Title: Pattern forming method and apparatus for fabricating semiconductor device
Abstract: A resist film is formed out of a resist material on a substrate, and then pre-baked. Next, the pre-baked resist film is exposed to extreme ultraviolet radiation through a photomask. Then, the exposed resist film is developed, thereby defining a resist pattern on the substrate. The pre-baking and exposing steps are carried out in a vacuum without subjecting the resist film to the air.
Patent Number: 6,855,485 Issued on 02/15/2005 to Irie
| Inventors:
|
Irie; Shigeo (Kyoto, JP)
|
| Assignee:
|
Matsushita Electric Industrial Co., Ltd. (Osaka, JP)
|
| Appl. No.:
|
891192 |
| Filed:
|
June 26, 2001 |
Foreign Application Priority Data
| Jun 27, 2000[JP] | 2000-192459 |
| Current U.S. Class: |
430/325; 430/313; 430/327; 430/330 |
| Intern'l Class: |
G03C 005//00 |
| Field of Search: |
430/313,314,315,312,317,322,324,325,327,329,330
|
References Cited [Referenced By]
U.S. Patent Documents
| 4764247 | Aug., 1988 | Leveriza et al. | 438/725.
|
| 6074804 | Jun., 2000 | Endo et al. | 430/322.
|
| 6245491 | Jun., 2001 | Shi | 430/322.
|
| 6368776 | Apr., 2002 | Harada et al. | 430/327.
|
| Foreign Patent Documents |
| 5-206020 | Aug., 1993 | JP.
| |
| 2000-131854 | May., 2000 | JP.
| |
Other References
www.lamrc.com, TCP.RTM. 9400DFM-Silicon Etch, Jul. 24, 2003, Lam
Research.RTM., 3 pgs.
|
Primary Examiner: Huff; Mark F.
Assistant Examiner: Mohamedulla; Saleha R.
Attorney, Agent or Firm: McDermott Will & Emery LLP
Claims
What is claimed is:
1. A pattern forming method comprising the steps of:
a) forming a resist film on a substrate;
b) pre-baking the resist film;
c) exposing the pre-baked resist film to extreme ultraviolet radiation; and
d) developing the exposed resist film, thereby defining a resist pattern on
the substrate,
wherein the steps b) and c) are carried out in a vacuum.
2. The method of claim 1, wherein the step b) comprises heating the resist
film while irradiating the resist film with a type of radiation having too
long a wavelength to sensitize the resist film.
3. A pattern forming method comprising the steps of:
a) forming a resist film on a substrate in a first processing chamber
containing air or an inert gas;
b) pre-baking the resist film in a vacuum in a second processing chamber;
c) transporting the pre-baked resist film in line to a vacuum in a third
processing chamber and then exposing the pre-baked resist film to extreme
ultraviolet radiation in the third processing chamber; and
d) transporting the exposed resist film in line to the first processing
chamber and then developing the exposed resist film in the first
processing chamber, thereby defining a resist pattern on the substrate.
4. The method of claim 3, wherein the step b) comprises heating the resist
film while irradiating the resist film with a type of radiation having too
long a wavelength to sensitize the resist film.
5. A pattern forming method comprising the steps of:
a) forming a resist film out of a chemically amplified resist material on a
substrate;
b) pre-baking the resist film;
c) exposing the pre-baked resist film to extreme ultraviolet radiation;
d) post-baking the exposed resist film; and
e) developing the post-baked resist film, thereby defining a resist pattern
on the substrate,
wherein the steps b), c) and d) are carried out in a vacuum.
6. The method of claim 5, wherein the step b) comprises heating the resist
film while irradiating the resist film with a type of radiation having too
long a wavelength to sensitize the resist film.
7. A pattern forming method comprising the steps of:
a) forming a resist film out of a chemically amplified resist material on a
substrate in a first processing chamber containing air or an inert gas;
b) pre-baking the resist film in a vacuum in a second processing chamber;
c) transporting the pre-baked resist film in line to a vacuum in a third
processing chamber and then exposing the pre-baked resist film to extreme
ultraviolet radiation in the third processing chamber;
d) transporting the exposed resist film in line to the second processing
chamber and then post-baking the exposed resist film in the second
processing chamber; and
e) transporting the post-baked resist film in line to the first processing
chamber and then developing the post-baked resist film in the first
processing chamber, thereby defining a resist pattern on the substrate.
8. The method of claim 7, wherein the step b) comprises heating the resist
film while irradiating the resist film with a type of radiation having too
long a wavelength to sensitize the resist film.
9. A pattern forming method comprising the steps of:
a) forming a resist film out of a chemically amplified resist material on a
substrate;
b) pre-baking the resist film;
c) exposing the pre-baked resist film to extreme ultraviolet radiation;
d) post-baking the exposed resist film;
e) forming a silylated layer selectively on the surface of the post-baked
resist film; and
f) dry-developing the resist film, on which the silylated layer has been
formed, using the silylated layer as a hard mask, thereby defining a
resist pattern on the substrate,
wherein the steps b), c), d), e) and f) are carried out in a vacuum.
10. The method of claim 9, wherein the step b) comprises heating the resist
film while irradiating the resist film with a type of radiation having too
long a wavelength to sensitize the resist film.
11. A pattern forming method comprising the steps of:
a) forming a resist film on a substrate in a first processing chamber
containing air or an inert gas;
b) pre-baking the resist film in a vacuum in a second processing chamber;
c) transporting the pre-baked resist film in line to a vacuum in a third
processing chamber and then exposing the pre-baked resist film to extreme
ultraviolet radiation in the third processing chamber;
d) transporting the exposed resist film in line to the second processing
chamber and then post-baking the exposed resist film in the second
processing chamber;
e) transporting the post-baked resist film in line to a vacuum in a fourth
processing chamber and then forming a silylated layer selectively on the
surface of the post-baked resist film in the fourth processing chamber;
and
f) transporting the resist film, on which the silylated layer has been
formed, in line to a vacuum in a fifth processing chamber and then
dry-developing the resist film, having the silylated layer thereon, using
the silylated layer as a hard mask in the fifth processing chamber,
thereby defining a resist pattern on the substrate.
12. The method of claim 11, wherein the step b) comprises heating the
resist film while irradiating the resist film with a type of radiation
having too long a wavelength to sensitize the resist film.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a fine-line resist
pattern by exposing a resist film to extreme ultraviolet (EUV) radiation
through a photomask and also relates to an apparatus for fabricating a
semiconductor device by utilizing the pattern forming method.
As semiconductor devices for a semiconductor integrated circuit have been
downsized, it has become increasingly necessary to further reduce the
feature size of a line-and-space pattern. And to define a fine-line
pattern, a lithography technique is indispensable. Particularly when a
pattern with a line width of 0.07 .mu.m or less should be defined, a
lithography technique using EUV radiation with a wavelength of around 13
nm as an exposing radiation is expected to be very effective.
In a known lithographic process using krypton fluoride (KrF) excimer laser
radiation (with a wavelength of around 248 nm) or argon fluoride (ArF)
excimer laser radiation (with a wavelength of around 193 nm), an exposure
process is carried out in the air or nitrogen ambient. However, if the
same exposure process is performed in such an ambient using EUV radiation,
then the radiation is absorbed into oxygen or nitrogen molecules contained
in the ambient, because the EUV radiation has a much shorter wavelength.
This is why the EUV exposure process should be carried out in a vacuum.
For that reason, a known process of forming a resist pattern out of a
chemically amplified resist material, for example, using the EUV radiation
is carried out in the following manner.
First, a chemically amplified resist material is applied onto a substrate
in the air to deposit a resist film thereon. Next, the resist film is
pre-baked to vaporize a solvent contained in the resist film.
Then, the resist film is exposed through a photomask to Euv radiation in a
vacuum, thereby transferring the pattern of the photomask onto the resist
film.
Subsequently, the resist film is subjected to a post-exposure baking
process in the air so that the acid diffuses in the exposed or non-exposed
parts of the resist film. Finally, the resist film is developed using a
developer, thereby defining a resist pattern.
Where a resist pattern should be formed out of a non-chemically-amplified
resist material, the resist film is exposed through a photomask to EUV
radiation in a vacuum and then developed immediately in the air without
being subjected to the post-exposure baking process.
The present inventor tentatively defined a resist pattern by exposing a
resist film to EUV radiation and then patterned a film on a substrate by
dry-etching it using the resist pattern obtained. As a result, the present
inventor found that the walls of the patterned film showed a
non-negligibly high degree of roughness.
SUMMARY OF THE INVENTION
An object of this invention is reducing the roughness at the walls of a
patterned film to a negligible degree where the patterned film is obtained
by dry-etching an original film using, as a mask, a resist pattern defined
through exposure of a resist film to EUV radiation.
The present inventor carried out intensive research to understand why the
walls of a patterned film showed an increased degree of roughness where
the patterned film had been formed by dry-etching an original film using,
as a mask, a resist pattern defined through exposure of a resist film to
EUV radiation. As a result, the present inventor found the following.
Firstly, in an EUV exposure process, a resist film is exposed to EUV
radiation with as high an energy as about 100 eV in a vacuum, thus
degassing the resist film. A gas (e.g., CO.sub.2 gas), given off from the
resist film, produces some reactants (e.g., CO.sub.x (where x>2)),
which soon deposit themselves on the walls of a resultant resist pattern
to increase the roughness at the walls of the resist pattern. For that
reason, the walls of the film patterned would also increase their
roughness because the roughened pattern is transferred as it is onto the
film.
Also, where a patterned film is formed by plasma-etching an original film
using the resist pattern, a gas (e.g., CO.sub.2 gas) emanated from the
resist film mixes with the plasma generated in a chamber. Accordingly, the
chemical composition of the plasma is subject to change during the plasma
etching process, thus eventually increasing the roughness at the walls of
the patterned film.
Furthermore, where a resist film is formed out of a chemically amplified
resist material, the resist film is pre-baked in the air and then
transported to the vacuum chamber of an exposure apparatus as described
above. However, during this transportation, the surface of the resist film
might be affected by an alkaline substance such as ammonia to possibly
form an insoluble layer, which is hard to dissolve in an alkaline
developer, on the surface. In that case, it is very difficult to form a
fine-line resist pattern as intended.
The present inventor acquired the basic idea of this invention from these
findings.
Specifically, a first inventive pattern forming method includes the steps
of: a) forming a resist film out of a resist material on a substrate; b)
pre-baking the resist film; c) exposing the pre-baked resist film to
extreme ultraviolet radiation through a photomask; and d) developing the
exposed resist film, thereby defining a resist pattern on the substrate.
In this method, the steps b) and c) are carried out in a vacuum without
subjecting the resist film to the air.
A second inventive pattern forming method includes the steps of: a) forming
a resist film out of a resist material on a substrate in a first
processing chamber filled with the air or an inert gas; b) pre-baking the
resist film in a second processing chamber filled with a vacuum; c)
transporting the pre-baked resist film in line to a third processing
chamber filled with a vacuum and then exposing the pre-baked resist film
to extreme ultraviolet radiation through a photomask in the third
processing chamber; and d) transporting the exposed resist film in line to
the first processing chamber and then developing the exposed resist film
in the first processing chamber, thereby defining a resist pattern on the
substrate.
In the first and second pattern forming methods, the pre-baking step b) is
carried out in a vacuum, not in the air unlike the known process, so a gas
like CO.sub.2 gas is given off from the resist film in this pre-baking
step b). Accordingly, even if the resist film is exposed to high-energy
EUV radiation in a vacuum after that, the degassing phenomenon rarely
occurs in that exposing step c). That is to say, in this exposing step c),
the reactants, usually produced by the CO.sub.2 gas, etc., emanated from
the resist film during the exposure, will not deposit themselves on the
walls of the resultant resist pattern. This is because the gas has already
been released in the previous step b). Thus, those walls of the resist
pattern much less likely increase their roughness. As a result, the walls
of the patterned film will not increase their roughness, either.
Particularly, according to the second method, the pre-baking and exposing
steps b) and c) are performed in mutually different processing chambers.
In addition, a much smaller quantity of gas is released in the exposing
step c). Accordingly, almost no reactants will deposit themselves on the
surface of the resist film, photomask or optical system including mirrors.
Consequently, the resist pattern will not be deformed or the EUV radiation
exposure dose will not decrease.
A third inventive pattern forming method includes the steps of: a) forming
a resist film out of a chemically amplified resist material on a
substrate; b) pre-baking the resist film; c) exposing the pre-baked resist
film to extreme ultraviolet radiation through a photomask; d) post-baking
the exposed resist film; and e) developing the post-baked resist film,
thereby defining a resist pattern on the substrate. In this method, the
steps b), c) and d) are carried out in a vacuum without subjecting the
resist film to the air.
A fourth inventive pattern forming method includes the steps of: a) forming
a resist film out of a chemically amplified resist material on a substrate
in a first processing chamber filled with the air or an inert gas; b)
pre-baking the resist film in a second processing chamber filled with a
vacuum; c) transporting the pre-baked resist film in line to a third
processing chamber filled with a vacuum and then exposing the pre-baked
resist film to extreme ultraviolet radiation through a photomask in the
third processing chamber; d) transporting the exposed resist film in line
to the second processing chamber and then post-baking the exposed resist
film in the second processing chamber; and e) transporting the post-baked
resist film in line to the first processing chamber and then developing
the post-baked resist film in the first processing chamber, thereby
defining a resist pattern on the substrate.
In the third and fourth pattern forming methods, the pre-baking step b) is
carried out in a vacuum, not in the air unlike the known process, so a gas
like CO.sub.2 gas is given off from the resist film in this pre-baking
step b). Accordingly, even if the resist film is exposed to high-energy
EUV radiation in a vacuum after that, the degassing phenomenon rarely
occurs in that exposing step c). That is to say, in this exposing step c),
the reactants, usually produced by the CO.sub.2 gas, etc., emanated from
the resist film during the exposure, will not deposit themselves on the
walls of the resultant resist pattern. This is because the gas has already
been released in the previous step b). Thus, those walls of the resist
pattern much less likely increase their roughness. As a result, the walls
of the patterned film will not increase their roughness, either.
In addition, the post-baking step d) is also performed in a vacuum, so the
gas like CO.sub.2 gas emanates again from the resist film at this
post-baking step d). Accordingly, where a patterned film is formed by
etching an original film with a plasma, the gas released from the resist
film will not mix with the plasma generated in a chamber. This is because
the post-baking and plasma etching process steps are carried out in
mutually different (i.e., the second and first) chambers. For that reason,
the chemical composition of the plasma will not change during the plasma
etching process, so the walls of the patterned film will not increase
their roughness.
Furthermore, the pre-baking, exposing and post-baking steps b), c) and d)
are performed in a vacuum without subjecting the resist film to the air.
Thus, the resist film, made of a chemically amplified resist material, is
not affected by an alkaline substance like ammonia contained in the air,
and no insoluble layer, difficult to dissolve in an alkaline developer, is
formed on the surface of the resist film. Consequently, a fine-line resist
pattern can be formed just as intended.
Particularly, according to the fourth method, the pre- and post-baking
steps b) and d) are performed in a chamber different from the chamber in
which the exposing step c) is performed. In addition, a much smaller
quantity of gas is released in the exposing step c). Accordingly, almost
no reactants will deposit themselves on the surface of the resist film,
photomask or optical system including mirrors. Consequently, the resist
pattern will not be deformed or the EUV radiation exposure dose will not
decrease.
A fifth inventive pattern forming method includes the steps of: a) forming
a resist film out of a chemically amplified resist material on a
substrate; b) pre-baking the resist film; c) exposing the pre-baked resist
film to extreme ultraviolet radiation through a photomask; d) post-baking
the exposed resist film; e) forming a silylated layer selectively on the
surface of the post-baked resist film; and f) dry-developing the resist
film, on which the silylated layer has been formed, using the silylated
layer as a hard mask, thereby defining a resist pattern on the substrate.
In this method, the steps b), c), d), e) and f) are carried out in a
vacuum without subjecting the resist film to the air.
A sixth inventive pattern forming method includes the steps of: a) forming
a resist film out of a photoresist material on a substrate in a first
processing chamber filled with the air or an inert gas; b) pre-baking the
resist film in a second processing chamber filled with a vacuum; c)
transporting the pre-baked resist film in line to a third processing
chamber filled with a vacuum and then exposing the pre-baked resist film
to extreme ultraviolet radiation through a photo-mask in the third
processing chamber; d) transporting the exposed resist film in line to the
second processing chamber and then post-baking the exposed resist film in
the second processing chamber; e) transporting the post-baked resist film
in line to a fourth processing chamber filled with a vacuum and then
forming a silylated layer selectively on the surface of the post-baked
resist film in the fourth processing chamber; and f) transporting the
resist film, on which the silylated layer has been formed, in line to a
fifth processing chamber filled with a vacuum and then dry-developing the
resist film, having the silylated layer thereon, using the silylated layer
as a hard mask in the fifth processing chamber, thereby defining a resist
pattern on the substrate.
In the fifth and sixth pattern forming methods, the pre-baking step b) is
carried out in a vacuum, not in the air unlike the known process, so a gas
like CO.sub.2 gas is given off from the resist film in this pre-baking
step b). Accordingly, even if the resist film is exposed to high-energy
EUV radiation in a vacuum after that, the degassing phenomenon rarely
occurs in that exposing step c). That is to say, in this exposing step c),
the reactants, usually produced by the CO.sub.2 gas, etc., emanated from
the resist film during the exposure, will not deposit themselves on the
walls of the resultant resist pattern, because the gas has already been
released in the previous step b). Thus, those walls of the resist pattern
much less likely increase their roughness. As a result, the walls of the
patterned film will not increase their roughness, either.
In addition, the post-baking step d) is also performed in a vacuum, so the
gas like CO.sub.2 gas emanates again from the resist film at this
post-baking step d). Accordingly, when the resist film is dry-developed
(i.e., plasma-etched) using a silylated layer as a hard mask or when a
patterned film is formed by etching an original film with a plasma, the
gas released from the resist film will not mix with the plasma generated
in the chamber. For that reason, the chemical composition of the plasma
will not change during the plasma etching process.
Furthermore, the pre-baking, exposing, post-baking and silylating steps b),
c), d) and e) are performed in a vacuum without subjecting the resist film
to the air. Thus, the resist film, made of a chemically amplified resist
material, is not affected by an alkaline substance like ammonia contained
in the air, and no insoluble layer, difficult to dissolve in an alkaline
developer, is formed on the surface of the resist film. Consequently, a
good silylated layer can be formed on the surface of the resist film and a
fine-line resist pattern can be defined just as intended.
Particularly, according to the sixth method, the pre- and post-baking steps
b) and d) are performed in a chamber different from any of the chambers in
which the exposing, silylating and dry-developing steps c), e) and f) are
performed. In addition, a much smaller quantity of gas is released in the
exposing step c). Accordingly, almost no reactants will deposit themselves
on the surface of the resist film, photomask or optical system including
mirrors. Consequently, the resist pattern will not be deformed or the EUV
radiation exposure dose will not decrease.
As described above, according to the first through sixth inventive pattern
forming methods, a gas like CO.sub.2 gas is given off from the resist film
in the pre-baking step b). Thus, even if the resist film is exposed to
high-energy EUV radiation in a vacuum after that, the degassing phenomenon
rarely occurs in that exposing step c). That is to say, in this exposing
step c), the reactants, usually produced by the gas emanated from the
resist film during the exposure, will not deposit themselves on the walls
of the resultant resist pattern. As a result, the resist pattern can have
the very cross-sectional shape originally designed.
In one embodiment of the present invention, the pre-baking step b)
preferably includes heating the resist film while irradiating the resist
film with a type of radiation having too long a wavelength to sensitize
the resist film.
Then, an even greater quantity of gas is released from the resist film in
the pre-baking step b), thus increasing the throughput of the gas released
and further suppressing the degassing phenomenon in the exposing step.
A first inventive apparatus for fabricating a semiconductor device includes
first, second and third processing chambers. In the first processing
chamber, a resist film is formed out of a resist material on a substrate
and a resist pattern is defined on the substrate by developing the resist
film that has been exposed to extreme ultraviolet radiation. The second
processing chamber is filled with a vacuum, and is used to pre-bake the
resist film. The third processing chamber is also filled with a vacuum and
is used to expose the pre-baked resist film to the extreme ultraviolet
radiation through a photomask.
In the first apparatus, the pre-baking step can be carried out in the
second processing chamber filled with a vacuum, so a gas like CO.sub.2 gas
is given off from the resist film in this pre-baking step. Accordingly,
even if the resist film is exposed to high-energy EUV radiation in a
vacuum after that, the degassing phenomenon rarely occurs in that exposing
step. That is to say, in this exposing step, the reactants, usually
produced by the CO.sub.2 gas, etc., emanated from the resist film during
the exposure, will not deposit themselves on the walls of the resultant
resist pattern. This is because the gas has already been released in the
previous pre-baking step. Thus, those walls of the resist pattern much
less likely increase their roughness. As a result, the walls of the
patterned film will not increase their roughness, either.
In addition, the pre-baking and exposing steps are performed in mutually
different processing chambers. Moreover, a much smaller quantity of gas is
released in the exposing step. Accordingly, almost no reactants will
deposit themselves on the surface of the resist film, photomask or optical
system including mirrors. Consequently, the resist pattern will not be
deformed or the EUV radiation exposure dose will not decrease.
A second inventive apparatus for fabricating a semiconductor device also
includes first, second and third processing chambers. In the first
processing chamber, a resist film is formed out of a chemically amplified
resist material on a substrate and a resist pattern is defined on the
substrate by developing the resist film that has been exposed to extreme
ultraviolet radiation. The second processing chamber is filled with a
vacuum and is used to pre- and post-bake the resist film before and after
the resist film is exposed to the extreme ultraviolet radiation,
respectively. The third processing chamber is also filled with a vacuum
and is used to expose the pre-baked resist film to the extreme ultraviolet
radiation through a photomask.
In the second apparatus, the pre-baking step can be carried out in the
second processing chamber filled with a vacuum, so a gas like CO.sub.2 gas
is given off from the resist film in this pre-baking step. Accordingly,
even if the resist film is exposed to high-energy EUV radiation in a
vacuum after that, the degassing phenomenon rarely occurs in that exposing
step. That is to say, in this exposing step, the reactants, usually
produced by the CO.sub.2 gas, etc., emanated from the resist film during
the exposure, will not deposit themselves on the walls of the resultant
resist pattern. This is because the gas has already been released in the
previous pre-baking step. Thus, those walls of the resist pattern much
less likely increase their roughness. As a result, the walls of the
patterned film will not increase their roughness, either.
In addition, the pre- and post-baking steps are performed in a chamber
different from a chamber in which the exposing step is performed.
Moreover, a much smaller quantity of gas is released in the exposing step.
Accordingly, almost no reactants will deposit themselves on the surface of
the resist film, photomask or optical system including mirrors.
Consequently, the resist pattern will not be deformed or the EUV radiation
exposure dose will not decrease.
Furthermore, the pre-baking, exposing and post-baking steps are performed
in a vacuum without subjecting the resist film to the air. Thus, the
resist film, made of a chemically amplified resist material, is not
affected by an alkaline substance like ammonia contained in the air, and
no insoluble layer, difficult to dissolve in an alkaline developer, is
formed on the surface of the resist film. Consequently, a fine-line resist
pattern can be formed just as intended.
A third inventive apparatus for fabricating a semiconductor device includes
first, second, third, fourth and fifth processing chambers. In the first
processing chamber, a resist film is formed out of a chemically amplified
resist material on a substrate. The second processing chamber is filled
with a vacuum and is used to pre- and post-bake the resist film before and
after the resist film is exposed to extreme ultraviolet radiation,
respectively. The third processing chamber is also filled with a vacuum
and is used to expose the pre-baked resist film to the extreme ultraviolet
radiation through a photomask. In the fourth processing chamber, a
silylated layer is formed selectively on the surface of the post-baked
resist film. And in the fifth processing chamber, a resist pattern is
defined on the substrate by dry-developing the resist film, on which the
silylated layer has been formed, using the silylated layer as a hard mask.
In the third apparatus, the pre-baking step can be carried out in the
second processing chamber filled with a vacuum, so a gas like CO.sub.2 gas
is given off from the resist film in this pre-baking step. Accordingly,
even if the resist film is exposed to high-energy EUV radiation in a
vacuum after that, the degassing phenomenon rarely occurs in that exposing
step. That is to say, in this exposing step, the reactants, usually
produced by the CO.sub.2 gas, etc., emanated from the resist film during
the exposure, will not deposit themselves on the walls of the resultant
resist pattern. This is because the gas has already been released in the
previous pre-baking step. Thus, those walls of the resist pattern much
less likely increase their roughness. As a result, the walls of the
patterned film will not increase their roughness, either.
In addition, the pre- and post-baking steps are performed in a chamber
different from a chamber in which the exposing step is performed.
Moreover, a much smaller quantity of gas is released in the exposing step.
Accordingly, almost no reactants will deposit themselves on the surface of
the resist film, photomask or optical system including mirrors.
Consequently, the resist pattern will not be deformed or the EUV radiation
exposure dose will not decrease.
Furthermore, the pre-baking, exposing, post-baking and silylating steps are
performed in a vacuum without subjecting the resist film to the air. Thus,
the resist film, made of a chemically amplified resist material, is not
affected by an alkaline substance like ammonia contained in the air, and
no insoluble layer, difficult to dissolve in an alkaline developer, is
formed on the surface of the resist film. In addition, the acid can
diffuse sufficiently in the pre-baking step, so the contact between
exposed and non-exposed portions improves. Accordingly, a good silylated
layer can be formed on the surface of the resist film. Consequently, a
fine-line resist pattern can be formed accurately enough.
As described above, the first through third inventive apparatuses can
release a gas like CO.sub.2 gas from the resist film in the pre-baking
step. Accordingly, even if the resist film is exposed to high-energy EUV
radiation in a vacuum after that, the degassing phenomenon rarely occurs
in that exposing step. That is to say, in this exposing step, the
reactants, usually produced by the gas emanated from the resist film
during the exposure, will not deposit themselves on the walls of the
resultant resist pattern. As a result, the resist pattern can have the
very cross-sectional shape originally designed.
In one embodiment of the present invention, the second processing chamber
preferably includes means for irradiating the resist film with a type of
radiation having too long a wavelength to sensitize the resist film.
Then, an even greater quantity of gas is released from the resist film in
the pre-baking step, thus further suppressing the degassing phenomenon in
the exposing step.
In another embodiment of the present invention, the second processing
chamber preferably includes means for exhausting a gas, emanated from the
resist film, out of the second processing chamber.
Then, it is possible to avoid an unwanted situation where the gas, released
from the resist film in the pre-baking step, re-produce those harmful
reactants that easily deposit themselves on the surface of the resist
film.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A through 1D are cross-sectional views illustrating respective
process steps for forming a resist pattern according to a first embodiment
of the present invention.
FIGS. 2A through 2E are cross-sectional views illustrating respective
process steps for forming a resist pattern according to a second
embodiment of the present invention.
FIGS. 3A through 3F are cross-sectional views illustrating respective
process steps for forming a resist pattern according to a third embodiment
of the present invention.
FIG. 4 is a block diagram illustrating an apparatus for fabricating a
semiconductor device by carrying out a pattern forming method according to
a fourth embodiment of the present invention.
FIG. 5 is a block diagram illustrating an apparatus for fabricating a
semiconductor device by carrying out a pattern forming method according to
a fifth embodiment of the present invention.
FIG. 6 is a block diagram illustrating an apparatus for fabricating a
semiconductor device by carrying out a pattern forming method according to
a sixth embodiment of the present invention.
FIG. 7 is a cross-sectional view schematically illustrating the second
processing chamber of an apparatus for fabricating a semiconductor device
by carrying out the pattern forming method of the fourth, fifth or sixth
embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment 1
Hereinafter, a resist pattern forming method according to a first
embodiment of the present invention will be described with reference to
FIGS. 1A through 1D.
First, as shown in FIG. 1A, the surface of a semiconductor substrate 10 is
coated with a normal (i.e., non-chemically-amplified) photoresist material
using a spin coater, thereby forming a resist film 11 with a thickness of
130 nm, for example.
Next, as shown in FIG. 1B, the resist film 11 is pre-baked in a vacuum of
about 1.0.times.10.sup.-5 Pa by getting the substrate 10 heated by a
heater 12 to about 90.degree. C. for about 60 seconds, for example. As a
result of this pre-baking process step, a solvent vaporizes from the
resist film 11 and a gas (e.g., CO.sub.2 gas) is released from the resist
film 11. If the pre-baked resist film 11 is left in the vacuum for about
300 seconds, then the resist film 11 further gives off the gas like the
CO.sub.2 gas.
Then, as shown in FIG. 1C, the resist film 11 is exposed to Euv radiation
in a vacuum of about 1.0.times.10.sup.-6 Pa. Specifically, the EUV
radiation is emitted from an EUV radiation source (not shown) at a
wavelength of around 13 nm, for example, directed toward a reflective mask
13 and then reflected therefrom. Subsequently, the reflected part 14 of
the EUV radiation is condensed by a reflection/demagnification optical
system 15 to about 1/5, for example, and then allowed to be incident onto
the resist film 11. As a result, the resist film 11 comes to have exposed
and non-exposed portions 11a and 11b.
In the illustrated embodiment, radiation with a wavelength of around 13 nm
is used as the EUV radiation. Alternatively, any other radiation with a
wavelength somewhere between 3 and 50 nm may also be used. The reflective
mask 13 may be of any type. For example, the reflective mask 13 may
include a mask pattern formed on an EUV radiation reflective film. The
mask pattern may be made of tantalum, which absorbs EUV radiation, while
the EUV radiation reflective film may be a stack of molybdenum and silicon
films. The reflection/demagnification optical system 15 may be made up of
several reflective mirrors, each having a stack of molybdenum and silicon
films as its reflective surface.
Thereafter, as shown in FIG. 1D, the resist film 11 is subjected to a wet
developing process in the air using a developer of xylene, for example,
thereby forming a resist pattern 16 on the substrate 10 out of the
non-exposed portions 11b of the resist film 11.
In the first embodiment, the pre-baking step is carried out in a vacuum, so
a gas like CO.sub.2 gas is given off from the resist film 11 in this
pre-baking step. Accordingly, even if the resist film 11 is exposed to
high-energy EUV radiation in a vacuum after that, the degassing phenomenon
rarely occurs in that exposing step. That is to say, in this exposing
step, the reactants, usually produced by the CO.sub.2 gas, etc., emanated
from the resist film 11 during the exposure, will not deposit themselves
on the walls of the resultant resist pattern 16. This is because the gas
has already been released in the previous step. Thus, those walls of the
resist pattern 16 much less likely increase their roughness. Accordingly,
when a film to be etched, which has been deposited on the substrate 10, is
dry-etched and patterned, the walls of the patterned film will not
increase their roughness, either.
Embodiment 2
Hereinafter, a resist pattern forming method according to a second
embodiment of the present invention will be described with reference to
FIGS. 2A through 2E.
First, as shown in FIG. 2A, the surface of a semiconductor substrate 20 is
coated with a chemically amplified photoresist material using a spin
coater, thereby forming a resist film 21 with a thickness of 130 nm, for
example. The chemically amplified photoresist material may be a polyvinyl
phenol resin including a protecting group of tertiary butoxy carbonyl
(t-BOC).
Next, as shown in FIG. 2B, the resist film 21 is pre-baked in a vacuum of
about 1.0.times.10.sup.-5 Pa by getting the substrate 20 heated by a
heater 22 to about 110.degree. C. for about 60 seconds, for example. As a
result of this pre-baking process step, a solvent vaporizes from the
resist film 21 and a gas (e.g., CO.sub.2 gas) is given off from the resist
film 21. If the pre-baked resist film 21 is left in the vacuum for about
300 seconds, then the resist film 21 further gives off the gas like the
CO.sub.2 gas.
Then, as shown in FIG. 2C, the resist film 21 is exposed to EUV radiation
in a vacuum of about 1.0.times.10.sup.-6 Pa. Specifically, the EUV
radiation is emitted from an EUV radiation source (not shown) at a
wavelength of around 13 nm, for example, directed toward a reflective mask
23 and then reflected therefrom. Subsequently, the reflected part 24 of
the EUV radiation is condensed by a reflection/demagnification optical
system 25 to about 1/5, for example, and then allowed to be incident onto
the resist film 21. As a result, the resist film 21 comes to have exposed
and non-exposed portions 21a and 21b. In the illustrated embodiment,
radiation with a wavelength of around 13 nm is used as the EUV radiation.
Alternatively, any other radiation with a wavelength somewhere between 3
and 50 nm may also be used. The reflective mask 13 and
reflection/demagnification optical system 25 may be the same as those used
for the first embodiment.
Thereafter, as shown in FIG. 2D, the resist film 21 is post-baked in a
vacuum of about 1.0.times.10.sup.-5 Pa by getting the substrate 20 heated
again by a heater 26 to 130.degree. C. for 60 seconds, for example. Then,
the acid, which has been generated in the exposed or non-exposed portions
21a or 21b of the resist film 21 as a result of the exposure process,
further diffuses and the gas like the CO.sub.2 gas further emanates from
the resist film 21.
Finally, as shown in FIG. 2E, the resist film 21 is subjected to a wet
developing process in the air using a developer of trimethylammonium
hydroxide (TMAH), for example, thereby forming a resist pattern 27 on the
substrate 20 out of the non-exposed portions 21b of the resist film 21.
In the second embodiment, the pre-baking step is carried out in a vacuum,
so a gas like CO.sub.2 gas is given off from the resist film 21 in this
pre-baking step. Accordingly, even if the resist film 21 is exposed to
high-energy EUV radiation in a vacuum after that, the degassing phenomenon
rarely occurs in that exposing step. That is to say, in this exposing
step, the reactants, usually produced by the CO.sub.2 gas, etc., emanated
from the resist film 21 during the exposure, will not deposit themselves
on the walls of the resultant resist pattern 27. This is because the gas
has already been released in the previous step. Thus, those walls of the
resist pattern 27 much less likely increase their roughness. Accordingly,
when a film to be etched, which has been deposited on the substrate 20, is
dry-etched and patterned, the walls of the patterned film will not
increase their roughness, either.
In addition, the post-baking step is also performed in a vacuum.
Accordingly, where a patterned film is formed by etching an original film
with a plasma, the gas released from the resist film 21 will not mix with
the plasma generated in the chamber. For that reason, the chemical
composition of the plasma will not change during the plasma etching
process, so the walls of the patterned film will not increase their
roughness.
Embodiment 3
Hereinafter, a resist pattern forming method according to a third
embodiment of the present invention will be described with reference to
FIGS. 3A through 3F.
First, as shown in FIG. 3A, the surface of a semiconductor substrate 30 is
coated with a chemically amplified photoresist material using a spin
coater, thereby forming a resist film 31 with a thickness of 130 nm, for
example.
Next, as shown in FIG. 3B, the resist film 31 is pre-baked in a vacuum of
about 1.0.times.10.sup.-5 Pa by getting the substrate 30 heated by a
heater 32 to about 110.degree. C. for about 60 seconds, for example. As a
result of this pre-baking process step, a solvent vaporizes from the
resist film 31 and a gas (e.g., CO.sub.2 gas) is given off from the resist
film 31. If the pre-baked resist film 31 is left in the vacuum for about
300 seconds, then the resist film 31 further gives off the gas like the
CO.sub.2 gas.
Then, as shown in FIG. 3C, the resist film 31 is exposed to EUV radiation
in a vacuum of about 1.0.times.10.sup.-6 Pa. Specifically, the EUV
radiation is emitted from an EUV radiation source (not shown) at a
wavelength of around 13 nm, for example, directed toward a reflective mask
33 and then reflected therefrom. Subsequently, the reflected part 34 of
the EUV radiation is condensed by a reflection/demagnification optical
system 35 to about 1/5, for example, and then allowed to be incident onto
the resist film 31. As a result, the resist film 31 comes to have exposed
and non-exposed portions 31a and 31b. In the illustrated embodiment,
radiation with a wavelength of around 13 nm is used as the EUV radiation.
Alternatively, any other radiation with a wavelength somewhere between 3
and 50 nm may also be used. The reflective mask 33 and
reflection/demagnification optical system 35 may be the same as those used
for the first embodiment.
Thereafter, as shown in FIG. 3D, the resist film 31 is post-baked in a
vacuum of about 1.0.times.10.sup.-5 Pa by getting the substrate 30 heated
again by a heater 36 to 130.degree. C. for 60 seconds, for example. Then,
the acid, which has been generated in the exposed or non-exposed portions
31a or 31b of the resist film 31 as a result of the exposure process,
further diffuses and the gas like the CO.sub.2 gas further emanates from
the resist film 31.
Next, a silylating agent is supplied onto the surface of the resist film
31, thereby forming a silylated layer 37 selectively on the exposed or
non-exposed portions 31a or 31b, in which the acid has been generated as a
result of the exposure process, as shown in FIG. 3E. In the example
illustrated in FIG. 3E, the acid has been generated in the non-exposed
portions 31b.
Finally, the resist film 31 is dry-developed (i.e., plasma-etched) using
the silylated layer 37 as a hard mask, thereby forming a resist pattern 38
on the substrate 30 out of the non-exposed portions 31b of the resist film
31.
In the third embodiment, the pre-baking step is carried out in a vacuum, so
a gas like CO.sub.2 gas is given off from the resist film 31 in this
pre-baking step. Accordingly, even if the resist film 31 is exposed to
high-energy EUV radiation in a vacuum after that, the degassing phenomenon
rarely occurs in that exposing step. That is to say, in this exposing
step, the reactants, usually produced by the CO.sub.2 gas, etc., emanated
from the resist film 31 during the exposure, will not deposit themselves
on the walls of the resultant resist pattern 38. This is because the gas
has already been released in the previous step. Thus, those walls of the
resist pattern 38 much less likely increase their roughness. Accordingly,
when a film to be etched, which has been deposited on the substrate 30, is
dry-etched and patterned, the walls of the patterned film will not
increase their roughness, either.
In addition, the post-baking step is also performed in a vacuum.
Accordingly, when the resist film 31 is dry-developed (i.e.,
plasma-etched) to define the resist pattern 38 or when a patterned film is
formed by etching an original film with a plasma, the gas released from
the resist film 31 will not mix with the plasma generated in the chamber.
For that reason, the chemical composition of the plasma will not change
during the plasma etching process. As a result, a good resist pattern can
be defined and the walls of the patterned film will not increase their
roughness.
Embodiment 4
Hereinafter, a resist pattern forming method according to a fourth
embodiment of the present invention and an apparatus for fabricating a
semiconductor device for use in the method of the fourth embodiment will
be described with reference to FIGS. 1A through 1D and 4.
First, as shown in FIG. 1A, the surface of a semiconductor substrate 10 is
coated with a normal (i.e., non-chemically-amplified) photoresist material
in a first processing chamber 110 filled with the air at the atmospheric
pressure, thereby forming a resist film 11 thereon.
Next, the substrate 10 is transported in line from the first processing
chamber 110 to a second processing chamber 120 filled with a vacuum of
about 1.0.times.10.sup.-5 Pa. Then, in the second processing chamber 120,
the resist film 11 is pre-baked by getting the substrate 10 heated by a
heater 12 to about 90.degree. C. for about 60 seconds, for example, as
shown in FIG. 1B. In this manner, a solvent is vaporized from the resist
film 11 and a gas (e.g., CO.sub.2 gas) is given off from the resist film
11.
Subsequently, the substrate 10 is transported in line from the second
processing chamber 120 to a third processing chamber 130 filled with a
vacuum of about 1.0.times.10.sup.-6 Pa. Then, in the third processing
chamber 130, the resist film 11 is exposed to EUV radiation as shown in
FIG. 1C. Specifically, the EUV radiation with a wavelength of around 13
nm, for example, is directed toward a reflective mask 13 and then
reflected therefrom. Subsequently, the reflected part 14 of the EUV
radiation is condensed by a reflection/demagnification optical system 15
to about 1/5, for example, and then allowed to be incident onto the resist
film 11. As a result, the resist film 11 comes to have exposed and
non-exposed portions 11a and 11b.
Thereafter, the substrate 10 is transported in line from the third
processing chamber 130 to the first processing chamber 110. Then, in the
first processing chamber 110, the resist film 11 is subjected to a wet
developing process, thereby forming a resist pattern 16 on the substrate
10 out of the non-exposed portions 11b of the resist film 11 as shown in
FIG. 1D.
In the fourth embodiment, the pre-baking step is carried out in a vacuum,
so a gas like CO.sub.2 gas is given off from the resist film 11 in this
pre-baking step. Accordingly, even if the resist film 11 is exposed to
high-energy EUV radiation in a vacuum after that, the degassing phenomenon
rarely occurs in that exposing step.
It is not impossible to perform both the pre-baking and EUV exposure
process steps in the same vacuum chamber. In that case, however, the
reactants, produced by the CO.sub.2 gas, etc., emanated from the resist
film 11 in the pre-baking process step, might deposit themselves on the
surface of the resist film 11, reflective mask 13 or optical system
including the mirrors. If those reactants deposit themselves on the
surface of the resist film 11, then the resist pattern 16 might be
deformed. And if the reactants deposit themselves on the surface of the
reflective mask 13 or mirrors, then the exposure dose of the resist film
11, or the amount of EUV radiation reflected off from the mask 13 or
mirrors and then reaching the resist film 11, might decrease.
In contrast, according to the fourth embodiment, the pre-baking and
exposing steps are performed in mutually different processing chambers.
Accordingly, almost no reactants will deposit themselves on the surface of
the resist film 11, reflective mask 13 or optical system including
mirrors. Consequently, the resist pattern 16 will not be deformed or the
EUV radiation exposure dose will not decrease.
Embodiment 5
Hereinafter, a resist pattern forming method according to a fifth
embodiment of the present invention and an apparatus for fabricating a
semiconductor device for use in the method of the fifth embodiment will be
described with reference to FIGS. 2A through 2E and 5.
First, the surface of a semiconductor substrate 20 is coated with a
chemically amplified photoresist material in a first processing chamber
210 filled with the air at the atmospheric pressure, thereby forming a
resist film 21 thereon as shown in FIG. 2A.
Next, the substrate 20 is transported in line from the first processing
chamber 210 to a second processing chamber 220 filled with a vacuum of
about 1.0.times.10.sup.-5 Pa. Then, in the second processing chamber 220,
the resist film 21 is pre-baked by getting the substrate 20 heated by a
heater 22 to about 110.degree. C. for about 60 seconds, for example, as
shown in FIG. 2B. In this manner, a solvent is vaporized from the resist
film 21 and a gas (e.g., CO.sub.2 gas) is given off from the resist film
21.
Thereafter, the substrate 20 is transported in line from the second
processing chamber 220 to a third processing chamber 230 filled with a
vacuum of about 1.0.times.10.sup.-5 Pa. Then, in the third processing
chamber 230, the resist film 21 is exposed to EUV radiation as shown in
FIG. 2C. Specifically, the EUV radiation with a wavelength of around 13
nm, for example, is directed toward a reflective mask 23 and then
reflected therefrom. Subsequently, the reflected part 24 of the EUV
radiation is condensed by a reflection/demagnification optical system 25
to about 1/5, for example, and then allowed to be incident onto the resist
film 21. As a result, the resist film 21 comes to have exposed and
non-exposed portions 21a and 21b.
Thereafter, the substrate 20 is transported in line from the third
processing chamber 230 to the second processing chamber 220. Then, in the
second processing chamber 220, the resist film 21 is post-baked by getting
the substrate 20 heated again by a heater 26 to 130.degree. C. for 60
seconds, for example, as shown in FIG. 2D. In this manner, the acid, which
has been generated in the exposed or non-exposed portions 21a or 21b of
the resist film 21 as a result of the exposure process, further diffuses
and the gas like the CO.sub.2 gas further emanates from the resist film
21.
Subsequently, the substrate 20 is transported in line from the second
processing chamber 220 to the first processing chamber 210. Then, in the
first processing chamber 210, the resist film 21 is subjected to a wet
developing process using a developer of TMAH, for example, thereby forming
a resist pattern 27 on the substrate 20 out of the non-exposed portions
21b of the resist film 21 as shown in FIG. 2E.
In the fifth embodiment, the pre- and post-baking steps are carried out in
a vacuum, so a gas like CO.sub.2 gas is given off from the resist film 21
in these pre- and post-baking steps. Accordingly, even if the resist film
21 is exposed to high-energy EUV radiation in a vacuum after that, the
degassing phenomenon rarely occurs in that exposing step. Moreover, the
chemical composition of the plasma will not change while the film to be
patterned is plasma-etched.
Also, the pre- and post-baking steps are performed in a chamber different
from the chamber in which the exposing step is performed. In addition, a
much smaller quantity of gas is released in the exposing step.
Accordingly, almost no reactants will deposit themselves on the surface of
the resist film 21, reflective mask 23 or optical system including
mirrors. Consequently, the resist pattern 27 will not be deformed or the
EUV radiation exposure dose will not decrease.
Embodiment 6
Hereinafter, a resist pattern forming method according to a sixth
embodiment of the present invention and an apparatus for fabricating a
semiconductor device for use in the method of the sixth embodiment will be
described with reference to FIGS. 3A through 3F and 6.
First, the surface of a semiconductor substrate 30 is coated with a
chemically amplified photoresist material in a first processing chamber
310 filled with the air at the atmospheric pressure, thereby forming a
resist film 31 thereon as shown in FIG. 3A.
Next, the substrate 30 is transported in line from the first processing
chamber 310 to a second processing chamber 320 filled with a vacuum of
about 1.0.times.10.sup.-5 Pa. Then, in the second processing chamber 320,
the resist film 31 is pre-baked by getting the substrate 30 heated by a
heater 32 to about 110.degree. C. for about 60 seconds, for example, as
shown in FIG. 3B. In this manner, a solvent is vaporized from the resist
film 31 and a gas (e.g., CO.sub.2 gas) is given off from the resist film
31.
Subsequently, the substrate 30 is transported in line from the second
processing chamber 320 to a third processing chamber 330 filled with a
vacuum of about 1.0.times.10.sup.-6 Pa. Then, in the third processing
chamber 330, the resist film 31 is exposed to EUV radiation as shown in
FIG. 3C. Specifically, the EUV radiation with a wavelength of around 13
nm, for example, is directed toward a reflective mask 33 and then
reflected therefrom. Subsequently, the reflected part 34 of the EUV
radiation is condensed by a reflection/demagnification optical system 35
to about 1/5, for example, and then allowed to be incident onto the resist
film 31. As a result, the resist film 31 comes to have exposed and
non-exposed portions 31a and 31b.
Thereafter, the substrate 30 is transported in line from the third
processing chamber 330 to the second processing chamber 320. Then, in the
second processing chamber 320, the resist film 31 is post-baked by getting
the substrate 30 heated again by a heater 36 to 130.degree. C. for 60
seconds, for example, as shown in FIG. 3D. In this manner, the acid, which
has been generated in the exposed or non-exposed portions 31a or 31b of
the resist film 31 as a result of the exposure process, further diffuses
and the gas like the CO.sub.2 gas further emanates from the resist film
31.
Next, the substrate 30 is transported in line from the second processing
chamber 320 to a fourth processing chamber 340 filled with a vacuum of
about 1.0.times.10.sup.-5 Pa. Then, in the fourth processing chamber 340,
a silylating agent is supplied onto the surface of the resist film 31. In
this manner, a silylated layer 37 is formed on the exposed or non-exposed
portions 31a or 31b, in which the acid has been generated as a result of
the exposure process, as shown in FIG. 3E.
Subsequently, the substrate 30 is transported in line from the fourth
processing chamber 340 to a fifth processing chamber 350 filled with a
vacuum of about 1.0.times.10.sup.-6 Pa. Then, in the fifth processing
chamber 350, the resist film 31 is dry-developed using the silylated layer
37 as a hard mask, thereby forming a resist pattern 38 on the substrate 30
out of the non-exposed portions 31b of the resist film 31 as shown in FIG.
3F.
In the sixth embodiment, the pre-baking step is carried out in a vacuum, so
a gas like CO.sub.2 gas is given off from the resist film 31 in this
pre-baking step. Accordingly, even if the resist film 31 is exposed to
high-energy EUV radiation in a vacuum after that, the degassing phenomenon
rarely occurs in that exposing step.
In addition, the post-baking step is also performed in a vacuum.
Accordingly, when the resist film 31 is dry-developed (i.e.,
plasma-etched) to define the res
