern
lines, and it also has to completely displace the rinse liquid and
be chemically compatible with it.
[0038] Second, the polymer of which the solidified gap-fill layer
360 is comprised has to be readily removable. If a plasma etch
process is used for removal of gap-fill layer 360, it is important
that the gap-fill polymer plasma etch process have good selectivity
with respect to photoresist and other materials that are exposed to
the plasma etch process chemistry. In other embodiments, the
gap-fill layer can be caused to depolymerize (i.e. unzip) into
volatile monomer compounds which are readily evolved from the
surface of gap-fill layer 360 and pumped away, to expose the
photoresist line pattern 310. If a depolymerization removal process
is used, then the polymer needs to readily respond to the
application of a depolymerization agent, such as heat,
electromagnetic radiation, or a chemical catalyst, by breaking-up
into volatile monomer compounds.
[0039] In one exemplary embodiment, a polymeric compound can be
depolymerized by elevating the temperature of the substrate 300 and
all layers deposited thereupon, in a heating device such as high
temperature heating devices 175-178 of coating/developing system
100, of FIGS. 1-3. Other devices, such as pre-baking devices
181-184 and post-baking devices 185-189 of coating/developing
system 100, of FIGS. 1-3, can also be used to elevate the substrate
temperature to depolymerize the gap-fill layer material. An
exemplary schematic of a heating device 700 is shown in FIG. 8. The
heating device 700 comprises an enclosure 710, inside which a hot
plate 720 is disposed and configured to receive a substrate 730,
with a gap-fill layer 360 formed thereon. Heaters embedded in the
hot plate 720 are used to elevate the temperature of substrate 730
and the gap-fill layer 360. Optional lift pins 740 can be used to
elevate the substrate 730 from the hot plate 720 during the heating
step, to improve heating uniformity. The temperature to which the
substrate 300 and gap-fill layer 360 have to be heated depends on
the gap-fill material depolymerization (i.e. unzip) temperature,
the resistance of the photoresist and other surrounding materials
to elevated temperatures, etc. In general, the temperature used can
vary from about 10.degree. C. to 20.degree. C. below the gap-fill
material depolymerization temperature, to almost as high as the
temperature at which photoresist is damaged. With the above in
mind, and for typical gap-fill polymers and photoresist materials,
practical depolymerization temperatures will vary from 30.degree.
C. to 200.degree. C., and more preferably from 50.degree. C. to
150.degree. C.
[0040] In another exemplary embodiment, a polymeric compound can be
depolymerized by illumination with electromagnetic radiation. This
can be achieved in a module of coating/developing system 100, of
FIGS. 1-3 (not shown), in which a lamp, laser, or similar device,
are used as a source of electromagnetic radiation which causes the
gap-fill material to depolymerize. FIG. 9 shows an exemplary
schematic of an illumination device 800, to be used for
illumination of gap-fill layer 360 with electromagnetic radiation.
Illumination device 800 comprises an enclosure 810, inside which a
pedestal 820 is disposed to receive a substrate 830 with a gap-fill
layer 360 deposited thereupon. Optional lift pins 840 can be used
to elevate the substrate during illumination to reduce heat loss
from the substrate 830 during illumination. A light source 850 is
used to generate electromagnetic radiation for illumination of the
gap-fill layer 360. The light source 850 can be a lamp, laser, or a
combination of two or more thereof. In one exemplary embodiment, an
ultraviolet lamp can be used as light source 850, to illuminate the
gap-fill layer 360 with ultraviolet light of sufficiently high
photon energy to initiate polymer bond breakage, and
depolymerization. In another embodiment, a visible light or
infrared lamp can be used as light source 850, the latter causing
depolymerization primarily via a heating effect. In yet another
embodiment, a laser, such as a visible light or infrared laser, can
be used as light source 850. The laser comprising the light source
850 can be operated in continuous or pulsed (i.e. spike
illumination) mode, the latter being particularly suitable for
gap-fill layer illumination because an exact dose of
electromagnetic radiation can be delivered to the gap-fill layer
360 without causing undue heating of underlying layers and the
substrate, which allows safe processing of devices with a
relatively low thermal budget. Typical pulse (i.e. spike) times can
range from 1 ms to 100 ms, or more preferably from 1 ms to 10 ms.
Pulsed illumination is also possible with a lamp used as light
source 850. An optical waveguide 860 guides the electromagnetic
radiation from light source 850 to the beam shaping optics 870. The
beam shaping optics 870 ensure that the electromagnetic radiation
from light source 850 is evenly distributed over the substrate 830
and gap-fill layer 360. This even illumination can be achieved in a
number of ways. In one embodiment, a system of fixed optics (e.g.
mirrors, lenses, and waveguides) can be employed to spread the
electromagnetic radiation into light beam 880, reaching all points
on the substrate 830 and gap-fill layer 360, simultaneously.
Alternatively, beam shaping optics 870 can comprise an optical
scanner element that directs the light beam 880 onto just a portion
of substrate 830 and gap-fill layer 360, scanning the light beam
over time to process other portions of substrate 830. Alternatively
yet, fixed beam shaping optics 870 can be configured to illuminate
only a portion of substrate 830 and gap-fill layer 360, and the
pedestal 820 can be mounted on a translation and/or rotation stage
(not shown), allowing all portions of the substrate 830 and
gap-fill layer 360 to be illuminated by scanning the pedestal 820
with a substrate 830 under the light beam 880. In embodiments where
pulsed (i.e. spike) illumination is used, the pulse illumination
can optionally be synchronized with the scanning of light beam 880
or the scanning of pedestal 820, via a controller (not shown), to
evenly illuminate the entire gap-fill layer 360.
[0041] In yet another exemplary embodiment, a chemical catalyst
compound can be applied to the gap-fill layer 360 which will
initiate gap-fill material polymer bond breakage, and cause it to
depolymerize and evolve. Typically, an acid catalyst would be used
to initiate polymer bond breakage. The advantage of this embodiment
is that the gap-fill layer removal step 480 can be performed in the
developing device, i.e. without having to transport the substrate
to another module of the coating/developing system.
[0042] FIG. 7 shows an embodiment of a developing device, such as
one of developing devices 150-154 of coating/developing system 100,
of FIGS. 1-3, suitable for performing portions of the
photolithography process 400 outlined in FIGS. 4 and 5. Developing
device 500 comprises a cup 510 inside which a substrate chuck or
support structure 530 is configured to receive and clamp a
substrate 550 thereupon. The substrate chuck 530 has a first end
532 configured to clamp the substrate, typically using a vacuum or
electrostatic force, and a second end 535 attached to a spindle 540
of a drive motor (not shown) which is used to spin the substrate
during dispensing and spin-off steps. Excess dispensed liquid is
fed outside the cup 510 via liquid ports 520, and vapors are
pumped-out via vapor ports 522. During each dispensing step
performed in the developing device 500, a layer 560 of the
dispensed liquid is formed on the top surface of substrate 550.
[0043] With further reference to FIG. 7, the developing device 500
comprises at least four nozzles 620, 650, 680, and 695 used to
dispense developer, rinse liquid, gap-fill treatment liquid, and
catalyst liquid respectively. In some embodiments, multiple nozzles
or arrays of nozzles can be used to dispense a liquid, instead of
single nozzles 620, 650, 680, and 695. Also, the nozzles or nozzle
arrays can be stationary or movable to facilitate uniform
dispensing of liquids onto the substrate surface. Nozzles 620, 650,
680, and 695 are connected to developer source 600, rinse liquid
source 630, gap-fill treatment liquid source 660, and catalyst
liquid source 690, via tubing runs 610, 640, 670, and 692,
respectively. In performing the steps of photolithography process
400 of FIGS. 4 and 5, the nozzles 620, 650, 680, and 695 are
opened, and sources 600, 630, 660, and 690 are activated to
dispense the developer, rinse liquid, gap-fill treatment liquid, or
catalyst liquid during steps 440, 450, 460, and 480, respectively,
of photolithography process 400 depicted in FIG. 5. The addition of
a catalyst nozzle 695 to the developing device 500 allows
catalyst-initiated depolymerization of the gap-fill layer 360 to
occur immediately after drying step 470, and without the need for
removing the substrate 550 from developing device 500.
[0044] In another alternative embodiment, a developing device 500
can be equipped with a light source and beam shaping optics, such
as light source 850 and beam shaping optics 870, of illumination
device 800, to allow illumination of substrate 550 within the
developing device 500. This embodiment does not require that
separate illumination devices, such as illumination device 800, be
installed inside coating/developing system 100, of FIGS. 1-3.
[0045] FIG. 6 shows a number of polymer compounds that can be used
as a gap-fill treatment liquid and that may solidify into a
suitable gap-fill layer material. In general, most polymer
materials have very low depolymerization (i.e. ceiling)
temperatures, i.e. below typical ambient temperatures, so they are
typically end-capped to increase their stability. The process of
depolymerizing via application of one of the above depolymerizing
agents (heat, electromagnetic radiation, or a catalyst) starts by
the agent causing bond breakage "events", after which the polymer
fully "unzips".
[0046] In one exemplary embodiment, poly(methyl glyoxylate) is used
as a gap-fill polymer. This compound is a polymeric salt of the
poly(methyl glyoxylic acid), wherein the ion can be e.g. a sodium
ion Na.sup.+, or an ammonium ion NH.sub.4.sup.+. In a preferred
embodiment, the ammonium salt is used because upon application of
heat to this polymeric salt, two useful chemical changes occur.
First, the ammonium ion NH.sub.4.sup.+will give up a hydrogen atom
to the poly(methyl glyoxylate), and become ammonia NH.sub.3, which
readily evolves from the polymer. And second, because the polymer
has oxygen in its backbone, it is unstable, and will "unzip" if one
of the oxygen bonds are broken due to action of a depolymerization
agent, such as heat, with the resulting monomer compounds also
evolving from the polymer. Other compounds listed in FIG. 6 have
similar depolymerization mechanisms, some of which are described in
the literature, e.g. Brachais et al., "In Vitro Degradation of
poly(methyl glyoxylate) in Water", Polymer, vol. 39, pp. 883-890,
1998; Tsuda et al., "Acid-catalyzed Degradation Mechanism of
poly(phthalaldehyde): Unzipping Reaction of Chemical Amplification
Resist", Journal of Polymer Science: Part A, Polymer Chemistry,
vol. 35, pp. 77-89, 1997; and Belloncle et al., "Synthesis and
Degradation of poly(ethyl glyoxylate)", in "Polymer Degradation and
Performance", chap. 4, pp. 41-51, ACS Symposium Series, ACS 2009,
the contents of all of which are incorporated herein in their
entirety. Additionally, U.S. Pat. No. 6,576,714 entitled
"Production Process for Glyoxylic Acid (Salt)-Based Polymer", to
Saeki et al., provides useful background information about the
stability, end-capping, production, etc., of polymeric salts of the
glyoxylic acid, and is also incorporated herein in its
entirety.
[0047] With further reference to FIG. 6, the polymer compound
poly(phthalaldehyde), also known by its IUPAC name
poly(o-phthalaldeyde), is a polymer of monomer phthalaldehyde,
which monomer is also known by its IUPAC names o-phthalaldehyde and
ortho-phthalaldehyde.
[0048] In another embodiment, a gap-fill treatment liquid 350 can
be used, with or without a solvent, which would react with the
rinse liquid, e.g. deionized water present at the substrate, to
form an in-situ gel that fills inter-line spaces in the photoresist
line pattern 310. The gel would be removed using similar process
steps to those described above, e.g. using plasma etch, or
depolymerized the gel by applying heat, electromagnetic radiation,
or a chemical catalyst.
[0049] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structure,
material, or characteristic described in connection with the
embodiment is included in at least one embodiment of the invention,
but do not denote that they are present in every embodiment. Thus,
the appearances of the phrases "in one embodiment" or "in an
embodiment" in various places throughout this specification are not
necessarily referring to the same embodiment of the invention.
Furthermore, the particular features, structures, materials, or
characteristics may be combined in any suitable manner in one or
more embodiments.
[0050] Various operations will be described as multiple discrete
operations in turn, in a manner that is most helpful in
understanding the invention. However, the order of description
should not be construed as to imply that these operations are
necessarily order dependent. In particular, these operations need
not be performed in the order of presentation. Operations described
may be performed in a different order than the described
embodiment. Various additional operations may be performed and/or
described operations may be omitted in additional embodiments.
[0051] Persons skilled in the relevant art can appreciate that many
modifications and variations are possible in light of the above
teaching. Persons skilled in the art will recognize various
equivalent combinations and substitutions for various components
shown in the figures. It is therefore intended that the scope of
the invention be limited not by this detailed description, but
rather by the claims appended hereto.
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