U.S. patent application number 12/872461 was filed with the patent office on 2010-12-23 for copolymer for semiconductor lithography and producing method thereof, and composition.
This patent application is currently assigned to MARUZEN PETROCHEMICAL CO., LTD.. Invention is credited to Kiyomi Miki, Takayoshi Okada, Takanori YAMAGISHI, Satoshi Yamaguchi.
Application Number | 20100324245 12/872461 |
Document ID | / |
Family ID | 35241636 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100324245 |
Kind Code |
A1 |
YAMAGISHI; Takanori ; et
al. |
December 23, 2010 |
COPOLYMER FOR SEMICONDUCTOR LITHOGRAPHY AND PRODUCING METHOD
THEREOF, AND COMPOSITION
Abstract
In order to improve a resist pattern shape in a semiconductor
lithography process, which is a factor largely affecting on a
processing precision, an integration degree and yield, a copolymer
for semiconductor lithography where a composition of a hydroxyl
group-containing repeating unit in a low molecular weight region is
controlled, and a method of producing the same are provided.
According to the invention, in a copolymer for semiconductor
lithography, which is obtained by copolymerizing a monomer having a
hydroxyl group and a monomer having no hydroxyl group, when a
copolymer of which composition of a hydroxyl group-containing
repeating unit is controlled is used, the object can be
achieved.
Inventors: |
YAMAGISHI; Takanori;
(Funabashi-shi, JP) ; Okada; Takayoshi;
(Ichihara-shi, JP) ; Yamaguchi; Satoshi;
(Ichihara-shi, JP) ; Miki; Kiyomi; (Ichihara-shi,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
MARUZEN PETROCHEMICAL CO.,
LTD.
Chuo-ku
JP
|
Family ID: |
35241636 |
Appl. No.: |
12/872461 |
Filed: |
August 31, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11587592 |
Oct 25, 2006 |
|
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PCT/JP05/08168 |
Apr 28, 2005 |
|
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12872461 |
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Current U.S.
Class: |
526/270 ;
526/266; 526/313 |
Current CPC
Class: |
Y10S 430/106 20130101;
Y10S 430/111 20130101; G03F 7/0392 20130101; G03F 7/0046
20130101 |
Class at
Publication: |
526/270 ;
526/313; 526/266 |
International
Class: |
C08F 24/00 20060101
C08F024/00; C08F 12/24 20060101 C08F012/24 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 30, 2004 |
JP |
2004-136565 |
Claims
1. A copolymer for semiconductor lithography obtained by
copolymerizing a monomer having a hydroxyl group and a monomer
having no hydroxyl group, wherein a molar composition of a hydroxyl
group-containing repeating unit in a low molecular weight region
corresponding to 5% of a copolymer total peak by gel permeation
chromatography is within .+-.10% of an average molar composition of
hydroxyl group-containing repeating units in a total of the
copolymer.
2. The copolymer for semiconductor lithography according to claim
1, wherein the monomer having a hydroxyl group is selected from the
group consisting of a hydroxystyrene, a
hydroxyhalogenoalkylstyrene, a carboxylic acid having an ethylenic
double bond, a hydroxyalkyl ester of carboxylic acid having an
ethylenic double bond, and a hydroxyhalogenoalkyl ester of
carboxylic acid having an ethylenic double bond.
3. The copolymer for semiconductor lithography according to claim
2, wherein the monomer having a hydroxyl group is a
hydroxystyrene.
4. The copolymer for semiconductor lithography according to claim
2, wherein the monomer having a hydroxyl group is a
hydroxyhalogenoalkylstyrene.
5. The copolymer for semiconductor lithography according to claim
2, wherein the monomer having a hydroxyl group is a carboxylic acid
having an ethylenic double bond.
6. The copolymer for semiconductor lithography according to claim
2, wherein the monomer having a hydroxyl group is a hydroxyalkyl
ester of carboxylic acid having an ethylenic double bond.
7. The copolymer for semiconductor lithography according to claim
2, wherein the monomer having a hydroxyl group is a
hydroxyhalogenoalkyl ester of carboxylic acid having an ethylenic
double bond.
8. The copolymer for semiconductor lithography according to claim
1, wherein the monomer having no hydroxyl group is a monomer having
a hydroxyl group that is protected with a protecting group, wherein
the monomer having a hydroxyl group that is protected with a
protecting group is selected from the group consisting of a
hydroxystyrene, a hydroxyhalogenoalkylstyrene, a carboxylic acid
having an ethylenic double bond, a hydroxyalkyl ester of carboxylic
acid having an ethylenic double bond, and a hydroxyhalogenoalkyl
ester of carboxylic acid having an ethylenic double bond, and
wherein the protecting group is selected from the group consisting
of a saturated hydrocarbon group having 1-20 carbon atoms and an
oxygen-containing hydrocarbon group having 2-24 carbon atoms.
9. The copolymer for semiconductor lithography according to claim
8, wherein the monomer having a hydroxyl group that is protected
with a protecting group is a hydroxystyrene, and wherein the
protecting group is selected from the group consisting of a
saturated hydrocarbon group having 1-20 carbon atoms and an
oxygen-containing hydrocarbon group having 2-24 carbon atoms.
10. The copolymer for semiconductor lithography according to claim
8, wherein the monomer having a hydroxyl group that is protected
with a protecting group is a hydroxyhalogenoalkylstyrene, and
wherein the protecting group is selected from the group consisting
of a saturated hydrocarbon group having 1-20 carbon atoms and an
oxygen-containing hydrocarbon group having 2-24-carbon atoms.
11. The copolymer for semiconductor lithography according to claim
8, wherein the monomer having a hydroxyl group that is protected
with a protecting group is a carboxylic acid having an ethylenic
double bond, and wherein the protecting group is selected from the
group consisting of a saturated hydrocarbon group having 1-20
carbon atoms and an oxygen-containing hydrocarbon group having 2-24
carbon atoms.
12. The copolymer for semiconductor lithography according to claim
8, wherein the monomer having a hydroxyl group that is protected
with a protecting group is a hydroxyalkyl ester of carboxylic acid
having an ethylenic double bond, and wherein the protecting group
is selected from the group consisting of a saturated hydrocarbon
group having 1-20 carbon atoms and an oxygen-containing hydrocarbon
group having 2-24 carbon atoms.
13. The copolymer for semiconductor lithography according to claim
8, wherein the monomer having a hydroxyl group that is protected
with a protecting group is a hydroxyhalogenoalkyl ester of
carboxylic acid having an ethylenic double bond, and wherein the
protecting group is selected from the group consisting of a
saturated hydrocarbon group having 1-20 carbon atoms and an
oxygen-containing hydrocarbon group having 2-24 carbon atoms.
14. A semiconductor lithography composition comprising the
copolymer for semiconductor lithography according to claim 1.
15. A copolymer for semiconductor lithography produced by a process
comprising: copolymerizing a monomer having a hydroxyl group and a
monomer having no hydroxyl group in a polymerization reaction
solution comprising a polymerization solvent to produce the
copolymer; and bringing the copolymer, which is present in the
polymerization reaction solution, into contact with a poor solvent
comprising: a polar solvent having a hydroxyl group; and a nonpolar
solvent having no hydroxyl group, to reprecipitate or wash the
copolymer, wherein a molar composition of a hydroxyl
group-containing repeating unit in a low molecular weight region
corresponding to 5% of a copolymer total peak by gel permeation
chromatography is within .+-.10% of an average molar composition of
hydroxyl group-containing repeating units in a total of the
copolymer.
16. The copolymer for semiconductor lithography according to claim
15, wherein the monomer having a hydroxyl group is selected from
the group consisting of a hydroxystyrene, a
hydroxyhalogenoalkylstyrene, a carboxylic acid having an ethylenic
double bond, a hydroxyalkyl ester of carboxylic acid having an
ethylenic double bond, and a hydroxyhalogenoalkyl ester of
carboxylic acid having an ethylenic double bond.
17. The copolymer for semiconductor lithography according to claim
15, wherein the monomer having no hydroxyl group is a monomer
having a hydroxyl group that is protected with a protecting group,
wherein the monomer having a hydroxyl group that is protected with
a protecting group is selected from the group consisting of a
hydroxystyrene, a hydroxyhalogenoalkylstyrene, a carboxylic acid
having an ethylenic double bond, a hydroxyalkyl ester of carboxylic
acid having an ethylenic double bond, and a hydroxyhalogenoalkyl
ester of carboxylic acid having an ethylenic double bond, and
wherein the protecting group is selected from the group consisting
of a saturated hydrocarbon group having 1-20 carbon atoms and an
oxygen-containing hydrocarbon group having 2-24 carbon atoms.
18. A process for producing a copolymer for semiconductor
lithography, wherein said process comprises: copolymerizing a
monomer having a hydroxyl group and a monomer having no hydroxyl
group in a polymerization reaction solution comprising a
polymerization solvent to produce the copolymer; and bringing the
copolymer, which is present in the polymerization reaction
solution, into contact with a poor solvent comprising: a polar
solvent having a hydroxyl group; and a nonpolar solvent having no
hydroxyl group, to reprecipitate or wash the copolymer, wherein a
molar composition of a hydroxyl group-containing repeating unit in
a low molecular weight region corresponding to 5% of a copolymer
total peak by gel permeation chromatography is within .+-.10% of an
average molar composition of hydroxyl group-containing repeating
units in a total of the copolymer.
19. The process for producing a copolymer for semiconductor
lithography according to claim 18, wherein the monomer having a
hydroxyl group is selected from the group consisting of a
hydroxystyrene, a hydroxyhalogenoalkylstyrene, a carboxylic acid
having an ethylenic double bond, a hydroxyalkyl ester of carboxylic
acid having an ethylenic double bond, and a hydroxyhalogenoalkyl
ester of carboxylic acid having an ethylenic double bond.
20. The process for producing a copolymer for semiconductor
lithography according to claim 18, wherein the monomer having no
hydroxyl group is a monomer having a hydroxyl group that is
protected with a protecting group, wherein the monomer having a
hydroxyl group that is protected with a protecting group is
selected from the group consisting of a hydroxystyrene, a
hydroxyhalogenoalkylstyrene, a carboxylic acid having an ethylenic
double bond, a hydroxyalkyl ester of carboxylic acid having an
ethylenic double bond, and a hydroxyhalogenoalkyl ester of
carboxylic acid having an ethylenic double bond, and wherein the
protecting group is selected from the group consisting of a
saturated hydrocarbon group having 1-20 carbon atoms and an
oxygen-containing hydrocarbon group having 2-24 carbon atoms.
Description
TECHNICAL FIELD
[0001] The present invention relates to a copolymer suitable for
forming a coating film, such as a resist film used in a
semiconductor lithography process, an anti-reflective film or the
underlayer film of a multi-layered resist, to a method for the
production thereof, and to a composition containing said copolymer
for a semiconductor lithography.
BACKGROUND ART
[0002] In a lithography process employed for producing a
semiconductor, formation of a finer pattern is increasingly
required so as to match with an elevated degree of integration. For
formation of a finer pattern, it is essential that the length of
the light wave beaming from an exposure light source be made as
shorter as possible. At present, a lithography using a krypton
fluoride (KrF) excimer laser (wavelength: 248 nm) is becoming
mainstream, and a lithography using an argon fluoride (ArF) excimer
laser (wavelength: 193 nm), which enables a line width of 100 nm or
less, is expected to come into practical use. Furthermore, various
kinds of radiation lithography technologies using a short
wavelength, such as fluorine dimer (F.sub.2) excimer laser light
(wavelength: 157 nm), extreme-UV rays, X-rays or electron beams,
are in a developmental stage.
[0003] In semiconductor lithography processes, in a resist film
where by making use of a variation of the solubility to an alkali
developer under an action of acid, a resist pattern for
transferring on a substrate is formed, and in an upper layer of the
resist film or a lower layer of the resist film, various kinds of
coating films are used. It can be cited that as a coating film
applied to, for instance, a lower layer, that is, as a lower layer
film, an anti-reflective film that suppresses light from being
reflected from a substrate to accurately form a fine resist
pattern, a flattening film that is used in a lower layer of a
resist to make irregularity formed on a surface of the substrate
flat when a resist pattern is further formed on the substrate
thereon a pattern is formed, and an underlayer film or the like in
a multi-layered resist that is used to transfer a resist pattern
owing to dry etching.
[0004] These coating films can be formed in such a manner that a
coating solution where a copolymer for lithography, which has a
function of each of the coating films, other additives are
dissolved in an organic solvent is prepared, the coating solution
is coated on a substrate according to a method such as a spin
coating method, and as needs arise the solvent is removed by
heating or the like. In a copolymer used for lithography at that
time, in addition to the optical properties that are demanded for a
resist film and an anti-reflective film, chemical properties,
coating properties and physical properties such as the adhesiveness
to the substrate or the lower layer film, a fundamental property as
a coating copolymer such that foreign matters that disturb the
formation of a fine pattern are not present is demanded.
[0005] As a resist copolymer that is a copolymer used in a resist
film, there are a negative type copolymer in which owing to an
action of acid the solubility to an alkali developer is decreased
and a positive type copolymer in which owing to an action of acid
the solubility to an alkali developer is increased. The positive
type resist copolymer is constituted necessarily including a
repeating unit having a polar group that improves the adhesiveness
to a semiconductor substrate and an underlayer film, or controls
the solubility to a lithography organic solvent or an alkali
developer and a repeating unit having a structure where a nonpolar
substituent group is dissociated by acid to develop a polar group
soluble in an alkali developer, and, as needs arise, a repeating
unit having an acid-stable nonpolar substituent group for
controlling the solubility to the lithography organic solvent and
the alkali developer.
[0006] Specific examples of such a positive type resist copolymer
include, in the KrF lithography process, a copolymer that includes
a repeating unit derived from hydroxystyrene and a repeating unit
derived from acid-decomposable alkoxystyrene; a copolymer that
includes a repeating unit derived from hydroxystyrene and a
repeating unit derived from an acid-decomposable alkyl
(meth)acrylate; and a polymer wherein the hydroxystyrene-derived
repeating unit has been partially protected with an acetal are
known. In the ArF lithography process, a copolymer or the like that
includes a repeating unit derived from (meth)acrylate substituted
by a hydroxyalkyl group and a repeating unit derived from
acid-decomposable alkyl (meth)acrylate is known.
[0007] A repeating unit that has a hydroxyl group is readily
dissolved in an alkali developer. Accordingly, when the repeating
unit that has a hydroxyl group is used as for instance a resist
film, a resist pattern can be appropriately smoothed and the
roughness can be suppressed low and so on. Furthermore, the
solubility to the alkali developer is different depending on a
molecular weight of a copolymer as well. That is, in general, the
larger the molecular weight thereof is, the smaller the solubility
thereof is, and the smaller the molecular weight thereof is, the
larger the solubility thereof is. Accordingly, the higher a
composition of a repeating unit that is small in the molecular
weight and has the hydroxyl group is, the larger the solubility to
the alkali developer is. In general, when a copolymer is designed,
by taking such a nature into consideration, a composition of the
repeating unit having a hydroxyl group and a molecular weight
thereof are designed. Normally, a copolymer has a molecular weight
distribution, and a composition of the polymer is different between
a high molecular weight component and a low molecular weight
component (hereinafter, referred to as "composition in a molecular
weight direction"). Thus, when a composition of a hydroxyl group is
different in a molecular weight direction, a pattern as designed
cannot be depicted. For instance, when a repeating unit that
contains a hydroxyl group in a low molecular weight region is
contained much, a top shape of a pattern tends to be rounded, by
contrast, when the repeating unit that contains a hydroxyl group in
a low molecular weight region is contained less, the top shape of a
pattern tends to be angulated or rougher. Such a problem is
becoming incapable of neglecting as a pattern becomes finer.
[0008] As a copolymer of which composition in a molecular weight
direction is controlled, an example that is a copolymer containing
an alicyclic structure and a lactone structure, in which a lactone
composition in a molecular weight direction is controlled within
.+-.10%, is known (patent literature 1). Furthermore, an example
that is a copolymer between a monomer having an alicyclic structure
and p-acetoxystyrene, in which a p-acetoxystyrene composition in a
molecular weight direction is controlled within .+-.10%, is known
(patent literature 2). The technologies each have proposed a method
where, in a two-component copolymer that has an alicyclic structure
and a lactone structure or a monomer having an alicyclic structure
and p-acetoxystyrene, in order to improve the solubility to a
solvent, a lactone or p-acetoxystyrene composition is
controlled.
[0009] As a similar technology, a technology where a monomer having
a polar group such as a hydroxyl group and a monomer not containing
a polar group are supplied in a heated polymerization solvent
together with a polymerization initiator and a polymerization
catalyst to polymerize is known (patent literatures 3 and 4). The
technology has proposed, in order to improve the adhesiveness with
a substrate, a method of polymerizing a monomer having a polar
group-containing alicyclic functional group. However, in all of the
above-described technologies, the relationship between a
composition control in a low molecular weight region and the
lithography characteristics is not disclosed.
[0010] In a polymerization solution after a polymerization
reaction, other than a copolymer, there are low molecular weight
impurities such as an unreacted monomer and impurities derived from
the polymerization initiator or the polymerization catalyst. The
low molecular weight impurities are unfavorable because, in the
semiconductor lithography process, the impurities volatilize to
stick to an optical system of an exposure device, generate a defect
in a pattern or cause a variation in the nature of the copolymer
during storage. In this connection, a method is known where a
polymerization solution is mixed with a poor solvent to precipitate
a copolymer as a solid content (hereinafter, referred to as
"reprecipitation") or a precipitated copolymer is washed with a
poor solvent (hereinafter referred to as "washing"), and thereby
the copolymer is refined (hereinafter referred to "refining") owing
to solubility difference to the poor solvent of the copolymer and
the low molecular weight impurities. The refining process is
applied in almost all of the above referenced literatures. Other
than the above, a method where a composition of the solvent is
controlled so that a residual monomer may be 5% or less (patent
literature 5), a method where a copolymer-containing slurry
dispersed in a solvent is heated (patent literatures 6 and 7) and a
method where, by use of a poor solvent, reprecipitation or rinse is
applied to remove an insoluble content to improve the solvent
solubility (patent literature 8) or the like are known.
[0011] However, in all of the technologies, the poor solvent that
is brought into contact with the copolymer is, in each of
reprecipitation and/or washing step, only a polar solvent having a
hydroxyl group or only a nonpolar solvent that does not have a
hydroxyl group. In the refining step, since the solubility
difference between a low molecular weight region of the copolymer
and the low molecular weight impurities to be removed is small, the
low molecular weight region of the copolymer is partially removed.
Accordingly, there are problems in that, when a polar solvent
having a hydroxyl group is used to refine, a composition of a
hydroxyl group-containing repeating unit in the low molecular
weight region of the polymer is lowered, and when a nonpolar
solvent is used to refine, a composition of a hydroxyl
group-containing repeating unit in the low molecular weight region
of the polymer is raised.
[0012] From these backgrounds, in a copolymer for semiconductor
lithography, which is obtained by copolymerizing a monomer having a
hydroxyl group and a monomer that does not have a hydroxyl group,
only a polymer where a composition of a hydroxyl group-containing
repeating unit in the low molecular weight region is deviated from
an average composition is known. Accordingly, a problem relating to
a shape of a lithography pattern such as mentioned above is not yet
overcome.
Patent literature 1: WO99/50322 Patent literature 2: JP-A
2001-151823 Patent literature 3: JP-A 2002-194029 Patent literature
4: JP-A 2003-306514 Patent literature 5: JP-A 2001-109153 Patent
literature 6: JP-A 2002-201210 Patent literature 7: JP-A
2002-229220 Patent literature 8: JP-A 2003-213721
DISCLOSURE OF INVENTION
Problem that the Invention is to Solve
[0013] The object of the present invention is to provide a
copolymer for semiconductor lithography where in order to improve a
resist pattern shape in a semiconductor lithography process, which
is a large factor that largely affects on processing accuracy to
determine an integration degree and a yield, a composition of a
hydroxyl group-containing repeating unit in a low molecular weight
region is controlled, and a producing method thereof.
Means for Solving the Problem
[0014] The present inventors, after studying hard, found that, in a
copolymer for semiconductor lithography, which is obtained by
copolymerizing a monomer having a hydroxyl group and a monomer
having no hydroxyl group, when a copolymer is used where a molar
composition of a hydroxyl group-containing repeating unit in a low
molecular weight region is controlled, the above object can be
achieved, and thereby the invention came to completion. In general,
a kind of a copolymer, an average composition and an average
molecular weight are controlled to control a pattern shape.
However, it was found by the invention that, when only the
above-mentioned factors are controlled, a pattern shape as designed
could not be obtained. That is, when a composition of a hydroxyl
group in a molecular weight direction is controlled, a pattern as
designed, which can respond to a demand for miniaturization, can be
formed.
[0015] That is, the invention, in a copolymer for semiconductor
lithography, which is obtained by copolymerizing a monomer having a
hydroxyl group and a monomer having no hydroxyl group, provides a
copolymer for semiconductor lithography where a molar composition
of a hydroxyl group-containing repeating unit in a low molecular
weight region corresponding to 5% of a copolymer total peak in gel
permeation chromatography is within .+-.10% of an average molar
composition of the hydroxyl group-containing repeating unit in a
total copolymer and a composition for semiconductor lithography,
which contains the copolymer.
[0016] Furthermore, the invention provides a producing method of a
copolymer for semiconductor lithography, in which a copolymer for
semiconductor lithography, which is obtained by copolymerizing a
monomer having a hydroxyl group and a monomer having no hydroxyl
group, is obtained by undergoing, after a polymerization reaction,
a step of bringing an obtained copolymer into contact with a polar
solvent having a hydroxyl group to reprecipitate or wash; and a
step of bringing the obtained copolymer into contact with a
nonpolar solvent having no hydroxyl group to reprecipitate or
wash.
ADVANTAGE OF THE INVENTION
[0017] According to the invention, with a copolymer in which a
composition of a hydroxyl group-containing repeating unit of a low
molecular weight region, which largely affects particularly on a
pattern shape, is controlled, a fine pattern excellent in the
rectangularity can be formed and thereby a dense and fine
integrated circuit can be formed.
BEST MODE FOR CARRYING OUT THE INVENTION
[0018] A copolymer for semiconductor lithography according to the
invention necessarily includes, in order to improve the
adhesiveness with a semiconductor substrate or an underlayer film
and to control the solubility to a lithography organic solvent or
an alkali developer, at least a hydroxyl group-containing repeating
unit. Furthermore, the copolymer for semiconductor lithography
according to the invention is constituted including a repeating
unit that does not contain a hydroxyl group, which has functions
necessary for a resist layer, an underlayer film of a multi-layer
resist, an anti-reflection film and so on. Accordingly, the
copolymer for semiconductor lithography according to the invention
can be obtained by copolymerizing at least one kind of a monomer
having a hydroxyl group and at least one kind of a monomer having
no hydroxyl group.
[0019] When the copolymer is used in a positive type resist, the
copolymer necessarily includes, at least, a hydroxyl
group-containing repeating unit (A) that improves the adhesiveness
with a semiconductor substrate or an underlayer film or controls
the solubility to a lithography organic solvent or an alkali
developer; a repeating unit (B) that has a structure where a
substituent group having no hydroxyl group is dissociated by acid
to develop a polar group soluble in an alkali developer; and, as
needs arise, a repeating unit (C) having a polar group other than a
hydroxyl group or an acid-stable repeating unit (D) not having a
polar group such as a hydroxyl group to control the adhesiveness
and the solubility.
[0020] The hydroxyl group-containing repeating unit (A) that
controls the adhesiveness or the solubility can be introduced by
copolymerizing a monomer having a hydroxyl group. As such monomers,
for instance, compounds having a phenolic hydroxyl group, an
alcoholic hydroxyl group, a carboxyl group, a hydroxyhalogenoalkyl
group or the like can be cited. Specifically, 1) hydroxystyrenes,
2) hydroxyhalogenoalkyl styrenes, 3) carboxylic acids having an
ethylenic double bond, 4) hydroxylkyl esters of 3), 5)
hydroxyhalogenoalkyl esters of 3) and so on can be cited. Here, as
an alkyl group in a hydroxyalkyl or hydroxyhalogenoalkyl portion in
2), 4) and 5), a linear, branched or cyclic alkyl group having 1 to
20 carbon atoms can be cited. Furthermore, as a halogeno group, a
fluoro group, a chloro group or a bromo group can be cited. Still
furthermore, as a carboxylic acid having an ethylenic double bond,
(meth)acrylic acid is preferable.
[0021] Specific examples of such monomer include 1) hydroxystyrenes
such as p-hydroxystyrene, m-hydroxystyrene,
p-hydroxy-.alpha.-methylstyrene and so on; 2)
hydroxyhalogenoalkylstyrenes such as
p-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)styrene and so on; 3)
carboxylic acids having an ethylenic double bond such as acrylic
acid, methacrylic acid, maleic acid, fumaric acid,
.alpha.-trifluoromethylacrylic acid, 5-norbornene-2-carboxylic
acid, 2-trifluoromethyl-5-norbornene-2-carboxylic acid,
carboxytetracyclo[4.4.0.1.sup.2,5. 1.sup.7,10]dodecyl methacrylate
and so on; 4) hydroxyalkylesters where a carboxyl group of
carboxylic acid having an ethylenic double bond is substituted by a
hydroxyalkyly group such as a hydroxymethyl group, a hydroxyethyl
group, a hydroxypropyl group, a
hydroxy-8-tricyclo[5.2.1.0.sup.2'']decanyl group, a
3-hydroxy-1-adamantyl group or the like; and 5)
hydroxyhalogenoalkylesters where a carboxylic group of carboxylic
acid having an ethylenic double bond is substituted by a
(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)methyl group, a
5-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)methyl-2-norbornyl
group, a
5-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)methyl-3-norbornyl
group, a 5-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)-2-norbornyl
group, a
2-(4-(2-hydroxy-1,1,1,3,3,3-hexafluoro-2-propyl)cyclohexyl)-1,1,1,3,3,3-h-
exafluoropropyl group and so on.
[0022] The repeating unit (B) that has a structure where a
substituent group having no hydroxyl group is dissociated by acid
to develop a polar group soluble in an alkali developer can be
obtained by polymerizing a monomer having a structure that is
decomposed by acid to be alkali soluble or, after a monomer having
an alkali soluble structure is polymerized, by protecting the
alkali soluble group with a group (acid dissociative group) that is
not dissolved in alkali but is dissociated by acid.
[0023] As acid dissociative group having no hydroxyl group,
saturated hydrocarbon groups such as a tert-butyl group, a
tert-amyl group, a 1-methyl-1-cyclopentyl group, a
1-ethyl-1-cyclopentyl group, a 1-methyl-1-cyclohexyl group, a
1-ethyl-1-cyclohexyl group, a 2-methyl-2-adamantyl group, a
2-ethyl-2-adamantyl group, a 2-propyl-2-adamantyl group, a
2-(1-adamantyl)-2-propyl group, a
8-methyl-8-tricyclo[5.2.1.0.sup.2,6]decanyl group, a
8-ethyl-8-tricyclo[5.2.1.0.sup.2,6]decanyl group, a
8-methyl-8-tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodecanyl group, a
8-ethyl-8-tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodecanyl group and
the like; and oxygen-containing hydrocarbon groups such as a
1-methoxyethyl group, a 1-ethoxyethyl group, a 1-iso-propoxyethyl
group, a 1-n-butoxyethyl group, a 1-tert-butoxyethyl group, a
1-cyclopentyloxyethyl group, a 1-cyclohexyloxyethyl group, a
1-tricyclo[5.2.1.0.sup.2,6]decanyloxyethyl group, a methoxymethyl
group, a ethoxymethyl group, an iso-propoxymethyl group, a
n-butoxymethyl group, a tert-butoxymethyl group, a
cyclopentyloxymethyl group, a cyclohexyloxymethyl group, a
tricyclo[5.2.1.0.sup.2,6]decanyloxymethyl group, a
tetrahydropyranyl group, a tert-butoxycarbonyl group and the like
can be cited. Here, as a saturated hydrocarbon group, a linear,
branched or an alicyclic hydrocarbon group having 1 to 20 carbon
atoms is preferable. Furthermore, as an oxygen-containing
hydrocarbon group, a linear, branched or an alicyclic hydrocarbon
group having an ether bond or an ester bond having 2 to 24 carbon
atoms in total.
[0024] As a monomer that has an acid dissociative group, a compound
where a hydroxyl group of a compound shown in for instance (A) is
protected with an acid dissociative group that does not have the
hydroxyl group or the like can be cited. Furthermore, when after a
monomer having an alkali soluble group that is not protected is
polymerized, the alkali soluble group is protected with an alkali
insoluble acid dissociative group, the monomer having the alkali
soluble group is polymerized as it is, followed by, in the presence
of an acid catalyst, reacting with a compound that gives rise to an
alkali-insoluble substituent group such as vinyl ether or
halogenated alkyl ether. As an acid catalyst that is used in a
reaction, p-toluene sulfonic acid, trifluoroacetic acid, a strong
acidic ion exchange resin and so on can be cited.
[0025] The repeating unit (C) having a polar group other than a
hydroxyl group for controlling the adhesiveness and the solubility
can be introduced by copolymerizing a monomer having a polar group
other than a hydroxyl group. As an example of such a monomer, a
compound where a hydroxyl group of a monomer having a hydroxyl
group exemplified in (A) is substituted by a substitution group
having a polar structure such as, in addition to maleic anhydride
and maleimide, lactone, acid anhydride, imide, nitrile, carbonate
or the like can be cited. A particularly preferable polar
substituent group is a substituent group containing a lactone
structure. Examples of substituent group having a lactone structure
include substituent groups containing a lactone structure having 4
to 20 carbon atoms in total such as .gamma.-butyrolactone,
.gamma.-valerolactone, .delta.-valerolactone, 1,3-cyclohexane
carbolactone, 2,6-norbornane carbolactone,
4-oxatricyclo[5.2.1.0.sup.2,6]decane-3-one, mevaloic acid
.delta.-lactone and so on, and ester compounds where by the
substituent group a carboxyl group of carboxylic acids having an
ethylenic double bond such as acrylic acid, methacrylic acid,
maleic acid, fumaric acid, .alpha.-trifluoromethylacrylicacid,
5-norbornene-2-carboxylic acid,
2-trifluoromethyl-5-norbornene-2-carboxylic acid,
carboxytetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodecyl methacrylate
or the like is substituted can be cited.
[0026] The acid stable repeating unit (D) not having a polar group
such as a hydroxyl group can be introduced by copolymerizing a
monomer that has an acid stable substituent group that does not
contain a polar group. Examples of such a compound include aromatic
compounds such as styrene, .alpha.-methyl styrene, p-methyl
styrene, indene or the like; and ester compounds where a carboxyl
group of carboxylic acids having an ethylenic double bond such as
acrylic acid, methacrylic acid, maleic acid, fumaric acid,
.alpha.-trifluoromethyl acrylic acid, 5-norbornene-2-carboxylic
acid, 2-trifluoromethyl-5-norbornene-2-carboxylic acid,
carboxytetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodecyl methacrylate
and so on is substituted by a saturated hydrocarbon group having 1
to 20 carbon atoms such as a methyl group, an ethyl group, an
iso-propyl group, a cyclopentyl group, a cyclohexyl group, a
1-ethyl-1-cyclohexyl group, a 2-methyl-2-adamantyl group, a
2-ethyl-2-adamantyl group, a 2-propyl-2-adamantyl group, a
2-(1-adamantyl)-2-propyl group, a
8-methyl-8-tricyclo[5.2.1.0.sup.2,6]decanyl group, a
8-ethyl-8-tricyclo[5.2.1.0.sup.2,6]decanyl group, a
8-methyl-8-tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodecanyl group, a
8-ethyl-8-tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodecanyl group and
the like.
[0027] The copolymer according to the invention includes the
repeating units (A) and (B) indispensably and, as needs arise, (C)
and (D) and may include at least one kind or two kinds of each of
these. A composition ratio of each of the respective repeating
units in an obtained resist polymer can be selected within a range
that does not disturb the fundamental performance thereof. That is,
in general, a composition ratio of the repeating unit (A) is
preferably in the range of 10 to 90 mole percent and more
preferably in the range of 10 to 80 mole percent. Furthermore, a
composition ratio of the repeating unit (B) is preferably in the
range of 10 to 70 mole percent and more preferably in the range of
10 to 60 mole percent. A composition ratio of the repeating unit
(C) is preferably in the range of 0 to 70 mole percent and more
preferably in the range of 0 to 60 mole percent. A composition
ratio of the repeating unit (D) is preferably in the range of 0 to
40 mole percent and more preferably in the range of 0 to 30 mole
percent.
[0028] When the copolymer for semiconductor lithography of the
invention is used as an underlayer film of a multilayer resist, a
repeating unit (A') for improving the adhesiveness with a
semiconductor substrate and for reacting with a compound having a
bifunctional or more reactive group to crosslink and a repeating
unit (B') for controlling the solubility to a lithography organic
solvent are necessarily contained. As the repeating unit (A'), the
repeating unit (A) can be preferably used and, as the repeating
unit (B'), the repeating unit (D) can be preferably used.
Furthermore, a copolymer for an underlayer film of the multilayer
resist may include the repeating unit (B) and/or (C). When the
copolymer for semiconductor lithography is used as an
anti-reflection film, a structure that absorbs radiation irradiated
in the lithography process is necessarily included in the repeating
unit (A) and/or (D).
[0029] The structure that absorbs the radiation differs depending
on a wavelength of the radiation used. For instance, a naphthalene
skeleton or anthracene skeleton is preferable for KrF excimer laser
and a benzene skeleton is preferable for ArF laser. Examples of a
polymerizable compound that imparts a repeating unit having the
structure include styrenes such as styrene, .alpha.-methylstyrene,
p-methylstyrene, p-hydroxystyrene, m-hydroxystyrene and so on
derivatives thereof; and aromatic group-containing esters having an
ethylenic double bond such as substituted or unsubstituted phenyl
(meth)acrylate, substituted or unsubstituted naphthalene
(meth)acrylate, substituted or unsubstituted anthracene methyl
(meth)acrylate and so on. The repeating unit having a structure
that absorbs radiation, depending on the presence of a polar group,
may be contained in either one of the repeating unit (A) or (D) or
in both thereof. A composition ratio of the repeating unit having a
structure that absorbs radiation is preferably selected in the
range of 10 to 100 mole percent.
[0030] A copolymer for semiconductor lithography of the invention
is a copolymer obtained by copolymerizing the above-exemplified
monomer having a hydroxyl group and a monomer having no hydroxyl
group, in which a molar composition of a hydroxyl group-containing
repeating unit in a low molecular weight region corresponding to an
area of 5% of a copolymer total peak obtained by gel permeation
chromatography (GPC) is within .+-.10% of an average molar
composition of the hydroxyl group-containing repeating unit in a
whole of the copolymer. That is, with an average molar composition
as a %, the molar composition falls in the range of 0.90a to 1.10a.
When the molar composition is higher than the range, since a
component that is too high in the solubility to an alkali developer
is present together, a top shape of a pattern is rounded. On the
contrary, when the molar composition is lower than the range, since
a component that is too low in the solubility to an alkali
developer is present together, a top shape is angulated or becomes
coarser to be incapable of obtaining a pattern high in the
rectangularity. That is, a demand for miniaturization of the
pattern cannot be satisfied.
[0031] Here, a composition of the hydroxyl group-containing
repeating unit in a molecular weight direction can be obtained by
subjecting a solution separated by the GPC to infrared spectroscopy
(IR), nuclear magnetic resonance (NMR) or the like to analyze.
However, preferably, after a solution separated by the GPC is
sprayed on a rotating disc and dried, with the disc rotating, FT-IR
is applied, and thereby, a composition in a molecular weight
direction can be analyzed in detail. An average composition of the
hydroxyl group-containing repeating unit can be analyzed by means
of the IR, NMR and so on. However, preferably, .sup.13C-NMR can be
applied to obtain more accurate information.
[0032] A producing method of the invention of a copolymer is not
particularly restricted, as far as it can produce a copolymer where
a mole composition of a hydroxyl group-containing repeating unit in
a low molecular weight region corresponding to an area of 5% of a
copolymer total peak obtained in the GPC is within .+-.10% of an
average molar composition of the hydroxyl group-containing
repeating unit in a whole of the copolymer. However, in order to
readily produce the copolymer like this, a method described below
can be preferably applied to produce.
[0033] In the beginning, as a method of polymerizing a copolymer of
the invention, it is preferable that, in the presence of a
polymerization solvent, by use of a polymerization initiator, at
least two kinds of polymerizable compounds selected from
above-described monomer groups are radical polymerized to
obtain.
[0034] A polymerization initiator used in a polymerization reaction
is not particularly restricted, as far as it can be generally used
as a radical generator. For instance, azo compounds such as
2,2'-azobisisobutylo nitrile, 2,2'-azobis(2-methylbutylonitrile),
2,2'-azobisisobutyric acid dimethyl,
1,1'-azobis(cyclohexanone-1-carbonitrile),
4,4'-azobis(4-cyanovaleric acid) and so on; and organic peroxide
compounds such as decanoyl peroxide, lauroyl peroxide, benzoyl
peroxide, bis(3,5,5-trimethylhexanoyl)peroxide, succinic peroxide,
tert-butylperoxy-2-ethylhexanoate and so on can be used singularly
or in a combination thereof.
[0035] Other than the above, a thiol compound can be used as a
chain transfer agent. As such thiol compounds, known thiol
compounds such as dodecyl mercaptan, mercaptoethanol,
mercaptopropanol, mercaptoacetic acid, mercaptopropionic acid,
4,4-bis(trifluoromethyl)-4-hydroxy-1-mercaptobutane and so on can
be used singularly or in a combination thereof.
[0036] Usage amounts of the polymerization initiator and the chain
transfer agent are different depending on producing conditions such
as kinds of a raw material monomer, a polymerization initiator and
a chain transfer agent that are used in a polymerization reaction,
a polymerization temperature, a polymerization solvent, a
polymerization method, a refining condition and so on. Accordingly,
the usage amounts cannot be specified in a clear-cut manner, but
optimum amounts for obtaining a desired molecular weight are used.
In general, when a weight-average molecular weight of a copolymer
is too high, the solubility to a solvent that is used during the
formation of a film and an alkali developer becomes low; on the
other hand, when a weight-average molecular weight is too low, film
properties are deteriorated. Accordingly, the weight-average
molecular weight is preferably controlled so as to be in the range
of 2,000 to 40,000 and more preferably so as to be in the range of
3,000 to 30,000.
[0037] As a method of a polymerization reaction, a so-called batch
polymerization method where all monomers, a polymerization
initiator, and, as needs arise, a chain transfer agent are
dissolved in a polymerization solvent and heated to a
polymerization temperature; an initiator addition method where,
after monomers are dissolved in a solvent and heated to a
polymerization temperature, a polymerization initiator is added;
and a dropwise addition polymerization method where monomers, a
polymerization initiator and a chain transfer agent are partially
or all mixed or independently dropped in a polymerization system
heated to a polymerization temperature can be applied. Among these,
the dropwise addition method is preferable to make differences
between lots smaller, and, in particular, in viewpoint of stably
retaining undropped monomer during dropping, a method where
monomers and a polymerization initiator are separately retained and
dropped is preferable.
[0038] The solvent that is used in the polymerization reaction is
not particularly restricted, as far as it can stably dissolve raw
material monomers, an obtained copolymer, a polymerization
initiator and a chain transfer agent. Specific examples of the
polymerization solvent include ketones such as acetone, methyl
ethyl ketone, methyl amyl ketone, cyclohexanone and so on; ethers
such as tetrahydrofuran, dioxane, glyme, propylene glycol
monomethyl ether and so on; esters such as ethyl acetate, ethyl
lactate and so on; ether esters such as propylene glycol methyl
ether acetate and so on; and lactones such as
.gamma.-butyrolactone. These can be used singularly or in a
combination thereof. A usage amount of the polymerization solvent
is not particularly restricted. However, the usage amount thereof
is, to one part by weight of the monomer, normally in the range of
0.5 to 20 parts by weight and preferably in the range of 1 to 10
parts by weight. When the usage amount of the solvent is too small,
in some cases, the monomer precipitates or the viscosity becomes
too high to be incapable of maintaining a polymerization system
homogeneous. On the contrary, when the usage amount of the solvent
is too much, in some Oases, the conversion rate of the monomer
becomes insufficient or a molecular weight of the copolymer cannot
be heightened to a desired value.
[0039] A polymerization reaction condition is not particularly
restricted. In general, a reaction temperature is preferably in the
range of substantially 40 to 100.degree. C. In order to make
differences of a copolymer between lots of the copolymer smaller, a
polymerization temperature is necessarily controlled severely, that
is, preferably controlled within a setting temperature
.+-.1.degree. C. As to a reaction time, in the case of the dropwise
addition polymerization, since when a dropping time is longer, a
monomer composition and concentration and a radical concentration
in the system can be maintained constant, a composition and a
molecular weight of a polymer generated during dropping preferably
tend to be homogeneous. On the other hand, a longer dropping time
unfavorably lowers the production efficiency per unit hour and
disturbs the stability of the monomer during dropping. Accordingly,
the dropping time is selected between 0.5 to 20 hr and preferably
between 1 to 10 hrs. After the dropping comes to completion, since
unreacted monomer remains, for a constant time, a polymerization
temperature is preferably maintained to age. An aging time is less
than 8 hrs and preferably selected between 1 to 6 hrs. In the case
of the batch polymerization, an aging time after a polymerization
temperature is attained is selected between 1 to 24 hrs and
preferably between 2 to 12 hrs.
[0040] Since a copolymer obtained by polymerization contains low
molecular weight impurities such as an unreacted monomer, oligomer,
polymerization initiator and chain transfer agent and reaction
byproducts thereof, these have to be removed by refining.
Specifically, a polymerization reaction solution, after as needs
arise adding a good solvent to dilute, is brought into contact with
a poor solvent to precipitate the copolymer as a solid, and thereby
the impurities are extracted in a poor solvent phase (hereinafter,
referred to as "reprecipitation") or a polymerization reaction
solution is rendered liquid-liquid two-phases to extract the
impurities in a solvent phase. When the reprecipitation is
conducted, further purification can be applied by a step where
after the precipitated solid is separated from the solvent by
filtration, decantation or the like, the resulting solid is
redissolved by a good solvent, followed by further adding a poor
solvent thereto to reprecipitate, or by a step where the
precipitated solid is washed with a poor solvent or a solvent
mixture of poor solvent and good solvent. When the liquid-liquid
two-phase separation is conducted, further precipitation can be
applied by separating the poor solvent phase by phase separation,
followed by adding a poor solvent or a solvent mixture of poor
solvent and good solvent to the obtained copolymer solution to
reprecipitate or separate in liquid-liquid two-phase. These
operations may be conducted by repeating the same operation or by
combining different operations.
[0041] In the refining step, the copolymer and the impurities are
separated by use of the difference of the solubility to the
solvent. However, since a low molecular weight region of the
copolymer is small in the difference of the solubility particularly
from the impurities, the low molecular weight region is partially
extracted together with the impurities. In particular, in the case
of a copolymer for semiconductor lithography, which is obtained by
copolymerizing a plurality of monomers different in the polarity,
depending on the polarity of the poor solvent, a composition of an
extracted low molecular weight copolymer is different. That is,
when a polar poor solvent is used, a low molecular weight copolymer
high in a high polarity repeating unit composition is extracted,
and, when a nonpolar poor solvent is used, a low molecular weight
copolymer high in a low polarity repeating unit composition is
extracted.
[0042] Accordingly, a method of producing a copolymer for
semiconductor lithography, which is a copolymer according to the
invention and obtained by copolymerizing a monomer having a
hydroxyl group and a monomer having no hydroxyl group and where a
molar composition of a hydroxyl group-containing repeating unit in
a low molecular weight region corresponding to an area of 5% of a
copolymer total peak in the GPC is within .+-.10% of an average
molar composition of the hydroxyl group-containing repeating unit
in a whole of the copolymer preferably includes a step of bringing
a copolymer obtained by polymerizing into contact with a polar
solvent having a hydroxyl group to reprecipitate or wash; and a
step of bringing the obtained copolymer into contact with a
nonpolar solvent having no hydroxyl group to reprecipitate or wash.
When the step of bringing into contact with a polar solvent having
a hydroxyl group is applied singularly, a composition of the
hydroxyl group-containing repeating unit in a low molecular weight
region becomes unfavorably low and, on the other hand, when the
step of bringing into contact with a polar solvent having no
hydroxyl group is applied singularly, a composition of the hydroxyl
group-containing repeating unit in a low molecular weight region
becomes unfavorably high.
[0043] In the invention, typical examples of a polar solvent having
a hydroxyl group include compounds having an alcoholic hydroxyl
group such as water, methanol, ethanol, isopropanol, ethylene
glycol, ethyl lactate and so on and typical examples of a nonpolar
solvent having no hydroxyl group include linear, branched and
alicyclic hydrocarbons such as pentane, n-hexane, iso-hexane,
n-heptane, cyclopentane, methyl cyclohexane and so on; or aromatic
hydrocarbons such as toluene, xylene and so on. These solvents can
be used singularly or in a mixture thereof. Furthermore, the
polymerization solvents and solvents exemplified in the coating
film forming solvent described below can be mixed and used as
well.
[0044] A kind and an amount of the poor solvent (polar solvent
having a hydroxyl group and nonpolar solvent having no hydroxyl
group) used in the refining are not particularly restricted, as far
as a copolymer can be separated from low molecular weight
impurities. However, the kind and amount of the poor solvent can be
appropriately selected corresponding to the solubility to the poor
solvent of the copolymer, a kind and an amount of a solvent used to
polymerize, a kind and an amount of the impurity and so on. An
amount of the poor solvent is generally, to a total amount of a
polymerization reaction solution diluted with a good solvent as
needs arise, in the range of 0.5 to 50 times, preferably in the
range of 1 to 20 times and more preferably in the range of 2 to 10
times. In all cases, when a usage amount of the solvent is less,
impurities such as the unreacted monomer, polymerization initiator,
chain transfer agent and reaction byproducts thereof can be
insufficiently separated. On the contrary, when the usage amount of
the solvent is too much, the waste liquid increases to cause
inconvenience from the viewpoint of the workability and the
cost.
[0045] A temperature of a refining step largely affects on a
molecular weight and a molecular weight distribution of a
lithography copolymer, the removal rates of the impurities such as
residual monomers and the initiator residue and various
characteristics in the lithography process; accordingly, the
temperature has to be rigidly controlled. When the temperature of
the refining step is too low, since the solubility of the
impurities to a reprecipitation solvent and a washing solvent
becomes insufficient, the impurities are insufficiently removed to
be inefficient. On the other hand, when the temperature of the
refining step is too high, since the copolymer is eluted in the
reprecipitation solvent and the washing solvent, a composition
balance in the low molecular weight region of the copolymer may
collapse or the yield is unfavorably deteriorated. Accordingly, the
refining step is carried out at a temperature in the range of 0 to
40.degree. C. and preferably in the range of 0 to 30.degree. C.
[0046] Thus refined copolymer can be taken out as powder after
drying or as a solution by charging in a good solvent before or
after drying to redissolve. As a good solvent that is used to
redissolve, ones cited as the polymerization solvent can be
similarly used. A redissolved solution is preferably passed through
a filter having an average pore diameter preferably of 0.5 .mu.m or
less and more preferably of 0.1 .mu.m or less to remove minute
solid content, insoluble foreign matters or metals, or the
like.
[0047] The refined copolymer solution can be finished into a
coating film forming solution by further distilling away other
solvents used in the refining step under reduced pressure while
supplying a coating film forming solvent. As a solvent for forming
a coating film is not particularly restricted. However, normally,
the solvent for forming a coating film is selected by taking a
boiling temperature, an effect on a semiconductor substrate or
other coating films and absorption of radiation used in the
lithography into consideration. Examples of the solvent generally
used to form a coating film include solvents such as propylene
glycol methyl ether acetate, ethyl lactate, propylene glycol
monomethyl ether, methyl amyl ketone, .gamma.-butyrolactone,
cyclohexanone and so on. A usage amount of the solvent is not
particularly restricted and is normally in the range of 1 to 20
parts by weight to one part by weight of the copolymer.
[0048] When a copolymer is used in a resist, to the coating film
forming solution, a radiation-sensitive acid generator and an acid
diffusion inhibitor such as a nitrogen-containing compound or the
like, which inhibits acid from diffusing into a portion that has
not been exposed to radiation can be further added to complete a
resist composition. As the radiation-sensitive acid generator, ones
that are generally used as resist raw materials such as an onium
salt compound, a sulfone compound, a sulfone acid ester compound, a
sulfone imide compound, a disulfonyldiazomethane compound and so on
can be used. Furthermore, to the resist composition, as needs
arise, compounds used to be used as resist additives such as a
dissolution inhibitor, a sensitizer, a dye and so on can be further
added. A blending ratio of each of the components (excluding the
resist solvent) in the resist composition is, though not
particularly restricted, generally selected in the range of 5 to 50
mass percent for the polymer concentration, in the range of 0.1 to
10 mass percent for the radiation-sensitive acid generator and in
the range of 0.001 to 10 mass percent for the acid diffusion
inhibitor.
[0049] Furthermore, when the obtained copolymer is used as an
antireflection film, the polymer is used singularly or blended with
bifunctional or more isocyanate, amine, epoxide or the like capable
of crosslinking between polymers.
EXAMPLE
[0050] In what follows, the invention will be detailed with
reference to examples. However, the invention is not restricted to
the examples. An average copolymer composition (average molar
composition of a repeating unit) of the obtained copolymer was
obtained from a measurement of .sup.13C-NMR. Furthermore, a weight
average molecular weight Mw, a degree of dispersion Mw/Mn and a
residual monomer concentration were obtained from measurements by
gel permeation chromatography (GPC). A copolymer composition in
each of the molecular weights (molar composition of a repeating
unit) was obtained by GPC-IR. A pattern evaluation of the obtained
copolymer was carried out with a 248 nm exposing device.
[0051] (1) Average Copolymer Composition of Copolymer
[0052] Into 20 parts by weight of heavy acetone, 10 parts by weight
of a copolymer and one parts by weight of chromium (III)
acetylacetonate were dissolved to prepare a sample solution. The
sample solution was charged in an NMR tube followed by analyzing by
.sup.13C-NMR (at 400 MHz, manufactured by Bruker).
[0053] (2) Mw and Mw/Mn of Copolymer
[0054] In 100 parts by weight of tetrahydrofuran (hereinafter,
referred to as THF), 4 parts by weight of the copolymer were
dissolved to prepare a sample solution. In a GPC unit (trade name:
GPC8220, manufactured by Tosoh Corporation) with GPC columns (trade
name: KF-804L.times.4, manufactured by SHOWA DENKO KK), 20 .mu.L of
the sample solution was charged with THF as an elution solution,
and an eluted solution was detected with a differential refractive
index (R1) detector. The Mw and Mw/Mn were calculated based on a
calibration curve prepared in advance with standard
polystyrene.
[0055] (3) Copolymer Composition in Low Molecular Weight Region
Corresponding to 5% of Copolymer Peak in GPC
[0056] In a GPC unit (trade name: GPC8220, manufactured by Tosoh
Corporation) with GPC columns (trade name: KF-804L.times.4,
manufactured by SHOWA DENKO KK), 150 .mu.L of the sample solution
prepared in (2) was charged with THF as an elution solution, and an
eluted solution was introduced in a LC-Transform Model 410 (trade
name, manufactured by Lab Connections) and, under heating at
110.degree. C., sprayed onto a germanium disc rotating at a
constant speed. The disc was set to a rotating stage of a FT-IR
optical module and, by use of FT-IR (trade name, manufactured by
JEOL. Ltd.), while rotating the disc, infrared absorption of the
copolymer coated on the disc was measured at 100 points. Based on
the results and the .sup.13C-NMR analysis results, a composition of
a hydroxyl group-containing repeating unit in a low molecular
weight region corresponding to 5% of a copolymer peak in GPC was
obtained. In what follows, examples of calculations are shown.
Without restricting to examples below, of other copolymers as well,
a composition of a hydroxyl group-containing repeating unit in a
low molecular weight region corresponding to 5% of a copolymer peak
in GPC can be obtained.
Calculation Example 1
Hydroxystyrene-Alkyl Acrylate Copolymer
[0057] With a hydroxystyrene composition obtained by .sup.13C-NMR
as N.sub.OH(%), an alkyl acrylate composition as N.sub.E, peak
areas of a hydroxyl group and a carbonyl group of acrylic acid
ester in a FT-IR analysis at each of respective points of a region
corresponding to the copolymer as A.sub.OH and A.sub.E, and sum
totals of all points of a region corresponding to the copolymer as
.SIGMA.A.sub.OH and .SIGMA.A.sub.E, a repeating unit concentration
(expressed as C.sub.OH) derived from hydroxystyrene in each of the
points, a repeating unit concentration (expressed as C.sub.E)
derived from alkyl acrylate, and a copolymer concentration
(expressed as C.sub.P) can be calculated by formulas below.
C.sub.OH.dbd.N.sub.OH.times.(A.sub.OH/A.sub.OH)(%) (Formula 1)
C.sub.E.dbd.N.sub.E.times.(A.sub.E/A.sub.E)(%)
C.sub.P.dbd.C.sub.OH+C.sub.E(%)
[0058] When a low molecular weight region corresponding to 5% of a
copolymer peak in GPC is set up to a point where a total of C.sub.P
from the lowest molecular weight of the copolymer is 5% to a point
where a sum total of C.sub.Ps of all points in a region
corresponding to the copolymer and a concentration of the hydroxyl
group-containing repeating unit and a copolymer concentration in
the region, respectively, are expressed with .SIGMA..sub.5%C.sub.OH
and E.sub.5%C.sub.P, difference (expressed with D.sub.OH) between
the low molecular weight region of the hydroxyl group-containing
repeating unit and an average composition is calculated by a
formula below.
D.sub.OH=[{(.SIGMA..sub.5%C.sub.OH/.SIGMA..sub.5%C.sub.P)/N.sub.OH}-1].t-
imes.100(%) (Formula 2)
Calculation Example 2
Hydroxyl Group-Containing Acrylate-Lactone-Containing
Acrylate-Alkyl Acrylate Copolymer
[0059] When a hydroxyl group-containing acrylate composition
obtained by .sup.13C-NMR is expressed with N.sub.OH (%), peak areas
of a hydroxyl group and a carbonyl group of acrylic ester in a
FT-IR analysis at each of points of a region corresponding to a
copolymer, respectively, are expressed with A.sub.OH and A.sub.E
and sum totals of all points of a region corresponding to the
copolymer, respectively, are expressed with .SIGMA.A.sub.OH and
.SIGMA.A.sub.E, a concentration of the hydroxyl group-containing
acrylate (expressed with C.sub.OH) and a copolymer concentration
(expressed with C.sub.O) at each of points are calculated by
formulas below.
C.sub.OH.dbd.N.sub.OH.times.(A.sub.OH/.SIGMA.A.sub.OH)(%) (Formula
3)
C.sub.P=A.sub.E/.SIGMA.A.sub.E(%)
[0060] When a low molecular weight region corresponding to 5% of a
copolymer peak in GPC is set up to a point where a total of C.sub.P
from the lowest molecular weight of the copolymer is 5% to a sum
total of C.sub.Ps of all points in a region corresponding to the
copolymer and a concentration of the hydroxyl group-containing
repeating unit and a copolymer concentration in the region,
respectively, are expressed with .SIGMA..sub.5%C.sub.OH and
.SIGMA..sub.5%C.sub.P, difference (expressed with D.sub.OH) between
the low molecular weight region of the hydroxyl group-containing
repeating unit and an average composition is calculated by a
formula below.
D.sub.OH=[{(.SIGMA..sub.5%C.sub.OH/.SIGMA..sub.5%C.sub.P)/N.sub.OH}-1].t-
imes.100(%) (Formula 4)
[0061] (4) Evaluation of Resist Pattern
[0062] To a 15% by weight PGMEA solution that includes 60 parts by
weight of a copolymer and 360 parts by weight of PGMEA, 1.0 parts
by weight of trifluoromethanesulfonic acid triphenylsulfonium as a
photo acid generator and 0.1 parts by weight of triethanol amine
were added and dissolved, followed by filtering with a 0.05 .mu.m
membrane filter, and thereby a resist composition was prepared. The
resist composition was spin coated on a Si wafer, dried on a
hotplate at 120.degree. C. for 90 sec, and thereby a resist thin
film having a film thickness of 500 .mu.m was prepared. The resist
thin film was exposed with a KrF excimer laser stepper (NA=0.6,
manufactured by Nikon Corporation), immediately thereafter followed
by baking at 120.degree. C. for 90 sec, further followed by
developing with a 2.38% by weight tetramethylammonium hydroxide
aqueous solution at room temperature for 60 sec, still further
followed by rinsing with pure water to obtain a resist pattern. An
optimum exposure amount for obtaining a 200 nm line and space
pattern (1:1) was obtained and this was taken as the optimum
exposure amount. Furthermore, a pattern shape at that time was
observed with a scanning electron microscope (SEM). The sensitivity
and observation results of pattern shapes are summarized in Table
1.
Example 1
[0063] In a monomer solution preparation tank maintained in a
nitrogen atmosphere, 158 kg of a p-ethylphenol solution containing
24% of p-hydroxystyrene (hereinafter referred to as "PHS"), 23% of
methanol and 10% of water, 19.0 kg of tert-butyl acrylate and 1.5
kg of AIBN were charged and dissolved, thereby a monomer solution
was prepared. To a polymerization tank, 35 kg of the monomer
solution was transferred, followed by heating to 80.degree. C.
under stirring, further followed by feeding a remaining monomer
solution into the polymerization tank kept at 80.degree. C. over 2
hrs to polymerize. After the completion of the feeding, the monomer
solution was aged for 2 hrs with a polymerization temperature kept
at 80.degree. C., followed by cooled to room temperature. The
obtained polymerization solution was dropped in 620 kg of toluene
to precipitate a polymer, followed by removing a supernatant
solution. In the next place, the polymer was dissolved with 36 kg
of methanol, followed by reprecipitating in 620 kg of toluene,
further followed twice by removing a supernatant solution, followed
by redissolving in 90 kg of methanol. Furthermore, 55 kg of water
was added to reprecipitate, followed by removing a supernatant
solution, further followed twice by redissolving in 90 kg of
methanol, and an obtained methanol solution was passed through a
filter 40QSH (trade name, manufactured by Cuno Incorporated). A
filtered methanol solution is partially sampled and dried in a
reduced pressure dryer, and an obtained pale yellow solid was
analyzed with .sup.13C-NMR and GPC-IR to obtain an average
composition, Mw and Mw/Mn of a copolymer and a copolymer
composition in a low molecular weight region corresponding to 5% of
a copolymer peak. Furthermore, with a remaining methanol solution
heating under reduced pressure to drive away a low boiling
temperature solvent such as methanol, propylene glycol methyl ether
acetate (hereinafter referred to as "PGMEA") was charged, and
thereby a PGMEA solution containing 15% of the copolymer was
prepared. Thereafter, according to a method described in the (4), a
resist composition was prepared, followed by evaluating a resist
pattern. Results are shown in Table 1.
Example 2
[0064] Except that, in place of 19.0 kg of tert-butyl acrylate and
1.5 kg of AIBN in example 1, 20.5 kg of 1-ethyl-1-cyclopentyl
acrylate and 2.2 kg of AIBN were used, similarly to example 1, a
copolymer was obtained, and an average composition, Mw and Mw/Mn of
a copolymer and a copolymer composition in a low molecular weight
region corresponding to 5% of a copolymer peak were analyzed and a
resist pattern was evaluated. Results are shown in Table 1.
Example 3
[0065] In a raw material preparation tank maintained in a nitrogen
atmosphere, 63.0 kg of methyl ethyl ketone (hereinafter, referred
to as "MEK"), 15.6 kg of 5-methacryloyloxy-2,6-norbornane
carbolactone (hereinafter, referred to as "NLM"), 17.8 kg of
2-methyl-2-adamantyl methacrylate (hereinafter, referred to as
"MAM") and 8.1 kg of 3-hydroxy-1-adamantyl methacrylate
(hereinafter, referred to as "HAM") were charged and stirred to
dissolve at a temperature in the range of 20 to 25.degree. C.,
thereby a monomer solution was prepared. Furthermore, in a separate
tank kept in a nitrogen atmosphere, 10.0 kg of MEK and 1.0 kg of
dimethyl-2,2'-azobisisobutyrate were charged, followed by stirring
at a temperature in the range of 10 to 20.degree. C. to dissolve,
and thereby an initiator solution was prepared. In a polymerization
tank kept in a nitrogen atmosphere, after 24.0 kg of MEK was
charged and heated to 80.degree. C. under stirring, the initiator
solution kept at room temperature (ca 20.degree. C.) and the
monomer solution heated in the range of 25 to 30.degree. C.,
respectively, were simultaneously began to feed in a polymerization
tank kept at 80.degree. C. and fed at constant speeds over 4 hrs.
After completion of the feeding, the polymerization temperature was
kept at 80.degree. C. to age for 2 hrs, followed by cooling to room
temperature, and a polymerization solution was taken out. An
obtained polymerization solution was dropped in 420 kg of n-hexane
to precipitate a polymer, followed by filtering, and an obtained
wet cake was twice repeated to wash with 350 kg of methanol
containing 5% by weight of water and filter. The obtained wet cake
was partially sampled and dried in a reduced-pressure dryer, and an
obtained white powder was analyzed by .sup.13C-NMR and GPC-IR to
obtain an average composition, Mw and Mw/Mn of the copolymer and a
copolymer composition in a low molecular weight region
corresponding to 5% of a copolymer peak. A remaining wet cake was
redissolved in MEK and filtered with a filter 40QSH (trade name,
manufactured by Cuno Incorporated), followed by charging PGMEA
while driving away MEK by heating under reduced pressure, and
thereby a PGMEA solution containing 15% of the copolymer was
prepared. Thereafter, similarly to example 1, a resist pattern was
evaluated. Results are shown in Table 1.
Example 4
[0066] In a raw material preparation tank maintained in a nitrogen
atmosphere, 61.0 kg of MEK, 13.3 kg of
.alpha.-methacryloyloxy-.gamma.-butyrolactone (hereinafter referred
to as "GBLM"), 19.7 kg of MAM and 9.0 kg of HAM were charged and
stirred at a temperature in the range of 20 to 25.degree. C.,
thereby a monomer solution was prepared. Furthermore, in a separate
tank kept in a nitrogen atmosphere, 11.0 kg of MEK and 1.1 kg of
AIBN were charged, followed by stirring at a temperature in the
range of 10 to 20.degree. C. to dissolve, and thereby an initiator
solution was prepared. In a polymerization tank maintained in a
nitrogen atmosphere, 25.0 kg of MEK was charged. Operations after
that were carried out similarly to example 3, an average
composition, Mw and Mw/Mn of a copolymer and a copolymer
composition in a low molecular weight region corresponding to 5% of
a copolymer peak were analyzed and a resist pattern was evaluated.
Results are shown in Table 1.
Comparative Example 1
[0067] Except that in place of, after 55 kg of water is added to
reprecipitate and a supernatant solution is discarded, an operation
of redissolving with 90 kg of methanol being repeated twice, 540 kg
of n-hexane was added to reprecipitate and a supernatant solution
was discarded, followed by once redissolving with 90 kg of
methanol, operations other than the above were carried out
similarly to example 1, and an average composition, Mw and Mw/Mn of
a copolymer and a copolymer composition in a low molecular weight
region corresponding to 5% of a copolymer peak were analyzed and a
resist pattern was evaluated. Results are shown in Table 1.
Comparative Example 2
[0068] Except that in place of, after 55 kg of water is added to
reprecipitate and a supernatant solution is discarded, an operation
of redissolving with 90 kg of methanol being repeated twice, 540 kg
of n-hexane was added to reprecipitate and a supernatant solution
was discarded, followed by once redissolving with 90 kg of
methanol, operations other than the above were carried out
similarly to example 2, and an average composition, Mw and Mw/Mn of
a copolymer and a copolymer composition in a low molecular weight
region corresponding to 5% of a copolymer peak were analyzed and a
resist pattern was evaluated. Results are shown in Table 1.
Comparative Example 3
[0069] Except that a polymerization solution was dropped not in 420
kg of n-hexane but in 700 kg of methanol containing 5% by weight of
water, operations other than that were carried out similarly to
example 3, and an average composition, Mw and Mw/Mn of a copolymer
and a copolymer composition in a low molecular weight region
corresponding to 5% of a copolymer peak were analyzed and a resist
pattern was evaluated. Results are shown in Table 1.
Comparative Example 4
[0070] The same process as that described in Example 4 was carried
out except that a polymerization solution was dropped not in 420 kg
of n-hexane but in 700 kg of methanol containing 5% by weight of
water, and an average composition, Mw and Mw/Mn of a copolymer and
a copolymer composition in a low molecular weight region
corresponding to 5% of a copolymer peak were analyzed and a resist
pattern was evaluated. Results are shown in Table 1.
TABLE-US-00001 PHS HAM NLM GBLM TBA ECPA MAM Composition
Composition Composition Composition Composition Composition
Composition (mole %) (mole %) (mole %) (mole %) (mole %) (mole %)
(mole %) Mw .times. 10.sup.3 Example 65.4 34.6 20.3 Example 69.9
30.1 14.9 Example 20.8 39.7 39.5 10.2 Example 20.3 39.7 40.0 10.3
Comparat 66.8 33.2 19.7 Comparat 71.0 29.0 14.5 Comparat 20.2 39.9
39.9 10.4 Comparat 19.8 39.8 40.4 10.5 Average OH 5% area OH
Sensitivity Pattern composition composition Deviation PD
mJ/cm.sup.2 Shape (mole %) (mole %) (%) Example 1.99 45 Excellent
65.4 70.3 7.5% Example 1.77 40 Excellent 69.9 72.4 3.6% Example
1.89 43 Excellent 20.8 21.8 5.0% Example 1.84 41 Excellent 20.3
21.7 6.9% Comparat 2.05 43 R-top 66.8 78.4 17.4% Comparat 1.82 39
R-top 71.0 80.2 13.0% Comparat 1.86 45 T-top 20.2 17.0 -15.5%
Comparat 1.81 421 T-top 19.8 16.4 -16.9% In the table, R-top means
that a top shape of a pattern is rounded and T-top means that a top
shape of a pattern angulated in T-shape.
* * * * *