U.S. patent application number 13/722548 was filed with the patent office on 2013-05-02 for method of slimming radiation-sensitive material lines in lithographic applications.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. The applicant listed for this patent is Tokyo Electron Limited. Invention is credited to Michael A. Carcasi, Benjamen M. Rathsack, Mark H. Somervell.
Application Number | 20130107237 13/722548 |
Document ID | / |
Family ID | 44625756 |
Filed Date | 2013-05-02 |
United States Patent
Application |
20130107237 |
Kind Code |
A1 |
Carcasi; Michael A. ; et
al. |
May 2, 2013 |
METHOD OF SLIMMING RADIATION-SENSITIVE MATERIAL LINES IN
LITHOGRAPHIC APPLICATIONS
Abstract
A method and system for patterning a substrate using a
radiation-sensitive material is described. The method and system
include forming a layer of radiation-sensitive material on a
substrate, exposing the layer of radiation-sensitive material to a
pattern of radiation, and then performing a post-exposure bake
following the exposing. The imaged layer of radiation-sensitive
material is then positive-tone developed to remove a region having
high radiation exposure to form radiation-sensitive material lines.
An exposure gradient within the radiation-sensitive material lines
is then removed, followed by slimming the radiation-sensitive
material lines.
Inventors: |
Carcasi; Michael A.;
(Austin, TX) ; Rathsack; Benjamen M.; (Austin,
TX) ; Somervell; Mark H.; (Austin, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tokyo Electron Limited; |
Tokyo |
|
JP |
|
|
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
44625756 |
Appl. No.: |
13/722548 |
Filed: |
December 20, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12751362 |
Mar 31, 2010 |
8338086 |
|
|
13722548 |
|
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Current U.S.
Class: |
355/30 |
Current CPC
Class: |
G03F 7/40 20130101; G03F
7/26 20130101; H01L 21/67207 20130101; G03F 7/2024 20130101 |
Class at
Publication: |
355/30 |
International
Class: |
G03F 7/26 20060101
G03F007/26 |
Claims
1. A platform configured for patterning a substrate, comprising: a
track system configured to coat a substrate with a layer of
radiation-sensitive material; a lithography system including a
pattern exposure system configured to expose said substrate to
patterned EM radiation; an exposure gradient removal system
configured to expose said substrate to an exposure gradient removal
treatment; and a transfer system configured to transfer said
substrate between said track system, said pattern exposure system,
and said exposure gradient removal system.
2. The platform of claim 1, wherein said exposure gradient removal
system is integrated with said pattern exposure system within said
lithography system.
3. The platform of claim 2, wherein said pattern exposure system
comprises a radiation source, a mask imaging system, and a
substrate holder.
4. The platform of claim 1, wherein said exposure gradient removal
system is a flood exposure system and a post-flood exposure
system.
5. The platform of claim 1, wherein said exposure gradient removal
system is an acid wash and post-acid wash bake system.
6. The platform of claim 1, wherein said exposure gradient removal
system is an temperature control apparatus capable of heating said
layer of radiation-sensitive material to a thermal decomposition
temperature.
7. The platform of claim 1, wherein said exposure gradient removal
system is integrated within said track system.
8. The platform of claim 1, wherein said exposure gradient removal
system comprises a stand-alone module separate from said track
system and said pattern exposure system, and coupled to said track
system or said pattern exposure system or both.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of co-pending
U.S. patent application Ser. No. 12/751,362 filed Mar. 31, 2010,
and entitled METHOD OF SLIMMING RADIATION-SENSITIVE MATERIAL LINES
IN LITHOGRAPHIC APPLICATIONS, the disclosure of which is
incorporated herein by reference in its entirety as if completely
set forth herein below.
FIELD OF THE INVENTION
[0002] The invention relates to methods of patterning a substrate.
In particular, the invention relates to methods of decreasing line
dimension (slimming) in radiation-sensitive materials.
BACKGROUND OF THE INVENTION
[0003] The need to remain competitive in cost and performance in
the production of semiconductor devices has caused a continuous
increase in device density of integrated circuits. To accomplish
higher integration and miniaturization in a semiconductor
integrated circuit, miniaturization of a circuit pattern formed on
a semiconductor wafer must also be accomplished.
[0004] Design rules define the space tolerance between devices or
interconnect lines so as to ensure that the devices or lines do not
interact with one another in any unwanted manner. One important
layout design rule that tends to determine the overall size and
density of the semiconductor device is the critical dimension (CD).
A critical dimension of a circuit is defined as the smallest width
of a line or the smallest space between two lines. Another critical
design rule is minimum pitch, which is defined as the minimum width
of a given feature plus the distance to the adjacent feature
edge.
[0005] Photolithography is a standard technique utilized to
manufacture semiconductor wafers by transferring geometric shapes
and patterns on a mask to the surface of a semiconductor wafer. The
basic photolithographic process includes projecting a patterned
light source onto a layer of radiation-sensitive material, such as
a photoresist layer, which is then followed by a development
step.
[0006] To create finely detailed patterns with small critical
dimensions and pitch requires projecting a clearly imaged light
pattern. But the ability to project a clear image of a small
feature onto the semiconductor wafer is limited by the wavelength
of the light that is used, and the ability of a reduction lens
system to capture enough diffraction orders from the illuminated
mask. Current state-of-the-art photolithography tools use deep
ultraviolet (DUV) light with wavelengths of 248 or 193 nm, which
allow minimum feature sizes down to about 50 nm.
[0007] The minimum feature size that a projection system can print
is given approximately by:
CD=k.sub.1.lamda./N.sub.A
[0008] where CD is the minimum feature size or the critical
dimension; k.sub.1 is a coefficient that encapsulates
process-related factors, and typically equals 0.4 for production;
.lamda. is the wavelength of light used; and N.sub.A is the
numerical aperture of the lens, as seen from the semiconductor
wafer. According to this equation, minimum feature sizes can be
decreased by decreasing the wavelength and/or by increasing the
numerical aperture to achieve a tighter focused beam and a smaller
spot size.
[0009] A photolithographic process utilizes an exposure tool to
irradiate the layer of radiation-sensitive material on a wafer
through a mask to transfer the pattern on the mask to the wafer. As
the critical dimensions of the pattern layout approach the
resolution limit of the lithography equipment, optical proximity
effects (OPE) begin to influence the manner in which features on a
mask transfer to the layer of radiation-sensitive material such
that the mask and actual layout patterns begin to differ. Optical
Proximity effects are known to result from optical diffraction in
the projection system. The diffraction causes adjacent features to
interact with one another in such a way as to produce
pattern-dependent variations; the closer together features are, the
more proximity effect is seen. Thus, the ability to locate line
patterns close together encroaches on optical parameter
limitations.
[0010] In accordance with the above description, new and improved
methods for patterning semiconductor devices are therefore
necessary, so as to accomplish the continued miniaturization of a
circuit pattern formed on a semiconductor wafer. One non-optical
approach is to narrow the line width of the radiation-sensitive
material after the imaging, and the first developing are completed.
Narrowing of line width is also known as "slimming" or "shrinking",
those terms being used herein synonymously.
[0011] As discussed above, patterning of a semiconductor wafer
generally involves coating a surface of the wafer (substrate) with
a thin film or layer of a radiation-sensitive material, such as a
photoresist, and then exposing the layer of radiation-sensitive
material to a pattern of radiation by projecting radiation from a
radiation source through a mask. Thereafter, a developing process
is performed to remove various regions of the radiation-sensitive
material. The specific region being removed is dependent upon the
tone of the material and the developing chemistry. As an example,
in the case of a positive-tone photoresist, the irradiated regions
may be removed using a first developing chemistry and the
non-irradiated regions may be removed using a second developing
chemistry. Conversely, in the case of a negative-tone photoresist,
the non-irradiated regions may be removed using a third developing
chemistry and the irradiated regions may be removed using a fourth
developing chemistry. The removed regions of photoresist expose the
underlying wafer surface in a pattern that is ready to be etched
into the surface.
[0012] As an example for positive-tone pattern development, a
typical lithographic patterning technique is shown in FIGS. 1A and
1B. As shown in FIG. 1A, a layer of radiation-sensitive material
102 is formed on a substrate 101. The layer of radiation-sensitive
material 102 is exposed to electromagnetic (EM) radiation 107
through a mask 103. Reticle or mask 103 includes transparent
regions 104 and opaque regions 108 that form a pattern, with a
distance (or pitch) 109 being defined between opaque regions 108,
as shown in FIG. 1A. The transparent regions 104 transmit EM
radiation 107 to the layer of radiation-sensitive material 102, and
the opaque regions 108 prevent EM radiation 107 from being
transmitted to the layer radiation-sensitive material 102. As a
result, the layer of radiation-sensitive material 102 has exposed
regions 105 that are exposed to EM radiation 107 and unexposed
regions 106 that are not exposed to EM radiation 107. As shown in
FIG. 1A, opaque regions 108 are imaged onto the layer of
radiation-sensitive material 102 to produce corresponding
radiation-sensitive material features aligned with unexposed
regions 106.
[0013] As shown in FIG. 1B, after removing exposed regions 105 of
the layer of radiation-sensitive material 102 by a developing
process, unexposed regions 106 remain on substrate 101 and form the
pattern transferred from mask 103. The regions of
radiation-sensitive material remaining after removal of the exposed
regions 105 are referred to as radiation-sensitive material lines.
As shown in FIGS. 1A and 1B, opaque regions 108 are imaged onto the
layer of radiation-sensitive material 102 to produce corresponding
radiation-sensitive material features (i.e., unexposed regions
106). As shown in FIGS. 1A and 1B, pitch 110 between unexposed
regions 106 is determined by pitch 109 between opaque regions 108
of mask 103. In this example, the pitch 110 of the patterned
feature is approximately twice the width of the critical dimension
111 of the radiation-sensitive material lines. Thus, the critical
dimension 111 is determined by the distance between opaque regions
of mask 103 and the development process. To further reduce the
critical dimension 111 of the radiation-sensitive material lines
requires additional processing, as discussed next.
[0014] One typical method for reducing radiation-sensitive material
line width involves plasma-based etching of the unexposed region
106 of the radiation-sensitive material after a positive-tone
development conducted at nominal temperature. Plasma-based etching
suffers from various issues such as process stability and higher
front end costs. Other slimming or shrinking methods include wet
methods, such as performing a positive-tone development at elevated
temperatures. But wet developing methods may suffer from
anisotropic slimming caused by or exacerbated by variations in the
photolithographic image, as will be discussed further below.
[0015] Additional details of the photolithographic image are
provided in FIG. 2. A layer of radiation-sensitive material 202 is
formed on a substrate 201. The layer of radiation-sensitive
material 202 is exposed to EM radiation 207 through a mask 203.
Mask 203 includes transparent regions 204 and opaque regions 208
that form a pattern, as shown in FIG. 2. A distance (or pitch) 209
between opaque regions 208 is shown in FIG. 2. The transparent
regions 204 transmit EM radiation 207 to the layer of positive-tone
radiation-sensitive material 202, and the opaque regions 208
prevent EM radiation 207 from being transmitted to the layer of
radiation-sensitive material 202.
[0016] While it would be desirable to produce only two types of
image patterns, i.e., exposed and unexposed, FIG. 2 shows three
regions of radiation-sensitive material 202 having different levels
of exposure to EM radiation 107. Exposed regions 205 and unexposed
regions 206 are separated by a partially exposed region 214,
wherein an exposure gradient extends across the width of partially
exposed region 214. This exposure gradient may be affected by
various factors, such as the radiation-sensitive material
thickness, the depth of focus and proximity effect. Thus, this
exposure variation or gradient induces anisotropic slimming, which
may produce weak points in the radiation-sensitive material
lines.
[0017] In view thereof, new methods of slimming radiation-sensitive
material lines that overcome the problems of the prior art are
needed.
SUMMARY OF THE INVENTION
[0018] Embodiments of the invention provide a method of patterning
a substrate, wherein the dimensions of radiation-sensitive material
lines are decreased. The methods comprise forming a layer of
radiation-sensitive material on a substrate; exposing the layer of
radiation-sensitive material to a pattern of radiation, wherein the
pattern includes: a first region having a high radiation exposure,
a second region having a low radiation exposure, and a third region
having an exposure gradient ranging from about said high radiation
exposure to about said low radiation exposure. The methods further
comprise performing a post-exposure bake following the exposing the
layer of radiation-sensitive material to the pattern of radiation;
performing positive-tone developing of the layer of
radiation-sensitive material to remove the first region from the
substrate; removing the exposure gradient of the third region by
transforming the second region and the third region to a fourth
region having a substantially uniform level of radiation exposure
or de-protection, or a combination thereof; and slimming the fourth
region.
[0019] Other embodiments of the invention provide a platform
configured for patterning a substrate. The platform comprises a
track system configured to coat a substrate with a layer of
radiation-sensitive material; a lithography system that includes a
pattern exposure system configured to expose the substrate to
patterned EM radiation; an exposure gradient removal system that is
configured to expose the substrate to an exposure gradient removal
treatment; and a transfer system configured to transfer the
substrate between the track system, the pattern exposure system,
and the exposure gradient removal system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In the accompanying drawings:
[0021] FIGS. 1A and 1B illustrate a lithographic patterning
technique utilizing a radiation-sensitive material according to the
prior art;
[0022] FIG. 2 illustrates further details in the lithographic
pattern of the exposed radiation-sensitive material of FIG. 1A;
[0023] FIG. 3 illustrates a method of patterning a substrate;
[0024] FIGS. 4A through 4E illustrate a method of patterning a
substrate;
[0025] FIG. 5 illustrates a method of patterning a substrate
according to one embodiment of the invention;
[0026] FIG. 6 illustrates a method of patterning a substrate
according to another embodiment of the invention;
[0027] FIG. 7 illustrates a method of patterning a substrate
according to another embodiment of the invention;
[0028] FIG. 8 illustrates a method of patterning a substrate
according to yet another embodiment of the invention;
[0029] FIG. 9 illustrates various methods of slimming the
dimensions of a radiation-sensitive material line according to
embodiments of the invention; and
[0030] FIGS. 10A through 10C provide a schematic illustration of a
platform for patterning a substrate according to several
embodiments.
DETAILED DESCRIPTION OF THE DRAWINGS
[0031] A method and system for patterning a substrate is disclosed
in various embodiments. However, one skilled in the relevant art
will recognize that the various embodiments may be practiced
without one or more of the specific details, or with other
replacement and/or additional methods, materials, or components. In
other instances, well-known structures, materials, or operations
are not shown or described in detail to avoid obscuring aspects of
various embodiments of the invention.
[0032] Similarly, for purposes of explanation, specific numbers,
materials, and configurations are set forth in order to provide a
thorough understanding of the invention. Nevertheless, the
invention may be practiced without specific details. Furthermore,
it is understood that the various embodiments shown in the figures
are illustrative representations and are not necessarily drawn to
scale.
[0033] Reference throughout this specification to "one embodiment"
or "an embodiment" or variation thereof 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
such as "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. Various
additional layers and/or structures may be included and/or
described features may be omitted in other embodiments.
[0034] Additionally, it is to be understood that "a" or "an" may
mean "one or more" unless explicitly stated otherwise.
[0035] 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.
[0036] Methods for patterning a substrate, including methods to
reduce the critical dimension of a pattern that can be transferred
onto a substrate for a given lithographic tool and mask, are
described herein. Multiple chemical treatments are used to achieve
an isotropic reduction in a critical dimension of a
radiation-sensitive material line.
[0037] Referencing FIG. 3, in accordance with embodiments of the
present invention, a layer of radiation-sensitive material is
formed on a substrate 301. The substrate 301 may comprise a
semiconductor, e.g., mono-crystalline silicon, germanium, and any
other semiconductor. In alternate embodiments, substrate 301 may
comprise any material used to fabricate integrated circuits,
passive microelectronic devices (e.g., capacitors, inductors) and
active microelectronic devices (e.g., transistors, photo-detectors,
lasers, diodes). Substrate 301 may include insulating materials
that separate such active and passive microelectronic devices from
a conductive layer or layers that are formed on top of them. In one
embodiment, substrate 301 comprises a p-type mono-crystalline
silicon substrate that includes one or more insulating layers e.g.,
silicon dioxide, silicon nitride, sapphire, and other insulating
materials.
[0038] As described above, the substrate 301 may comprise a film
stack having one or more thin films or layers disposed between a
base layer and the layer of radiation-sensitive material 302. Each
thin film in substrate 301 may comprise a conductive layer, a
non-conductive layer, or a semi-conductive layer. For instance, the
thin film may include a material layer comprising a metal, metal
oxide, metal nitride, metal oxynitride, metal silicate, metal
silicide, silicon, poly-crystalline silicon (poly-silicon), doped
silicon, silicon dioxide, silicon nitride, silicon carbide, silicon
oxynitride, etc. Additionally, for instance, the thin film may
comprise a low dielectric constant (i.e., low-k) or ultra-low
dielectric constant (i.e., ultra-low-k) dielectric layer having a
nominal dielectric constant value less than the dielectric constant
of SiO.sub.2, which is approximately 4 (e.g., the dielectric
constant for thermal silicon dioxide can range from 3.8 to 3.9).
More specifically, the thin film may have a dielectric constant of
less than 3.7, or a dielectric constant ranging from 1.6 to
3.7.
[0039] According to embodiments of the invention, the layer of
radiation-sensitive material 302 may comprise, for example, a 248
nm radiation-sensitive material, a 193 nm radiation-sensitive
material, a 157 nm radiation-sensitive material, or an extreme
ultraviolet radiation-sensitive material, or a combination of two
or more thereof. According to another embodiment, the layer of
radiation-sensitive material 302 comprises
poly(hydroxystyrene)-based resist or a (meth)acrylate-based resist.
According to another embodiment, the layer of radiation-sensitive
material 302 comprises a material that switches solubility due to a
change in polarity upon performing an exposure to radiation of the
appropriate wavelength and thereafter performing a first
post-exposure bake following the exposure. According to another
embodiment, the layer of radiation-sensitive material 302 comprises
a material that provides acid-catalyzed de-protection upon
performing an exposure to radiation having the appropriate
wavelength and thereafter performing a first post-exposure bake
following the exposure. According to another embodiment, the layer
of radiation-sensitive material 302 comprises a material that
provides acid-catalyzed de-protection upon performing a thermal
decomposition bake following the exposure to radiation. According
to yet another embodiment, the layer of radiation-sensitive
material 302 comprises a material that provides acid-catalyzed
de-protection upon performing an acid wash and performing a
post-acid wash bake.
[0040] According to yet another embodiment, the layer of
radiation-sensitive material 302 comprises an acid generator, such
as a photo acid generator, a thermal acid generator and/or
combinations thereof. Reference herein to "an acid generator"
should be understood to synonymously refer to "one or more acid
generators." According to yet another embodiment, the layer of
radiation-sensitive material 302 comprises a protected polymer that
undergoes de-protection upon heating to a temperature equal to or
greater than a thermal decomposition temperature of said protected
polymer. According to yet another embodiment, the layer of
radiation-sensitive material 302 comprises a protected polymer that
undergoes de-protection upon heating to a temperature equal to or
greater than a thermal decomposition temperature of said protected
polymer, after performing an acid wash treatment.
[0041] The layer of radiation-sensitive material 302 may be formed
using a track system. For example, the track system can comprise a
Clean Track ACT 8, ACT 12, or Lithius resist coating and developing
system commercially available from Tokyo Electron Limited (TEL).
Other systems and methods for forming a layer of
radiation-sensitive material on a substrate are well known to those
skilled in the art of spin-on resist technology.
[0042] Following the application of the layer of
radiation-sensitive material 302 to substrate 301, the layer of
radiation-sensitive material may be thermally treated in a
post-application bake (PAB). For example, a temperature of the
substrate may be elevated to between about 50.degree. C. and about
200.degree. C., for a duration of about 30 seconds to about 180
seconds. A track system having post-application substrate heating
and cooling equipment may be used to perform the PAB, for example,
one of the track systems described above. Other systems and methods
for thermally treating an exposed radiation-sensitive material film
on a substrate are well known to those skilled in the art of
spin-on resist technology.
[0043] As shown in FIG. 3, the layer of radiation-sensitive
material 302 is exposed to radiation 307 through a mask 303. The
mask 303 comprises opaque regions 310 that prevent radiation 307
from being transmitted to the layer of radiation-sensitive material
302 and transparent regions 304 that transmit the radiation 307 to
the layer of radiation-sensitive material 302. The mask 303 may
include any mask suitable for use in wet (e.g., immersion) or dry
lithography, including wavelengths ranging from about 365 nm to
about 13 nm. The mask 303 may include a binary mask or chrome on
glass mask. Alternatively, the mask 303 may include an alternating
phase shift mask, or an embedded phase shift mask.
[0044] The exposure of the layer of radiation-sensitive material
302 to the pattern of EM radiation may be performed in a dry or wet
photo-lithography system. The lithography system may be capable of
providing a pattern of EM radiation at wavelengths of 365 nm, 248
nm, 193 nm, 157 nm, and 13 nm, for example. The image pattern can
be formed using any suitable conventional stepping lithographic
system, or scanning lithographic system. For example, the
photo-lithographic system may be commercially available from ASML
Netherlands B.V. (De Run 6501, 5504 DR Veldhoven, The Netherlands),
or Canon USA, Inc., Semiconductor Equipment Division (3300 North
First Street, San Jose, Calif. 95134). The mask 303 can be
illuminated, for example, with normal incident light and off-axis
illumination light, such as annular illumination, quadrupole
illumination, and dipole illumination. These methods of
illumination and exposing the layer of radiation-sensitive material
302 to radiation using the mask 303 are known to one of ordinary
skill in the art of microelectronic device manufacturing.
[0045] A track system, as described above, having post-exposure
substrate heating and cooling equipment may be used to perform a
post-exposure bake (PEB). Other systems and methods for thermally
treating an exposed layer of radiation-sensitive material on a
substrate are well known to those skilled in the art of spin-on
resist technology.
[0046] In further reference to FIG. 3, there is shown a radiation
exposure profile 305 and a response profile 306 produced in the
layer of radiation-sensitive material 302 by a pattern of radiation
resulting from the projection of radiation 307 through the mask 303
using a lithography system. As shown in FIG. 3, the first regions
312 that correspond to the transparent regions 304 receive a high
radiation exposure from radiation 307, the second regions 313 that
correspond to the opaque regions 310 receive a low radiation
exposure from radiation 307, and the third regions 314 that
approximately correspond to edges of the opaque regions 310 receive
an intermediate or gradient radiation exposure that ranges from
about a high radiation exposure to about an low radiation exposure
from radiation 307. The response profile 306 corresponding to the
first regions 312 of the layer of radiation-sensitive material 302
is higher than an upper threshold 308, while the response profile
306 corresponding to the second regions 313 is lower than a lower
threshold 309. Further, the response profile 306 corresponding to
the third regions 314 lies between the lower threshold 309 and the
upper threshold 308. Further, the response profile 306
corresponding to the third regions 314 may represent a gradient of
exposure across a width of the third regions 314.
[0047] In one embodiment, the response profile 306 may represent
the acid concentration in the layer of radiation-sensitive material
302 that is proportional to radiation exposure profile 305, as
shown in FIG. 3. The acid present in the layer of
radiation-sensitive material 302 may facilitate the acid-catalyzed
de-protection of a protected polymer. As such, the acid
concentration may be proportional to the chemical concentration of
de-protected polymers in the layer of radiation-sensitive material
302. Thus, in another embodiment, the response profile 306 may
represent a chemical concentration of de-protected polymers in the
layer of radiation-sensitive material 302 that is approximately
proportional to the radiation exposure profile 305.
[0048] In one embodiment, the upper threshold 308 corresponds to a
first threshold of solubility of the layer of radiation-sensitive
material 302 when a first developing chemistry is applied. In one
embodiment, the lower threshold 309 corresponds to a second
threshold of solubility of the layer of radiation-sensitive
material 302 when a second developing chemistry is applied.
[0049] In one embodiment, the first regions 312 of the layer of
radiation-sensitive material 302 that correspond to the transparent
regions 304 of the mask 303 and that have high radiation exposure
in the radiation exposure profile 305 are selectively removed from
the substrate 301 using a first developing chemistry. The second
regions 313 of the layer of radiation-sensitive material 302 that
have low radiation exposure in the radiation exposure profile 305
may be selectively unaffected or minimally-affected by exposure to
the first developing chemistry. The third regions 314 that
correspond approximately to the edges of opaque regions 310 and
that have intermediate exposure in the radiation exposure profile
305 (i.e., radiation exposure between the upper threshold 308 and
the lower threshold 309) may remain on the substrate 301, but may
show a selectivity of resistance to the first developing chemistry
that would be proportional to the relative level of protection.
[0050] Conversely, the second regions 313 of the layer of
radiation-sensitive material 302, which have low radiation exposure
in the radiation exposure profile 305, may be selectively removed
by exposure to the second developing chemistry. The first regions
312 of the layer of radiation-sensitive material 302, which
correspond to the transparent regions 304 and have high radiation
exposure in the radiation exposure profile 305, may be selectively
unaffected or minimally-affected by exposure to the second
developing chemistry. The third regions 314, which correspond
approximately to the edges of opaque regions 310 and have
intermediate exposure in the radiation exposure profile 305 (i.e.,
radiation exposure between the upper threshold 308 and the lower
threshold 309), may remain on the substrate 301 but show a
resistance to the second developing chemistry that would be
proportional to the relative level of exposure.
[0051] In one embodiment, for the first regions 312, the response
profile 306 includes a concentration of acid in the layer of
radiation-sensitive material 302 that is higher than the upper
threshold 308 of acid concentration. In one embodiment, the upper
threshold 308 represents an acid level solubility threshold of the
layer of radiation-sensitive material 302. For example, if an acid
concentration in the layer of radiation-sensitive material 302 is
higher than the upper threshold 308 of acid concentration, the
layer of radiation-sensitive material 302 becomes soluble when a
first developing chemistry is applied.
[0052] In one embodiment, for the second regions 313, the response
profile 306 includes a concentration of acid in the layer of
radiation-sensitive material 302 that is lower than the lower
threshold 309 of acid concentration. In one embodiment, the lower
threshold 309 represents another acid level solubility threshold of
the layer of radiation-sensitive material 302. For example, if acid
concentration in the layer of radiation-sensitive material 302 is
lower than lower threshold 309 of acid concentration, the layer of
radiation-sensitive material 302 becomes soluble when a second
developing chemistry is applied.
[0053] In one embodiment, the upper threshold 308 of acid
concentration ranges from about 30% to about 60% of the clear field
acid level and the lower threshold 309 of acid concentration ranges
from about 10% to about 25% of the clear field acid concentration.
In one embodiment, the clear field acid concentration is defined as
the acid level of the radiation-sensitive material completely
exposed to radiation. In another embodiment, the clear field acid
concentration is defined as the acid concentration when
substantially all the acid generator material has reacted with
radiation 307 to produce acid species or when substantially all the
thermal acid generator has decomposed to produce acid species.
[0054] Due to diffraction of radiation 307 by the mask 303, the
third regions 314 corresponding to intermediate radiation exposure
are created. In one embodiment, the third regions 314 comprise an
acid concentration between the upper threshold 308 and the lower
threshold 309. The first regions 312 corresponding to high
radiation exposure may be selectively removed from the substrate
301 using a first developing chemistry. The second regions 313
corresponding to low radiation exposure may be selectively removed
from the substrate 301 using a second developing chemistry. The
third regions 314 corresponding to intermediate radiation exposure
may substantially remain on substrate 301 during the first and/or
second developing chemistries.
[0055] Referring still to FIG. 3, the first regions 312 may be
characterized by a first critical dimension 320. For example, the
first critical dimension may be related to a positive-tone critical
dimension following positive-tone developing. Additionally, the
second regions 313 may be characterized by a second critical
dimension 322. For example, the second critical dimension 322 may
be related to a negative-tone critical dimension following
negative-tone developing.
[0056] A third critical dimension 324 may be related to a
positive-tone developing of an imaged radiation-sensitive material.
The third critical dimension 324 includes the second region 313 and
the adjoining third region(s) 314. A fourth critical dimension 326
may be related to a negative-tone developing of an imaged
radiation-sensitive material. The fourth critical dimension 326
includes the first region 312 and the adjoining third region(s)
314.
[0057] As used herein, positive-tone developing chemistry refers to
a solvent system that selectively removes the first regions 312
having a high radiation exposure and includes a base, e.g., alkali,
amines, etc. In one embodiment, the positive-tone developing
chemistry to selectively remove the first regions 312 includes
tetramethylammonium hydroxide (TMAH). In another embodiment, the
positive-tone developing chemistry to selectively remove the first
regions 312 includes a base, water, and an optional surfactant.
[0058] As used herein, a negative-tone developing chemistry refers
to a solvent system that selectively removes the second regions
313, having the low radiation exposure, and may comprise an organic
solvent. The negative-tone developing chemistry may further
comprise an organic solvent, optionally water, and an optional
surfactant.
[0059] To better understand the properties of the development
chemistries utilized to develop imaged radiation-sensitive
materials, the following terms are defined. R.sub.MIN is defined as
the minimum development rate. R.sub.MAX is defined as the maximum
development rate. Development rates may be conveniently described
in nanometers per second. For positive-tone development, the
R.sub.MIN is observed at low levels of de-protection, whereas
R.sub.MAX is observed at high levels of de-protection. In contrast,
for negative-tone development, the R.sub.MIN is observed at high
levels of de-protection, whereas R.sub.MAX is observed at low
levels of de-protection
[0060] An exemplary embodiment comprising a radiation-sensitive
material is shown in FIGS. 4A-4E. Film stack 400 comprises a
substrate 401 coated with a layer of radiation-sensitive material
402 that comprises an acid generator that is capable of converting
to acid when exposed to radiation. Radiation 407 is projected
through a mask 403 onto the layer of radiation-sensitive material
402. As shown in FIG. 4B, the first regions 412 in the layer of
radiation-sensitive material 402 correspond to the transparent
regions 404 in the mask 403 and receive a high radiation exposure
from radiation 407. The second regions 413 in the layer of
radiation-sensitive material 402 correspond to opaque regions 410
in the mask 403 and receive a low radiation exposure from radiation
407. The third regions 414 in the layer of radiation-sensitive
material 402 approximately correspond to edges of the opaque
regions 410 in the mask 403 and receive an intermediate radiation
exposure ranging from about the high radiation exposure to about
the low radiation exposure from radiation 407.
[0061] As further characterization of the regions 412-414, in one
embodiment, the first region 412 may have a high percent conversion
of acid generator to acid as a result of the high radiation
exposure, the second region 413 may have a low percent conversion
of acid generator to acid as a result of the low radiation
exposure, and the third region 414 may have an exposure gradient
wherein the percent conversion of acid generator to acid ranges
from about the high percent conversion to about the low percent
conversion as a result of the intermediate radiation exposure that
ranges from high to low.
[0062] Referring still to FIG. 4B, the first regions 412 may be
characterized by a first critical space dimension 420. For example,
the first critical space dimension 420 may be related to a
positive-tone critical dimension following positive-tone
developing. Additionally, the second regions 413 may be
characterized by a second critical space dimension 422. For
example, the second critical space dimension 422 may be related to
a negative-tone critical dimension following negative-tone
developing. Conversely, a third critical dimension 424 may be
related to the layer of radiation-sensitive material 402 remaining
following a positive-tone developing, and a fourth critical
dimension 426 maybe related to the layer of radiation-sensitive
material 402 remaining following a negative-tone developing. The
layer of radiation-sensitive material 402 remaining after
developing, such as those features characterized by the third and
fourth critical dimensions 424, 426 are commonly referred to as
radiation-sensitive material lines. For example, when the
radiation-sensitive material is a photoresist, features defined by
the third and fourth critical dimensions 424, 426 are commonly
referred to as photoresist lines.
[0063] In one embodiment, the first regions 412 corresponding to
high radiation exposure receive about 50% or more of radiation 407
incident on substrate 401, the second regions 413 corresponding to
low radiation exposure receive less than 15% of the radiation 407
incident on substrate 401, and the third regions 414 corresponding
to intermediate radiation exposure receive between about 15% and
about 50% of the radiation 407 incident on substrate 401.
[0064] In one embodiment, high exposure to radiation 407 increases
the concentration of an acid in the first regions 412 to a level
higher than an upper acid concentration threshold. The upper acid
concentration threshold is a first threshold of solubility of the
layer of radiation-sensitive material 402. In one embodiment, when
the concentration of the acid in the first regions 412 increases to
a level higher than the first threshold of solubility of the layer
of radiation-sensitive material 402 (e.g., acid concentration
threshold), the first regions 412 become soluble when a first
developing chemistry is applied.
[0065] In another embodiment, when the chemical concentration of
de-protected polymers in the first regions 412 increases to a level
higher than the first threshold of solubility of the layer of
radiation-sensitive material 402 (e.g., acid concentration
threshold), the first regions 412 become soluble when a first
developing chemistry is applied.
[0066] In the second regions 413 corresponding to low radiation
exposure, a concentration of an acid and/or chemical concentration
of de-protected polymers is less than a lower threshold of
solubility of the layer of radiation-sensitive material 402 (e.g.,
acid concentration threshold). The second regions 413 become
soluble when a second developing chemistry is applied.
[0067] Typically, the first solubility threshold and the second
solubility threshold are determined by a material property of the
layer of radiation-sensitive material 402. The third regions 414
corresponding to an intermediate radiation exposure have an
exposure gradient wherein an acid concentration ranges between
about the first solubility threshold and the second solubility
threshold. That is, the third regions 414 are not readily soluble
when either of the first developing chemistry or the second
developing chemistry is applied to layer of radiation-sensitive
material 402.
[0068] Following the exposure of the layer of radiation-sensitive
material 402 to EM radiation 407, the exposed layer of
radiation-sensitive material 402 may be thermally treated in a
first post-exposure bake (PEB). For example, a temperature of the
substrate may be elevated to between about 50.degree. C. and about
200.degree. C. for a duration of about 30 seconds to about 180
seconds. The PEB may be performed in a module of the track
system.
[0069] Referring now to FIG. 4C, the first regions 412
corresponding to high radiation exposure may be selectively removed
using a first developing process comprising a first developing
chemistry. The first developing process may comprise positive-tone
developing of the layer of radiation-sensitive material 402. In one
embodiment, the first developing chemistry to selectively remove
the first regions 412 includes a base, e.g., alkali, amines, etc.
In one embodiment, the first developing chemistry to selectively
remove the first regions 412 includes tetramethylammonium hydroxide
(TMAH). In another embodiment, the first developing chemistry to
selectively remove the first regions 412 includes a base, water,
and an optional surfactant.
[0070] In one embodiment, substrate 401 having the exposed layer of
radiation-sensitive material 402 is brought into contact with a
development solution containing the first developing chemistry to
remove first regions 412 that are soluble in the first developing
chemistry. Thereafter, the substrate 401 is dried. The developing
process may be performed for a pre-specified time duration (e.g.,
about 30 seconds to about 180 seconds), a pre-specified temperature
(e.g., room temperature), and a pre-specified pressure (e.g.,
atmospheric pressure). The developing process can include exposing
the substrate to a developing solution in a developing system, such
as a track system, for example, the track systems described
above.
[0071] As shown in FIG. 4C, a first critical dimension 420'
(corresponding to the areas where the first regions 412 have been
removed), a second critical dimension 422' (corresponding to the
second regions 413), a third critical dimension 424' (corresponding
to a second region 413 having a third region 414 on both sides),
and a fourth critical dimension 426' (corresponding to a removed
area having a third region 414 on both sides) may be adjusted,
controlled, and/or optimized, as will be discussed below.
[0072] As illustrated in FIG. 4C, the second regions 413 and the
third regions 414 remain on substrate 401 and make up the
radiation-sensitive material lines.
[0073] In reference to FIG. 4D, after performing the first
developing chemistry treatment of the layer of radiation-sensitive
material 402, the exposed layer of radiation-sensitive material 402
is subjected to conditions that form a fourth region 430. The third
regions 414 and the second regions 413 are converted to
substantially uniform levels of radiation exposure or
de-protection, or a combination thereof, and thereby form the
fourth regions 430.
[0074] In one embodiment, the fourth regions 430 have a
substantially uniform high percent conversion of acid generator to
acid which subsequently lead to substantially uniform regions of
de-protected polymers. Exemplary methods of affecting the high
percent conversion of the acid generator to acid in the third
region 414 and the second region 413 to form the fourth region 430
include a flood exposure of radiation, acid wash treatment,
performing a bake at an elevated temperature, and combinations
thereof. In another aspect of this embodiment, the fourth regions
430 are substantially uniform regions of de-protected polymers. The
substantial uniformity of the de-protection level in the fourth
regions 430 permits uniform reactivity with a subsequent chemistry,
i.e., the uniformity permits isotropic slimming. Thus, after the
removal of the exposure gradient, a dimension W.sub.O (i.e., the
existing critical dimension 424') may be slimmed to the desired or
target critical dimension W.sub.f, as shown in FIG. 4E, by a
substantially isotropic removal of a thickness x from the fourth
region 430 to form the desired fifth region 432.
[0075] In reference to FIG. 4E, according to embodiments of the
invention, substantially isotropic removal of thickness x from
radiation-sensitive material lines, i.e., fourth region 430, to
provide a slimmed radiation-sensitive material line, i.e., fifth
region 432, having a critical dimension W.sub.f may be accomplished
by: adjusting a composition of a negative-tone developing
chemistry, adjusting a concentration of the positive-tone
developing chemistry, adjusting a composition of the layer of
radiation-sensitive material to provide a muted layer; adjusting a
duration for applying the negative- or positive-tone developing
chemistry; adjusting a temperature of the developing chemistry, or
a combination of two or more thereof, as will be discussed further
below.
[0076] Referring now to FIG. 5, a flow chart 500 of a method of
patterning a substrate is presented according to an embodiment of
the present invention. Flow chart 500 begins in 510 with forming a
layer of radiation-sensitive material, which includes a protected
polymer and an acid generator, on a substrate. In 520, the method
includes performing a patterned exposure of the layer of
radiation-sensitive material. During the patterned exposure, the
layer of radiation-sensitive material is exposed to a pattern of
electromagnetic radiation (EM) radiation using a mask having a mask
critical dimension (CD) to form first regions, second regions, and
third regions. The mask CD may include any critical dimension to
characterize opaque regions of the mask, transparent regions of the
mask, mask pitch, etc. The first regions may be characterized as
having high radiation exposure. The second regions may be
characterized as having low radiation exposure. The third regions
may be characterized as having intermediate radiation exposure.
[0077] In 530, a post-exposure bake (PEB) is performed, wherein a
temperature of the substrate is elevated to a post-exposure
temperature. The PEB may comprise setting the post-exposure
temperature, a time the substrate is elevated to the post-exposure
temperature, a heating rate for achieving the post-exposure
temperature, a cooling rate for reducing the post-exposure
temperature, a pressure of a gaseous environment surrounding the
substrate during the elevation of the substrate to the
post-exposure temperature, or a composition of a gaseous
environment surrounding the substrate during the elevation of the
substrate to the post-exposure temperature, or a combination of two
or more thereof. The post-exposure temperature may be ramped, or
stepped.
[0078] In 540, positive-tone developing of the layer of
radiation-sensitive material is performed, wherein the first
regions are removed from the substrate using a first developing
chemistry. The removal of the first regions may be characterized by
a first critical dimension. The positive-tone developing process
may comprise setting a composition of the first developing
chemistry, time duration for applying the first developing
chemistry, or a temperature for applying the first developing
chemistry, or any combination of two or more thereof. The first
developing chemistry may comprise a base solution. The first
developing chemistry may further comprise a base solution, water,
and an optional surfactant. Thereafter, what remains is a layer of
radiation-sensitive material comprising second regions having low
radiation exposure, with third regions having intermediate exposure
located immediately adjacent the second regions. It is this
combination of second and third regions that form the
radiation-sensitive material lines.
[0079] In 550, the layer of radiation-sensitive material, which
comprises third regions, as well as second regions, are exposed to
chemistry and/or conditions that affect a high percent conversion
of the acid generator to acid and/or affect a high percent
de-protection of the polymer. The exposure gradient removal can be
achieved by performing an operation, such as a flood exposure that
is followed by a post-flood exposure bake; a thermal decomposition
bake, or acid wash that is followed by a post-acid wash bake. These
methods of removing the exposure gradient yield a de-protected
fourth region, derived from combination of the third regions and
the second regions. These methods render the fourth region
approximately uniformly de-protected and in-sensitive to
radiation.
[0080] According to one embodiment of the invention, flood exposure
of the layer of radiation-sensitive material may be performed.
During the flood exposure, the layer of radiation-sensitive
material is exposed to un-patterned radiation. The flood exposure
may comprise exposing the substrate to electromagnetic (EM)
radiation without a mask or reticle. The EM radiation may possess a
wavelength in the visible spectrum, or a wavelength in the
ultraviolet spectrum, or a combination thereof. Additionally, the
flood exposure may comprise exposing the substrate to continuous EM
radiation, pulsed EM radiation, poly-chromatic EM radiation,
mono-chromatic EM radiation, broad-band EM radiation, or
narrow-band radiation, or a combination thereof.
[0081] For example, the flood exposure may comprise exposing the
substrate to 436 nm EM radiation, 365 nm EM radiation, 248 nm EM
radiation, 193 nm EM radiation, 157 nm EM radiation, or deep
ultraviolet (DUV) EM radiation, or any combination of two or more
thereof. Additionally, for example, the flood exposure may comprise
exposing the substrate to EM radiation at a wavelength capable of
creating acid in the layer of radiation-sensitive material.
[0082] Subsequent to the flood exposure, a post-flood exposure bake
(PFEB) is performed, wherein a temperature of the substrate is
elevated to a PEFB temperature. The post-flood exposure bake may
comprise setting the PFEB temperature, a time the substrate is
elevated to the PFEB temperature, a heating rate for achieving the
PFEB temperature, a cooling rate for reducing the PFEB temperature,
a pressure of a gaseous environment surrounding the substrate
during the elevation of the substrate to the PFEB temperature, or a
composition of a gaseous environment surrounding the substrate
during the elevation of the substrate to the PFEB temperature, or a
combination of two or more thereof.
[0083] According to another embodiment of the invention, thermal
decomposition bake (TDB) of the layer of radiation-sensitive
material may be performed. For a thermal decomposition bake, the
TDB temperature may include a temperature at which an acid
generator will substantially undergo a thermal decomposition to
produce acid and thereby facilitate the acid-catalyzed
decomposition of the radiation-sensitive material; or a temperature
at which a protected polymer, such as a tert-butyl carbonate (tBOC)
protected radiation-sensitive material, will substantially
de-protect. In any event, the end result is substantially removing
the exposure gradient of the third region, as well as substantially
de-protecting/decomposing the previously unexposed second region of
the layer of radiation-sensitive material. It should be noted that
the baking temperature should not exceed the glass transition
temperature (Tg) of the layer of radiation-sensitive material.
[0084] According to yet another embodiment of the invention, an
acid wash of the layer of radiation-sensitive material may be
performed. An acid wash may provide a sufficient quantity of acid
to the surface of the layer of radiation-sensitive material that
upon heating to a sufficient temperature, it may facilitate or
enhance de-protection or thermal decomposition of the
radiation-sensitive material. A suitable acid wash may comprise
exemplary acidic compounds, such as sulfuric acid and
dichloroacetic acid.
[0085] In 560, slimming of the fourth region is performed, wherein
the dimensions of a radiation-sensitive material line are reduced
in a substantially uniform manner. According to embodiments of the
present invention, this can be achieved by various methods, as will
be discussed further below.
[0086] In reference to FIG. 6, a flow chart 600 of a method of
patterning a substrate is presented according to an embodiment of
the present invention. Flow chart 600 begins in 610 with forming a
layer of radiation-sensitive material on a substrate, and in 620,
performing a patterned exposure of the layer of radiation-sensitive
material. In 630, a first post-exposure bake (PEB) is performed,
wherein a temperature of the substrate is elevated to a PEB
temperature. In 640, positive-tone developing of the imaged layer
of radiation-sensitive material is performed, wherein the first
regions are removed from the substrate using a first developing
chemistry. In 650, a flood exposure of the layer of
radiation-sensitive material may be performed. During the flood
exposure, the layer of radiation-sensitive material is exposed to
un-patterned radiation. In 660, a post-flood exposure bake (PFEB)
is performed, wherein a temperature of the substrate is elevated to
a PEFB temperature. In 670, slimming of the radiation-sensitive
material is performed, wherein the dimensions of a
radiation-sensitive material line are reduced.
[0087] In reference to FIG. 7, a flow chart 700 of a method of
patterning a substrate is presented according to another embodiment
of the present invention. Flow chart 700 begins in 710 with forming
a layer of radiation-sensitive material on a substrate, and in 720,
performing a patterned exposure of the layer of radiation-sensitive
material. In 730, a post-exposure bake (PEB) is performed, wherein
a temperature of the substrate is elevated to a PEB temperature. In
740, positive-tone developing of the imaged layer of
radiation-sensitive material is performed, wherein the first
regions are removed from the substrate using a first developing
chemistry. In 750, a thermal decomposition bake (TDB) of the layer
of radiation-sensitive material is performed. In 760, slimming of
the radiation-sensitive material is performed, wherein the
dimensions of a radiation-sensitive material line are reduced.
[0088] In reference to FIG. 8, a flow chart 800 of a method of
patterning a substrate is presented according to yet another
embodiment of the present invention. Flow chart 800 begins in 810
with forming a layer of radiation-sensitive material on a
substrate, and in 820, performing a patterned exposure of the layer
of radiation-sensitive material. In 830, a post-exposure bake (PEB)
is performed, wherein a temperature of the substrate is elevated to
a PEB temperature. In 840, positive-tone developing of the imaged
layer of radiation-sensitive material is performed, wherein the
first regions are removed from the substrate using a first
developing chemistry. In 850, an acid wash of the layer of
radiation-sensitive material is performed. In 860, a post-acid wash
bake is performed, wherein a temperature of the substrate is
elevated to a thermal decomposition temperature. In 870, slimming
of the layer radiation-sensitive material is performed, wherein the
dimensions of a radiation-sensitive material line are reduced.
[0089] In reference to FIG. 9, a chart 900 provides alternative
methods of slimming a layer of a substantially de-protected
radiation-sensitive material, i.e., performing the slimming in 560,
670, 760, and 870 in FIGS. 5-8. As described above, the
substantially de-protected fourth region is relatively soluble when
a positive-tone developing chemistry is applied, but relatively
insoluble when a negative-tone developing chemistry is applied.
[0090] According to embodiments of the invention, the developing
chemistries may be tailored or adjusted to provide isotropic
dissolution rates that enable predictable and reproducible
performance simply by controlling the duration of exposure to the
developing chemistry. For example, developing chemistries and/or
conditions may be modified to establish a dissolution rate ranging
from about 0.1 nm/sec to about 5 nm/sec; about 0.2 nm/sec to about
4 nm/sec; or about 0.5 to about 2 nm/sec. In one example, the
dissolution rate may be about 1 nm/sec.
[0091] In alternative 910, the slimming may be accomplished by
performing a negative-tone developing. Negative-tone developing
chemistry, while generally selective to removing low de-protection
regions, may still provide the desired removal of high
de-protection regions but at a much reduced development rate.
Negative-tone developing chemistries generally comprise an organic
solvent, and may further comprise one or more organic co-solvents,
optionally water, and an optional surfactant. Thus, slimming of
highly de-protected radiation-sensitive material lines may be
affected by negative-tone development at an R.sub.MIN. Optimization
of the negative-tone development chemistry can be readily achieved
by selecting a solvent or solvent mixture to obtain the desired
dissolution rate.
[0092] In alternatives 920-940, slimming may be accomplished by
utilizing a positive-tone developing chemistry. Positive-tone
developing chemistry, while generally selective toward highly
de-protected radiation-sensitive materials, may still be employed
under modified conditions to provide a reduced development rate.
The dissolution rate of the positive-tone developing chemistry may
be reduced by methods, such as diluting the positive-tone chemistry
solution, including a muting agent in the layer of
radiation-sensitive material, or performing the positive-tone
developing chemistry at an ultra-cold temperature. As stated above,
positive-tone developing chemistries generally include a base,
e.g., alkali, amines, etc.; water; and an optional surfactant. One
exemplary base is tetramethylammonium hydroxide (TMAH).
[0093] In alternative 920, slimming may be accomplished by
performing a positive-tone developing with a dilute positive-tone
developing chemistry solution. For example, the development rate
may be reduced by diluting the positive-tone developing chemistry
by a factor of 100, 200, 500, or 1000. Optimization of the diluted
positive-tone development chemistry can be readily achieved by
selecting an appropriate dilution factor to obtain the desired
dissolution rate.
[0094] In alternative 930, slimming may be accomplished by
performing a positive-tone developing with a positive-tone
developing chemistry on a muted or inhibited layer of
radiation-sensitive material. For example, during the formation of
the film stack, a radiation-sensitive material solution may further
comprise a muting agent. As such, this process makes use of a
positive-tone developing chemistry that at high levels of
de-protection develops at or near R.sub.MAX, but the presence of
the muting agent reduces the effective dissolution rate of the
highly de-protected radiation-sensitive material to a desired
dissolution rate. One exemplary muting agent is cholic acid.
[0095] In alternative 940, the slimming may be accomplished by
performing a positive-tone developing with a positive-tone
developing chemistry at an ultra-cold temperature. As used herein,
ultra-cold temperature is defined as a temperature greater than the
freezing point of the developing chemistry and less than room
temperature. For example, the ultra-cold temperature may range from
about 0.degree. C. to about 20.degree. C.; from about 0.degree. C.
to about 15.degree. C.; or from about 5.degree. C. to about
10.degree. C.
[0096] Moreover, the foregoing slimming methods may be combined.
The slimming step may be accomplished by adjusting the composition
of the negative-tone developing chemistry, adjusting the
concentration of the positive-tone developing chemistry, adjusting
a composition of the layer of radiation-sensitive material;
adjusting the duration for applying the negative or positive
developing chemistry; adjusting the temperature of developing
chemistry, or a combination of two or more thereof.
[0097] Referring now to FIG. 10A, a platform 1000 configured for
patterning a substrate is illustrated according to an embodiment.
The platform 1000 comprises a track system 1010 configured to coat
a substrate with a layer of radiation-sensitive material; a
lithography system 1020 including a pattern exposure system 1040
configured to expose the substrate to patterned EM radiation; an
exposure gradient removal system 1050 configured to affect the
substantially complete de-protection of the layer of the
radiation-sensitive material; and a transfer system 1030 configured
to transfer the substrate between the track system 1010, the
pattern exposure system 1040, and the exposure gradient removal
system 1050.
[0098] As shown in FIG. 10A, the exposure gradient removal system
1050 may be integrated with the pattern exposure system 1040 within
the lithography system 1020. The pattern exposure system 1040 may
include a radiation source, a mask imaging system, and a substrate
holder. When the exposure gradient removal system comprises a flood
exposure system, the exposure gradient removal system 1050 may
include the radiation source, a mask-less imaging system, a
temperature control apparatus, and the substrate holder. In
addition to the temperature control apparatus being suitable for
performing post-exposure bakes, it may also be suitable to lower
the temperature for performing the slimming process at an
ultra-cold temperature, as discussed above.
[0099] In the embodiment of FIG. 10A, the exposure gradient removal
system 1050 may be configured to expose the substrate to continuous
EM radiation, pulsed EM radiation, poly-chromatic EM radiation,
mono-chromatic EM radiation, broad-band EM radiation, or
narrow-band radiation, or a combination thereof. The exposure
gradient removal system 1050 may comprise a radiation source having
one or more lamps, one or more LEDs, or one or more lasers, or a
combination of two or more thereof.
[0100] Referring now to FIG. 10B, a platform 1100 configured for
patterning a substrate is illustrated according to another
embodiment. The platform 1100 comprises: a track system 1110
configured to coat a substrate with a layer of radiation-sensitive
material; a lithography system 1120 including a pattern exposure
system 1140 configured to expose the substrate to patterned EM
radiation; an exposure gradient removal system 1150 configured to
perform a thermal decomposition bake and thereby affect the
substantially complete de-protection of the layer of the
radiation-sensitive material; and a transfer system 1130 configured
to transfer the substrate between the track system 1110, the
pattern exposure system 1140, and the exposure gradient removal
system 1150.
[0101] As shown in FIG. 10B, the exposure gradient removal system
1150 may be integrated within the track system 1110. The exposure
gradient removal system 1150 includes a temperature control
apparatus for performing a thermal decomposition bake. In addition
to the temperature control apparatus being suitable for performing
a post-exposure bake and a thermal decomposition bake, it may also
be suitable to lower the temperature for performing the slimming
process at an ultra-cold temperature, as discussed above.
[0102] Referring now to FIG. 10C, a platform 1200 configured for
patterning a substrate is illustrated according to another
embodiment. The platform 1200 comprises: a track system 1210
configured to coat a substrate with a layer of radiation-sensitive
material; a lithography system 1220 including a pattern exposure
system 1240 configured to expose the substrate to patterned EM
radiation; an exposure gradient removal system 1250 configured to
expose the substrate an acid wash and a post-acid wash bake to
thereby affect the substantially complete de-protection of the
layer of the radiation-sensitive material; and a transfer system
1230 configured to transfer the substrate between the track system
1210, the pattern exposure system 1240, and the exposure gradient
removal system 1250.
[0103] As shown in FIG. 10C, the exposure gradient removal system
1250 may comprise a stand-alone module separate from the track
system 1210 and the lithography system 1220, and coupled to the
track system 1210 or the lithography system 1220 or both. The
exposure gradient removal system 1250 may include an acid wash
station, a temperature control apparatus, and the substrate holder.
In addition to the temperature control apparatus being suitable for
performing post-exposure and post-acid wash bakes, it may also be
suitable to lower the temperature for performing the slimming
process at an ultra-cold temperature, as discussed above.
[0104] Although only certain embodiments of this invention have
been described in detail above, those skilled in the art will
readily appreciate that many modifications are possible in the
embodiments without materially departing from the novel teachings
and advantages of this invention. Accordingly, all such
modifications are intended to be included within the scope of this
invention.
[0105] While the present invention has been illustrated by a
description of one or more embodiments thereof and while these
embodiments have been described in considerable detail, they are
intended to restrict or in any way limit the scope of the appended
claims to such detail. Additional advantages and modifications will
readily appear to those skilled in the art. The invention in its
broader aspects is therefore not limited to the specific details,
representative apparatus and method, and illustrative examples
shown and described. Accordingly, departures may be made from such
details without departing from the scope of the general inventive
concept.
* * * * *