U.S. patent application number 14/978672 was filed with the patent office on 2017-06-08 for upper layer-forming composition and resist patterning method.
This patent application is currently assigned to JSR Corporation. The applicant listed for this patent is JSR Corporation. Invention is credited to Takahiro Hayama, Kazunori Kusabiraki, Ken Maruyama, Yukio Nishimura, Kiyoshi Tanaka.
Application Number | 20170160637 14/978672 |
Document ID | / |
Family ID | 44991757 |
Filed Date | 2017-06-08 |
United States Patent
Application |
20170160637 |
Kind Code |
A9 |
Hayama; Takahiro ; et
al. |
June 8, 2017 |
UPPER LAYER-FORMING COMPOSITION AND RESIST PATTERNING METHOD
Abstract
A liquid immersion lithography upper-layer film-forming
composition includes (A) a polymer that includes a structural unit
(I) shown by the following formula (1), and (S) a solvent. R.sup.1
in the formula (1) represents a hydrogen atom, a methyl group, or a
trifluoromethyl group. The polymer (A) preferably further includes
a structural unit (II) that includes a sulfo group. The polymer (A)
preferably further includes a structural unit (III) shown by the
following formula (3). R.sup.2 in the formula (3) represents a
hydrogen atom, a methyl group, or a trifluoromethyl group. R.sup.3
represents a linear or branched monovalent hydrocarbon group having
1 to 12 carbon atoms or a monovalent alicyclic group having 3 to 20
carbon atoms, provided that at least one hydrogen atom of the
hydrocarbon group or the alicyclic group is substituted with a
fluorine atom. ##STR00001##
Inventors: |
Hayama; Takahiro; (Tokyo,
JP) ; Kusabiraki; Kazunori; (Tokyo, JP) ;
Nishimura; Yukio; (Tokyo, JP) ; Maruyama; Ken;
(Tokyo, JP) ; Tanaka; Kiyoshi; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JSR Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
JSR Corporation
Tokyo
JP
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20160109801 A1 |
April 21, 2016 |
|
|
Family ID: |
44991757 |
Appl. No.: |
14/978672 |
Filed: |
December 22, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13110855 |
May 18, 2011 |
9261789 |
|
|
14978672 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08F 220/24 20130101;
G03F 7/0046 20130101; C08F 220/18 20130101; C08F 228/02 20130101;
G03F 7/2041 20130101; G03F 7/0397 20130101; C08F 220/30 20130101;
G03F 7/11 20130101 |
International
Class: |
G03F 7/11 20060101
G03F007/11; G03F 7/20 20060101 G03F007/20 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2010 |
JP |
2010-114802 |
Aug 7, 2010 |
JP |
2010-178223 |
Claims
1-7. (canceled)
8. A photoresist pattern-forming method comprising: applying a
photoresist composition to a substrate to form a photoresist film;
applying a composition to the photoresist film to form a liquid
immersion lithography upper-layer film, the composition comprising:
(A) a polymer that comprises a structural unit (I) shown by a
formula (1); and (S) a solvent, ##STR00014## wherein R.sup.1
represents a hydrogen atom, a methyl group, or a trifluoromethyl
group; exposing the photoresist film and the liquid immersion
lithography upper-layer film via an immersion medium and a mask
having a given pattern, the immersion medium being disposed between
the liquid immersion lithography upper-layer film and a lens; and
developing the photoresist film and the liquid immersion
lithography upper-layer film that have been exposed.
9. The photoresist pattern-forming method according to claim 8,
wherein the polymer (A) further includes a structural unit (IV)
shown by formula (4), ##STR00015## wherein R.sup.4 represents a
hydrogen atom, a methyl group, or a trifluoromethyl group, and
R.sup.5 represents a linear or branched monovalent hydrocarbon
group having 1 to 12 carbon atoms or a monovalent alicyclic group
having 3 to 20 carbon atoms.
10. The photoresist pattern-forming method according to claim 9,
wherein the polymer (A) further comprises a structural unit (III)
shown by formula (3), ##STR00016## wherein R.sup.2 represents a
hydrogen atom, a methyl group, or a trifluoromethyl group, and
R.sup.3 represents a linear or branched monovalent hydrocarbon
group having 1 to 12 carbon atoms or a monovalent alicyclic group
having 3 to 20 carbon atoms, provided that at least one hydrogen
atom of the hydrocarbon group or the alicyclic group is substituted
with a fluorine atom.
11. The photoresist pattern-forming method according to claim 8,
wherein the composition further comprises (B) a polymer that
includes the structural unit (I) and a structural unit (III) shown
by formula (3), and has a fluorine atom content higher than that of
the polymer (A), ##STR00017## wherein R.sup.2 represents a hydrogen
atom, a methyl group, or a trifluoromethyl group, and R.sup.3
represents a linear or branched monovalent hydrocarbon group having
1 to 12 carbon atoms or a monovalent alicyclic group having 3 to 20
carbon atoms, provided that at least one hydrogen atom of the
hydrocarbon group or the alicyclic group is substituted with a
fluorine atom.
12. The photoresist pattern-forming method according to claim 9,
wherein the composition further comprises (B) a polymer that
includes the structural unit (I) and a structural unit (III) shown
by formula (3), and has a fluorine atom content higher than that of
the polymer (A), ##STR00018## wherein R.sup.2 represents a hydrogen
atom, a methyl group, or a trifluoromethyl group, and R.sup.3
represents a linear or branched monovalent hydrocarbon group having
1 to 12 carbon atoms or a monovalent alicyclic group having 3 to 20
carbon atoms, provided that at least one hydrogen atom of the
hydrocarbon group or the alicyclic group is substituted with a
fluorine atom.
13. The photoresist pattern-forming method according to claim 8,
wherein a content of the structural unit (I) in the polymer (A) is
20 to 99 mol % based on a total of structural units included in the
polymer (A).
14. The photoresist pattern-forming method according to claim 9,
wherein a content of the structural unit (IV) in the polymer (A) is
5 to 55 mol % based on a total of structural units included in the
polymer (A).
15. The photoresist pattern-forming method according to claim 10,
wherein a content of the structural unit (III) in the polymer (A)
is 5 to 70 mol % based on a total of structural units included in
the polymer (A).
16. The photoresist pattern-forming method according to claim 8,
wherein the polymer (A) further comprises a structural unit (V)
which is shown by formula (5-1) or formula (5-2), ##STR00019##
wherein R.sup.10 and R.sup.11 each represent a hydrogen atom, a
methyl group, or a trifluoromethyl group, R.sup.12 represents a
single bond, a linear or branched alkanediyl group having 1 to 6
carbon atoms which is other than a 1,2-ethylene group, or a
divalent alicyclic group having 4 to 12 carbon atoms, R.sup.13
represents a single bond, a linear or branched alkanediyl group
having 1 to 6 carbon atoms, or a divalent alicyclic group having 4
to 12 carbon atoms, and R.sup.14 represents a linear or branched
hydrocarbon group having 1 to 10 carbon atoms or a monovalent
alicyclic group having 3 to 10 carbon atoms, provided that at least
one hydrogen atom of the hydrocarbon group or the alicyclic group
represented by R.sup.14 is substituted with a fluorine atom.
17. The photoresist pattern-forming method according to claim 8,
wherein a content of the polymer (A) in the composition is 20 mass
% or more based on a total of polymers included in the
composition.
18. The photoresist pattern-forming method according to claim 8,
wherein a content of the polymer (A) in the composition is 40 mass
% or more based on a total of polymers included in the
composition.
19. The photoresist pattern-forming method according to claim 8,
wherein a content of the polymer (A) in the composition is 60 mass
% or more based on a total of polymers included in the composition.
Description
TECHNICAL FIELD
[0001] The invention relates to a liquid immersion lithography
upper-layer film-forming composition and a photoresist
pattern-forming method.
BACKGROUND ART
[0002] A semiconductor device production process or the like
utilizes a stepping or step-and-scan projection aligner that
transfers the pattern of a reticle (photomask) to each shot area of
a wafer via a projection optical system, a photoresist film being
formed on the wafer. The resolution of the projection optical
system included in the projection aligner increases as the exposure
wavelength decreases and the numerical aperture of the projection
optical system increases. Therefore, a shorter exposure wavelength
has been used for the projection aligner along with miniaturization
of integrated circuits, and the numerical aperture of the
projection optical system has been increased.
[0003] The depth of focus is also important for exposure. The
resolution R and the depth of focus .delta. are defined by the
following expressions. The depth of focus .delta. increases while
obtaining an identical resolution R when using radiation having a
shorter wavelength.
R=k1.lamda./NA
.delta.=k2.lamda./NA.sup.2
where, .lamda. is the exposure wavelength, NA is the numerical
aperture of the projection optical system, and k1 and k2 are
process coefficients.
[0004] A projection aligner has been normally designed so that the
wafer placement space is filled with air or nitrogen. The
resolution R and the depth of focus 6 are shown by the following
expressions when the space between the wafer and the lens of the
projection aligner is filled with a medium having a refractive
index of n.
R=k1(.lamda./n)/NA
.delta.=k2n.lamda./NA.sup.2
[0005] For example, when using water as the medium of an ArF
process (the refractive index n of light having a wavelength of 193
nm in water is 1.44), the resolution R is 69.4% and the depth of
focus is 144% as compared with the case of using air or nitrogen as
the medium. An exposure method that utilizes such a medium is
referred to as liquid immersion lithography. Liquid immersion
lithography makes it possible to transfer a finer pattern using
radiation having a shorter wavelength (see Japanese Patent
Application Publication (KOKAI) No. 11-176727).
[0006] When using water as the medium for liquid immersion
lithography, water may permeate the photoresist film formed on the
wafer when the photoresist film and the lens of the projection
aligner come in contact with water, so that the resolution of the
photoresist film may decrease. Moreover, the components of the
photoresist composition may be eluted into water, and may
contaminate the surface of the lens of the projection aligner.
[0007] Therefore, a liquid immersion lithography upper-layer film
(protective film) may be formed on the photoresist film in order to
isolate the photoresist film from the medium (e.g., water). It is
normally desired that the liquid immersion lithography upper-layer
film exhibits sufficient transmittance at the wavelength of
radiation, can be formed on the photoresist film without being
intermixed with the photoresist film, is not eluted into the medium
(e.g., water) (i.e., is stable), and is not easily dissolved in the
developer (e.g., alkaline solution) (see Japanese Patent
Application Publication (KOKAI) No. 2005-264131, Japanese Patent
Application Publication (KOKAI) No. 2006-64711, and Japanese Patent
Application Publication (KOKAI) No. 2008-139789).
[0008] When using a scan-type liquid immersion lithography system,
the immersion medium may not follow the movement of the lens, so
that watermark defects (i.e., waterdrops remain on the exposed
photoresist film) may occur. This may make it difficult to increase
the scan speed, so that the production efficiency may decrease. A
liquid immersion lithography upper-layer film-forming composition
that contains a polymer that exhibits high water repellency
(hydrophobicity) has been known (WO08/047678). However, since a
liquid immersion lithography upper-layer film that exhibits high
hydrophobicity exhibits low solubility in the developer, bridge
defects (i.e., the lines of a line-and-space pattern are connected
in the top area) may occur due to undissolved residues of the
liquid immersion lithography upper-layer film.
RELATED-ART DOCUMENT
Patent Document
[0009] [Patent Document 1] Japanese Patent Application Publication
(KOKAI) No. 11-176727 [0010] [Patent Document 2] Japanese Patent
Application Publication (KOKAI) No. 2005-264131 [0011] [Patent
Document 3] Japanese Patent Application Publication (KOKAI) No.
2006-64711 [0012] [Patent Document 4] Japanese Patent Application
Publication (KOKAI) No. 2008-139789 [0013] [Patent Document 5]
WO08/047678
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0014] The invention was conceived in view of the above situation.
An object of the invention is to provide a liquid immersion
lithography upper-layer film-forming composition that can form a
liquid immersion lithography upper-layer film that exhibits
moderate water repellency and high solubility in a developer, and
can suppress occurrence of various defects such as watermark
defects and bridge defects even if a high scan speed is
employed.
Means for Solving the Problems
[0015] According to one aspect of the invention, a liquid immersion
lithography upper-layer film-forming composition includes (A) a
polymer that includes a structural unit (I) shown by a formula (1)
(hereinafter may be referred to as "polymer (A)"), and (5) a
solvent,
##STR00002##
[0016] wherein R.sup.1 represents a hydrogen atom, a methyl group,
or a trifluoromethyl group.
[0017] The polymer (A) preferably further includes a structural
unit (II) that includes a sulfo group.
[0018] The polymer (A) preferably further includes a structural
unit (III) shown by a formula (3),
##STR00003##
[0019] wherein R.sup.2 represents a hydrogen atom, a methyl group,
or a trifluoromethyl group, and [0020] R.sup.3 represents a linear
or branched monovalent hydrocarbon group having 1 to 12 carbon
atoms or a monovalent alicyclic group having 3 to 20 carbon atoms,
provided that at least one hydrogen atom of the hydrocarbon group
or the alicyclic group is substituted with a fluorine atom.
[0021] The polymer (A) preferably further includes a structural
unit (IV) shown by a formula (4),
##STR00004##
[0022] wherein R.sup.4 represents a hydrogen atom, a methyl group,
or a trifluoromethyl group, and R.sup.5 represents a linear or
branched monovalent hydrocarbon group having 1 to 12 carbon atoms
or a monovalent alicyclic group having 3 to 20 carbon atoms.
[0023] The liquid immersion lithography upper-layer film-forming
composition preferably further includes (B) a polymer that includes
the structural units (I) and (III), and has a fluorine atom content
higher than that of the polymer (A) (hereinafter may be referred to
as "polymer (B)").
[0024] The polymer (B) preferably further includes the structural
unit (IV).
[0025] According to another aspect of the invention, a photoresist
pattern-forming method includes (1) applying a photoresist
composition to a substrate to form a photoresist film, (2) applying
the liquid immersion lithography upper-layer film-forming
composition to the photoresist film to form a liquid immersion
lithography upper-layer film, (3) exposing the photoresist film and
the liquid immersion lithography upper-layer film via an immersion
medium and a mask having a given pattern, the immersion medium
being disposed between the liquid immersion lithography upper-layer
film and a lens, and (4) developing the photoresist film and the
liquid immersion lithography upper-layer film that have been
exposed.
Effect of the Invention
[0026] The liquid immersion lithography upper-layer film-forming
composition can thus form a liquid immersion lithography
upper-layer film that exhibits moderate water repellency and high
solubility in a developer, and can suppress occurrence of various
defects such as watermark defects and bridge defects even if a high
scan speed is employed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a cross-sectional view schematically showing the
shape of a line-and-space pattern.
[0028] FIG. 2 is a schematic view showing a state in which an
8-inch silicon wafer is placed on a silicone rubber sheet so that
leakage of ultrapure water does not occur when measuring the
elution volume from an upper-layer film formed using a liquid
immersion lithography upper-layer film-forming composition.
[0029] FIG. 3 is a cross-sectional view showing a state when
measuring the elution volume from an upper-layer film formed using
a liquid immersion lithography upper-layer film-forming
composition.
DESCRIPTION OF EMBODIMENTS
Liquid Immersion Lithography Upper-Layer Film-Forming
Composition
[0030] A liquid immersion lithography upper-layer film-forming
composition according to one embodiment of the invention is used to
form a liquid immersion lithography upper-layer film on the surface
of a photoresist film formed using a photoresist composition, and
includes the polymer (A) and the solvent (S). The liquid immersion
lithography upper-layer film-forming composition may preferably
further include the polymer (B). The liquid immersion lithography
upper-layer film-forming composition may further include an
additional polymer and an optional component as long as the effects
of the invention are not impaired. Each component is described in
detail below.
Polymer (A)
[0031] The polymer (A) includes a structural unit (I) shown by the
formula (1). When the liquid immersion lithography upper-layer
film-forming composition includes the polymer (A) that includes the
structural unit (I), the resulting liquid immersion lithography
upper-layer film exhibits moderate water repellency and solubility
in a developer. Therefore, a photoresist film can be protected
during liquid immersion lithography (i.e., the photoresist film
exhibits stability, and is not eluted into a medium (e.g., water)),
and defects (e.g., watermark defects, bubble defects, pattern
defects, and bridge defects) can be effectively suppressed, so that
a high-resolution resist pattern can be formed. It is preferable
that the polymer (A) further include structural units (II), (III),
and (IV). The polymer (A) may include two or more types of each
structural unit. Each structural unit is described in detail
below.
Structural unit (I) The structural unit (I) is shown by the formula
(1). R.sup.1 in the formula (1) represents a hydrogen atom, a
methyl group, or a trifluoromethyl group. It is preferable to use
(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-butyl)(meth)acrylate
as a monomer that produces the structural unit (I).
[0032] The content of the structural unit (I) in the polymer (A) is
preferably 20 to 99 mol % based on the total structural units
included in the polymer (A). If the content of the structural unit
(I) is within the above range, a situation in which the liquid
immersion lithography upper-layer film undergoes bridge defects can
be further suppressed.
Structural Unit (II)
[0033] The structural unit (II) includes a sulfo group. Examples of
the structural unit (II) include structural units shown by the
following formulas (2-1) and (2-2), and the like.
##STR00005##
wherein R.sup.6 and R.sup.7 individually represent a hydrogen atom,
a methyl group, or a trifluoromethyl group, and R.sup.8 and R.sup.9
individually represent a single bond, a linear or branched divalent
hydrocarbon group having 1 to 6 carbon atoms, a divalent alicyclic
group having 4 to 12 carbon atoms, or a divalent aromatic
hydrocarbon group having 6 to 12 carbon atoms.
[0034] Examples of the linear or branched divalent hydrocarbon
group having 1 to 6 carbon atoms represented by R.sup.8 and R.sup.9
include a methylene group, an ethylene group, a 1,3-propylene
group, a 1,2-propylene group, a tetramethylene group, a
pentamethylene group, a hexamethylene group, a
1-methyl-1,3-propylene group, a 2-methyl-1,3-propylene group, a
2-methyl-1,2-propylene group, a 1-methyl-1,4-butylene group, a
2-methyl-1,4-butylene group, and the like.
[0035] Examples of the divalent alicyclic group having 4 to 12
carbon atoms represented by R.sup.8 and R.sup.9 include a
monocyclic hydrocarbon group, a bridged cyclic hydrocarbon group,
and the like. Examples of the monocyclic hydrocarbon group include
a cyclobutylene group (e.g., 1,3-cyclobutylene group), a
cyclopentylene group (e.g., 1,3-cyclopentylene group), a
cyclohexylene group (e.g., 1,4-cyclohexylene group), a
cyclooctylene group (e.g., 1,5-cyclooctylene group)), and the like.
Examples of the bridged cyclic hydrocarbon group include a
norbornylene group (e.g., 1,4-norbornylene group and
2,5-norbornylene group), an adamantylene group (e.g.,
1,5-adamantylene group and 2,6-adamantylene group), and the
like.
[0036] Examples of the divalent alicyclic group having 6 to 12
carbon atoms represented by R.sup.8 and R.sup.9 include a phenylene
group, a tolylene group, and the like.
[0037] R.sup.8 in the formula (2-1) preferably represents a single
bond, a linear or branched divalent hydrocarbon group having 1 to 6
carbon atoms, or a divalent aromatic hydrocarbon group having 6 to
12 carbon atoms, and more preferably represents a single bond, a
methylene group, or a phenylene group. R.sup.9 in the formula (2-2)
preferably represents the linear or branched divalent hydrocarbon
group having 1 to 6 carbon atoms, and more preferably represents a
2-methylpropane-2,3-diyl group.
[0038] The structural unit (II) is preferably any of the structural
units shown by the following formulas.
##STR00006##
[0039] wherein R.sup.7 is the same as defined for the formula
(2-2).
[0040] The content of the structural unit (II) in the polymer (A)
is preferably 1 to 20 mol % based on the total structural units
included in the polymer (A). If the content of the structural unit
(II) is within the above range, a situation in which the liquid
immersion lithography upper-layer film undergoes bridge defects can
be further suppressed.
Structural Unit (III) The structural unit (III) is shown by the
formula (3). R.sup.2 in the formula (3) represents a hydrogen atom,
a methyl group, or a trifluoromethyl group. R.sup.3 in the formula
(3) represents a linear or branched monovalent hydrocarbon group
having 1 to 12 carbon atoms or a monovalent alicyclic group having
3 to 20 carbon atoms. At least one hydrogen atom of the hydrocarbon
group or the alicyclic group is substituted with a fluorine
atom.
[0041] R.sup.3 preferably represents a saturated chain-like
hydrocarbon group (e.g., methyl group, ethyl group, 1,3-propyl
group, 1,2-propyl group, butyl group, pentyl group, hexyl group,
heptyl group, octyl group, nonyl group, decyl group,
1-methyl-1,3-propyl group, 2-methyl-1,3-propyl group,
2-methyl-1,2-propyl group, 1-methyl-1,4-butyl group, or
2-methyl-1,4-butyl group), a monocyclic hydrocarbon group (e.g.,
1,3-cyclobutyl group, 1,3-cyclopentyl group, 1,4-cyclohexyl group,
or 1,5-cyclooctyl group), or a partial fluorinated group or a
perfluoroalkyl group of a polycyclic hydrocarbon group (e.g.,
1,4-norbornyl group, 2,5-norbornyl group, 1,5-adamantyl group, or
2,6-adamantyl group).
[0042] Examples of the structural unit (III) include the structural
units disclosed in Japanese Patent Application Publication (KOKAI)
No. 2007-304537, the structural units disclosed in Japanese Patent
Application Publication (KOKAI) No. 2008-088343, structural units
shown by the following formulas, and the like.
##STR00007##
wherein R.sup.2 is the same as defined for the formula (3).
[0043] Examples of a preferable monomer that produces the
structural unit (III) include trifluoromethyl(meth)acrylate,
2,2,2-trifluoroethyl(meth)acrylate, perfluoroethyl(meth)acrylate,
perfluoro-n-propyl(meth)acrylate, perfluoro-i-propyl(meth)acrylate,
perfluoro-n-butyl(meth)acrylate, perfluoro-i-butyl(meth)acrylate,
perfluoro-t-butyl(meth)acrylate,
2-(1,1,1,3,3,3-hexafluoropropyl)(meth)acrylate,
1-(2,2,3,3,4,4,5,5-octafluoropentyl)(meth)acrylate,
perfluorocyclohexylmethyl(meth)acrylate,
1-(2,2,3,3,3-pentafluoropropyl)(meth)acrylate,
1-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)(meth)acryla-
te,
1-(5-trifluoromethyl-3,3,4,4,5,6,6,6-octafluorohexyl)(meth)acrylate,
and the like.
[0044] The content of the structural unit (III) in the polymer (A)
is preferably 5 to 70 mol % based on the total structural units
included in the polymer (A). If the content of the structural unit
(III) is within the above range, a situation in which the liquid
immersion lithography upper-layer film undergoes bridge defects or
bubble defects can be further suppressed.
Structural Unit (IV)
[0045] The structural unit (IV) is shown by the formula (4).
R.sup.4 in the formula (4) represents a hydrogen atom, a methyl
group, or a trifluoromethyl group. R.sup.5 in the formula (4)
represents a linear or branched monovalent hydrocarbon group having
1 to 12 carbon atoms or a monovalent alicyclic group having 3 to 20
carbon atoms.
[0046] R.sup.5 preferably represents a methyl group, an ethyl
group, a 1,3-propyl group, a 1,2-propyl group, a tetramethyl group,
a pentamethyl group, a hexamethyl group, a heptamethyl group, an
octamethyl group, a nonamethyl group, a decamethyl group, a
1-methyl-1,3-propyl group, a 2-methyl-1,3-propyl group, a
2-methyl-1,2-propyl group, a 1-methyl-1,4-butyl group, a
2-methyl-1,4-butyl group, a methylidyne group, an ethylidene group,
a propylidene group, a 2-propylidene group, a 1,3-cyclobutyl group,
a 1,3-cyclopentyl group, a 1,4-cyclohexyl group, a 1,5-cyclooctyl
group, a 1,4-norbornyl group, a 2,5-norbornyl group, a
1,5-adamantyl group, or a 2,6-adamantyl group.
[0047] Examples of a monomer that produces the structural unit (IV)
include methyl methacrylate, ethyl methacrylate, butyl
methacrylate, pentyl methacrylate, cyclohexyl methacrylate,
adamantyl methacrylate, dicyclopentyl methacrylate, and the
like.
[0048] The content of the structural unit (IV) in the polymer (A)
is preferably 5 to 55 mol % based on the total structural units
included in the polymer (A). If the content of the structural unit
(IV) is within the above range, a situation in which the liquid
immersion lithography upper-layer film undergoes bridge defects or
bubble defects can be further suppressed.
Structural Unit (V)
[0049] The polymer (A) may further include a structural unit (V) as
an additional structural unit as long as the effects of the
invention are not impaired.
[0050] Examples of the structural unit (V) include structural units
shown by the following formulas (5-1) and (5-2), and the like.
##STR00008##
[0051] wherein R.sup.10 and R.sup.11 represent a hydrogen atom, a
methyl group, or a trifluoromethyl group, R.sup.12 represents a
single bond, a linear or branched alkanediyl group having 1 to 6
carbon atoms (excluding a 1,2-ethylene group), or a divalent
alicyclic group having 4 to 12 carbon atoms, R.sup.13 represents a
single bond, a linear or branched alkanediyl group having 1 to 6
carbon atoms, or a divalent alicyclic group having 4 to 12 carbon
atoms, and R.sup.14 represents a linear or branched hydrocarbon
group having 1 to 10 carbon atoms or a monovalent alicyclic group
having 3 to 10 carbon atoms, provided that at least one hydrogen
atom of the hydrocarbon group or the alicyclic group is substituted
with a fluorine atom.
[0052] R.sup.12 and R.sup.13 preferably represent a methylene
group, a 1,1-ethylene group, a 1,3-propylene group, a
1,2-propylene, a tetramethylene group, a pentamethylene group, a
hexamethylene group, a 1-methyl-1,3-propylene group, a
2-methyl-1,3-propylene group, a 2-methyl-1,2-propylene group, a
1-methyl-1,4-butylene group, a 2-methyl-1,4-butylene group, a
1,3-cyclobutylene, a 1,3-cyclopentylene, a 1,4-cyclohexylene group,
a 1,5-cyclooctylene group, a 1,4-norbornylene group, a
2,5-norbornylene group, a 1,5-adamantylene group, or a
2,6-adamantylene group.
[0053] When R.sup.12 represents a divalent alicyclic group, it is
preferable that an alkanediyl group having 1 to 4 carbon atoms be
inserted between the bistrifluoromethylhydroxymethyl group and the
alicyclic hydrocarbon group as a spacer. R.sup.12 preferably
represents a hydrocarbon group including a 2,5-norbornylene group
or a propylene group.
[0054] R.sup.14 preferably represents a trifluoromethyl group.
[0055] Examples of a preferable monomer that produces the repeating
unit (V) include
(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-3-propyl)(meth)acrylate,
(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl)(meth)acrylate,
2-{[5-(1',1',1'-trifluoro-2'-trifluoromethyl-2'-hydroxy)propyl]bicyclo[2.-
2.1]heptyl}(meth)acrylate,
3-{[8-(1',1',1'-trifluoro-2'-trifluoromethyl-2'-hydroxy)propyl]tetracyclo-
[6.2.1.1.sup.3,6.0.sup.2,7]dodecyl}(meth)acrylate,
(((trifluoromethyl)sulfonyl)amino)ethyl-1-methacrylate, and
2-(((trifluoromethyl)sulfonyl)amino)ethyl-1-acrylate.
[0056] The content of the polymer (A) in the liquid immersion
lithography upper-layer film-forming composition is preferably 20
mass % or more, more preferably 40 mass % or more, and particularly
preferably 60 mass % or more, based on the total amount (=100 mass
%) of the polymer component. If the content of the polymer (A) is
less than 20 mass %, defects may occur.
[0057] Polymer (B) The liquid immersion lithography upper-layer
film-forming composition may further include the polymer (B) that
includes at least one structural unit selected from the structural
units (I) and (V), and the structural unit (III), and has a
fluorine atom content higher than that of the polymer (A). If the
content of the structural units (I) and (V) is within the above
range, the resulting liquid immersion lithography upper-layer film
has a sufficiently high receding contact angle, and occurrence of
defects can be suppressed. Since the polymer (B) has a fluorine
atom content higher than that of the polymer (A), the polymer (B)
exhibits excellent water repellency as compared with the polymer
(A). Specifically, when the liquid immersion lithography
upper-layer film-forming composition further includes the polymer
(B), the polymer (B) is distributed in the surface area, so that
occurrence of watermark defects due to remaining droplets can be
prevented while maintaining the receding contact angle.
[0058] It is preferable that the polymer (B) further include the
structural unit (IV). The description given above in connection
with the polymer (A) may be applied to the structural units (I),
(III), (IV), and (V). The polymer (B) may include two or more types
of each structural unit.
[0059] The content of at least one structural unit selected from
the structural units (I) and (V) in the polymer (B) is preferably
20 to 80 mol % based on the total structural units included in the
polymer (B). The content of the structural unit (III) in the
polymer (B) is preferably 5 to 80 mol % based on the total
structural units included in the polymer (B). If the content of the
structural unit (I) and the content of the structural unit (III)
are within the above range, the resulting liquid immersion
lithography upper-layer film has a sufficiently high receding
contact angle, and occurrence of defects can be suppressed. The
content of the structural unit (IV) in the polymer (B) is
preferably 5 to 55 mol %, and more preferably 5 to 50 mol %, based
on the total structural units included in the polymer (B). If the
content of the structural unit (IV) is within the above range, the
receding contact angle and the advancing contact angle of the
liquid immersion lithography upper-layer film are
well-balanced.
[0060] The content of the polymer (B) in the liquid immersion
lithography upper-layer film-forming composition is preferably 60
mass % or less, more preferably 50 mass % or less, and particularly
preferably 40 mass % or less, based on the total amount (=100 mass
%) of the polymer component. If the content of the polymer (B)
exceeds 60 mass %, defects may occur.
Additional Polymer
[0061] The liquid immersion lithography upper-layer film-forming
composition may further include an additional polymer other than
the polymers (A) and (B) as long as the effects of the invention
are not impaired. Examples of the additional polymer include (i) a
polymer that includes the structural units (V) and (II), (ii) a
polymer that includes a structural unit (VI) (described later) and
the structural unit (II), and the like. The description given above
in connection with the polymer (A) may be applied to the structural
units (II), (III), and (V).
[0062] The content of the structural unit (V) in the polymer (i) is
preferably 20 to 99 mol %, and more preferably 30 to 99 mol %,
based on the total structural units included in the polymer (i). If
the content of the structural unit (V) is within the above range,
occurrence of bridge defects can be suppressed. The content of the
structural unit (II) in the polymer (i) is preferably 1 to 20 mol
%, and more preferably 1 to 15 mol %, based on the total structural
units included in the polymer (i). If the content of the structural
unit (II) is within the above range, occurrence of blob defects can
be suppressed.
Structural Unit (VI)
[0063] Examples of the structural unit (VI) include structural
units shown by the following formulas (6-1), (6-2), and (6-3), and
the like.
##STR00009##
wherein R.sup.15, R.sup.16, and R.sup.17 individually represent a
hydrogen atom, a methyl group, or a trifluoromethyl group, and
R.sup.18, R.sup.19, and R.sup.20 individually represent a linear or
branched divalent hydrocarbon group having 1 to 6 carbon atoms or a
divalent alicyclic group having 4 to 12 carbon atoms.
[0064] Examples of the linear or branched divalent hydrocarbon
group having 1 to 6 carbon atoms represented by R.sup.18, R.sup.19,
and R.sup.20 include an ethylene group, a 1,3-propylene group, a
1,2-propylene group, a tetramethylene group, a pentamethylene
group, a hexamethylene group, a 1-methyl-1,3-propylene group, a
2-methyl-1,3-propylene group, a 2-methyl-1,2-propylene group, a
1-methyl-1,4-butylene group, a 2-methyl-1,4-butylene group, and the
like.
[0065] Examples of the divalent alicyclic group having 4 to 12
carbon atoms represented by R.sup.18, R.sup.19, and R.sup.20
include an arylene group (e.g., phenylene group and tolylene
group), a cyclobutylene group (e.g., 1,3-cyclobutylene group), a
cyclopentylene group (e.g., 1,3-cyclopentylene group), a
cyclohexylene group (e.g., 1,4-cyclohexylene group), a
cyclooctylene group (e.g., 1,5-cyclooctylene group), a norbornylene
group (e.g., 1,4-norbornylene group and 2,5-norbornylene group),
and an adamantylene group (e.g., 1,5-adamantylene group and
2,6-adamantylene group).
[0066] Examples of a monomer that produces the structural unit (VI)
include 2-methacryloyloxyethyl hexahydrophthalate,
3-methacryloyloxypropyl hexahydrophthalate, 4-methacryloyloxybutyl
hexahydrophthalate, 2-methacryloyloxy cyclohexacarboxylate,
3-methacryloyloxy propylcarboxylate, (meth)acrylic acid, and the
like.
[0067] When the liquid immersion lithography upper-layer
film-forming composition includes the polymer (ii) that includes
the structural unit (VI), occurrence of blob defects can be further
suppressed.
[0068] The content of the structural unit (VI) in the polymer (ii)
is preferably 20 to 99 mol %, and more preferably 30 to 99 mol %,
based on the total structural units included in the polymer (ii).
If the content of the structural unit (VI) is less than 20 mol %,
the polymer may remain undissolved due to a decrease in solubility
in an alkaline developer. If the content of the structural unit
(VI) exceeds 99 mol %, the polymer may exhibit poor solubility in
the solvent. The content of the structural unit (II) in the polymer
(ii) is preferably 1 to 20 mol %, and more preferably 1 to 15 mol
%, based on the total structural units included in the polymer
(ii). If the content of the structural unit (II) is within the
above range, occurrence of blob defects can be suppressed.
[0069] Examples of a monomer that produces an additional structural
unit that may be included in a polymer other than the polymers (i)
and (ii) include dicarboxylic diesters such as diethyl maleate,
diethyl fumarate, and diethyl itaconate; aryl(meth)acrylates such
as phenyl(meth)acrylate and benzyl(meth)acrylate; aromatic vinyls
such as styrene, .alpha.-methylstyrene, m-methylstyrene,
p-methylstyrene, vinyltoluene, and p-methoxystyrene; nitrile
group-containing radically polymerizable monomers such as
acrylonitrile and methacrylonitrile; amide bond-containing
radically polymerizable monomers such as acrylamide and
methacrylamide; fatty acid vinyl esters such as vinyl acetate;
chlorine-containing radically polymerizable monomers such as vinyl
chloride and vinylidene chloride; conjugated diolefins such as
1,3-butadiene, isoprene, and 1,4-dimethylbutadiene; and the like.
The content of the additional structural unit is preferably 50 mol
% or less, and more preferably 40 mol % or less, based on the total
structural units included in the polymer.
Synthesis of Polymer
[0070] Each polymer may be synthesized by radically polymerizing a
monomer that produces each structural unit in a polymerization
solvent in the presence of an initiator and a chain transfer agent,
for example.
[0071] Examples of the polymerization solvent include alcohols,
cyclic ethers, alkyl ethers of polyhydric alcohols, alkyl ether
acetates of polyhydric alcohols, aromatic hydrocarbons, ketones,
and esters. Among these, cyclic ethers, polyhydric alcohol alkyl
ethers, polyhydric alcohol alkyl ether acetates, ketones, esters,
and the like are preferable.
[0072] The polystyrene-reduced weight average molecular weight (Mw)
of each polymer determined by gel permeation chromatography (GPC)
is preferably 2000 to 100,000, and more preferably 2500 to 50,000.
If the Mw of each polymer is within the above range, the resulting
liquid immersion lithography upper-layer film exhibits good water
resistance, mechanical properties, and solubility in the solvent.
The molecular weight distribution (Mw/Mn) of each polymer is
preferably 1 to 5, and more preferably 1 to 3.
[0073] Note that the Mw and Mn refer to values determined by GPC
under the following conditions.
System: HLC-8120 (manufactured by Tosoh Corporation) Column:
G2000H.sub.XL.times.2, G3000H.sub.XL.times.1, G4000H.sub.XL.times.1
(manufactured by Tosoh Corporation) Eluant: tetrahydrofuran Column
temperature: 40.degree. C. Flow rate: 1.0 ml/min Standard:
monodisperse polystyrene
[0074] The polymer component included in the liquid immersion
lithography upper-layer film-forming composition is a resin that
can form a liquid immersion lithography upper-layer film that is
stable to an immersion medium during exposure to radiation, and can
be dissolved in a developer used to form a resist pattern. The
expression "stable to an immersion medium" used herein means that a
change in thickness measured by a stability evaluation test is
within 3% of the initial thickness. The stability evaluation test
is performed as follows. Specifically, the liquid immersion
lithography upper-layer film-forming composition is spin-coated
onto an 8-inch silicon wafer using a coater/developer ("CLEAN TRACK
ACT 8" manufactured by Tokyo Electron Ltd.), and pre-baked at
90.degree. C. for 60 seconds to form a liquid immersion lithography
upper-layer film having a thickness of 90 nm. The initial thickness
of the liquid immersion lithography upper-layer film is measured
using a spectroscopic film thickness measurement system ("Lambda
Ace VM-2010" manufactured by Dainippon Screen Mfg. Co., Ltd.).
Ultrapure water is discharged (60 seconds) to the surface of the
wafer on which the liquid immersion lithography upper-layer film is
formed through the rinse nozzle of the coater/developer, and the
wafer is spin-dried at 4000 rpm for 15 seconds. The thickness of
the upper-layer film is again measured, and a change in thickness
of the upper-layer film is calculated. When a decrease in thickness
of the upper-layer film is within 3% of the initial thickness, the
liquid immersion lithography upper-layer film is determined to be
stable to the immersion medium. The expression "can be dissolved in
a developer" means that the upper-layer film is removed so that no
residue is observed on the resist pattern with the naked eye after
development using an alkaline aqueous solution.
Solvent (S)
[0075] The liquid immersion lithography upper-layer film-forming
composition according to one embodiment of the invention includes
the solvent (S) that dissolves the polymer component. The solvent
(S) is preferably a solvent that does not cause a deterioration in
lithographic performance (e.g., due to intermixing with the
photoresist film) when applied to the photoresist film.
[0076] Examples of the solvent (S) include monohydric alcohols,
polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric
alcohol alkyl ether acetates, ethers, cyclic ethers, higher
hydrocarbons, aromatic hydrocarbons, ketones, esters, water, and
the like.
[0077] Examples of monohydric alcohols include 1-butyl alcohol,
2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol,
2-pentanol, 3-pentanol, tert-amyl alcohol, neopentyl alcohol,
2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol,
cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol,
2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol,
3,3-dimethyl-2-butanol, 2-diethyl-1-butanol, 2-methyl-1-pentanol,
2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol,
3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol,
4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol, and the
like.
[0078] Examples of polyhydric alcohols include ethylene glycol,
propylene glycol, and the like.
[0079] Examples of polyhydric alcohol alkyl ethers include ethylene
glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene
glycol dimethyl ether, ethylene glycol diethyl ether, diethylene
glycol monomethyl ether, diethylene glycol monoethyl ether,
diethylene glycol dimethyl ether, diethylene glycol diethyl ether,
diethylene glycol ethyl methyl ether, dipropylene glycol dimethyl
ether, propylene glycol monomethyl ether, propylene glycol
monoethyl ether, propylene glycol mono-n-propyl ether, ethylene
glycol monoisobutyl ether, and the like.
[0080] Examples of polyhydric alcohol alkyl ether acetates include
ethylene glycol ethyl ether acetate, diethylene glycol ethyl ether
acetate, propylene glycol ethyl ether acetate, propylene glycol
monomethyl ether acetate, and the like.
[0081] Examples of ethers include dipropyl ether, diisopropyl
ether, butyl methyl ether, butyl ethyl ether, butyl propyl ether,
dibutyl ether, diisobutyl ether, tert-butyl methyl ether,
tert-butyl ethyl ether, tert-butyl propyl ether, di-tert-butyl
ether, dipentyl ether, diisoamyl ether, cyclopentyl methyl ether,
cyclohexyl methyl ether, cyclopentyl ethyl ether, cyclohexyl ethyl
ether, cyclopentyl propyl ether, cyclopentyl 2-propyl ether,
cyclohexyl propyl ether, cyclohexyl 2-propyl ether, cyclopentyl
butyl ether, cyclopentyl tert-butyl ether, cyclohexyl butyl ether,
cyclohexyl tert-butyl ether, and the like.
[0082] Examples of cyclic ethers include tetrahydrofuran, dioxane,
and the like.
[0083] Examples of higher hydrocarbons include decane, dodecane,
undecane, and the like.
[0084] Examples of aromatic hydrocarbons include benzene, toluene,
xylene, and the like.
[0085] Examples of ketones include acetone, methyl ethyl ketone,
methyl isobutyl ketone, cyclohexanone,
4-hydroxy-4-methyl-2-pentanone, diacetone alcohol, and the
like.
[0086] Examples of esters include ethyl acetate, butyl acetate,
ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate,
ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl
hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl
3-methoxypropionate, ethyl 3-methoxypropionate, ethyl
3-ethoxypropionate, methyl 3-ethoxypropionate, and the like.
[0087] Among these, monohydric alcohols, ethers, cyclic ethers,
alkyl ethers of polyhydric alcohols, alkyl ether acetates of
polyhydric alcohol, and higher hydrocarbons are preferable.
Optional Component
[0088] The liquid immersion lithography upper-layer film-forming
composition may further include an optional component (e.g.,
surfactant) in order to improve the applicability, defoamability,
and leveling properties, and the like of the composition as long as
the desired effects are not impaired.
[0089] Examples of commercially available products of the
surfactant include BM-1000, BM-1100 (manufactured by BM Chemie),
Megafac F142D, Megafac F172, Megafac F173, Megafac F183
(manufactured by DIC Corporation), Fluorad FC-135, Fluorad FC-170C,
Fluorad FC-430, Fluorad FC-431 (manufactured by Sumitomo 3M, Ltd.),
Surflon S-112, Surflon S-113, Surflon S-131, Surflon S-141, Surflon
S-145 (manufactured by Asahi Glass Co., Ltd.), SH-28PA, SH-190,
SH-193, SZ-6032, SF-8428 (manufactured by Dow Corning Toray
Silicone Co., Ltd.), Emulgen A-60, Emulgen 104 P, Emulgen 306P
(manufactured by Kao Corporation), and the like. The surfactant is
preferably used in an amount of 5 mass % or less based on 100 mass
% of the polymer component. These surfactants may be used either
individually or in combination.
Production of Liquid Immersion Lithography Upper-Layer Film-Forming
Composition
[0090] The liquid immersion lithography upper-layer film-forming
composition is produced as a solution or a dispersion by mixing the
polymer (A), the polymer (B) (optional), the additional polymer
(optional), and an optional component with the solvent (S). The
liquid immersion lithography upper-layer film-forming composition
may be produced by preparing a solution so that the desired total
solid content is achieved, and filtering the solution through a
filter having a pore size of about 200 nm. The solid content is not
particularly limited, but is normally 0.1 to 20.0 mass %.
[0091] It is preferable that the liquid immersion lithography
upper-layer film-forming composition have an impurity (e.g.,
halogen ions and metals) content as low as possible. The liquid
immersion lithography upper-layer film-forming composition exhibits
improved applicability and improved (uniform) solubility in an
alkaline developer by reducing the impurity content. The polymer
component may be purified by chemical purification (e.g., washing
with water or liquid-liquid extraction), or a combination of
chemical purification and physical purification (e.g.,
ultrafiltration or centrifugation), for example.
Photoresist Pattern-Forming Method
[0092] A photoresist pattern-forming method according to one
embodiment of the invention includes (1) applying a photoresist
composition to a substrate to form a photoresist film (hereinafter
may be referred to as "step (1)"), (2) applying the liquid
immersion lithography upper-layer film-forming composition to the
photoresist film to form a liquid immersion lithography upper-layer
film (hereinafter may be referred to as "step (2)"), (3) exposing
the photoresist film and the liquid immersion lithography
upper-layer film via an immersion medium and a mask having a given
pattern, the immersion medium being disposed between the liquid
immersion lithography upper-layer film and a lens (hereinafter may
be referred to as "step (3)"), and (4) developing the photoresist
film and the liquid immersion lithography upper-layer film that
have been exposed (hereinafter may be referred to as "step
(4)").
[0093] According to the above photoresist pattern-forming method,
it is possible to form a liquid immersion lithography upper-layer
film that exhibits sufficient transmittance at an exposure
wavelength of 248 nm(KrF) or 193 nm (ArF), suppresses intermixing
with the photoresist film, is rarely eluted into the immersion
medium (e.g., water) during liquid immersion lithography (i.e., is
stable), forms a high-resolution resist pattern, and has a
sufficiently high receding contact angle. Specifically, it is
possible to effectively suppress occurrence of watermark defects
and pattern defects at a normal scan speed (e.g., 500 mm/s), and
effectively suppress occurrence of defects even at a high scan
speed (e.g., 700 mm/s)
Step (1)
[0094] The step (1) includes applying a photoresist composition to
a substrate to form a photoresist film A silicon wafer, an
aluminum-coated silicon wafer, or the like may normally be used as
the substrate. An organic or inorganic antireflective film may be
formed on the substrate in order to maximize the properties of the
photoresist film (see Japanese Examined Patent Publication (KOKOKU)
No. 6-12452, for example).
[0095] The photoresist composition may be appropriately depending
on the application (objective) of the resist. A
chemically-amplified positive-tone resist material that includes an
acid generator is preferably used as the photoresist composition.
Examples of the chemically-amplified positive-tone resist material
include a radiation-sensitive polymer composition that includes an
acid-dissociable group-modified alkali-soluble resin and a
photoacid generator as essential components, and the like. The
radiation-sensitive polymer composition is designed so that an acid
is generated by the acid generator upon application of radiation
(exposure), and the acid-dissociable group that protects an acidic
group (e.g., carboxyl group) included in the polymer dissociates
due to the acid so that the acidic group is exposed. As a result,
the alkaline-solubility of the exposed area of the resist
increases. Therefore, the exposed area is dissolved and removed by
an alkaline developer to obtain a positive-tone resist pattern.
[0096] The polymer preferably includes a structural unit that
includes an acid-dissociable group. The content of the structural
unit that includes an acid-dissociable group in the polymer is
preferably 30 to 60 mol % based on the total structural units
included in the polymer.
[0097] Examples of the polymer include a polymer that includes a
structural unit shown by any of the following formulas.
##STR00010##
[0098] Examples of the acid generator include triphenylsulfonium
nonafluoro-n-butane sulfonate, 4-cyclohexylphenyldiphenylsulfonium
nonafluoro-n-butanesulfonate,
1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiophenium
nonafluoro-n-butanesulfonate, triphenylsulfonium
2-(bicyclo[2.2.1]hept-2'-yl)-1,1,2,2-tetrafluoroethanesulfonate,
1-(4-n-butoxynaphthyl)tetrahydrothiophenium
2-(bicyclo[2.2.1]hept-2'-yl)-1,1,2,2-tetrafluoroethanesulfonate,
triphenylsulfonium
2-(bicyclo[2.2.1]hept-2'-yl)-1,1-difluoroethanesulfonate, and the
like.
[0099] The photoresist film may be formed by adding a solvent to a
polymer component so that the total solid content is 0.2 to 20 mass
%, filtering the solution through a filter having a pore size of
about 30 nm to prepare a coating liquid, and applying the coating
liquid to a substrate by a known coating method (e.g., spin
coating, cast coating, or roll coating). The photoresist film
(coating liquid) may be prebaked in order to volatilize the
solvent.
Step (2)
[0100] The step (2) includes applying the liquid immersion
lithography upper-layer film-forming composition to the photoresist
film to form a liquid immersion lithography upper-layer film. A
situation in which the immersion medium comes in direct contact
with the photoresist film during liquid immersion lithography can
be prevented by forming the liquid immersion lithography
upper-layer film. This makes it possible to effectively prevent a
situation in which the lithographic performance of the photoresist
film deteriorates due to permeation of the immersion medium, or the
lens of the projection aligner is contaminated due to components
eluted from the photoresist film.
[0101] It is preferable that the thickness of the liquid immersion
lithography upper-layer film be close to an odd multiple of 214m
(where, 2 is the wavelength of radiation, and m is the refractive
index of the protective film) as much as possible. This makes it
possible to increase the antireflective effect at the interface
with the photoresist film.
Step (3)
[0102] The step (3) includes exposing the photoresist film and the
liquid immersion lithography upper-layer film via an immersion
medium and a mask having a given pattern, the immersion medium
being disposed between the liquid immersion lithography upper-layer
film and a lens.
[0103] A liquid having a refractive index higher than that of air
is normally used as the immersion medium. It is preferable to use
water (more preferably purified water) as the immersion medium. The
pH of the immersion medium may optionally be adjusted. The
photoresist film is exposed by applying radiation to the
photoresist film via the mask having a given pattern in a state in
which the immersion medium is interposed between the liquid
immersion lithography upper-layer film and the lens (i.e., the
space between the lens of the exposure system and the photoresist
film is filled with the immersion medium).
[0104] Radiation used for liquid immersion lithography may be
appropriately selected depending on the types of the photoresist
film and the liquid immersion lithography upper-layer film. For
example, visible light, ultraviolet rays (e.g., g-line or i-line),
deep ultraviolet rays (e.g., excimer laser light), X-rays (e.g.,
synchrotron radiation), charged particle rays (e.g., electron
beams), or the like may be used. Among these, ArF excimer laser
light (wavelength: 193 nm) and KrF excimer laser light (wavelength:
248 nm) are preferable. The exposure conditions (e.g., dose) may be
appropriately set depending on the composition of the photoresist
composition, the type of additive, and the like.
[0105] It is preferable to perform post-exposure bake (PEB) in
order to improve the resolution, the pattern shape, the
developability, and the like of the photoresist film. The PEB
temperature is appropriately selected depending on the type of the
photoresist composition, but is normally 30 to 200.degree. C., and
preferably 50 to 150.degree. C.
Step (4)
[0106] The step (4) includes developing the photoresist film and
the liquid immersion lithography upper-layer film that have been
exposed. It is preferable to use an alkaline aqueous solution as
the developer used for development. Examples of the alkali include
sodium hydroxide, potassium hydroxide, sodium carbonate, sodium
silicate, sodium metasilicate, aqueous ammonia, ethylamine,
n-propylamine, diethylamine, di-n-propylamine, triethylamine,
methyldiethylamine, dimethylethanolamine, triethanolamine,
tetramethylammonium hydroxide, tetraethylammonium hydroxide,
pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene,
1,5-diazabicyclo-[4.3.0]-5-nonane, and the like. It is preferable
to use a tetraalkylammonium hydroxide aqueous solution as the
developer.
[0107] An appropriate amount of a water-soluble organic solvent
(e.g., methanol or ethanol) or a surfactant may be added to the
developer. When developing the photoresist film using an alkaline
aqueous solution, the photoresist film is normally washed with
water after development. The photoresist film is then appropriately
dried to form the desired photoresist pattern.
EXAMPLES
[0108] The invention is further described below by way of examples.
Note that the invention is not limited to the following
examples.
Synthesis of Polymer
[0109] The following monomers were used to produce the polymers.
[0110] M-1: (1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-butyl)
methacrylate [0111] M-2: vinylsulfonic acid [0112] M-3:
(2,2,2-trifluoroethyl) methacrylate [0113] M-4:
(1-trifluoromethyl-2,2,2-trifluoroethyl) methacrylate [0114] M-5:
dicyclopentyl methacrylate [0115] M-6:
(1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-3-propyl) methacrylate
[0116] M-7: (1,1,1-trifluoro-2-trifluoromethyl-2-hydroxy-4-pentyl)
methacrylate [0117] M-8: 2-methacryloyloxyethyl
hexahydrophthalate
##STR00011## ##STR00012##
[0117] Synthesis of Polymer
Synthesis Example 1
[0118] 46.81 g (85 mol %) of the monomer (M-1) that produces the
structural unit (I) and 4.53 g of 2,2'-azobis(methyl
2-methylpropionate) (initiator) were dissolved in 40.00 g of
isopropanol to prepare a monomer solution. A three-necked flask
(200 ml) equipped with a thermometer and a dropping funnel was
charged with 50 g of isopropanol, and purged with nitrogen for 30
minutes. The inside of the flask was then heated to 80.degree. C.
with stirring using a magnetic stirrer. The monomer solution was
added dropwise to the flask using the dropping funnel over 2 hours.
After the dropwise addition, the mixture was reacted for 1 hour. 10
g of an isopropanol solution containing 3.19 g (15 mol %) of the
monomer (M-2) that produces the structural unit (II) was added to
the mixture over 30 minutes. After reacting the mixture for 1 hour,
the mixture was cooled to 30.degree. C. or less to obtain a
copolymer solution. The copolymer solution was concentrated to 150
g, and put in a separating funnel. 50 g of methanol and 600 g of
n-hexane were added to the separating funnel to effect separation
and purification. The lower-layer solution thus separated was
collected. The lower-layer solution was diluted with isopropanol so
that the amount of the diluted solution was 100 g, and put in the
separating funnel. 50 g of methanol and 600 g of n-hexane were
added to the separating funnel to effect separation and
purification, and the lower-layer solution was collected. The
solvent of the lower-layer solution was replaced with
4-methyl-2-pentanol so that the total amount of the mixture was 250
g. 250 g of water was then added to the mixture to effect
separation and purification, and the upper-layer solution was
collected. The solvent of the upper-layer solution thus collected
was replaced with 4-methyl-2-pentanol to obtain a resin solution.
The solid content of the resin solution was calculated from the
mass of residues obtained by placing 0.3 g of the resin solution on
an aluminum dish, and heating the resin solution on a hot plate at
140.degree. C. for 1 hour, and used when producing the liquid
immersion lithography upper-layer film-forming composition
solution, and calculating the yield. A copolymer (P-1) contained in
the resin solution had an Mw of 10,010 and an Mw/Mn ratio of 1.55.
The yield was 75%. The ratio of the content of the structural unit
(I) to the content of the structural unit (II) was 98:2 (mol
%).
Synthesis Examples 2 to 7, 14, 15, and 25
[0119] A polymer was synthesized in the same manner as in Synthesis
Example 1, except for changing the monomers as shown in Table 1.
The symbol "-" in Table 1 indicates that the corresponding monomer
was not used. The values in Table 1 indicate the content (%) of the
structural unit produced by each monomer.
Synthesis of Additional Polymer
Synthesis Example 16
[0120] 37.3 g of the monomer (M-7) that produces the structural
unit (V) was dissolved in 4.5 g of methyl ethyl ketone to prepare a
monomer solution. A three-necked flask (500 ml) equipped with a
thermometer and a dropping funnel was charged with 69.6 g of the
monomer (M-4) that produces the structural unit (III), 4.5 g of
2,2-azobis(methyl 2-methylisopropionate), and 95.5 g of methyl
ethyl ketone, and purged with nitrogen for 30 minutes. The inside
of the flask was then heated to 75.degree. C. with stirring using a
magnetic stirrer. The monomer solution was added dropwise to the
flask using the dropping funnel over 5 minutes, and aged for 6
hours. The mixture was cooled to 30.degree. C. or less to obtain a
copolymer solution. The copolymer solution was concentrated to 150
g, and put in a separating funnel. 150 g of methanol and 750 g of
n-hexane were added to the separating funnel to effect separation
and purification, and the lower-layer solution was collected. The
solvent of the lower-layer solution was then replaced with
4-methyl-2-pentanol. The resulting copolymer (P-16) had an Mw of
7500 and an Mw/Mn ratio of 1.50. The yield was 50%. The ratio of
the content of the structural unit (V) to the content of the
structural unit (III) was 60:40 (mol %).
Synthesis Examples 8 to 13 and 17 to 21
[0121] An additional polymer was synthesized in the same manner as
in Synthesis Example 16, except for changing the monomers as shown
in Table 1. The symbol "-" in Table 1 indicates that the
corresponding monomer was not used. The values in Table 1 indicate
the content (%) of the structural unit produced by each
monomer.
Synthesis Example 22
[0122] 46.95 g (85 mol %) of the monomer (M-8) that produces the
structural unit (VI) and 6.91 g of 2,2'-azobis(methyl
2-methylpropionate) (initiator) were dissolved in 100 g of
isopropanol to prepare a monomer solution. A three-necked flask
(500 ml) equipped with a thermometer and a dropping funnel was
charged with 50 g of isopropanol, and purged with nitrogen for 30
minutes. The inside of the flask was then heated to 80.degree. C.
with stirring using a magnetic stirrer. The monomer solution was
added dropwise to the flask using the dropping funnel over 2 hours.
After the dropwise addition, the mixture was reacted for 1 hour. 10
g of an isopropanol solution containing 3.05 g (15 mol %) of the
monomer (M-2) that produces the structural unit (II) was added to
the mixture over 30 minutes. After reacting the mixture for 1 hour,
the mixture was cooled to 30.degree. C. or less to obtain a
copolymer solution. The copolymer solution was concentrated to 150
g, and put in a separating funnel. 50 g of methanol and 600 g of
n-hexane were added to the separating funnel to effect separation
and purification. The lower-layer solution thus separated was
collected. The lower-layer solution was diluted with isopropanol so
that the amount of the diluted solution was 100 g, and put in the
separating funnel. 50 g of methanol and 600 g of n-hexane were
added to the separating funnel to effect separation and
purification, and the lower-layer solution was collected. The
solvent of the lower-layer solution was replaced with
4-methyl-2-pentanol so that the total amount of the mixture was 250
g. 250 g of water was then added to the mixture to effect
separation and purification, and the upper-layer solution was
collected. The solvent of the upper-layer solution thus collected
was replaced with 4-methyl-2-pentanol to obtain a resin solution. A
copolymer (P-22) contained in the resin solution had an Mw of
11,060 and an Mw/Mn ratio of 1.55. The yield was 75%. The ratio of
the content of the structural unit (VI) to the content of the
structural unit (II) was 96:4 (mol %).
TABLE-US-00001 TABLE 1 Content (moL %) of structural unit M-8 M-1
M-2 M-3 M-4 M-5 M-6 M-7 Structural Structural unit (I) Structural
unit (I) Structural unit (III) Structural unit (IV) Structural unit
(V) unit (VI) Synthesis Example 1 P-1 98 2 -- -- -- -- -- --
Synthesis Example 2 P-2 99 1 -- -- -- -- -- -- Synthesis Example 3
P-3 80 20 -- -- -- -- -- -- Synthesis Example 4 P-4 94 1 5 -- -- --
-- -- Synthesis Example 5 P-5 25 20 55 -- -- -- -- -- Synthesis
Example 6 P-6 94 1 -- -- 5 -- -- -- Synthesis Example 7 P-7 25 20
-- -- 55 -- -- -- Synthesis Example 8 P-8 60 -- -- 40 -- -- -- --
Synthesis Example 9 P-9 20 -- -- 80 -- -- -- -- Synthesis Example
10 P-10 80 -- -- 20 -- -- -- -- Synthesis Example 11 P-11 30 -- --
70 -- -- -- -- Synthesis Example 12 P-12 80 -- -- 15 5 -- -- --
Synthesis Example 13 P-13 20 -- -- 50 30 -- -- -- Synthesis Example
14 P-14 -- 2 -- -- -- 98 -- -- Synthesis Example 15 P-15 -- 5 -- --
-- 95 -- -- Synthesis Example 16 P-16 -- -- -- 40 -- -- 60 --
Synthesis Example 17 P-17 -- -- -- 80 -- -- 20 -- Synthesis Example
18 P-18 -- -- -- 20 -- -- 80 -- Synthesis Example 19 P-19 -- -- --
70 -- -- 30 -- Synthesis Example 20 P-20 -- -- -- 15 5 -- 80 --
Synthesis Example 21 P-21 -- -- -- 50 30 -- 20 -- Synthesis Example
22 P-22 -- 4 -- -- -- -- -- 96 Synthesis Example 23 P-23 -- 2 -- --
-- -- 98
Production of Liquid Immersion Lithography Upper-Layer Film-Forming
Composition
Example 1
[0123] 92 parts by mass of the polymer (P-1) (polymer (A)), 3 parts
by mass of the polymer (P-8) (polymer (B)), 5 parts by mass of the
polymer (P-22) (additional polymer), 5634 parts by mass of
4-methyl-2-pentanol (solvent (S)), and 1409 parts by mass of
diisoamyl ether were mixed. The mixture was stirred for 2 hours,
and filtered through a filter having a pore size of 200 nm to
obtain a liquid immersion lithography upper-layer film-forming
composition (solid content: 1.4 mass %).
Examples 2 to 108 and Comparative Examples 1 to 14
[0124] A liquid immersion lithography upper-layer film-forming
composition was produced in the same manner as in Example 1, except
for changing the polymers (type and amount) as shown in Tables 2 to
4. Note that the symbol "-" in Tables 2 to 4 indicates that the
corresponding component was not used.
Synthesis of Photoresist Composition Polymer
[0125] The monomers shown by the following formulas were used to
produce the photoresist composition polymers.
##STR00013##
Synthesis Example 23
[0126] A monomer solution was prepared by dissolving 53.93 g (50
mol %) of the compound (M-9), 35.38 g (40 mol %) of the compound
(M-10), and 10.69 g (10 mol %) of the compound (M-11) in 200 g of
2-butanone, and adding 5.58 g of dimethyl
2,2'-azobis(2-methylpropionate) to the solution. Separately, a
three-necked flask (500 ml) was charged with 100 g of 2-butanone,
and purged with nitrogen for 30 minutes. The flask was then heated
to 80.degree. C. with stirring, and the monomer solution was added
dropwise to the flask using a dripping funnel over 3 hours. The
monomers were polymerized for 6 hours from the start of dropwise
addition of the monomer solution. After completion of
polymerization, the polymer solution was cooled with water to
30.degree. C. or less, and poured into 2000 g of methanol. A
precipitated white powder was collected by filtration. The
collected white powder was washed twice with 400 g of methanol in a
slurry state, collected by filtration, and dried at 50.degree. C.
for 17 hours to obtain a white powdery polymer (D-1) (74 g, yield:
74%). The polymer (D-1) had an Mw of 6900 and an Mw/Mn ratio of
1.70. The ratio of structural units derived from the compounds
(M-9), (M-10), and (M-11) contained in the polymer (D-1) as
determined by .sup.13C-NMR analysis was 53.0:37.2:9.8 (mol %). The
content of low-molecular-weight components derived from the
monomers in the polymer (D-1) was 0.03 mass %.
Synthesis Example 24
[0127] A monomer solution was prepared by dissolving 47.54 g (46
mol %) of the compound (M-9), 12.53 g (15 mol %) of the compound
(M-10), and 39.93 g (39 mol %) of the compound (M-12) in 200 g of
2-butanone, and adding 4.08 g of 2,2'-azobis(isobutylonitrile) to
the solution. Separately, a three-necked flask (1000 ml) was
charged with 100 g of 2-butanone, and purged with nitrogen for 30
minutes. The flask was then heated to 80.degree. C. with stirring,
and the monomer solution was added dropwise to the flask using a
dropping funnel over 3 hours. The monomers were polymerized for 6
hours from the start of dropwise addition of the monomer solution.
After completion of polymerization, the polymer solution was cooled
with water to 30.degree. C. or less, and poured into 2000 g of
methanol. A precipitated white powder was collected by filtration.
The collected white powder was washed twice with 400 g of methanol
in a slurry state, collected by filtration, and dried at 50.degree.
C. for 17 hours to obtain a white powdery polymer (D-2) (73 g,
yield: 73%). The polymer (D-2) had an Mw of 5700 and an Mw/Mn ratio
of 1.7. The ratio of structural units derived from the compounds
(M-9), (M-10), and (M-12) contained in the polymer (D-2) as
determined by .sup.13C-NMR analysis was 51.4:14.6:34.0 (mol %).
Production of Photoresist Composition
Synthesis Example 25
[0128] 30 parts by mass of the polymer (D-1), 70 parts by mass of
the polymer (D-2), 4 parts by mass of triphenylsulfonium
nonafluoro-n-butanesulfonate (acid generator), 5 parts by mass of
1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiophenium
nonafluoro-n-butanesulfonate (acid generator), 0.83 parts by mass
of R-(+)-(tert-butoxycarbonyl)-2-piperidinemethanol (acid diffusion
controller), 1710 parts by mass of propylene glycol monomethyl
ether acetate (solvent), and 730 parts by mass of cyclohexanone
(solvent) were mixed to obtain a photoresist composition.
Evaluation
[0129] The following items were evaluated using each liquid
immersion lithography upper-layer film-forming composition and the
photoresist composition.
Removability of Liquid Immersion Lithography Upper-Layer Film
[0130] The liquid immersion lithography upper-layer film-forming
composition was spin-coated onto an 8-inch silicon wafer using a
coater/developer ("CLEAN TRACK ACT 8" manufactured by Tokyo
Electron Ltd.), and baked at 90.degree. C. for 60 seconds to form a
liquid immersion lithography upper-layer film having a thickness of
90 nm. The thickness was measured by using a spectroscopic film
thickness measurement system ("Lambda Ace VM90" manufactured by
Dainippon Screen Mfg. Co., Ltd.). The film was subjected to paddle
development (developer: 2.38% TMAH aqueous solution) for 60 seconds
using the coater/developer ("CLEAN TRACK ACT 8"), and the wafer was
spin-dried. The surface of the wafer was then observed. The liquid
immersion lithography upper-layer films formed using the liquid
immersion lithography upper-layer film-forming compositions of
Examples 1 to 108 were developed so that residues did not remain on
the surface of the wafer (i.e., exhibited excellent
removability).
Receding Contact Angle (.degree.)
[0131] The liquid immersion lithography upper-layer film-forming
composition was spin-coated onto an 8-inch silicon wafer, and
prebaked on a hot plate at 90.degree. C. for 60 seconds to form a
liquid immersion lithography upper-layer film having a thickness of
30 nm. The receding contact angle (.degree.) was immediately
measured at a temperature of 23.degree. C. (room temperature) and a
humidity of 45% under atmospheric pressure using a contact angle
meter ("DSA-10" manufactured by KRUS). Specifically, the position
of the wafer stage of the contact angle meter ("DSA-10") was
adjusted, and the wafer was placed on the stage. After injecting
water into the needle, the position of the needle was adjusted to
the initial position at which a waterdrop can be formed on the
wafer. Water was discharged from the needle to form a waterdrop (25
.mu.l) on the wafer. After removing the needle, the needle was
again moved downward to the initial position, and introduced into
the waterdrop. The waterdrop was sucked via the needle for 90
seconds at a rate of 10 .mu.l/min, and the contact angle was
measured every second (90 times in total). The average value of
twenty contact angle measured values (20 seconds) after the
measured value became stable was calculated, and taken as the
receding contact angle (.degree.). The liquid immersion lithography
upper-layer films formed using the liquid immersion lithography
upper-layer film-forming compositions of Examples 1 to 108 had a
receding contact angle of 65.0.degree. or more.
Advancing Contact Angle (.degree.)
[0132] The photoresist composition was spin-coated onto an 8-inch
silicon wafer, and prebaked on a hot plate at 90.degree. C. for 60
seconds to form a photoresist film having a thickness of 120 nm.
The advancing contact angle (.degree.) was immediately measured at
a temperature of 23.degree. C. (room temperature) and a humidity of
45% under atmospheric pressure using the contact angle meter
("DSA-10"). Specifically, the position of the wafer stage of the
contact angle meter ("DSA-10") was adjusted, and the wafer was
placed on the stage. After injecting water into the needle, the
position of the needle was adjusted to the initial position at
which a waterdrop can be formed on the wafer. Water was discharged
from the needle to form a waterdrop (15 .mu.l) on the wafer. After
removing the needle, the needle was again moved downward to the
initial position, and introduced into the waterdrop. The waterdrop
was discharged via the needle for 90 seconds at a rate of 10
.mu.l/min, and the contact angle was measured every second (90
times in total). The average value of twenty contact angle measured
values (20 seconds) after the measured value became stable was
calculated, and taken as the advancing contact angle (.degree.).
The liquid immersion lithography upper-layer films formed using the
liquid immersion lithography upper-layer film-forming compositions
of Examples 1 to 108 had an advancing contact angle of 95.0.degree.
or less.
Intermixing
[0133] The photoresist composition was spin-coated onto an 8-inch
silicon wafer that was subjected to a hexamethyldisilazane (HMDS)
treatment (100.degree. C., 60 seconds) in advance using the
coater/developer ("CLEAN TRACK ACT 8"). The photoresist composition
was prebaked on a hot plate at 90.degree. C. for 60 seconds to form
a photoresist film having a thickness of 120 nm. The liquid
immersion lithography upper-layer film-forming composition was
spin-coated onto the photoresist film, and prebaked at 90.degree.
C. for 60 seconds to form a liquid immersion lithography
upper-layer film having a thickness of 30 nm. Ultrapure water was
discharged (60 seconds) to the wafer through the rinse nozzle of
the coater/developer ("CLEAN TRACK ACT 8"), and the wafer was
spin-dried at 4000 rpm for 15 seconds. The wafer was then subjected
to puddle development (developer: 2.38% TMAH aqueous solution)
using the LD nozzle of the coater/developer ("CLEAN TRACK ACT 8")
to remove the liquid immersion lithography upper-layer film Note
that the photoresist film that was not exposed remained on the
wafer after puddle development. The thickness of the photoresist
film was measured before and after development using a
spectroscopic film thickness measurement system ("Lambda Ace VM90"
manufactured by Dainippon Screen Mfg. Co., Ltd.). When a change in
thickness was within 5%, it was determined that intermixing did not
occur between the photoresist film and the upper-layer film. The
liquid immersion lithography upper-layer films formed using the
liquid immersion lithography upper-layer film-forming compositions
of Examples 1 to 108 did not undergo intermixing.
Elution Volume (Mol/Cm.sup.2)
[0134] As shown in FIGS. 2 and 3, an 8-inch silicon wafer 3 was
subjected to an HMDS treatment (100.degree. C., 60 seconds) using
the coater/developer ("CLEAN TRACK ACT 8") to form an HMDS-treated
layer 4. A square (30.times.30 cm) silicone rubber sheet 5
(manufactured by Kureha Elastomer Co., Ltd., thickness: 1.0 mm)
having a circular center opening (diameter: 11.3 cm) was placed on
the side of the wafer 3 on which the HMDS-treated layer 4 was
formed. The silicone rubber sheet 5 was placed so that the center
opening (opening 6) was positioned at the center of the wafer 3.
The opening 6 of the silicone rubber sheet 5 was filled with 10 ml
of ultrapure water 7 using a 10 ml whole pipette. An 8-inch silicon
wafer 10 on which a lower-layer antireflective film 8, a
photoresist film 11, and a liquid immersion lithography upper-layer
film 9 were formed was provided. The wafer 10 was placed on the
wafer 3 so that the liquid immersion lithography upper-layer film 9
was positioned on the silicone rubber sheet 5 (i.e., the liquid
immersion lithography upper-layer film 9 came in contact with the
ultrapure water 7 so that leakage of the ultrapure water 7 did not
occur). The lower-layer antireflective film 8, the photoresist film
11, and the liquid immersion lithography upper-layer film 9 were
formed on the wafer 10 as follows. Specifically, a lower-layer
antireflective film-forming composition ("ARC29A" manufactured by
Brewer Science) was applied to the wafer 10 using the
coater/developer ("CLEAN TRACK ACT 8") to form the lower-layer
antireflective film 8 having a thickness of 77 nm. The photoresist
composition was spin-coated onto the lower-layer antireflective
film 8 using the coater/developer ("CLEAN TRACK ACT 8"), and baked
at 115.degree. C. for 60 seconds to form the photoresist film 11
having a thickness of 205 nm. The liquid immersion lithography
upper-layer film-forming composition was applied to the photoresist
film 11 to form the liquid immersion lithography upper-layer film
9. The wafer 10 was placed on the wafer 3 so that the liquid
immersion lithography upper-layer film 9 was positioned on the
silicone rubber sheet 5, and allowed to stand for 10 seconds. After
removing the wafer 10, the ultrapure water 7 that came in contact
with the liquid immersion lithography upper-layer film 9 was
collected using a glass syringe. The collected ultrapure water 7
was used as an analysis sample. The recovery rate of the ultrapure
water 7 with which the opening 6 of the silicone rubber sheet 5 was
filled was 95% or more. The peak intensity of the anion site of the
acid generator included in the analysis sample (ultrapure water)
was measured under the following measurement conditions using a
liquid chromatograph mass spectrometer (LC-MS) (LC section: "SERIES
1100" manufactured by AGILENT Corp., MS section: "Mariner"
manufactured by PerSeptive Biosystems, Inc.). The peak intensity of
an aqueous solution (1 ppb, 10 ppb, or 100 ppb) of the acid
generator used to produce the photoresist composition was measured
under the following measurement conditions, and a calibration curve
was drawn. The elution volume of the acid generator (anion site)
eluted into water was calculated using the calibration curve.
Likewise, the peak intensity of an aqueous solution (1 ppb, 10 ppb,
or 100 ppb) of the acid diffusion controller was measured under the
following measurement conditions, and a calibration curve was
drawn. The elution volume of the acid diffusion controller eluted
into water was calculated using the calibration curve. The elution
volume was evaluated as "Acceptable" when the sum of the elution
volume of the anion site of the acid generator and the elution
volume of the acid diffusion controller was 5.0.times.10.sup.-12
mol/cm.sup.2 or less. The liquid immersion lithography upper-layer
films formed using the liquid immersion lithography upper-layer
film-forming compositions of Examples 1 to 108 showed an acceptable
elution volume. The following measurement conditions were used.
Column: CAPCELL PAK MG (manufactured by Shiseido Co., Ltd.) Flow
rate: 0.2 ml/min Eluant: water/methanol (3:7) mixture containing
0.1 wt % of formic acid Measurement temperature: 35.degree. C.
Blob Defects
[0135] An 8-inch silicon wafer was subjected to an HMDS treatment
(100.degree. C., 60 seconds) using the coater/developer ("CLEAN
TRACK ACT 8"). The photoresist composition was spin-coated onto the
8-inch silicon wafer, and prebaked on a hot plate at 90.degree. C.
for 60 seconds to form a photoresist film having a thickness of 120
nm. The liquid immersion lithography upper-layer film-forming
composition was spin-coated onto the photoresist film, and prebaked
at 90.degree. C. for 60 seconds to form a liquid immersion
lithography upper-layer film having a thickness of 30 nm. The
liquid immersion lithography upper-layer film was then exposed via
frosted glass on which a pattern was not formed. Next, ultrapure
water was discharged (60 seconds) to the liquid immersion
lithography upper-layer film through the rinse nozzle of the
coater/developer ("CLEAN TRACK ACT 8"), and the wafer was
spin-dried at 4000 rpm for 15 seconds. The wafer was then subjected
to puddle development for 60 seconds using the LD nozzle of the
coater/developer ("CLEAN TRACK ACT 8") to remove the liquid
immersion lithography upper-layer film. A 2.38% TMAH aqueous
solution was used as the developer. The degree by which the liquid
immersion lithography upper-layer film remained undissolved was
measured using a system "KLA2351" (manufactured by KLA-Tencor) to
evaluate blob defects. A case where the number of detected
development defects was 200 or less was evaluated as "Acceptable".
The number of development defects detected when using the liquid
immersion lithography upper-layer films formed using the liquid
immersion lithography upper-layer film-forming compositions of
Examples 1 to 108 was 200 or less.
Patterning Capability
[0136] A lower-layer antireflective film-forming composition
("ARC29A" manufactured by Brewer Science) was applied to an 8-inch
silicon wafer using the coater/developer ("CLEAN TRACK ACT 8"), and
prebaked at 205.degree. C. for 60 seconds to form a lower-layer
antireflective film having a thickness of 77 nm. The photoresist
composition was spin-coated onto the lower-layer antireflective
film, and prebaked at 90.degree. C. for 60 seconds to form a
photoresist film having a thickness of 120 nm. The liquid immersion
lithography upper-layer film-forming composition was spin-coated
onto the photoresist film, and prebaked at 90.degree. C. for 60
seconds to form a liquid immersion lithography upper-layer film
having a thickness of 30 nm. The liquid immersion lithography
upper-layer film was exposed using an ArF projection aligner
("S306C" manufactured by Nikon Corporation) (NA: 0.78, .sigma.:
0.85, 2/3 Ann). Next, ultrapure water was discharged (60 seconds)
to the wafer through the rinse nozzle of the coater/developer
("CLEAN TRACK ACT 8"), and the wafer was spin-dried at 4000 rpm for
15 seconds. The wafer was then subjected to post-exposure bake
(115.degree. C., 60 seconds) using the hot plate of the
coater/developer ("CLEAN TRACK ACT 8"), and subjected to puddle
development (30 seconds) (developer: 2.38% TMAH aqueous solution)
using the LD nozzle of the coater/developer ("CLEAN TRACK ACT 8").
The wafer was rinsed with ultrapure water, and spin-dried at 4000
rpm for 15 seconds. A dose at which a 1:1 line-and-space (1L1S)
pattern having a line width of 90 nm was formed was taken as an
optimum dose. A scanning electron microscope ("S-9380" manufactured
by Hitachi High-Tech Fielding Corporation) was used for the
measurement. The cross-sectional shape of the line-and-space
pattern (line width: 90 nm) was observed using a scanning electron
microscope ("S-4200" manufactured by Hitachi High-Tech Fielding
Corporation). As shown in FIG. 1, a line width Lb in an
intermediate area of a photoresist pattern 2 formed on a substrate
1 and a line width La at the top of the photoresist pattern were
measured. The patterning capability was evaluated as "Acceptable"
when 0.9<La/Lb<1.1. The liquid immersion lithography
upper-layer films formed using the liquid immersion lithography
upper-layer film-forming compositions of Examples 1 to 108
exhibited an acceptable patterning capability.
Watermark Defects and Bubble Defects
[0137] A 12-inch silicon wafer on which a lower-layer
antireflective film (thickness: 77 nm) ("ARC29A" manufactured by
Brewer Science) was formed was used as a substrate. The lower-layer
antireflective film was formed using a coater/developer ("CLEAN
TRACK ACT 12" manufactured by Tokyo Electron Ltd.). The photoresist
composition was spin-coated onto the substrate using the
coater/developer ("CLEAN TRACK ACT 12"), and prebaked at 90.degree.
C. for 60 seconds to form a photoresist film having a thickness of
120 nm. The liquid immersion lithography upper-layer film-forming
composition was spin-coated onto the photoresist film, and prebaked
at 90.degree. C. for 60 seconds to form a liquid immersion
lithography upper-layer film having a thickness of 30 nm. The
liquid immersion lithography upper-layer film was exposed via a
mask pattern using an ArF projection aligner ("S610C" manufactured
by Nikon Corporation, NA 0.85, .sigma.0/.sigma.1=0.97/0.78,
Azimuth). In this case, purified water (immersion medium) was
provided between the upper side of the liquid immersion lithography
upper-layer film and the lens of the ArF projection aligner (liquid
immersion lithography system). The liquid immersion lithography
upper-layer film was baked at 115.degree. C. for 60 seconds,
developed at 23.degree. C. for 60 seconds using a 2.38 mass %
tetramethylammonium hydroxide aqueous solution, washed with water,
and dried to form a positive-tone photoresist pattern. Defects were
detected using a system "KLA2810" (manufactured by KLA-Tencor), and
the resulting line-and-space (1L1S) pattern (line width: 100 nm)
was observed using a scanning electron microscope ("S-9380"
manufactured by Hitachi High Technologies Corporation) to classify
the defects into watermark defects (i.e., defects considered to be
caused by liquid immersion lithography using ArF excimer laser
light) and bubble defects. A case where the number of watermark
defects detected was less than 30 was evaluated as "AA", a case
where the number of watermark defects detected was 30 or more and
less than 50 was evaluated as "A" (acceptable), a case where the
number of watermark defects detected was 50 or more and less than
100 was evaluated as "B" (fair), and a case where the number of
watermark defects detected was more than 100 was evaluated as "C"
(unacceptable). The evaluation results are shown in Tables 2 to 4
(see the item "Watermark defects"). A case where the number of
bubble defects detected was 50 or less was evaluated as
"Acceptable". The number of bubble defects detected when using the
liquid immersion lithography upper-layer films formed using the
liquid immersion lithography upper-layer film-forming compositions
of Examples 1 to 108 was 50 or less.
Bridge Defects
[0138] A positive-tone photoresist pattern was formed in the same
manner as described above (see the section entitled "Watermark
defects"). Bridge defects were detected using a system "KLA2810"
(manufactured by KLA-Tencor), and the resulting line-and-space
(1L1S) pattern (line width: 100 nm) was observed using a scanning
electron microscope ("S-9380" manufactured by Hitachi High
Technologies Corporation). A case where the number of bridge
defects detected was less than 50 was evaluated as "A"
(acceptable), a case where the number of bridge defects detected
was 50 or more and less than 100 was evaluated as "B" (fair), and a
case where the number of bridge defects detected was more than 100
was evaluated as "C" (unacceptable). The results are shown in
Tables 2 to 4.
TABLE-US-00002 TABLE 2 Polymer Amount Amount Amount Watermark
Bridge Type (parts by mass) Type (parts by mass) Type (parts by
mass) defects defects Example 1 P-1 92 P-8 3 P-22 5 AA A Example 2
P-1 75 P-8 20 P-22 5 AA A Example 3 P-1 37 P-8 3 P-22 60 AA A
Example 4 P-1 20 P-8 20 P-22 60 AA A Example 5 P-1 100 -- -- -- --
A A Example 6 P-1 97 P-8 3 -- -- AA A Example 7 P-1 80 P-8 20 -- --
AA A Example 8 P-1 92 P-16 3 P-22 5 AA A Example 9 P-1 65 P-16 15
P-22 20 AA A Example 10 P-1 75 P-16 20 P-22 5 AA A Example 11 P-1
37 P-16 3 P-22 60 AA A Example 12 P-1 20 P-16 20 P-22 60 AA A
Example 13 P-1 100 -- -- -- -- A A Example 14 P-1 97 P-16 3 -- --
AA A Example 15 P-1 85 P-16 15 -- -- AA A Example 16 P-1 80 P-16 20
-- -- AA A Example 17 P-2 92 P-8 3 P-22 5 AA A Example 18 P-2 75
P-8 20 P-22 5 AA A Example 19 P-2 37 P-8 3 P-22 60 AA A Example 20
P-2 20 P-8 20 P-22 60 AA A Example 21 P-2 100 -- -- -- -- A A
Example 22 P-2 97 P-8 3 -- -- AA A Example 23 P-2 80 P-8 20 -- --
AA A Example 24 P-3 92 P-8 3 P-22 5 AA A Example 25 P-3 75 P-8 20
P-22 5 AA A Example 26 P-3 37 P-8 3 P-22 60 AA A Example 27 P-3 20
P-8 20 P-22 60 AA A Example 28 P-3 100 -- -- -- -- A A Example 29
P-3 97 P-8 3 -- -- AA A Example 30 P-3 80 P-8 20 -- -- AA A Example
31 P-4 92 P-8 3 P-22 5 AA A Example 32 P-4 75 P-8 20 P-22 5 AA A
Example 33 P-4 37 P-8 3 P-22 60 AA A Example 34 P-4 20 P-8 20 P-22
60 AA A Example 35 P-4 100 -- -- -- -- A A Example 36 P-4 97 P-8 3
-- -- AA A Example 37 P-4 80 P-8 20 -- -- AA A Example 38 P-5 92
P-8 3 P-22 5 AA A Example 39 P-5 75 P-8 20 P-22 5 AA A Example 40
P-5 37 P-8 3 P-22 60 AA A Example 41 P-5 20 P-8 20 P-22 60 AA A
Example 42 P-5 100 -- -- -- -- A A Example 43 P-5 97 P-8 3 -- -- AA
A Example 44 P-5 80 P-8 20 -- -- AA A Example 45 P-6 92 P-8 3 P-22
5 AA A Example 46 P-6 75 P-8 20 P-22 5 AA A Example 47 P-6 37 P-8 3
P-22 60 AA A Example 48 P-6 20 P-8 20 P-22 60 AA A Example 49 P-6
100 -- -- -- -- A A Example 50 P-6 97 P-8 3 -- -- AA A
TABLE-US-00003 TABLE 3 Polymer Amount Amount Amount Watermark
Bridge Type (parts by mass) Type (parts by mass) Type (parts by
mass) defects defects Example 51 P-6 80 P-8 20 -- -- AA A Example
52 P-7 92 P-8 3 P-22 5 AA A Example 53 P-7 75 P-8 20 P-22 5 AA A
Example 54 P-7 37 P-8 3 P-22 60 AA A Example 55 P-7 20 P-8 20 P-22
60 AA A Example 56 P-7 100 -- -- -- -- A A Example 57 P-7 97 P-8 3
-- -- AA A Example 58 P-7 80 P-8 20 -- -- AA A Example 59 P-8 3
P-14 92 P-22 5 A A Example 60 P-8 20 P-14 75 P-22 5 A A Example 61
P-8 3 P-14 37 P-22 60 A A Example 62 P-8 20 P-14 20 P-22 60 A A
Example 63 P-8 3 P-14 97 -- -- A A Example 64 P-8 20 P-14 80 -- --
A A Example 65 P-1 77 P-8 3 P-22 20 AA A Example 66 P-1 60 P-8 20
P-22 20 AA A Example 67 P-1 77 P-9 3 P-22 20 AA A Example 68 P-1 60
P-9 20 P-22 20 AA A Example 69 P-1 97 P-9 3 -- -- AA A Example 70
P-1 80 P-9 20 -- -- AA A Example 71 P-1 77 P-10 3 P-22 20 AA A
Example 72 P-1 60 P-10 20 P-22 20 AA A Example 73 P-1 97 P-10 3 --
-- AA A Example 74 P-1 80 P-10 20 -- -- AA A Example 75 P-1 77 P-16
3 P-22 20 AA A Example 76 P-1 60 P-16 20 P-22 20 AA A Example 77
P-1 97 P-16 3 -- -- AA A Example 78 P-1 80 P-16 20 -- -- AA A
Example 79 P-1 77 P-16 3 P-22 20 AA A Example 80 P-1 60 P-16 20
P-22 20 AA A Example 81 P-1 97 P-17 3 -- -- AA A Example 82 P-1 80
P-17 20 -- -- AA A Example 83 P-1 77 P-16 3 P-22 20 AA A Example 84
P-1 60 P-16 20 P-22 20 AA A Example 85 P-1 97 P-18 3 -- -- AA A
Example 86 P-1 80 P-18 20 -- -- AA A Example 87 P-1 77 P-11 3 P-22
20 AA A Example 88 P-1 65 P-11 15 P-22 20 AA A Example 89 P-1 60
P-11 20 P-22 20 AA A Example 90 P-1 77 P-12 3 P-22 20 AA A
TABLE-US-00004 TABLE 4 Polymer Amount Amount Amount Watermark
Bridge Type (parts by mass) Type (parts by mass) Type (parts by
mass) defects defects Example 91 P-1 60 P-12 20 P-22 20 AA A
Example 92 P-1 97 P-12 3 -- -- AA A Example 93 P-1 80 P-12 20 -- --
AA A Example 94 P-1 77 P-13 3 P-22 20 AA A Example 95 P-1 60 P-13
20 P-22 20 AA A Example 96 P-1 97 P-13 3 -- -- AA A Example 97 P-1
80 P-13 20 -- -- AA A Example 98 P-1 77 P-16 3 P-22 20 AA A Example
99 P-1 60 P-16 20 P-22 20 AA A Example 100 P-1 77 P-19 3 P-22 20 AA
A Example 101 P-1 70 P-19 10 P-22 20 AA A Example 102 P-1 60 P-19
20 P-22 20 AA A Example 103 P-1 97 P-20 3 -- -- AA A Example 104
P-1 80 P-20 20 -- -- AA A Example 105 P-1 77 P-16 3 P-22 20 AA A
Example 106 P-1 60 P-16 20 P-22 20 AA A Example 107 P-1 97 P-21 3
-- -- AA A Example 108 P-1 80 P-21 20 -- -- AA A Comparative
Example 1 P-14 92 P-16 3 P-22 5 A B Comparative Example 2 P-14 75
P-16 20 P-22 5 A B Comparative Example 3 P-14 37 P-16 3 P-22 60 A B
Comparative Example 4 P-14 20 P-16 20 P-22 60 A B Comparative
Example 5 P-14 100 -- -- -- -- A B Comparative Example 6 P-14 97
P-16 3 -- -- A B Comparative Example 7 P-14 80 P-16 20 -- -- A B
Comparative Example 8 P-15 92 P-16 3 P-22 5 B A Comparative Example
9 P-15 75 P-16 20 P-22 5 B A Comparative Example 10 P-15 37 P-16 3
P-22 60 B A Comparative Example 11 P-15 20 P-16 20 P-22 60 B A
Comparative Example 12 P-15 100 -- -- -- -- B A Comparative Example
13 P-15 97 P-16 3 -- -- B A Comparative Example 14 P-15 80 P-16 20
-- -- B A Comparative Example 15 P-23 92 P-16 3 P-22 5 A B
Comparative Example 16 P-23 75 P-16 20 P-22 5 A B Comparative
Example 17 P-23 37 P-16 3 P-22 60 A B Comparative Example 18 P-23
20 P-16 20 P-22 60 A B Comparative Example 19 P-23 100 -- -- -- --
A B Comparative Example 20 P-23 97 P-16 3 -- -- A B Comparative
Example 21 P-23 80 P-16 20 -- -- A B
[0139] As is clear from the results shown in Tables 2 to 4, it was
confirmed that the liquid immersion lithography upper-layer
film-forming compositions of Examples 1 to 108 could form a liquid
immersion lithography upper-layer film that can suppress occurrence
of watermark defects and bridge defects. On the other hand, the
liquid immersion lithography upper-layer film-forming compositions
of Comparative Examples 1 to 7 using the polymer that did not
include the structural unit (I) could not sufficiently suppress
occurrence of bridge defects. The liquid immersion lithography
upper-layer film-forming compositions of Comparative Examples 8 to
14 could not sufficiently suppress occurrence of watermark
defects.
INDUSTRIAL APPLICABILITY
[0140] The invention thus provides a liquid immersion lithography
upper-layer film-forming composition that can form a liquid
immersion lithography upper-layer film that exhibits moderate water
repellency and high solubility in a developer, and can suppress
occurrence of various defects such as watermark defects and bridge
defects even if a high scan speed is employed. Therefore, the
liquid immersion lithography upper-layer film-forming composition
may suitably be used for the production of semiconductor devices
that are expected to be further scaled down in the future.
EXPLANATION OF SYMBOLS
[0141] 1 substrate [0142] 2 photoresist pattern [0143] 3 8-inch
silicon wafer [0144] 4 hexamethyldisilazane-treated layer [0145] 5
silicon rubber sheet [0146] 6 opening [0147] 7 ultra-pure water
[0148] 8 lower-layer antireflective film [0149] 9 liquid immersion
lithography upper-layer film [0150] 10 8-inch silicon wafer [0151]
11 photoresist film
* * * * *