U.S. patent application number 10/546358 was filed with the patent office on 2006-06-29 for immersion exposure process-use resist protection film forming material, composite film, and resist pattern forming method.
Invention is credited to Taku Hirayama, Mitsuru Sato, Ryoichi Takasu, Koki Tamura, Kazumasa Wakiya, Masaaki Yoshida.
Application Number | 20060141400 10/546358 |
Document ID | / |
Family ID | 32913150 |
Filed Date | 2006-06-29 |
United States Patent
Application |
20060141400 |
Kind Code |
A1 |
Hirayama; Taku ; et
al. |
June 29, 2006 |
Immersion exposure process-use resist protection film forming
material, composite film, and resist pattern forming method
Abstract
Provided are a material for forming a resist protecting film
which is for use in a liquid immersion lithography process and
which is formed on a resist film, wherein the material has the
following properties of: being transparent with respect to exposure
light; having substantially no compatibility with a liquid for
liquid immersion lithography; and causing no mixing with the resist
film, a composite film comprising a protective film formed from the
material and a resist film, and a method for forming a resist
pattern using them. These can prevent both the resist film and the
liquid used from changing in properties during the liquid immersion
lithography, so that a resist pattern with high resolution can be
formed using the liquid immersion lithography.
Inventors: |
Hirayama; Taku;
(Kawasaki-shi, JP) ; Takasu; Ryoichi;
(Kawasaki-shi, JP) ; Sato; Mitsuru; (Kawasaki-shi,
JP) ; Wakiya; Kazumasa; (Kawasaki-shi, JP) ;
Yoshida; Masaaki; (Kawasaki-shi, JP) ; Tamura;
Koki; (Kawasaki-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
32913150 |
Appl. No.: |
10/546358 |
Filed: |
February 20, 2004 |
PCT Filed: |
February 20, 2004 |
PCT NO: |
PCT/JP04/01956 |
371 Date: |
January 27, 2006 |
Current U.S.
Class: |
430/395 ;
430/449 |
Current CPC
Class: |
G03F 7/11 20130101; G03F
7/2041 20130101 |
Class at
Publication: |
430/395 ;
430/449 |
International
Class: |
G03F 7/00 20060101
G03F007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2003 |
JP |
2003-043394 |
May 9, 2003 |
JP |
2003-132288 |
Jul 10, 2003 |
JP |
2003-195409 |
Jul 31, 2003 |
JP |
2003-205001 |
Claims
1. A material for forming a resist protecting film which is for use
in a liquid immersion lithography process and which is formed on a
resist film, the material having the following properties of: being
transparent with respect to exposure light; having substantially no
compatibility with a liquid for liquid immersion lithography; and
causing no mixing with the resist film.
2. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 1, wherein
the liquid immersion lithography process is of a construction in
which the resist film is exposed through the liquid for liquid
immersion lithography present at least on the resist film in a path
of the lithography exposure light toward the resist film, wherein
the liquid has a predetermined thickness and has a refractive index
larger than that of air and smaller than that of the resist film,
whereby improving the resolution of a resist pattern.
3. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 1, wherein
the liquid for liquid immersion lithography is water substantially
comprised of pure water or deionized water.
4. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 1, wherein
the resist film is formed from a resist composition comprised of a
base polymer which is a polymer comprising (meth)acrylic ester
units.
5. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 1, wherein
the resist film is formed from a resist composition comprised of a
base polymer which is a polymer having dicarboxylic acid
anhydride-containing constitutional units.
6. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 1, wherein
the resist film is formed from a resist composition comprised of a
base polymer which is a polymer having phenolic hydroxyl
group-containing constitutional units.
7. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 1, wherein
the resist film is formed from a resist composition comprised of a
base polymer which is a silsesquioxane resin.
8. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 1, wherein
the resist film is formed from a resist composition comprised of a
base polymer which is a polymer having
.alpha.-(hydroxyalkyl)acrylic acid units.
9. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 1, wherein
the resist film is formed from a resist composition comprised of a
base polymer which is a polymer having dicarboxylic acid monoester
units.
10. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 1, which
has the following properties: having substantially no compatibility
with pure water or deionized water; and causing no mixing with the
resist film.
11. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 1, which is
a composition comprising at least a fluorine-substituted
polymer.
12. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 11, wherein
the fluorine-substituted polymer is comprised of any one of cyclic
perfluoroalkyl polyether and chain perfluoroalkyl polyether or
both.
13. The material for forming a resist protecting film for use in a
liquid immersion lithography process according to claim 12, wherein
the composition is obtained by dissolving any one of the cyclic
perfluoroalkyl polyether and the chain perfluoroalkyl polyether or
both in a fluorine solvent.
14. A composite film for use in a liquid immersion lithography
process, the composite film comprising a protective film and a
resist film, wherein the protective film has the following
properties: being transparent with respect to exposure light;
having substantially no compatibility with a liquid for liquid
immersion lithography; and causing no mixing with the resist film,
and wherein the protective film is formed on the resist film.
15. The composite film for liquid immersion lithography process
according to claim 14, wherein the liquid immersion lithography
process is of a construction in which the composite film is exposed
through the liquid for liquid immersion lithography present at
least on the resist film in a path of the lithography exposure
light toward the resist film, wherein the liquid has a
predetermined thickness and has a refractive index larger than that
of air and smaller than that of the resist film, thus improving the
resolution of a resist pattern.
16. The composite film for liquid immersion lithography process
according to claim 14, wherein the liquid for liquid immersion
lithography is water substantially comprised of pure water or
deionized water.
17. The composite film for liquid immersion lithography process
according to claim 14, wherein the protective film has the
following properties: having no compatibility with pure water or
deionized water; and causing no chemical mixing with the resist
film.
18. The composite film for liquid immersion lithography process
according to claim 14, wherein the protective film is a coating
film of a composition comprising at least a fluorine-substituted
polymer.
19. The composite film for liquid immersion lithography process
according to claim 18, wherein the fluorine-substituted polymer is
comprised of any one of cyclic perfluoroalkyl polyether and chain
perfluoroalkyl polyether or both.
20. The composite film for liquid immersion lithography process
according to claim 19, wherein the composition is obtained by
dissolving any one of the cyclic perfluoroalkyl polyether and the
chain perfluoroalkyl polyether or both in a fluorine solvent.
21. The composite film for liquid immersion lithography process
according to claim 14, wherein the resist film is formed from a
resist composition comprised of a base polymer which is a polymer
comprising (meth)acrylic ester units.
22. The composite film for liquid immersion lithography process
according to claim 14, wherein the resist film is formed from a
resist composition comprised of a base polymer which is a polymer
having dicarboxylic acid anhydride-containing constitutional
units.
23. The composite film for liquid immersion lithography process
according to claim 14, wherein the resist film is formed from a
resist composition comprised of a base polymer which is a polymer
having phenolic hydroxyl group-containing constitutional units.
24. The composite film for liquid immersion lithography process
according to claim 14, wherein the resist film is formed from a
resist composition comprised of a base polymer which is a
silsesquioxane resin.
25. The composite film for liquid immersion lithography process
according to claim 14, wherein the resist film is formed from a
resist composition comprised of a base polymer which is a polymer
having .alpha.-(hydroxyalkyl)acrylic acid units.
26. The composite film for liquid immersion lithography process
according to claim 14, wherein the resist film is formed from a
resist composition comprised of a base polymer which is a polymer
having dicarboxylic acid monoester units.
27. A method for forming a resist pattern using a liquid immersion
lithography process, the method comprising: forming a photoresist
film on a substrate; forming, on the resist film, a protective film
having the following properties of: being transparent with respect
to exposure light, having substantially no compatibility with a
liquid for liquid immersion lithography, and causing no mixing with
the resist film; directly placing the liquid for liquid immersion
lithography having a predetermined thickness at least on the
protective film on the substrate having the resist film and the
protective film stacked thereon; selectively irradiating the resist
film with light through the liquid for liquid immersion lithography
and the protective film, and optionally subjecting the resultant
resist film to heat treatment; removing the protective film from
the resist film irradiated; and developing the resist film from
which the protective film is removed to obtain a resist
pattern.
28. The method for forming a resist pattern according to claim 27,
wherein the liquid immersion lithography process is of a
construction in which the resist film is exposed through the liquid
for liquid immersion lithography present at least on the resist
film in a ray of the lithography exposure light toward the resist
film, wherein the liquid has a predetermined thickness and has a
refractive index larger than that of air and smaller than that of
the resist film, whereby improving the resolution of a resist
pattern.
Description
TECHNICAL FIELD
[0001] The present invention relates to a material for forming a
resist protecting film which is advantageously used in a liquid
immersion lithography process, especially in a liquid immersion
lithography process of the construction in which a resist film is
exposed with lithographic exposure light through a liquid present
at least on the resist film in a path of the exposure light toward
the resist film wherein the liquid has a predetermined thickness
and has a refractive index higher than that of air and lower than
that of the resist film, thus improving the resolution of a resist
pattern. The present invention also relates to a resist film having
thereon a protective film formed from the material for forming a
protecting film, and to a method for forming a resist pattern using
the protective film.
BACKGROUND ART
[0002] In the fabrication of a variety of electronic devices with
microstructures, such as semiconductor devices and liquid crystal
devices, a lithography method is widely used, and, as the device
structures are miniaturized, resist patterns in the lithography
process are desired to be miniaturized.
[0003] Currently, in a state-of-the-art lithography technique, a
fine resist pattern having a line width as small as, for example,
90 nm can be formed by the lithography method, and the formation of
a further finer pattern will be needed in the future.
[0004] A first point for achieving the formation of such a fine
pattern that is smaller than 90 nm, is to develop an improved
exposure system and a corresponding resist. The point of the
development of the improved exposure system generally includes
provision of a light source, such as an F.sub.2 laser, an EUV
(extreme ultraviolet light), an electron beam, or an X-ray, a soft
X-ray, with a shorter wavelength and of a lens having an increased
numerical aperture (NA).
[0005] However, the light source having a shorter wavelength has a
problem in that it requires a new expensive exposure system, and
the increase of NA has a problem in that since there is a trade-off
between the resolution and the depth of focus, the increase in the
resolution lowers the depth of focus.
[0006] Recently, as a lithography technique which can solve the
problems, a liquid immersion lithography method has been reported
(cf., for example, Literature 1 (J. Vac. Sci. Technol. B(1999)
17(6), p3306-3309), Literature 2 (J. Vac. Sci. Technol. B(2001)
19(6), p2353-2356, and Literature 3 (Proceedings of SPIE Vol. 4691
(2002), p459-465). In this method, a resist film is exposed through
a liquid refractive index medium (refractive index liquid,
immersion liquid), such as pure water or a fluorocarbon inert
liquid, having a predetermined thickness, with the liquid
refractive index medium lying at least on the resist film between a
lens and the resist film on a substrate. In this method, the space
of the path of exposure light, which has conventionally been filled
with an inert gas, such as air or nitrogen gas, is replaced by a
liquid having a larger refractive index (n), for example, pure
water, with the result that even though a light source having a
wavelength for the exposure conventionally used is employed, high
resolution can be achieved without lowering the depth of focus like
the case where a light source having a shorter wavelength or a lens
having a higher NA is used.
[0007] By employing the liquid immersion lithography, a resist
pattern having a higher resolution and an excellent depth of focus
can be formed at a low cost using a lens mounted on the existing
exposure system, so that the liquid immersion lithography has
attracted a considerable attention.
[0008] However, in the liquid immersion lithography process, the
resist film is directly in contact with the refractive index liquid
(immersion liquid) during the exposure, and hence the resist film
is vulnerable to invasion by the liquid. Therefore, it is necessary
to check whether the resist composition conventionally used can be
applied as is to the liquid immersion lithography process.
[0009] The resist composition currently commonly used are
established compositions that were obtained as a result of
examination of a wide variety of candidate resins in respect of the
transparency to the exposure light, which is the most essential
property to the resist compositions. The inventors of the present
invention have made experiments and studies with a view to
obtaining from the currently proposed resist compositions a resist
composition having properties suitable for the liquid immersion
lithography as such or after slightly adjusting the formulation of
the resist composition. As a result, it has been found that a
promising resist composition from a practical point of view is
present. On the other hand, it has been confirmed that there are a
number of resist compositions which cannot achieve satisfactory
resolution of pattern in the liquid immersion lithography due to a
change in their properties by the liquid, but which exhibit fine
and high resolution in ordinary lithography employing the exposure
through a layer of air. Such resist compositions have been
established by spending considerable resources on the development,
and are excellent in various resist properties, such as
transparency to the exposure light, development properties, and
storage stability. These resist compositions include a number of
compositions which are poor only in the resistance to the immersion
liquid. Some examples of the compositions, which are not suitable
for the liquid immersion lithography but achieve high resolution in
the lithography through a layer of air, are shown in the
Comparative Examples of the present invention described later.
[0010] It has also been confirmed that, even when the resist film
suitable for the liquid immersion lithography is used in the liquid
immersion lithography, the quality and non-defective yield are
slightly poor, as compared to those obtained in the exposure
through a layer of air.
[0011] The suitability for liquid immersion lithography of the
conventional resist film was evaluated based on the following
analysis on the liquid immersion lithography process.
[0012] Specifically, for evaluating the performance of formation of
a resist pattern by the liquid immersion lithography, it is
considered to be necessary and sufficient to confirm three points,
i.e., (i) the performance of the optical system in the liquid
immersion lithography process, (ii) the effect of the resist film
on the immersion liquid, and (iii) the change of properties of the
resist film due to the immersion liquid.
[0013] With respect to the performance of the optical system in
(i), as is apparent from the case where for example, a photographic
sensitive plate having a surface resistance to water is immersed in
water and the surface of the plate is irradiated with a pattern
light, there will be no problem in principle if no light
transmission loss, such as reflection, occurs at the water surface
and the interface between the water and the surface of the
sensitive plate. The light transmission loss in this case can be
easily removed by optimizing the angle of incidence of the exposure
light. Thus, it is considered that any objects of the exposure, for
example, a resist film, a photographic sensitive plate, and an
image screen, cause no change in the performance of the optical
system, so far as they are inert to the immersion liquid, namely,
they are not affected by the immersion liquid, and they do not
affect the immersion liquid. Therefore, a check test for this point
is not required.
[0014] The effect of the resist film on the immersion liquid in
(ii) specifically indicates that the component of the resist film
is dissolved in the immersion liquid to change the refractive index
of the liquid. Theoretically, when the refractive index of the
immersion liquid changes, the optical resolution of the pattern
exposure is sure to change, and experiments are unnecessary. It is
enough to simply check whether the component of the resist film
immersed in a liquid is dissolved in the liquid to change the
formulation or refractive index of the immersion liquid, and it is
unnecessary to check the resolution by actual irradiation of a
pattern light and development.
[0015] Conversely, when the resist film immersed in the liquid is
irradiated with a pattern light and developed to check the
resolution, it is possible to know as to whether the resolution is
excellent or poor. However, it is difficult to judge whether the
resolution is affected by the change of properties of the immersion
liquid or the change of properties of the resist material or
both.
[0016] With respect to the phenomenon in which the resolution is
lowered by the change of properties of the resist film due to the
immersion liquid in (iii), an evaluation test such that "the resist
film after the exposure is showered with the immersion liquid and
then developed, and the resultant resist pattern is examined in
respect of the resolution" is satisfactory. In this evaluation
method, the resist film is directly showered with the liquid, and
hence the conditions for immersion are very stringent. In this
point, in the test in which the resist film completely immersed in
the liquid is exposed, it is difficult to judge whether the
resolution is changed by the change of properties of the immersion
liquid, the change of properties of the resist composition due to
the immersion liquid, or both.
[0017] The phenomena (ii) and (iii) above are two sides of the same
coin, and can be grasped by merely checking the change of
properties of the resist film due to the liquid.
[0018] Based on the results of the analysis, the suitability for
liquid immersion lithography of the resist film currently proposed
was evaluated by an evaluation test such that "the resist film
after the exposure is showered with the immersion liquid and then
developed, and the resultant resist pattern is examined in respect
of the resolution". The suitability can also be evaluated by
simulating the practical production process using a "two-beam
interferometry exposure method" that includes using an interfered
light caused by a prism as a pattern light for exposure and
subjecting a sample immersed in a liquid to exposure.
[0019] As mentioned above, for producing a new resist film suitable
for the liquid immersion lithography, a large investment of
resources for the development is surely needed. On the other hand,
it has been confirmed that resist compositions having qualities
slightly lowered but having properties suitable for the liquid
immersion lithography are obtained from the currently proposed
resist compositions by using the resin compositions as such or by
adjusting the formulation of the resin compositions. It has also
been confirmed that there are a number of resist films which cannot
achieve satisfactory resolution of pattern in the liquid immersion
lithography due to the change of properties by the immersion
liquid, but which exhibit fine and high resolution in ordinary
lithography employing the exposure through a layer of air.
DISCLOSURE OF THE INVENTION
[0020] The present invention has been achieved in view of the above
problems accompanying the conventional technique, and an object of
the invention is to provide a technique for applying a resist film
obtained from the conventional resist composition established by
spending considerable resources on the development to the liquid
immersion lithography. Specifically, an object the invention is to
provide a specific protective film temporarily formed on the
surface of a conventional resist film, thus making it possible not
only to prevent both the resist film and the liquid used from
changing in properties during the liquid immersion lithography but
also to form a resist pattern with high resolution using the liquid
immersion lithography.
[0021] For solving the above problems, the material for forming a
resist protecting film for use in a liquid immersion lithography
process of the present invention is a material for forming a resist
protecting film which is for use in a liquid immersion lithography
process and which is formed on a resist film, wherein the material
has the following properties of: being transparent with respect to
exposure light; having substantially no compatibility with a liquid
for liquid immersion lithography; and causing no mixing with the
resist film.
[0022] The composite film for use in a liquid immersion lithography
process of the present invention comprises a protective film and a
resist film, wherein the protective film has the following
properties of: being transparent with respect to exposure light;
having substantially no compatibility with a liquid for liquid
immersion lithography; and causing no mixing with the resist film,
and wherein the protective film is formed on the surface of the
resist film.
[0023] The method for forming a resist pattern of the present
invention is a method for forming a resist pattern using a liquid
immersion lithography process, wherein the method comprises:
forming a photoresist film on a substrate; forming, on the resist
film, a protective film having the following properties of: being
transparent with respect to exposure light, having substantially no
compatibility with a liquid for liquid immersion lithography, and
causing no mixing with the resist film; directly placing the liquid
for liquid immersion lithography having a predetermined thickness
at least on the protective film on the substrate having the resist
film and the protective film stacked thereon; irradiating the
resist film with predetermined pattern light through the liquid for
liquid immersion lithography and the protective film, and
optionally subjecting the resultant resist film to heat treatment;
removing the protective film from the resist film irradiated; and
developing the resist film from which the protective film is
removed to obtain a resist pattern.
[0024] Among the above-mentioned constructions, the liquid
immersion lithography process preferably is of the construction in
which the resist film is exposed with lithographic exposure light
through a liquid for liquid immersion lithography present at least
on the resist film in a path of the exposure light toward the
resist film, wherein the liquid has a predetermined thickness and
has a refractive index larger than that of air and smaller than
that of the resist film, thus improving the resolution of a resist
pattern.
EMBODIMENTS OF THE INVENTION
[0025] In the present invention having the above construction, the
liquid for liquid immersion lithography that can be preferably used
includes water substantially comprised of pure water or deionized
water, or a fluorocarbon inert liquid, more preferably water from
the viewpoint of cost reduction and ease of the post-treatment.
[0026] The resist films that can be used in the present invention
include any resist films obtained using a conventional resist
composition, and are not limited particularly. This is the most
unique feature of the present invention.
[0027] The protective film according to the present invention has
essential properties as described above, that the film is
transparent to the exposure light and substantially incompatible
with the refractive index liquid and causes no mixing with the
resist film, and the protective film has excellent adhesion to the
resist film and is easily removable from the resist film. A
protective film material which can be used to form a protective
film having such properties includes a composition obtained by
dissolving a fluororesin in a fluorocarbon solvent is used.
[0028] Examples of the fluororesin that can be used include linear
perfluoroalkyl polyethers, cyclic perfluoroalkyl polyethers,
polychlorotrifluoroethylenes, polytetrafluoroethylenes,
tetrafluoroethylene-perfluoroalkoxyethylene copolymers, and
tetrafluoroethylene-hexafluoropropylene copolymers.
[0029] In practice, among commercially available fluororesins,
DEMNUM S-20, DEMNUM S-65, DEMNUM S-100, and DEMNUM S-200 which are
linear perfluoroalkyl polyethers (each manufactured by DAIKIN
INDUSTRIES, LTD.), CYTOP series which are cyclic perfluoroalkyl
polyethers (manufactured by ASAHI GLASS CO., LTD.), and TEFLON
(R)-AF1600 and TEFLON (R)-AF2400 (each manufactured by DuPont) can
be used.
[0030] Among the fluororesins, mixed resins comprised of linear
perfluoroalkyl polyethers and cyclic perfluoroalkyl polyethers are
preferred.
[0031] The fluorocarbon solvent is not particularly limited as long
as it can dissolve the fluororesin. Examples of the fluorocarbon
solvent that can be used include perfluoroalkanes or
perfluorocycloalkanes, such as perfluorohexane and
perfluoroheptane, perfluoroalkenes having a double bond remaining
in the corresponding perfluoroalkanes or perfluorocycloalkanes,
perfluoro cyclic ethers, such as perfluorotetrahydrofuran and
perfluoro(2-butyltetrahydrofuran), perfluorotributylamine,
perfluorotetrapentylamine, and perfluorotetrahexylamine.
[0032] Other organic solvents compatible with the fluorine solvent,
surfactants and so on can be appropriately used in admixture.
[0033] The concentration of the fluororesin is not particularly
limited as long as a film can be formed therefrom. However, from
the viewpoint of achieving excellent coating properties, it is
preferred that the fluororesin concentration be about 0.1 to about
30 wt %.
[0034] A preferred material for the protective film comprises a
mixed resin comprised of a linear perfluoroalkyl polyether and a
cyclic perfluoroalkyl polyether dissolved in
perfluorotributylamine.
[0035] As mentioned above, the resist film materials that can be
used in the liquid immersion lithography process of the present
invention include commonly used positive resists or negative
photoresists. Specific examples of positive or negative
photoresists are shown below.
[0036] Resin components that can be used in the positive
photoresist include an acrylic resin, a cycloolefin resin, or a
silsesquioxane resin.
[0037] Preferred examples of the acrylic resin include a resin
having, for example, constitutional units (al) derived from a
(meth)acrylic ester having an acid-dissociative, dissolution
inhibiting group and comprising 80 mol % or more, preferably 90 mol
% (most preferably 100 mol %) of constitutional units derived from
a (meth)acrylic ester including constitutional units derived from
another (meth)acrylic ester other than the constitutional units
(a1).
[0038] For achieving excellent resolution and excellent resistance
to dry etching as well as fine pattern form, the resin component
comprises units (a1) and a combination of a plurality of monomer
units having different functions other than the units (a1), for
example, the following constitutional units.
[0039] Specifically, there can be mentioned constitutional units
derived from a (meth)acrylic ester having a lactone unit
(hereinafter, "(a2)" or "units (a2)"), constitutional units derived
from a (meth)acrylic ester having an alcoholic hydroxyl
group-containing polycyclic group (hereinafter, "(a3)" or "units
(a3)"), and constitutional units having a polycyclic group
different from the acid-dissociative, dissolution inhibiting group
in the units (a1), the lactone unit in the units (a2), and the
alcoholic hydroxyl group-containing polycyclic group in the units
(a3) (hereinafter, "(a4)" or "units (a4)"). (a2), (a3), and/or (a4)
can be appropriately combined depending on, for example, the
properties required. Preferably, when the resin component comprises
(a1) and at least one type of units selected from (a2), (a3), and
(a4), excellent resolution and excellent resist pattern form can be
achieved. With respect to each of the units (a1) to (a4), a
plurality of different units may be used in combination.
[0040] The constitutional units derived from a methacrylic ester
and the constitutional units derived from an acrylic ester are
advantageously used in such a manner that there are 10 to 85 mol %,
preferably 20 to 80 mol % of the constitutional units derived from
the methacrylic ester and 15 to 90 mol %, preferably 20 to 80 mol %
of the constitutional units derived from the acrylic ester based on
the total mole of the constitutional units derived from the
methacrylic ester and the constitutional units derived from the
acrylic ester.
[0041] Next, the units (a1) to (a4) are described in detail.
[0042] The units (a1) are constitutional units derived from a
(meth)acrylic ester having an acid-dissociative, dissolution
inhibiting group. The acid-dissociative, dissolution inhibiting
group in (a1) is not particularly limited as long as the group has
alkali-dissolution inhibiting properties such that it makes the
entire resin component alkali-insoluble before the exposure and the
group dissociates due to the action of acid generated after the
exposure to change the entire resin component to be alkali-soluble.
Generally, groups that form cyclic or chain tertiary alkyl esters
with the carboxyl group of (meth)acrylic acid, tertiary
alkoxycarbonyl groups, and chain alkoxyalkyl groups are widely
known.
[0043] Examples of the acid-dissociative, dissolution inhibiting
group in (a1) that can be preferably used include
acid-dissociative, dissolution inhibiting groups containing
aliphatic polycyclic groups.
[0044] Examples of the polycyclic groups include groups obtained by
eliminating one hydrogen element from a bicycloalkane, a
tricycloalkane, or a teroracycloalkane, which may be unsubstituted
or substituted with a fluorine atom or a fluoroalkyl group.
Specific examples thereof include groups obtained by eliminating
one hydrogen atom from a polycycloalkane, such as adamantane,
norbornane, isobornane, tricyclodecane, or tetracyclododecane. Such
a polycyclic group can be appropriately selected from a number of
polycyclic groups proposed for ArF resists. Among these, preferred
are an adamantyl group, a norbornyl group, and a
tetracyclododecanyl group from an industrial point of view.
[0045] Monomer units represented by the general formulae (1) to (7)
below are preferred as (a1) above. In the general formulae (1) to
(7), R represents a hydrogen atom or a methyl group, R.sub.1
represents a lower alkyl group, each of R.sub.2 and R.sub.3
independently represents a lower alkyl group, R.sub.4 represents a
tertiary alkyl group, R.sub.5 represents a methyl group, R.sub.6
represents a lower alkyl group, and R.sub.7 represents a lower
alkyl group.
[0046] Each of R.sub.1 to R.sub.3, R.sub.6, and R.sub.7 is
preferably a linear or branched lower alkyl group having 1 to 5
carbon atoms, and examples thereof include a methyl group, an ethyl
group, a propyl group, an isopropyl group, an n-butyl group, an
isobutyl group, a tert-butyl group, a pentyl group, an isopentyl
group, and a neopentyl group. From an industrial point of view,
preferred is a methyl group or an ethyl group.
[0047] R.sub.4 is a tertiary alkyl group, such as a tert-butyl
group or a tert-amyl group, and preferred is a tert-butyl group
from an industrial point of view. ##STR1## ##STR2##
[0048] Among the above examples of units (a1), especially,
constitutional units represented by the general formula (1), (2),
or (3) are more preferred since a pattern having high transparency
and high resolution as well as excellent resistence to dry etching
can be formed therefrom.
[0049] The units (a2) above have a lactone unit, and hence are
effective in enhancing the hydrophilicity with a developer
solution.
[0050] The units (a2) may be any units that have a lactone unit and
are copolymerizable with the other constitutional units in the
resin component.
[0051] Examples of monocyclic lactone units include groups obtained
by eliminating one hydrogen atom from .gamma.-butyro-lactone.
Examples of polycyclic lactone units include groups obtained by
eliminating one hydrogen atom from a lactone-containing
polycycloalkane.
[0052] Monomer units represented by the general formulae (10) to
(12) below are preferred as (a2). In the general formulae, R
represents a hydrogen atom or a methyl group. ##STR3##
[0053] A (meth) acrylic acid .gamma.-butyrolactone ester having an
ester linkage at the .alpha.-carbon represented by the general
formula (12) above and a (meth)acrylic acid norbornane lactone
ester represented by the general formula (10) or (11) above are
especially preferred since they are easily commercially
available.
[0054] The units (a3) above are constitutional units derived from a
(meth)acrylic ester having an alcoholic hydroxyl group-containing
polycyclic group.
[0055] The hydroxyl group in the alcoholic hydroxyl
group-containing polycyclic group is a polar group, and therefore
the use of this increases the collective hydrophilicity of the
resin component with a developer solution to improve the exposed
portion in alkali-solubility. Thus, the resin component having (a3)
preferably improves the resolution.
[0056] The polycyclic group in (a3) can be appropriately selected
from the aliphatic polycyclic groups described above as examples in
connection with (a1).
[0057] The alcoholic hydroxyl group-containing polycyclic group in
(a3) is not particularly limited. For example, a hydroxyl
group-containing adamantyl group is preferably used.
[0058] The hydroxyl group-containing adamantyl group represented by
the general formula (13) below is preferred since it has an effect
of improving the resistance to dry etching and squareness of the
pattern cross-sectional form. In the general formula, 1 is an
integer of 1 to 3. ##STR4##
[0059] The units (a3) may be any units that have the
above-described alcoholic hydroxyl group-containing polycyclic
group and being copolymerizable with the other constitutional units
in the resin component.
[0060] Specifically, constitutional units represented by the
general formula (14) below are preferred. In the general formula
(14), R represents a hydrogen atom or a methyl group. ##STR5##
[0061] In the units (a4), the polycyclic group "different from the
acid-dissociative, dissolution inhibiting group, the lactone unit,
and the alcoholic hydroxyl group-containing polycyclic group" means
that the polycyclic group in units (a4) in the resin component
overlaps neither the acid-dissociative, dissolution inhibiting
group in units (a1), the lactone unit in units (a2), nor the
alcoholic hydroxyl group-containing polycyclic group in units (a3),
that is, units (a4) have neither the acid-dissociative, dissolution
inhibiting group in units (a1), the lactone unit in units (a2), nor
the alcoholic hydroxyl group-containing polycyclic group in units
(a3) that constitute the resin component.
[0062] The polycyclic group in the units (a4) is not particularly
limited as long as it is selected so as not to overlap the
constitutional units used as the units (a1) to (a3) in the same
resin component. For example, as the polycyclic group in units
(a4), the aliphatic polycyclic group as exemplified in connection
with the units (a1) can be used, and a number of groups
conventionally known in the ArF positive resist materials can be
used.
[0063] Especially preferred is at least one member selected from
the tricyclodecanyl group, adamantyl group, and tetracyclododecanyl
group from the viewpoint of easy industrial availability.
[0064] The units (a4) may be any units that have the
above-described polycyclic group and are copolymerizable with the
other constitutional units in the resin component.
[0065] Preferred examples of (a4) are represented by the general
formulae (15) to (17) below. In the general formulae, R represents
a hydrogen atom or a methyl group. ##STR6##
[0066] With respect to the composition of the acrylic resin
component, the amount of units (a1) may be 20 to 60 mol %,
preferably 30 to 50 mol %, based on the total mole of the
constitutional units constituting the resin component, since
excellent resolution can be achieved.
[0067] The amount of units (a2) may be 20 to 60 mol %, preferably
30 to 50 mol %, based on the total mole of the constitutional units
constituting the resin component, since excellent resolution can be
achieved.
[0068] When the units (a3) are used, the amount of the units (a3)
may be 5 to 50 mol %, preferably 10 to 40 mol %, based on the total
mole of the constitutional units constituting the resin component,
since excellent resist pattern form can be achieved.
[0069] When the units (a4) are used, the amount of the units (a4)
may be 1 to 30 mol %, preferably 5 to 20 mol %, based on the total
mole of the constitutional units constituting the resin component,
since the separate pattern or semi-dense pattern is excellent in
resolution.
[0070] The units (a1) and at least one type of units selected from
the units (a2), (a3), and (a4) can be appropriately used in
combination depending on the purpose. However, a ternary polymer
comprising units (a1) and units (a2) and (a3) is preferred since
the resist pattern form, the exposure margin, the heat resistance,
and the resolution are excellent. In this case, with respect to the
respective contents of the constitutional units (a1) to (a3), it is
preferred that the content of (a1) is 20 to 60 mol %, the content
of (a2) is 20 to 60 mol %, and the content of (a3) is 5 to 50 mol
%.
[0071] A mass average molecular weight (as measured using
polystyrene for molecular weight calibration; this applies to the
following description) of the resin in the resin component in the
present invention is not particularly limited and it is preferably
5,000 to 30,000, more preferably 8,000 to 20,000. When the mass
average molecular weight is larger than the upper limit of the
range, the solubility in a resist solvent may become poor, and,
when it is smaller than the lower limit of the range, the
resistance to dry etching or the resist pattern cross-sectional
form may become poor.
[0072] The cycloolefin resin is preferably a resin comprising
constitutional units (a5) represented by the general formula (18)
below, which are optionally copolymerized with one or more of the
constitutional units obtained from (a1): ##STR7## wherein R.sub.8
represents a substituent mentioned above as an example of the
acid-dissociative, dissolution inhibiting group in the units (a1),
and m is an integer of 0 to 3.
[0073] In the units (a5), when m is 0, copolymers having units (a1)
are preferably used.
[0074] Examples of the silsesquioxane resins include resins having
constitutional units (a6) represented by the following general
formula (19), and resins having constitutional units (a7)
represented by the following general formula (20): ##STR8## wherein
R.sub.9 represents an acid-dissociative, dissolution inhibiting
group comprised of a hydrocarbon group containing an aliphatic
monocyclic or polycyclic group, Rlo represents a.linear, branched,
or cyclic saturated aliphatic hydrocarbon group, X represents an
alkyl group having 1 to 8 carbon atoms and having at least one
hydrogen atom replaced by a fluorine atom, and m is an integer of 1
to 3; ##STR9## wherein R.sub.11 represents a hydrogen atom or a
linear, branched, or cyclic alkyl group, R.sub.12 represents a
linear, branched, or cyclic saturated aliphatic hydrocarbon group,
and X represents an alkyl group having 1 to 8 carbon atoms and
having at least one hydrogen atom replaced by a fluorine atom.
[0075] In (a6) and (a7), the acid-dissociative, dissolution
inhibiting group of R.sub.9 is a group which has alkali-dissolution
inhibiting properties such that it makes the entire silsesquioxane
resin alkali-insoluble before the exposure, and which dissociates
due to the action of an acid generated from the acid generator
after the exposure to change the entire silsesquioxane resin to be
alkali-soluble.
[0076] Examples of such acid-dissociative, dissolution inhibiting
groups include acid-dissociative, dissolution inhibiting groups
represented by the general formulae (21) to (25) below include
hydrocarbon groups containing a bulky aliphatic monocyclic or
polycyclic group. By using the acid-dissociative, dissolution
inhibiting group, the dissolution inhibiting group after
dissociation is unlikely to undergo gasification, thus preventing a
degasification phenomenon. ##STR10##
[0077] R.sub.9 has preferably 7 to 15, more preferably 9 to 13
carbon atoms since the dissolution inhibiting group after
dissociation is unlikely to undergo gasification and appropriate
solubility in a resist solvent or in a developer solution can be
obtained.
[0078] The acid-dissociative, dissolution inhibiting group can be
appropriately selected from a number of groups proposed for the
resins for use in, for example, ArF excimer laser resist
compositions depending on the light source used as long as it is an
acid-dissociative, dissolution inhibiting group comprised of a
hydrocarbon group containing an aliphatic monocyclic or polycyclic
group. Generally, those groups that form cyclic tertiary alkyl
esters with a carboxyl group of (meth)acrylic acid are widely
known.
[0079] It is especially preferred that the acid-dissociative,
dissolution inhibiting group contains an aliphatic polycyclic
group. The aliphatic polycyclic group can be appropriately selected
from a number of aliphatic polycyclic groups proposed for the ArF
resist. Examples of the aliphatic polycyclic groups include those
groups obtained by eliminating one hydrogen atom from a
bicycloalkane, a tricycloalkane, or a tetracycloalkane, and more
specifically, those groups obtained by eliminating one hydrogen
atom from a polycycloalkane such as adamantane, norbornane,
isobornane, tricyclodecane, or tetracyclododecane.
[0080] Among the above general formulae, those silsesquioxane
resins having any one of the 2-methyl-2-adamantyl group represented
by the general formula (23) and the 2-ethyl-2-adamantyl group
represented by the general formula (24) or both are preferred since
they are unlikely to cause degasification and have excellent resist
properties including resolution and heat resistance.
[0081] Each of R.sub.10 and R.sub.11 has preferably 1 to 20, more
preferably 5 to 12 carbon atoms from the viewpoint of controlling
the solubility in resist solvents and the molecular size.
Particularly, a saturated cyclic aliphatic hydrocarbon group
preferably has advantages in that the resultant silsesquioxane
resin has high transparency to high-energy light, and has a high
glass transition temperature (Tg), which makes easy controlling the
acid generation from an acid generator during the PEB
(post-exposure bake).
[0082] The saturated cyclic aliphatic hydrocarbon group may be
either a monocyclic group or a polycyclic group. Examples of the
polycyclic groups include those groups obtained by eliminating two
hydrogen atoms from a bicycloalkane, a tricycloalkane, or a
teroracycloalkane, more specifically, those groups obtained by
eliminating two hydrogen atoms from a polycycloalkane such as
adamantane, norbornane, isobornane, tricyclodecane, or
tetracyclododecane.
[0083] More specific examples of R.sub.10 and R.sub.12 include
those groups obtained by eliminating two hydrogen atoms from
respective alicyclic compounds represented by the general formulae
(26) to (31) below or derivatives thereof. ##STR11##
[0084] The derivatives mean the alicyclic compounds of the chemical
formulae (26) to (31) above having at least one hydrogen atom
replaced by a group, e.g., a lower alkyl group, such as a methyl
group or an ethyl group; an oxygen atom; or a halogen atom, such as
fluorine, chlorine, or bromine. Among these, preferred is a group
obtained by eliminating two hydrogen atoms from an alicyclic
compound selected from the group consisting of the chemical
formulae (26) to (31) since high transparency is obtained and it is
easily industrially available.
[0085] R.sub.11 is a lower alkyl group having preferably 1 to 10,
more preferably 1 to 4 from the viewpoint of obtaining appropriate
solubility in resist solvents. More specific examples of alkyl
groups include a methyl group, an ethyl group, a propyl group, an
isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl
group, a cyclopentyl group, a cyclohexyl group, a 2-ethylhexyl
group, and an n-octyl group.
[0086] R.sub.11 can be appropriately selected from the above
candidate examples depending on the desired alkali-solubility of
the silsesquioxane resin. When R.sub.11 is a hydrogen atom, the
alkali-solubility of the silsesquioxane resin is highest. When the
alkali-solubility is higher, there can be obtained an advantage in
that the sensitivity is improved.
[0087] On the other hand, the larger the number of carbon atoms of
the alkyl group, or the more bulky the alkyl group, the lower the
alkali-solubility of the silsesquioxane resin. When the
alkali-solubility is lowered, the resistance to an alkaline
developer solution is enhanced, and therefore the exposure margin
in forming a resist pattern using the silsesquioxane resin is
improved and thus the size change caused during the exposure is
reduced. In addition, uneven development is prevented, suppressing
roughness of the resultant resist pattern at the edge portion.
[0088] In the general formulae (19) and (20) above, X is especially
preferably a linear alkyl group. The alkyl group may be a lower
alkyl group having 1 to 8, preferably 1 to 4 carbon atoms from the
viewpoint of obtaining the silsesquioxane resin having appropriate
glass transition (Tg) temperature or solubility in a resist
solvent. The alkyl group preferably has more hydrogen atoms
replaced by fluorine atoms since the transparency to high-energy
light or electron beam of 200 nm or shorter is improved, and the
alkyl group is most preferably a perfluoroalkyl group having its
all hydrogen atoms replaced by fluorine atoms. X's may be the same
or different. In the general formula (19), m may be an integer of
to 1 to 3, preferably 1 for permitting the acid-dissociative,
dissolution inhibiting group to easily dissociate.
[0089] More specific examples of the silsesquioxane resins include
those resins represented by the following general formula (32) or
(33): ##STR12## wherein R.sub.5, Root R.sub.12, and n are as
defined above.
[0090] The amount of the constitutional units represented by (a6)
and (a7) may be 30 to 100 mol %, preferably 70 to 100%, more
preferably 100 mol %, based on the total mole of the constitutional
units constituting the silsesquioxane resin in the present
invention.
[0091] The amount of the constitutional units represented by (a6)
is preferably 5 to 70 mol %, more preferably 10 to 40 mol %, based
on the total mole of the constitutional units represented by (a6)
and (a7). The amount of the constitutional units represented by
(a7) is preferably 30 to 95 mol %, more preferably 60 to 90 mol %,
based on the total mole of the constitutional units represented by
(a6) and (a7).
[0092] When the amount of the constitutional units represented by
(a6) falls in the above range, the amount of the acid-dissociative,
dissolution inhibiting group is naturally determined, so that the
silsesquioxane resin as a base resin of the positive resist
composition advantageously changes in alkali-solubility before and
after the exposure.
[0093] The silsesquioxane resin may have constitutional units other
than the constitutional units represented by (a6) and (a7) in such
an amount that the effect aimed at by the present invention is not
sacrificed. Examples thereof include those units used in a
silsesquioxane resin for ArF excimer laser resist compositions,
e.g., alkylsilsesquioxane units represented by the general formula
(34) below, having an alkyl group (R'), such as a methyl group, an
ethyl group, a propyl group, or a butyl group. ##STR13##
[0094] The mass average molecular weight (Mw) (as measured by gel
permeation chromatography using polystyrene for molecular weight
calibration) of the silsesquioxane resin is not particularly
limited, and it is preferably 2,000 to 15,000, more preferably
3,000 to 8,000. When the mass average molecular weight is larger
than the upper limit of the range, the solubility in a resist
solvent may become poor, and, when it is smaller than the lower
limit of the range, the resist pattern cross-sectional form may
become poor.
[0095] The mass average molecular weight (Mw)/number average
molecular weight (Mn), i.e., polymer distribution is not
particularly limited, and it is preferably 1.0 to 6.0, more
preferably 1.5 to 2.5. When it is larger than the upper limit of
the range, the resolution and the pattern form may become poor.
[0096] The silsesquioxane resin in the present invention is a
polymer having in its basic skeleton a silsesquioxane comprising
the constitutional units represented by (a6) and (a7), and hence
has high transparency to high-energy light or electron beam of 200
nm or shorter. Therefore, the positive resist composition
containing the silsesquioxane resin in the present invention is
advantageously used in lithography using a light source at a
wavelength shorter than that of, e.g., an ArF excimer laser, and,
particularly in a single-layer process, the resist composition can
form a fine resist pattern having a line width as small as 150 nm
or less, and further 120 nm or less. When using a two-layer resist
laminate as an upper layer, the resist composition is
advantageously used in a process forming a fine resist pattern as
small as 120 nm or less, and further 100 nm or less.
[0097] The resin component used in the negative resist composition
is not particularly limited as long as it is a resin component
commonly used. Specific preferred examples thereof are as
follows.
[0098] As the resin component, there is preferably used a resin
(a8) constituting a resin component that becomes alkali-insoluble
due to acid, and having in its molecule two types of functional
groups which can react with each other to form an ester, and which
undergo dehydration due to the action of the acid generated from an
acid generator added to the resist material together with the resin
to form an ester, thus making the resin component alkali-insoluble.
The two types of functional groups which can react with each other
to form an ester mean, for example, a hydroxyl group and a carboxyl
group or a carboxylic acid ester for forming a carboxylic acid
ester. In other words, they mean two types of functional groups for
forming an ester. Preferred examples of such resins include those
resins having a hydroxyalkyl group and at least one of a carboxyl
group and a carboxylic acid ester group at the side chain of the
main skeleton of the resin.
[0099] Further, the resin component is preferably a resin component
(a9) comprised of a polymer having dicarboxylic acid monoester
units.
[0100] In other words, (a8) is a resin component having at least
constitutional units represented by the following general formula
(35): ##STR14## wherein R.sub.13 represents a hydrogen atom, a
C.sub.1-C.sub.6 alkyl group, or an alkyl group having a polycyclic
ring skeleton, such as a bornyl group, an adamantyl group, a
tetracyclododecyl group, or a tricyclodecyl group.
[0101] Preferred examples of such resins include polymers
(homopolymers or copolymers) (a8-1) comprised of at least one type
of monomers selected from an .alpha.-(hydroxyalkyl)-acrylic acid
and an alkyl .alpha.-(hydroxyalkyl)acrylate, and copolymers (a8-2)
comprised of at least one type of monomers selected from an
ax-(hydroxyalkyl)acrylic acid and an alkyl
.alpha.-(hydroxyalkyl)acrylate and at least one type of monomers
selected from another ethylenically unsaturated carboxylic acid and
an ester of another ethylenically unsaturated carboxylic acid.
[0102] The polymers (a8-1) preferably include copolymers of an
.alpha.-(hydroxyalkyl)acrylic acid and an alkyl
.alpha.-(hydroxy-alkyl)acrylate, and, the copolymer (a8-2)
preferably include copolymers that contain, as the another
ethylenically unsaturated carboxylic acid or ester of another
ethylenically unsaturated carboxylic acid, at least one member
selected from acrylic acid, methacrylic acid, an alkyl acrylate,
and an alkyl methacrylate.
[0103] Examples of the hydroxyalkyl groups in the
.alpha.-(hydroxyalkyl)acrylic acid or alkyl
.alpha.-(hydroxyalkyl)-acrylate include lower hydroxyalkyl groups,
such as a hydroxymethyl group, a hydroxyethyl group, a
hydroxypropyl group, and a hydroxybutyl group. Among these,
preferred is a hydroxyethyl group or a hydroxymethyl group since it
readily forms an ester.
[0104] Examples of the alkyl groups in the alkyl ester portion of
the alkyl .alpha.-(hydroxyalkyl)acrylate include lower alkyl
groups, such as a methyl group, an ethyl group, a propyl group, an
isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl
group, and an amyl group; and bridged polycyclic ring hydrocarbon
groups, such as a bicyclo[2.2.1]heptyl group, a bornyl group, an
adamantyl group, a tetracyclo[4.4.0.1.sup.2.5.1.sup.7.10]dodecyl
group, and a tricyclo[5.2.1.0.sup.2.6]decyl group. When the alkyl
group in the ester portion is a polycyclic ring hydrocarbon group,
the resultant polymer is effective in enhancing the resistance to
dry etching. Among these alkyl groups, especially preferred are
lower alkyl groups, such as a methyl group, an ethyl group, a
propyl group, and a butyl group, since an inexpensive and easily
available alcohol component for forming an ester can be used.
[0105] Like a carboxyl group, a lower alkyl ester undergoes
esterification with a hydroxyalkyl group, but an ester of a bridged
polycyclic ring hydrocarbon is unlikely to undergo such
esterification. Therefore, when the ester of a bridged polycyclic
ring hydrocarbon is introduced into the resin, it is preferred that
a carboxyl group be also present in the side chain of the
resin.
[0106] On the other hand, examples of another ethylenically
unsaturated carboxylic acids and esters of the ethylenically
unsaturated carboxylic acid in (a8-2) include unsaturated
carboxylic acids, such as acrylic acid, methacrylic acid, maleic
acid, and fumaric acid, and alkyl esters of the unsaturated
carboxylic acid, such as methyl, ethyl, propyl, isopropyl, n-butyl,
isobutyl, n-hexyl, and octyl esters. As the alkyl group in the
ester portion, there can be used an ester of acrylic acid or
methacrylic acid having a bridged polycyclic ring hydrocarbon
group, such as a bicyclo[2.2.1]heptyl group, a bornyl group, an
adamantyl group, a tetracyclo[4.4.0.1.sup.2.5.1.sup.7.10]dodecyl
group, or a tricyclo[5.2.1.0.sup.2.6]decyl group. Among these,
preferred are acrylic acid, methacrylic acid, and lower alkyl
esters thereof, such as methyl, ethyl, propyl, and n-butyl esters,
since they are inexpensive and easily available.
[0107] In the resin in resin component (a8-2), the molar ratio of
at least one type of monomer units selected from an
.alpha.-(hydroxyalkyl)acrylic acid and an alkyl
.alpha.-(hydroxyalkyl)acrylate to at least one type of monomer
units selected from anther ethylenically unsaturated carboxylic
acid and an ethylenically unsaturated carboxylic acid ester is
preferably in the range of from 20:80 to 95:5, especially
preferably 50:50 to 90:10. When the ratio between the units falls
in the above range, an ester is easily formed in the molecule or
between the molecules, so that excellent resist patterns can be
obtained.
[0108] The resin component (a9) is a resin component having at
least constitutional units represented by the following general
formula (36) or (37): ##STR15## wherein each of R.sub.14 and
R.sub.15 represents an alkyl chain having 0 to 8 carbon atoms,
R.sub.16 represents a substituent having at least two or more
alicyclic structures, and each of R.sub.17 and R.sub.18 represents
a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.
[0109] The negative resist composition containing a resin component
having the dicarboxylic acid monoester monomer units is preferred
from the viewpoint of improved resolution and suppressed line edge
roughness. In addition, the negative resist composition improves
the swelling resistance and is more preferably used in the liquid
immersion lithography process.
[0110] Examples of the dicarboxylic acid monoester compounds
include fumaric acid, itaconic acid, mesaconic acid, glutaconic
acid, and traumatic acid.
[0111] Preferred examples of resins having the dicarboxylic acid
monoester units include polymers or copolymers (a9-1) comprised of
dicarboxylic acid monoester monomers, and copolymers (a9-2)
comprised of dicarboxylic acid monoester monomers and at least one
type of monomers selected from the .alpha.-(hydroxyalkyl)acrylic
acid, alkyl .alpha.-(hydroxyalkyl)-acrylate, another ethylenically
unsaturated carboxylic acid, and ester of another ethylenically
unsaturated carboxylic acid.
[0112] The resin components used in the negative resist may be used
individually or in combination. The resin component may have a
weight average molecular weight of 1,000 to 50,000, preferably
2,000 to 3,0000.
[0113] The positive resist that includes the acrylic resin ((a1) to
(a4)) among the above resins corresponds to a positive resist
containing a resin having a relatively high resistance to water
liquid immersion. However, the resolution of a pattern formed from
this resist tends to be lowered as the size is closer to the
resolution limit in the liquid immersion lithography. The cause of
lowering of the resolution is not a single factor, and, for
removing such factors, it is considerably effective to form the
protective film of the present invention to completely separate the
immersion liquid from the resist film.
[0114] The positive resist that includes the silsesquioxane resin
((a6) and (a7)) or the negative resist that includes any one of the
specific resins (aB) and (a9) or both is considered to have poor
liquid immersion resistance, as compared to the positive resist
using the acrylic resin, and the suitability of this resist for the
liquid immersion lithography can be improved by using the
protective film of the present invention.
[0115] Further, as seen in the Comparative Examples in the present
invention, it is known that the resist that includes a cycloolefin
resin has a very poor liquid immersion lithography resistance,
which makes it impossible to form a pattern. Even the positive
resist containing such a resin can be applied to the liquid
immersion lithography by using the protective film of the present
invention.
[0116] The acid generator used in combination with the resin
component of the positive or negative resist may be any acid
generators appropriately selected from known acid generators used
in a conventional chemically amplified resist.
[0117] Specific examples of the acid generators include onium
salts, such as diphenyliodonium trifluoromethanesulfonate,
(4-methoxyphenyl)phenyliodonium trifluotomethanesulfonate,
bis(p-tert-butylphenyl)iodonium trifluoromethanesulfonate,
triphenylsulfonium trifluoromethanesulfonate,
(4-methoxy-phenyl)diphenylsulfonium trifluoromethanesulfonate,
(4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate,
(4-methylphenyl)diphenylsulfonium nonafluorobutanesulfonate,
(p-tert-butylphenyl)diphenylsulfonium trifluoromethane-sulfonate,
diphenyliodonium nonafluorobutanesulfonate,
bis(p-tert-butylphenyl)iodonium nonafluorobutanesulfonate,
triphenylsulfonium nonafluorobutanesulfonate,
(4-trifluoro-methylphenyl)diphenylsulfonium
trifluoromethanesulfonate,
(4-trifluoromethylphenyl)diphenylsulfonium
nonafluoro-butanesulfonate, and tri(p-tert-butylphenyl)sulfonium
trifluoromethanesulfonate.
[0118] Of the onium salts, triphenylsulfonium salts are preferably
used since they are unlikely to decompose to generate organic gas.
The amount of the triphenylsulfonium salt incorporated is
preferably 50 to 100 mol %, more preferably 70 to 100 mol %, most
preferably 100 mol %, based on the total mole of the acid
generators.
[0119] Among the triphenylsulfonium salts, a triphenylsulfonium
salt represented by the general formula (38) below having a
perfluoroalkylsulfonic acid ion as anion is especially preferably
used since high sensitivity can be achieved: ##STR16## wherein each
of R.sub.19, R.sub.20, and R.sub.21 independently represents a
hydrogen atom, a lower alkyl group having 1 to 8, preferably 1 to 4
carbon atoms, or a halogen atom, such as chlorine, fluorine, or
bromine; and p is an integer of 1 to 12, preferably 1 to 8, and
more preferably 1 to 4.
[0120] The acid generators may be used individually or in
combination.
[0121] The amount of the acid generator incorporated may be 0.5
part by mass, preferably 1 to 10 parts by mass, based on 100 parts
by mass of the resin component. When the amount of the acid
generator is less than 0.5 part by mass, pattern formation is not
satisfactorily achieved, and, when the amount is more than 30 parts
by mass, a uniform solution is difficult to obtain, leading to the
lowering of the storage stability.
[0122] The positive or negative resist composition in the present
invention is produced by dissolving the resin component and the
acid generator and the arbitrary component mentioned below
preferably in an organic solvent.
[0123] The organic solvent may be any organic solvents as long as
they can dissolve the resin component and the acid generator to
form a uniform solution. Any one or more types of solvent
appropriately selected from the known solvents for conventional
chemically amplified resists can be used.
[0124] Examples of the organic solvents include ketones, such as
acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone,
and 2-heptanone; polyhydric alcohols and derivatives thereof, such
as monomethyl ether, monoethyl ether, monopropyl ether, monobutyl
ether, or monophenyl ether of ethylene glycol, ethylene glycol
monoacetate, diethylene glycol, diethylene glycol monoacetate,
propylene glycol, propylene glycol monoacetate, dipropylene glycol,
or dipropylene glycol monoacetate; cyclic ethers, such as dioxane;
and esters, such as methyl lactate, ethyl lactate, methyl acetate,
ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate,
methyl methoxypropionate, and ethyl ethoxypropionate. These organic
solvents may be used individually or in the form of a mixed solvent
composed of two or more of them.
[0125] To improve the form and stability with time of the resist
pattern, the positive or negative resist may further contain, as a
quencher, a known amine, preferably a secondary lower aliphatic
amine or a tertiary lower aliphatic amine, or an organic acid, such
as an organic carboxylic acid or an oxo-acid of phosphorus.
[0126] The lower aliphatic amine means an alkylamine or
alkylalcoholamine having 5 carbon atoms or less, and examples of
the secondary or tertiary amines include trimethylamine,
diethylamine, triethylamine, di-n-propylamine, tri-n-propylamine,
tribentylamine, diethanolamine, and triethanolamine, and especially
preferred is an alkanolamine, such as triethanolamine. These amines
may be used individually or in combination.
[0127] The amine is used in an amount in the range of generally
from 0.01 to 2.0% by mass, based on the mass of the resin
component.
[0128] Example of preferred organic carboxylic acids include
malonic acid, citric acid, malic acid, succinic acid, benzoic acid,
and salicylic acid.
[0129] Examples of the oxo-acids of phosphorus and derivatives
thereof include phosphoric acid and derivatives thereof, e.g.,
esters, such as phosphoric acid, di-n-butyl phosphate, and diphenyl
phosphate; phosphonic acid and derivatives thereof, e.g., esters,
such as phosphonic acid, dimethyl phosphonate, di-n-butyl
phosphonate, phenylphosphonic acid, diphenyl phosphonate, and
dibenzyl phosphonate; and phosphinic acid, such as phosphinic acid
and phenylphosphinic acid, and derivatives thereof, e.g., esters.
Of these, especially preferred is phosphonic acid.
[0130] The organic acid is used in an amount of 0.01 to 5.0 parts
by mass, based on 100 parts by mass of the resin component. The
organic acids may be used individually or in combination.
[0131] The amount of the organic acid used is preferably in the
range of the equimolar amount to the amine or smaller.
[0132] The positive resist composition of the present invention may
if desired contain an additive miscible with the composition, for
example, an additional resin for improving the performance of the
resist film, or a surfactant, a dissolution inhibitor, a
plasticizer, a stabilizer, a coloring agent, or a halation
preventing agent for improving the coating properties.
[0133] The negative resist composition of the present invention may
if necessary be blended with a cross-linking agent for further
increasing the cross-linking density to improve the form or
resolution of the resist pattern or the resistance to dry
etching.
[0134] The cross-linking agent is not particularly limited, and any
cross-linking agent appropriately selected from known cross-linking
agents for use in a conventional chemically amplified negative
resist can be used. Examples of the cross-linking agents include
alicyclic hydrocarbons having any one of a hydroxyl group and a
hydroxyalkyl group or both and oxygen-containing derivatives
thereof, such as 2,3-dihydroxy-5-hydroxymethylnorbornane,
2-hydroxy-5,6-bis(hydroxymethyl)norbornane, cyclohexanedimethanol,
3,4,8(or 9)-trihydroxytricyclodecane, 2-methyl-2-adamantanol,
1,4-dioxan-2,3-diol, and 1,3,5-trihydroxycyclohexane; and compounds
obtained by reacting an amino group-containing compound, such as
melamine, acetoguanamine, benzoguanamine, urea, ethyleneurea, or
glycoluril, with formaldehyde or formaldehyde and a lower alcohol
to replace a hydrogen atom in the amino group by a hydroxymethyl
group or a lower alkoxymethyl group. Specific examples thereof
include hexamethoxymethylmelamine, bismethoxymethylurea,
bismethoxymethylbismethoxyethyleneurea,
tetramethoxymethylglycoluril, and tetrabutoxymethylglycoluril, with
tetrabutoxymethylglycoluril being especially preferred.
[0135] The cross-linking agents may be used individually or in
combination.
[0136] Next, a method for forming a resist pattern by a liquid
immersion lithography process using the protective film of the
present invention is described.
[0137] A conventional resist composition is first applied onto a
substrate, such as a silicon wafer, by means of, e.g., a spinner,
and then subjected to prebake (PAB treatment).
[0138] An organic or inorganic antireflection coating film can be
formed between the substrate and the coating layer of the resist
composition to form a two-layer laminate.
[0139] The above steps can be conducted using a conventionally
known method. It is preferred that the conditions for procedure are
appropriately selected depending on the formulation or properties
of the resist composition used.
[0140] Subsequently, a protective film-forming material
composition, for example, "composition obtained by dissolving a
mixed resin comprised of chain perfluoroalkyl polyether and cyclic
perfluoroalkyl polyether in perfluorotributylamine" is uniformly
applied to the surface of the above-cured resist film (comprised of
a single layer or multiple layers), and then cured to form a resist
protecting film.
[0141] The thus obtained substrate having the resist film covered
with the protective film is immersed in a refractive index liquid
(liquid having a refractive index larger than the refractive index
of air and smaller than the refractive index of the resist
film).
[0142] The resist film on the substrate immersed in the liquid is
selectively exposed through a desired mask pattern. In this
instance, the exposure light passes through the refractive index
liquid and protective film and reaches the resist film.
[0143] In this case, the resist film is completely protected by the
protective film from the refractive index liquid, so that the
resist film does not undergo a change in properties, such as
swelling, due to attack of the refractive index liquid, or a
component of the resist film is not dissolved in the refractive
index liquid to change the refractive index liquid in optical
properties, e.g., refractive index.
[0144] The wavelength of light used in the above exposure is not
particularly limited, and radiation, such as an ArF excimer laser,
a KrF excimer laser, an F.sub.2 excimer laser, an EUV (extreme
ultraviolet light), a VUV (vacuum ultraviolet light), an electron
beam, an X-ray, or a soft X-ray can be used. The wavelength is
determined mainly by the characteristic of the resist film.
[0145] As mentioned above, in the method for forming a resist
pattern of the present invention, the resist film is exposed
through a liquid having a refractive index larger than that of air
and smaller than that of the resist film used (refractive index
liquid), the liquid being present on the resist film. Examples of
such refractive index liquid include water and fluorocarbon inert
liquids. Specific examples of the fluorocarbon inert liquids
include liquids comprised mainly of fluorocarbon compounds, such as
C.sub.3HCl.sub.2F.sub.5, C.sub.4F.sub.9OCH.sub.3,
C.sub.4F.sub.9OC.sub.2H.sub.5, or C.sub.5H.sub.3F.sub.7. Among
these, water is preferably used from the viewpoint of the cost,
safety, environmental issues, and general purpose properties.
[0146] The refractive index of the refractive index liquid used is
not particularly limited as long as the refractive index is "larger
than the refractive index of air and smaller than the refractive
index of the resist composition used".
[0147] After completion of the step of the exposure in an immersed
state, the substrate is taken out of the refractive index liquid,
and the liquid is removed from the substrate, and then the
protective film is removed. In the removal of the protective film,
a fluorine solvent capable of dissolving the fluororesin can be
directly used. From the viewpoint of facilitating the drying after
washing, a solvent having a boiling point of about 150.degree. C.
or lower is preferably used, and preferred is
perfluoro(2-butyltetra-hydrofuran)(boiling point: 102.degree. C.)
from this point of view.
[0148] Subsequently, the resist film exposed is subjected to PEB
(post-exposure bake), and then developed using an alkaline
developer solution comprised of an alkaline aqueous solution. The
PEB may be conducted before the step of removing the protective
film. Post-bake may be conducted after the development treatment.
Preferably, rinsing is carried out using pure water. The rinsing
with water is made by, for example, allowing water to fall dropwise
or spraying water against the surface of the substrate while
rotating the substrate to wash away the developer solution on the
substrate and the resist composition dissolved by the developer
solution. Then, drying is conducted to obtain a resist pattern
having a form patterned in the resist film according to the mask
pattern.
[0149] By forming a resist pattern by the above method, a resist
pattern having a fine line width, especially a line and space
pattern having a small pitch with excellent resolution can be
produced. The pitch in the line and space pattern means the total
distance of a resist pattern width and a space width in the
direction of the line width of the pattern.
EXAMPLES
[0150] While Examples of the present invention will be explained
below, these examples merely exemplify the invention preferably,
and do not limit the invention. In the following explanations,
Comparative Examples are described along with the Examples.
Example 1
[0151] The resin component, acid generator, and nitrogen-containing
organic compound shown below were uniformly dissolved in an organic
solvent to prepare positive resist composition 1.
[0152] As the resin component, 100 parts by mass of a
methacrylate-acrylate copolymer comprising three types of
constitutional units represented by the chemical formulae (39a),
(39b), and (39c) below was used. In the constitutional units used
in the preparation of the resin component, p, q, and r are as
follows: p=50 mol %, q=30 mol %, and r=20 mol %. The resin
component prepared had a mass average molecular weight of 10,000.
##STR17##
[0153] As the acid generator, 3.5 parts by mass of
triphenylsulfonium nonafluorobutanesulfonate and 1.0 part by mass
of (4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate were
used.
[0154] As the organic solvent, 1,900 parts by mass of a mixed
solvent of propylene glycol monomethyl ether acetate and ethyl
lactate (mass ratio: 6:4) was used.
[0155] Further, as the nitrogen-containing organic compound, 0.3
part by mass of triethanolamine was used.
[0156] Using the above-prepared positive resist composition 1, a
resist pattern was formed.
[0157] An organic antireflection coating composition "AR-19" (trade
name; manufactured by Shipley Limited) was first applied onto a
silicon wafer using a spinner, and dried by calcination on a hot
plate at 215.degree. C. for 60 seconds to form an organic
antireflection coating film having a thickness of 82 nm. Then,
positive resist composition 1 was applied onto the antireflection
coating film using a spinner, and dried by prebake on a hot plate
at 115.degree. C. for 90 seconds to form a resist film having a
thickness of 150 nm on the antireflection coating film.
[0158] A protective film material, which was obtained by dissolving
a mixed resin comprised of DEMNUM S-20 (manufactured by DAIKIN
INDUSTRIES, Ltd.) and CYTOP (manufactured by ASAHI GLASS CO.,
LTD.)(weight ratio=1:5) in perfluorotributylamine to have a resin
concentration of 2.5 wt %, was applied onto the resist film by spin
coating, and heated at 90.degree. C. for 60 seconds to form a
protective film having a thickness of 37 nm.
[0159] Subsequently, the resist film was irradiated (exposed)
through a mask pattern with pattern light using an ArF excimer
laser (wavelength: 193 nm) by means of an exposure system NSR-S302B
(manufactured by Nikon Corporation, NA (numerical aperture)=0.60,
.sigma.=0.75). Then, in a liquid immersion lithography, while
rotating the silicon wafer having the resist film exposed, pure
water at 23.degree. C. was allowed to fall dropwise against the
resist film for 5 minutes. This step corresponds to the step in the
practical production process in which the resist film completely
immersed in the liquid is exposed. However, the step has a
simplified construction such that pure water as a refractive index
liquid (immersion liquid) is applied to the resist film after the
exposure in order to achieve an evaluation of only the effect of
the immersion liquid on the resist film which is previously
exposed. This is because based on the above-stated analysis on the
liquid immersion lithography method, completion of the exposure in
the optics is theoretically guaranteed.
[0160] After the step of allowing pure water to fall dropwise, the
resultant resist film was subjected to PEB treatment under
conditions at 115.degree. C. for 90 seconds, and then the
protective film was removed using
perfluoro(2-butyltetra-hydrofuran). Then, the resist film was
developed using an alkaline developer solution at 23.degree. C. for
60 seconds. As the alkaline developer solution, a 2.38% by mass
aqueous solution of tetramethylammonium hydroxide was used.
[0161] The thus obtained resist pattern having a 130 nm line and
space of 1:1 was examined under a scanning electron microscope
(SEM). As a result, the pattern profile was found to be excellent
such that no fluctuation was observed.
Example 2
[0162] An antireflection coating film, an ArF positive resist, and
a protective film were formed on a substrate in accordance with the
same procedure as that in Example 1.
[0163] Using laboratory equipment prepared by Nikon Corporation
using a prism and a liquid and two-beam interferometry exposure at
a wavelength of 193 nm, the substrate having the protective film
formed thereon was subjected to immersion lithography (the bottom
surface of the prism was in contact with the protective film
through water).
[0164] The resultant substrate was subjected to PEB treatment in
the same manner as that in Example 1, and the protective film was
removed using perfluoro(2-butyltetrahydrofuran). Then, the resist
film was developed under the same conditions as those used in
Example 1.
[0165] The thus obtained resist pattern having a 65 nm line and
space of 1:1 was examined under a scanning electron microscope
(SEM). As a result, the pattern profile was found to be excellent
such that no fluctuation was observed. Further, the pattern
obtained was examined for a cross-sectional form under a focused
ion beam SEM (Altura 835; manufactured by FEI). As a result, it was
found that the cross-sectional form had excellent squareness.
Comparative Example 1
[0166] A resist pattern was formed in accordance with substantially
the same procedure as that in Example 2 except that no protective
film was formed.
[0167] As a result, although no change in the sensitivity was
found, slight fluctuation (partial narrowing of lines) was observed
in the pattern profile. Further, the pattern obtained was examined
for a cross-sectional form under a focused ion beam SEM (Altura
835; manufactured by FEI). As a result, a slight T-top form was
observed.
Comparative Example 2
[0168] The resin component, acid generator, and nitrogen-containing
organic compound shown below were uniformly dissolved in an organic
solvent to prepare positive resist composition 2.
[0169] As the resin component, 100 parts by mass of a polymer
comprising constitutional units represented by the chemical formula
(40) below was used. The resin component prepared had a mass
average molecular weight of 10,000. ##STR18##
[0170] As the acid generator, 3.5 parts by mass of
triphenylsulfonium nonafluorobutanesulfonate and 1.0 part by mass
of (4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate were
used.
[0171] As the organic solvent, 1,900 parts by mass of a mixed
solvent of propylene glycol monomethyl ether acetate and ethyl
lactate (mass ratio: 6:4) was used.
[0172] Further, as the nitrogen-containing organic compound, 0.3
part by mass of triethanolamine was used.
[0173] Using the above-prepared positive resist composition 2, a
resist pattern was formed.
[0174] An organic antireflection coating composition "AR-19" (trade
name; manufactured by Shipley Limited) was first applied onto a
silicon wafer using a spinner, and dried by calcination on a hot
plate at 215.degree. C. for 60 seconds to form an organic
antireflection coating film having a thickness of 82 nm. Then,
positive resist composition 1 was applied onto the antireflection
coating film using a spinner, and dried by prebake on a hot plate
at 115.degree. C. for 90 seconds to form a resist film having a
thickness of 150 nm on the antireflection coating film.
[0175] Subsequently, the resist film was irradiated (exposed)
through a mask pattern with pattern light using an ArF excimer
laser (wavelength: 193 nm) by means of an exposure system NSR-S302B
(manufactured by Nikon Corporation, NA (numerical aperture)=0.60,
.sigma.=0.75). Then, in a liquid immersion lithography, while
rotating the silicon wafer having the resist film exposed, pure
water at 23.degree. C. was allowed to fall dropwise against the
resist film for 5 minutes. This step corresponds to the step in the
practical production process in which the resist film completely
immersed in the liquid is exposed. However, the step has a
simplified construction such that pure water as a refractive index
liquid (immersion liquid) is applied to the resist film after the
exposure in order to achieve an evaluation of only the effect of
the immersion liquid on the resist film which is previously
exposed. This is because based on the above-stated analysis on the
liquid immersion lithography method, completion of the exposure in
the optics is theoretically guaranteed.
[0176] Subsequently, the resultant resist film was subjected to PEB
treatment under conditions at 115.degree. C. for 90 seconds, and
developed using an alkaline developer solution at 23.degree. C. for
60 seconds. As the alkaline developer solution, a 2.38% by mass
aqueous solution of tetramethylammonium hydroxide was used.
[0177] The thus obtained resist pattern having a 130 nm line and
space of 1:1 was examined under a scanning electron microscope
(SEM), and a sensitivity (Eth) was determined. As a result, it was
found that the sensitivity measured was 9.1 mJ/cm.sup.2 and the
lowering of the sensitivity was considerable as seen from the
comparisons made below.
[0178] Separately, using resist composition 2 in the present
Comparative Example 2, a resist pattern was formed by exposure
through a layer of air by the method conventionally used without
employing the liquid immersion lithography treatment. As a result,
the sensitivity was found to be 8.4 mJ/cm.sup.2. A ratio of the
sensitivity in the liquid immersion lithography treatment to the
sensitivity in the normal exposure (9.1/8.4) was determined to be
108.3.
Comparative Example 3
[0179] The resin component, acid generator, and nitrogen-containing
organic compound shown below were uniformly dissolved in an organic
solvent to prepare positive resist composition 3.
[0180] As the resin component, 100 parts by mass of a copolymer
comprising constitutional units comprising 63 mol % of
hydroxystyrene units, 24 mol % of styrene units, and 13 mol % of
tert-butyl acrylate units was used. The resin component prepared
had a mass average molecular weight of 12,000.
[0181] As the acid generator, 2.8 parts by mass of
bis(tert-butylphenyliodonium trifluoromethanesulfonate and 1.0 part
by mass of dimethylmonophenylsulfonium trifluoromethanesulfonate
were used.
[0182] As the organic solvent, 600 parts by mass of ethyl lactate
was used.
[0183] As the nitrogen-containing organic compound, 0.26 part by
mass of triethanolamine was used, and 0.28 part by mass of
phenylphosphonic acid was used as another component.
[0184] Using the above-prepared positive resist composition 3, a
resist pattern was formed.
[0185] An organic antireflection coating composition "AR-3" (trade
name; manufactured by Shipley Limited) was first applied onto a
silicon wafer using a spinner, and dried by calcination on a hot
plate at 220.degree. C. for 60 seconds to form an organic
antireflection coating film having a thickness of 62 nm. Then,
positive resist composition 3 was applied onto the antireflection
coating film using a spinner, and dried by prebake on a hot plate
at 110.degree. C. for 90 seconds to form a resist film having a
thickness of 280 nm on the antireflection coating film.
[0186] Subsequently, the resist film was irradiated (exposed)
through a mask pattern with pattern light using a KrF excimer laser
(wavelength: 248 nm) by means of an exposure system NSR-S203
(manufactured by Nikon Corporation, NA (numerical aperture)=0.60,
.sigma.=0.75). Then, in a liquid immersion lithography, while
rotating the silicon-wafer having the resist film exposed, pure
water at 23.degree. C. was allowed to fall dropwise against the
resist film for 5 minutes. This step corresponds to the step in the
practical production process in which the resist film completely
immersed in the liquid is exposed. However, the step has a
simplified construction such that pure water as a refractive index
liquid (immersion liquid) is applied to the resist film after the
exposure in order to achieve an evaluation of only the effect of
the immersion liquid on the resist film which is previously
exposed. This is because based on the above-stated analysis on the
liquid immersion lithography method, completion of the exposure in
the optics is theoretically guaranteed.
[0187] Subsequently, the resultant resist film was subjected to PEB
treatment under conditions at 115.degree. C. for 90 seconds, and
developed using an alkaline developer solution at 23.degree. C. for
60 seconds. As the alkaline developer solution, a 2.38% by mass
aqueous solution of tetramethylammonium hydroxide was used.
[0188] Thus obtained resist pattern having a 140 nm line and space
of 1:1 was examined under a scanning electron microscope (SEM), and
sensitivity (Eth) at that time was determined. As a result, it was
found that the sensitivity was 22.0 mJ/cm.sup.2. The resist pattern
had a T-top form and surface roughening was observed.
[0189] Separately, using resist composition 3 in the present
Comparative Example, a resist pattern was formed by exposure
through a layer of air by the method conventionally used without
employing the liquid immersion lithography treatment, and the
sensitivity was found to be 20.0 mJ/cm.sup.2. A ratio of the
sensitivity in the liquid immersion lithography treatment to the
sensitivity in the normal exposure (22.0/20.0) was determined to be
108.8. The resist pattern was excellent such that no surface
roughening was observed.
Comparative Example 4
[0190] The resin component, acid generator, and nitrogen-containing
organic compound shown below were uniformly dissolved in an organic
solvent to prepare positive resist composition 4.
[0191] As the resin component, a mixed resin of 70 parts by mass of
a copolymer comprising constitutional units comprising 64 mol % of
hydroxystyrene units and 36 mol % of 1-ethoxy-1-ethyloxystyrene
units and 30 parts by mass of a copolymer comprising constitutional
units comprising 67 mol % of hydroxystyrene units and 33 mol % of
tetrahydropyranyloxystyrene units was used. The resin components
prepared independently had a mass average molecular weight of
8,000.
[0192] As the acid generator, 4 parts by mass of
bis(cyclohexylsulfonyl)diazomethane and 1 part by mass of
tert-butylphenyliodonium trifluoromethanesulfonate were used.
[0193] As the organic solvent, 600 parts by mass of a mixed solvent
of propylene glycol monomethyl ether acetate and ethyl lactate
(mass ratio: 6:4) was used.
[0194] As the nitrogen-containing organic compound, 0.52 part by
mass of triisopropanolamine was used, and 0.54 part by mass of
dodecanoic acid was used as another component.
[0195] Using the above-prepared positive resist composition 4, a
resist pattern was formed.
[0196] An organic antireflection coating composition "DUV-44"
(trade name; manufactured by Brewer Science) was first applied onto
a silicon wafer using a spinner, and dried by calcination on a hot
plate at 225.degree. C. for 90 seconds to form an organic
antireflection coating film having a thickness of 65 nm. Then,
positive resist composition 4 was applied onto the antireflection
coating film using a spinner, and dried by prebake on a hot plate
at 90.degree. C. for 90 seconds to form a resist film having a
thickness of 280 nm on the antireflection coating film.
[0197] Subsequently, the resist film was irradiated (exposed)
through a mask pattern with pattern light using a KrF excimer laser
(wavelength: 248 nm) by means of an exposure system NSR-S203
(manufactured by Nikon Corporation, NA (numerical aperture)=060,
(=0.75). Then, in a liquid immersion lithography, while rotating
the silicon wafer having the resist film exposed, pure water at
23.degree. C. was allowed to fall dropwise against the resist film
for 5 minutes. This step corresponds to the step in the practical
production process in which the resist film completely immersed in
the liquid is exposed. However, the step has a simplified
construction such that pure water as a refractive index liquid
(immersion liquid) is applied to the resist film after the exposure
in order to achieve an evaluation of only the effect of the
immersion liquid on the resist film which is previously exposed.
This is because based on the above-stated analysis on the liquid
immersion lithography method, completion of the exposure in the
optics is theoretically guaranteed.
[0198] Next, the resultant resist film was subjected to PEB
treatment under conditions at 110.degree. C. for 90 seconds, and
developed using an alkaline developer solution at 23.degree. C. for
60 seconds. As the alkaline developer solution, a 2.38% by mass
aqueous solution of tetramethylammonium hydroxide was used.
[0199] The thus obtained resist pattern having a 140 nm line and
space of 1:1 was examined under a scanning electron microscope
(SEM), and sensitivity (Eth) at that time was determined. As a
result, it was found that the sensitivity was 26.5 mJ/cm.sup.2. The
resist pattern had a.T-top form and surface roughening was
observed.
[0200] Separately, using resist composition 4 in the present
Comparative Example, a resist pattern-was formed by exposure
through a layer of air by the method conventionally used without
employing the liquid immersion lithography treatment, and the
sensitivity was found to be 16.5 mJ/cm.sup.2. A ratio of the
sensitivity in the liquid immersion lithography treatment to the
sensitivity in the normal exposure (26.5/16.5) was determined to be
156.6. The resist pattern was excellent such that no surface
roughening was observed.
[0201] Examples 1 and 2 indicate that, in the liquid immersion
lithography in which a protective film is formed, a pattern of 130
nm line and space having excellent profile can be obtained without
lowering the properties required for pattern formation, e.g.,
sensitivity. In addition, it is apparent that the resist film used
in the Examples, which is a positive resist film, can be applied to
a negative resist film.
Example 3
[0202] The resin component, acid generator, and nitrogen-containing
organic compound shown below were uniformly dissolved in an organic
solvent to prepare a positive resist.
[0203] As the resin component, 100 parts by mass of a polymer
comprising constitutional units indicated by the above formula
(40). The resin component prepared had a mass average molecular
weight of 10,000.
[0204] As the acid generator, 3.5 parts by mass of
triphenylsulfonium nonafluorobutanesulfonate and 1.0 part by mass
of (4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate were
used.
[0205] As the organic solvent, 1,900 parts by mass of a mixed
solvent of propylene glycol monomethyl ether acetate and ethyl
lactate (mass ratio: 6:4) was used.
[0206] As the nitrogen-containing organic compound, 0.3 part by
mass of triethanolamine was used.
[0207] An antireflection coating film, an ArF positive resist, and
a protective film were formed on a substrate in accordance with
substantially the same procedure as in Example 1 except that the
above-prepared positive resist composition was used (the thickness
of the resist film was changed to 140 nm).
[0208] The substrate having the protective film formed thereon was
subjected to immersion lithography in the same manner as in Example
2.
[0209] The protective film was removed from the resist film under
the same conditions as those used in Example 1, and the resist film
was subjected to PEB treatment, followed by development.
[0210] The thus obtained resist pattern having a 90 nm line and
space of 1:1 was examined under a scanning electron microscope
(SEM), and, as a result, the pattern profile was found to be
excellent such that no fluctuation (pattern narrowing) was
observed.
Comparative Example 5
[0211] A resist pattern having a 90 nm line and space of 1:1 was
formed in accordance with entirely the same procedure as in Example
3 except that the positive photoresist shown in Example 3 was used
and that no protective film was formed, and it was examined under a
scanning electron microscope (SEM), but the fluctuation and
swelling of the pattern were too large to observe the pattern.
Example 4
[0212] The resin component, acid generator, and nitrogen-containing
organic compound shown below were uniformly dissolved in an organic
solvent to prepare a positive resist composition.
[0213] As the resin component, a polymer comprising constitutional
units represented by the general formulae (41) and (42) below (85
parts by mass of the units of formula (41) and 15 parts by mass of
the units of formula (42)) was used. The resin component had a mass
average molecular weight of 10,000.
[0214] As the acid generator, 3.0 parts by mass of
triphenylsulfonium nonafluorobutanesulfonate was used.
[0215] As the organic solvent, 1,900 parts by mass of a mixed
solvent of propylene glycol monomethyl ether acetate and ethyl
lactate (mass ratio: 6:4) was used.
[0216] As the nitrogen-containing organic compound, 0.25 part by
mass of triethanolamine was used. ##STR19## wherein, in formula
(42), j=50 mol %, k=30 mol %, and 1=20 mol %.
[0217] An antireflection coating film, an ArF positive resist, and
a protective film were formed on a substrate in accordance with the
same procedure as in Example 1 except that the above-prepared
positive resist composition was used (the thickness of the resist
film was changed to 140 nm).
[0218] The substrate having the protective film formed thereon was
subjected to immersion lithography in the same manner as in Example
2.
[0219] The protective film was removed from the resist film under
the same conditions as those used in Example 1, and the resist film
was subjected to PEB treatment, followed by development.
[0220] The thus obtained resist pattern having a 90 nm line and
space of 1:1 was examined under a scanning electron microscope
(SEM), and, as a result, the pattern profile was found to be
excellent such that no fluctuation (pattern narrowing) was
observed.
Comparative Example 6
[0221] A resist pattern having a 90 nm line and space of 1:1 was
formed in accordance with entirely the same procedure as in Example
4 except that the positive photoresist shown in Example 3 was used
and that no protective film was formed, and it was examined under a
scanning electron microscope (SEM), but the fluctuation and
swelling of the pattern occurred slightly.
Example 5
[0222] The resin component, acid generator, and nitrogen-containing
organic compound shown below were uniformly dissolved in an organic
solvent to prepare a negative resist composition.
[0223] As the resin component, a polymer comprising constitutional
units represented by the general formula (43) was used.
[0224] Based on the mass of the resin component, 10% by mass of a
cross-linking agent comprised of tetrabutoxymethylated glycoluril,
1% by mass of an acid generator comprised of triphenylsulfonium
nonafluorobutanesulfonate, and 0.6% by mass of an amine component
comprised of 4-phenylpyridine were dissolved in propylene glycol
monomethyl ether, and the resultant negative resist material having
a solids content of 8.1% by mass was used. ##STR20## wherein m:n is
84:16 (mol %).
[0225] Using the above-prepared negative resist composition, a
resist pattern was formed.
[0226] An organic antireflection coating composition "AR-19" (trade
name; manufactured by Shipley Limited) was first applied onto a
silicon wafer using a spinner, and dried by calcination on a hot
plate at 215.degree. C. for 60 seconds to form an organic
antireflection coating film having a thickness of 32 nm. Then, the
negative resist composition was applied onto the antireflection
coating film using a spinner, and dried by prebake on a hot plate
at 110.degree. C. for 60 seconds to form a resist film having a
thickness of 300 nm on the antireflection coating film.
[0227] A protective film material, which was obtained by dissolving
a mixed resin comprised of DEMNUM S-10 (manufactured by DAIKIN
INDUSTRIES, Ltd.) and CYTOP (manufactured by ASAHI GLASS CO.,
LTD.)(weight ratio=1:5) in perfluorotributylamine to have the resin
concentration 2.5 wt %, was applied onto the resist film by spin
coating, and heated at 90.degree. C. for 60 seconds to form a
protective film having a thickness of 37 nm.
[0228] The substrate having the protective film formed thereon was
subjected to exposure in the same manner as in Example 1, and then
water was allowed to fall dropwise against the resist film (the
treatment of allowing water to fall dropwise was continued for 2
minutes).
[0229] The protective film was removed from the resist film under
the same conditions as those used in Example 1, and the resist film
was subjected to PEB treatment, followed by development.
[0230] The thus obtained resist pattern having a 160 nm line and
space of 1:1 was examined under a scanning electron microscope
(SEM), and, as a result, the pattern profile was found to be
excellent such that no fluctuation (pattern narrowing) and swelling
were observed at all.
Comparative Example 7
[0231] A resist pattern having a 160 nm line and space of 1:1 was
formed in accordance with entirely the same procedure as in Example
4 except that the negative photoresist shown in Example 5 was used
and that no protective film was formed, and it was examined under a
scanning electron microscope (SEM), but the fluctuation and
swelling of the pattern occurred slightly.
[0232] In the descriptions in the present invention, the following
wording and different terms: "liquid having a refractive index
larger than that of air and smaller than that of the resist film";
liquid refractive index medium; refractive index liquid; and
immersion liquid, which were used for convenience of explanation,
designate the same medium.
Example 6
[0233] The resin component, acid generator, and nitrogen-containing
organic compound shown below were uniformly dissolved in an organic
solvent to prepare a positive resist composition.
[0234] As the resin component, 100 parts by mass of a methacrylate
copolymer comprising three types of constitutional units
represented by the general formula (44) below was used. In the
constitutional units used in the preparation of the resin
component, s, t, and u are as follows: s=40 mol %, t=40 mol %, and
u=20 mol %. The resin component prepared had a mass average
molecular weight of 10,000. ##STR21##
[0235] As the acid generator, 0.8 part by mass of
tri-(4-tert-butylphenyl)sulfonium trifluoromethanesulfonate and 2.0
parts by mass of (4-methylphenyl)diphenylsulfonium
nonafluorobutanesulfonate were used.
[0236] As the organic solvent, a mixed solvent of 1,520 parts by
mass of a mixed solvent of propylene glycol monomethyl ether
acetate and ethyl lactate (mass ratio: 6:4) and 380 parts by mass
of .gamma.-butyrolactone was used.
[0237] As the nitrogen-containing organic compound, 0.25 part by
mass of triethanolamine was used.
[0238] Using the above-prepared positive resist composition, a
resist pattern was formed.
[0239] An organic antireflection coating composition "AR-19" (trade
name; manufactured by Shipley Limited) was first applied onto a
silicon wafer using a spinner, and dried by calcination on a hot
plate at 215.degree. C. for 60 seconds to form an organic
antireflection coating film having a thickness of 82 nm. Then, the
positive resist composition was applied onto the antireflection
coating film using a spinner, and dried by prebake on a hot plate
at 130.degree. C. for 90 seconds to form a resist film having a
thickness of 200 nm on the antireflection coating film.
[0240] A protective film material, which was obtained by dissolving
a mixed resin comprised of DEMNUM S-20 (manufactured by DAIKIN
INDUSTRIES, Ltd.) and CYTOP (manufactured by ASAHI GLASS CO.,
LTD.)(weight ratio=1:5) in perfluorotributylamine to have the resin
concentration 2.5 wt %, was applied onto the resist film by spin
coating, and heated at 90.degree. C. for 60 seconds to form a
protective film having a thickness of 37 nm.
[0241] Subsequently, the resist film was irradiated (exposed)
through a mask pattern with pattern light using an ArF excimer
laser (wavelength: 193 nm) by means of an exposure system NSR-S302B
(manufactured by Nikon Corporation, NA (numerical aperture)=0.60,
2/3 annular illumination). Then, in a liquid immersion lithography,
while rotating the silicon wafer having the resist film exposed,
pure water at 23.degree. C. was allowed to fall dropwise against
the resist film for 2 minutes. This step corresponds to the step in
the practical production process in which the resist film
completely immersed in the liquid is exposed. However, the step has
a simplified construction such that pure water as a refractive
index liquid (immersion liquid) is applied to the resist film after
the exposure in order to achieve an evaluation of only the effect
of the immersion liquid on the resist film which is previously
exposed. This is because based on the above-stated analysis on the
liquid immersion lithography method, completion of the exposure in
the optics is theoretically guaranteed.
[0242] After the step of allowing pure water to fall dropwise, the
resultant resist film was subjected to PEB treatment under
conditions at 130.degree. C. for 90 seconds, and then the
protective film was removed using
perfluoro(2-butyltetra-hydrofuran). Then, the resist film was
developed using an alkaline developer solution at 23.degree. C. for
60 seconds. As the alkaline developer solution, a 2.38% by mass
aqueous solution of tetramethylammonium hydroxide was used.
[0243] Thus obtained resist pattern having a 130 nm line and space
of 1:1 was examined under a scanning electron microscope (SEM),
and, as a result, the pattern profile was found to be excellent
such that no fluctuation was observed at all.
[0244] The sensitivity was 17.0 mJ/cm.sup.2, and the depth of focus
was 1.0 .mu.m. An exposure margin in which a 130 nm line pattern
was obtained within .+-.10% was as excellent as 13.15%.
Example 7
[0245] The resin component, acid generator, and nitrogen-containing
organic compound shown below were uniformly dissolved in an organic
solvent to prepare a positive resist composition.
[0246] As the resin component, a polymer comprising constitutional
units represented by the general formulae (41) and (45) below (85
parts by mass of the units of formula (41) and 15 parts by mass of
the units of formula (45)) was used. The resin component had a mass
average molecular weight of 10,000.
[0247] As the acid generator, 2.4 parts by mass of
triphenylsulfonium nonafluorobutanesulfonate was used.
[0248] As the organic solvent, 1,900 parts by mass of a mixed
solvent of propylene glycol monomethyl ether acetate and ethyl
lactate (mass ratio: 6:4) was used.
[0249] As the nitrogen-containing organic compound, 0.27 part by
mass of triethanolamine was used. As the organic carboxylic acid,
0.26 part by mass of salicylic acid was used. ##STR22## wherein
x=40 mol %, y=40 mol %, and z=20 mol %.
[0250] An antireflection coating film, a positive resist using the
resist composition, and a protective film were formed on a
substrate in accordance with substantially the same procedure as in
Example 1 (except that the thickness of the resist film was changed
to 150 nm, that the prebake conditions were changed to those at
95.degree. C. for 90 seconds, and that the PEB conditions were
changed to those at 90.degree. C. for 90 seconds).
[0251] The substrate having the protective film formed thereon was
subjected to immersion lithography in the same manner as in Example
2.
[0252] The resist film was subjected to PEB treatment, and then the
protective film was removed under the same conditions as those used
in Example 1, and allowed to stand in a place having an amine
concentration of about 5 ppb in air for 180 seconds, followed by
development.
[0253] Thus obtained resist pattern having a 130 nm line and space
of 1:1 was examined under a scanning electron microscope (SEM),
and, as a result, the pattern profile was found to be excellent
such that no fluctuation (pattern narrowing) was observed. The
sensitivity was 26.0 mJ/cm.sup.2.
Comparative Example 8
[0254] The resist composition prepared in Example 7 was allowed to
stand for 180 seconds in the same manner as in Example 7, and then
a resist pattern was formed in substantially the same manner as in
Example 7 except that no protective film was used.
[0255] The resist pattern having a 130 nm line and space of 1:1 was
examined under a scanning electron microscope (SEM), and, as a
result, the pattern profile was found to have a T-TOP form. The
sensitivity was 33.0 mJ/cm.sup.2.
[0256] The reason for this resides in that no protective film was
used and hence amine contained in air deactivated acid on the
resist film.
[0257] As can be seen from the results of Example 7 and Comparative
Example 8, the use of the protective film can prevent the resist
film from being adversely affected by the amine contained in air.
That is, the post exposure delay is drastically improved.
Example 8
[0258] As component (A), a mixed resin of 85 parts by mass of a
silsesquioxane resin of the chemical formula (46) below and 15
parts by mass of a methacrylate-acrylate copolymer comprising three
types of constitutional units represented by the chemical formula
(47) below was used. In the constitutional units in the copolymer
of the chemical formula (47), v, w, and x are as follows: v=40 mol
%, w=40 mol %, and x=20 mol %, and the copolymer had a mass average
molecular weight of 10,000. ##STR23##
[0259] As component (B), 2.4 parts by mass of triphenylsulfonium
nonafluorobutanesulfonate was used.
[0260] As component (C), 1,900 parts by mass of a mixed solvent of
ethyl lactate and .gamma.-butyrolactone (mass ratio: 8:2) was
used.
[0261] As component (D), 0.27 part by mass of triethanolamine was
used.
[0262] As component (E), 0.26 part by mass of salicylic acid was
used.
[0263] Next, an organic antireflection coating composition "AR-19"
(trade name; manufactured by Shipley Limited) was applied onto a
silicon wafer using a spinner, and dried by calcination on a hot
plate at 215.degree. C. for 60 seconds to form an organic
antireflection coating film having a thickness of 82 nm. The
positive resist composition was applied onto the antireflection
coating film using a spinner, and dried by prebake on a hot plate
at 95.degree. C. for 90 seconds to form a resist layer having a
thickness of 150 nm on the antireflection coating film. Then, the
resist film was spin-coated with a fluorine protective film
material having a resin concentration of 2.5 wt %, which was
prepared by dissolving a mixed resin of DEMNUM S-10 (manufactured
by DAIKIN INDUSTRIES, Ltd.) and CYTOP (manufactured by ASAHI GLASS
CO., LTD.)(weight ratio=1:5) in perfluorotributylamine, and heated
at 90.degree. C. for 60 seconds to form a protective film having a
thickness of 37 nm.
[0264] Then, in the evaluation test 2, using laboratory equipment
prepared by Nikon Corporation, the resultant resist film was
subjected to immersion lithography by 193-nm two-beam
interferometry using a prism and water (two-beam interferometry
experiment). A similar method is disclosed in the document 2 (J.
Vac. Sci. Technol. B(2001) 19(6), p2353-2356) above, which is known
as a method by which a L&S pattern can be easily obtained in a
laboratory scale.
[0265] In the immersion lithography in Example 8, a solvent layer
of water as an immersion solvent was formed between the top surface
of the protective film and the bottom surface of the prism.
[0266] The exposure energy was selected so that the L&S pattern
was constantly obtained. Subsequently, the resist film was
subjected to PEB treatment under conditions at 90.degree. C. for 90
seconds, and the protective film was removed using
perfluoro(2-butyltetrahydrofuran). Then, the resist film was
developed in the same manner as in Example 1 to obtain a 65 nm line
and space (1:1). The pattern form obtained had high squareness.
[0267] As described above, in the present invention, even when a
resist film is formed using any resist composition commonly used, a
resist pattern with high resolution can be obtained by a liquid
immersion lithography process wherein the resist pattern is
advantageous not only in that the resist pattern does not suffer
surface roughening, e.g., T-top form and has high sensitivity and
excellent resist pattern profile form, but also in that the resist
pattern has excellent depth of focus and excellent exposure margin
as well as excellent post exposure delay. Therefore, the use of the
protective film according to the present invention makes it
possible to effectively form a resist pattern using the liquid
immersion lithography process.
REFERENCES
[0268] 1. Journal of Vacuum Science & Technology B (J. Vac.
Sci. Technol. B) (Published in the United States) 1999, Vol. 17,
6th edition, pp.3306-3309 [0269] 2. Journal of Vacuum Science &
Technology B (J. Vac. Sci. Technol. B) (Published in the United
States) 2001, Vol. 19, 6th edition, pp.2353-2356 [0270] 3.
Proceedings of SPIE Vol. 4691 (Published in the United States)
2002, Vol. 4691, pp.459-465
* * * * *