A radiation-sensitive composition comprising (A) a polymer having a recurring unit represented by formula (1): ##STR1## wherein R.sup.1 represents a substituted methyl group, a substituted ethyl group, a silyl group, a germyl group or an alkoxycarbonyl group, and R.sup.2 represents --OR.sup.3 or --NR.sup.4 R.sup.5 in which R.sup.3 is a hydrogen atom, a straight-chain alkyl group, a cyclic alkyl group, an aryl group, an aralkyl group, a substituted methyl group, a substituted ethyl group, a silyl group, a germyl group or an alkoxycarbonyl group, and R.sup.4 and R.sup.5 which may be the same or different, are hydrogen atoms, straight-chain alkyl groups, cyclic alkyl groups, aralkyl groups or aryl groups, and (B) a radiation-sensitive acid forming agent. Said radiation-sensitive composition can be suitably used as a resist composition which enables reliable fine processing, which has high sensitivity and high resolution degree, and which is superior in dry etching resistance, developability, adhesiveness, heat resistance and yield of residual film thickness.

The present invention relates to a radiation-sensitive composition, 
particularly to a radiation-sensitive composition which is suitably used 
as a resist composition in superfine processing employing a radiation such 
as far-ultraviolet rays (e.g. excimer laser), X-rays (e.g. synchrotron 
radiation), charged particle beams (e.g. electron beam ) or the like. 
In the field of fine processing, representative of which is production of 
integrated circuit elements, the processing size in lithography is 
becoming much smaller in order to obtain a higher degree of integration. 
In recent years, there has been required a technique enabling fine 
processing of 0.5 .mu.m or less reliably. In this connection, also in the 
resist used in fine processing, it is required to form a pattern of 0.5 
.mu.m or less with high precision. Formation of such a fine pattern with 
high precision, however, is extremely difficult by the conventional method 
employing a visible light (700-400 nm) or near-ultraviolet rays (400-300 
nm). Hence, a lithography employing a radiation having a short wavelength 
(300 nm or less) is under investigation. 
The short wavelength radiation referred to above includes far-ultraviolet 
rays, typical examples of which are bright line spectrum (254 nm) emitted 
from a mercury lamp and KrF excimer laser (248 nm); X-rays; charged 
particle beams; and so forth. Of these, the excimer laser is drawing 
special attention, and special attention is also directed to lithography 
using the excimer laser. For this reason, with respect to the resist used 
in the lithography, a resist is also required which can form a fine 
pattern of 0.5 .mu.m or less at a high sensitivity using an excimer laser 
and which has excellent developability (neither scums nor undeveloped 
portions remain during development), excellent adhesiveness (there is no 
stripping of resist pattern during development) and excellent heat 
resistance (there is no change of resist pattern by heat). Further, with 
respect to the resist used in the lithography, since the etching step is 
being changed to dry etching as integrated circuits are becoming finer, 
the dry etching resistance of resist has become an important requirement 
for obtaining good performance. 
The present inventors have made extensive research in order to solve the 
above-mentioned problems of the prior art and found that a combination of 
a special polymer and a radiation-sensitive acid-forming agent can solve 
the above problems. 
An object of the present invention is to provide a novel 
radiation-sensitive composition. 
Another object of the present invention is to provide a radiation-sensitive 
composition which can be suitably used as a resist composition enabling 
reliable fine processing, having high sensitivity and high resolution 
degree, and being superior in dry etching resistance, developability, 
adhesiveness, heat resistance, etc. 
Other objects and advantages of the present invention will become apparent 
from the following description. 
According to the present invention, there is provided a radiation-sensitive 
composition comprising (A) a polymer having a recurring unit represented 
by formula (1): 
##STR2## 
wherein R.sup.1 represents a substituted methyl group, a substituted ethyl 
group, a silyl group, a germyl group or an alkoxycarbonyl group, and 
R.sup.2 represents --OR.sup.3 or --NR.sup.4 R.sup.5 in which R.sup.3 is a 
hydrogen atom, a straight-chain alkyl group, a cyclic alkyl group, an 
aralkyl group, an aryl group, a substituted methyl group, a substituted 
ethyl group, a silyl group, a germyl group or an alkoxycarbonyl group, and 
R.sup.4 and R.sup.5, which may be the same or different, are hydrogen 
atoms, straight-chain alkyl groups, cyclic alkyl groups, aralkyl groups or 
aryl groups, and (B) a radiation-sensitive acid-forming agent. 
The polymer used as the component (A) in the present invention [said 
polymer is referred to hereinafter as polymer (A)] contains a recurring 
unit represented by formula (1). 
Examples of the substituted methyl group in the definition of R.sup.1 in 
formula (1) include a methoxymethyl group, a methylthiomethyl group, a 
methoxyethoxymethyl group, a tetrahydropyranyl group, a 
tetrahydrothiopyranyl group, a tetrahydrofuranyl group, a 
tetrahydrothiofuranyl group, a benzyloxymethyl group, a phenacyl group, a 
bromophenacyl group, a methoxyphenacyl group, an .alpha.-methylphenacyl 
group, a cyclopropylmethyl group, a cyclopentyl group, a cyclohexyl group, 
a benzyl group, a triphenylmethyl group, a diphenylmethyl group, a 
bromobenzyl group, a nitrobenzyl group, a methoxybenzyl group, a piperonyl 
group, a furfuryl group, etc.; examples of the substituted ethyl group 
include a 1-methoxyethyl group, a 1-ethoxyethyl group, an isopropyl group, 
a tert-butyl group, a 1,1-dimethylpropyl group, etc.; examples of the 
silyl group include a trimethyl-silyl group, a triethylsilyl group, a 
tertbutyldimethylsilyl group, an isopropyldimethylsilyl group, a 
phenyldimethylsilyl group, etc.; examples of the germyl group include a 
trimethylgermyl group, a triethylgermyl group, a tert-butyldimethylgermyl 
group, an isopropyldimethylgermyl group, a phenyldimethylgermyl group, 
etc.; and examples of the alkoxycarbonyl group include a methoxycarbonyl 
group, an ethoxycarbonyl group, a tert-butoxycarbonyl group, etc. 
Examples of the straight-chain alkyl group in the definition of R.sup.3 in 
formula (1) include a methyl group, an ethyl group, an n-propyl group, an 
n-butyl group, etc. Examples of the cyclic alkyl group in the definition 
of R.sup.3 include a cyclopentyl group, a cyclohexyl group, etc. Examples 
of the aralkyl group in the definition of R.sup.3 include a benzyl group, 
an .alpha.-methylbenzyl group, a diphenylmethyl group, a trityl group, 
etc. Examples of the aryl group in the definition of R.sup.3 include a 
phenyl group, a naphthyl group, a tolyl group, etc. Examples of the 
substituted methyl group, the substituted ethyl group, the silyl group, 
the germyl group and the alkoxycarbonyl group each in the definition of 
R.sup.3 include the respective examples of the substituted methyl group, 
the substituted ethyl group, the silyl group, the germyl group and the 
alkoxycarbonyl group each mentioned in the definition of R.sup.1. 
Examples of the straight-chain alkyl group, the cyclic alkyl group, the 
aralkyl group and the aryl group each in the definitions of R.sup.4 and 
R.sup.5 include the respective examples of the straight-chain alkyl group, 
the cyclic alkyl group, the aralkyl group and the aryl group each 
mentioned in the definition of R.sup.3. 
In the present invention, the polymer (A) may consist only of a recurring 
unit represented by formula (1), or may consist of said recurring unit and 
other recurring units. Said other recurring units are preferably those 
represented by formulas (2), (3) and (4): 
##STR3## 
wherein R.sup.6, R.sup.7 and R.sup.8, which may be the same or different, 
represent hydrogen atoms, halogen atoms, hydroxyl groups, amino groups, 
alkyl groups, preferably alkyl groups having 1-4 carbon atoms, or alkoxy 
groups, preferably alkoxy groups having 1-4 carbon atoms, and R.sup.9 
represents a hydrogen atom or a methyl group; 
##STR4## 
wherein R.sup.10 represents a hydrogen atom or an alkyl group, preferably 
an alkyl group having 1-4 carbon atoms, and R.sup.11 represents a hydrogen 
atom or a methyl group; 
##STR5## 
wherein R.sup.12 represents a hydrogen atom, a methyl group, a phenyl 
group or a hydroxyphenyl group; and a recurring unit formed by cleavage of 
the double bond of maleic anhydride, maleic acid, fumaric acid, 
fumaronitrile, acrylamide, acrylonitrile, vinylpyridine, vinylpyrrolidone, 
vinylimidazole or vinylaniline. Of the above-mentioned other recurring 
units, particularly preferable are recurring units formed by cleavage of 
the double bond of styrene and maleic anhydride. 
In the polymer (A) of the present invention, the proportion of the 
recurring unit represented by formula (1) cannot be uniquely defined 
because it can be varied depending upon the kind of said other recurring 
unit used; however, it is preferably 20% or more, more preferably 25% or 
more, particularly preferably 30% or more, based on the total recurring 
unit number. When the proportion is less than 20%, no sufficient effect is 
obtained for resist pattern formation. 
The polymer (A) of the present invention has preferably a 
polystyrene-reduced weight average molecular weight ( referred to 
hereinafter as Mw) of 1,000-50,000, particularly preferably 1,500-20,000. 
The polymer containing a recurring unit represented by formula (1) used in 
the present invention can be produced, for example, by hydrolyzing the 
maleic anhydride portion of a poly(styrene-maleic anhydride) or a 
polymaleic anhydride to convert the portion to a dicarboxylic acid and 
then bonding, to a part or the whole of the carboxylic acid portion, a 
substituted methyl group, a substituted ethyl group, a silyl group, a 
germyl group or an alkoxycarbonyl group, or by converting the maleic 
anhydride portion of the above polymer to a half ester or a half amide 
using a hydroxy compound or an amine and then bonding, to the carboxylic 
acid portion of the resulting material, a substituted methyl group, a 
substituted ethyl group, a silyl group, a germyl group or an 
alkoxycarbonyl group. 
The polymer (A) of the present invention may be used in admixture with 
other polymers. Examples of said other polymers are preferably polymers 
having a recurring unit formed by cleavage of the double bond of a double 
bond-containing compound such as hydroxystyrene, isopropenylphenol, 
acrylic acid, methacrylic acid, fumaric acid, maleic acid or the like. 
The radiation-sensitive acid-forming agent which is the component (B), is a 
compound which generates an acid upon irradiation with a radiation. Said 
compound includes an onium salt, a halogen-containing compound, a 
diazoketone compound, a sulfone compound, a sulfonic acid compound, a 
nitrobenzyl compound, etc. Specific examples thereof are shown below. 
Onium salts: Iodonium salts, sulfonium salts, phosphonium salts, diazonium 
salts, ammonium salts, etc., preferably, compounds represented by the 
following formulas: 
##STR6## 
wherein R.sup.13 to R.sup.15, which may be the same or different, 
represent hydrogen atoms, amino groups, nitro groups, cyano groups, alkyl 
groups, preferably alkyl groups having 1-4 carbon atoms or alkoxy groups, 
preferably alkoxy groups having 1-4 carbon atoms, and X represents 
##STR7## 
in which R.sup.16 is a hydrogen atom, an amino group, an anilino group, an 
alkyl group, preferably an alkyl group having 1-4 carbon atoms or an 
alkoxy group, preferably an alkoxy group having 1-4 carbon atoms, R.sup.17 
is an alkoxy group, preferably an alkoxy group having 1-4 carbon atoms, 
and R.sup.18 is a hydrogen atom, an amino group, an anilino group, an 
alkyl group, preferably an alkyl group having 1-4 carbon atoms or an 
alkoxy group, preferably an alkoxy group having 1-4 carbon atoms. 
Particularly preferable are triphenylsulfonium trifluoromethanesulfonate, 
diphenyliodonium hexafluoroantimonate, etc. Halogen-containing compounds: 
Haloalkyl group-containing hydrocarbon compounds, haloalkyl 
group-containing heterocyclic compounds, etc., preferably, compounds 
represented by the following formulas: 
##STR8## 
wherein R.sup.19 represents a trichloromethyl group, a phenyl group, a 
methoxyphenyl group, a naphthyl group or a methoxynaphthyl group, and 
R.sup.20 to R.sup.22, which may be the same or different, represent 
hydrogen atoms, halogen atoms, methyl groups, methoxy groups or hydroxyl 
groups. Particularly preferable are 1,1-bis (4-chlorophenyl 
)-2,2,2-trichloroethane, phenyl-bis (trichloromethyl)-s-triazine, 
naphthyl-bis (trichloromethyl)-s-triazine, etc. 
Diazoketone compounds: 1,3-Diketo-2-diazo compounds, diazobenzoquinone 
compounds, diazonaphthoquinone compounds, etc., preferably, compounds 
represented by the following formulas: 
##STR9## 
wherein R.sup.23 and R.sup.24, which may be the same or different, 
represent alkyl groups, preferably alkyl groups having 1-4 carbon atoms or 
substituted or unsubstituted aryl groups, preferably those having 6-20 
carbon atoms; R.sup.25 represents 
##STR10## 
R.sup.26 represents --CH.sub.2 --, 
##STR11## 
R.sup.27 represents a hydrogen atom or a methyl group; m represents an 
integer of 1-6; n represents an integer of 0-5, with a proviso that 
1.ltoreq.m+n.ltoreq.6. Particularly preferable are 
1,2-naphthoquinonediazide-4-sulfonyl chloride, 
1,2-naphthoquinonediazide-4-sulfonic acid ester of 
2,3,4,4'-tetrahydroxybenzophenone, 1,2-naphthoquinonediazide-4-sulfonic 
acid ester of 1,1,1-tris (4-hydroxyphenyl)ethane, 
1,2-naphthoquinonediazide-4-sulfonic acid ester of 1,1-bis 
(3,5-dimethyl-2-hydroxyphenyl)-1-[4-(4-hydroxybenzyl)phenyl ]ethane, etc. 
Sulfone compounds: .beta.-Ketosulfones, .beta.-sulfonylsulfones, etc., 
preferably, compounds represented by the following formula: 
##STR12## 
wherein X is 
##STR13## 
R.sup.28 to R.sup.31, which may be the same or different, represent alkyl 
groups, preferably alkyl groups having 1-4 carbon atoms or halogen atoms; 
and n is an integer of 0-3. Particularly preferable are 
4-trisphenacylsulfone, mesitylphenacylsulfone, bis 
(phenylsulfonyl)methane, etc. 
Nitrobenzyl compounds: Nitrobenzylsulfonate compounds, 
dinitrobenzylsulfonate compounds, etc., preferably, compounds represented 
by the following formula: 
##STR14## 
wherein R.sup.32 represents an alkyl group, preferably an alkyl group 
having 1-4 carbon atoms; n represents an integer of 1-3; R.sup.33 
represents a hydrogen atom or a methyl group; and 
##STR15## 
in which R.sup.35 is a hydrogen atom or an alkyl group, preferably an alkyl 
group having 1-4 carbon atoms, and R.sup.36 is an alkoxy group, preferably 
an alkoxy group having 1-4 carbon atoms. Particularly preferable are 
2-nitrobenzyl tosylate, 2,4-dinitrobenzyl tosylate, 4-nitrobenzyl 
9,10-diethoxyanthracene-2-sulfonate, etc. Sulfonic acid compounds: 
Alkylsulfonic acid esters, haloalkylsulfonic acid esters, arylsulfonic 
acid esters, iminosulfonates, etc., preferably, compounds represented by 
the following formulas: 
##STR16## 
wherein R.sup.37 and R.sup.40, which may be the same or different, 
represent hydrogen atoms or alkyl groups, preferably alkyl groups having 
1-4 carbon atoms; and R.sup.38 and R.sup.39, which may be the same or 
different, represent hydrogen atoms, alkyl groups, preferably alkyl groups 
having 1-4 carbon atoms, aryl groups, preferably aryl groups having 6-20 
carbon atoms or aralkyl groups, preferably aralkyl groups having 7-20 
carbon atoms; 
##STR17## 
wherein R.sup.41 represents a hydrogen atom or an alkyl group, preferably 
an alkyl group having 1-4 carbon atoms; and R.sup.42 and R.sup.43, which 
may be the same or different, represent alkyl groups, preferably alkyl 
groups having 1-4 carbon atoms or aryl groups, preferably aryl groups 
having 6-20 carbon atoms, with a proviso that R.sup.42 and R.sup.43 may be 
bonded to each other to form a ring; and 
##STR18## 
wherein R.sup.44 represents a methyl group, a trichloromethyl group, a 
trifluoromethyl group, a phenyl group, a tolyl group, a cyanophenyl group, 
a trichlorophenyl group, a trifluorophenyl group, a trifluoromethylphenyl 
group or a pentafluorophenyl group; and n represents an integer of 1-6. 
Particularly preferable are benzoin tosylate, pyrogallol tris( 
trifluoromethanesulfonate ), etc. 
Of these radiation-sensitive acid-forming agents, onium salts and 
diazoketone compounds are preferable. 
In the present invention, the radiation-sensitive acid-forming agent is 
used in a proportion of preferably 0.1-20 parts by weight, more preferably 
0.5-10 parts by weight, per 100 parts by weight of the polymer (A). The 
above radiation-sensitive acid-forming agents are used alone or in 
admixture of two or more. 
The composition of the present invention can comprise, if necessary, a 
compound which can be decomposed by the action of an acid to promote the 
dissolution of the composition in a developing solution [this compound is 
referred to hereinafter as component (C)]. The component (C) includes, for 
example, compounds represented by the following formulas: 
##STR19## 
wherein A represents --OR.sup.45, 
##STR20## 
in which R.sup.45 to R.sup.47 are substituted methyl groups, substituted 
ethyl groups, silyl groups, germyl groups or alkoxycarbonyl groups; each 
of a, b and c represents an integer of 0-3, excluding the case that a, b 
and c are all 0; and each of x, y and z represents an integer of 0-3. 
Examples of the substituted methyl groups, the substituted ethyl groups, 
the silyl groups, the germyl groups and the alkoxycarbonyl groups in the 
definitions of R.sup.45 to R.sup.47 are the same as the respective 
examples of the substituted methyl group, the substituted ethyl group, the 
silyl group, the germyl group and the alkoxycarbonyl group mentioned in 
the definition of R.sup.1. 
The amount of the component (C) used is preferably 100 parts by weight or 
less, more preferably 10-50 parts by weight, per 100 parts by weight of 
the polymer (A). 
The composition of the present invention may further comprise various 
additives if necessary. 
Such additives include, for example, surface active agents for improving 
the coatability of the composition, inhibiting the striation on the film 
formed, improving the developability of the radiation-irradiated portion, 
etc. The surface active agents include nonionic surfactants such as 
polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, 
polyoxyethylene oleyl ether, polyoxyethylene octylphenol ether, 
polyoxyethylene nonylphenol ether, polyethylene glycol dilaurate, 
polyethylene glycol distearate and the like; fluorine-containing 
surfactants such as F Top EF 301, EF 303 and EF 352 (products of Shin 
Akita Kasei K.K. ), Megafac F 171 and F 173 (products of DAINIPPON INK & 
CHEMICALS), Fluorad FC 430 and FC 431 (products of Sumitomo 3M Limited), 
Asahi Guard AG 710, Surflon S-382, Surflon SC 101, SC 102, SC 103, SC 104, 
SC 105 and SC 106 (products of Asahi Glass Co., Ltd. ) and the like; 
organosiloxane polymer KP 341 (product of Shin-Etsu Chemical Co., Ltd. ); 
and Polyflow No. 75 and No. 95 (products of Kyoeisha Yushikagaku Kogyo 
K.K. ) which are acrylic or methacrylic acid polymers; and the like. 
The amount of the surface active agents used is preferably 2 parts by 
weight or less per 100 parts by weight of the sum of the polymer (A) and 
the radiation-sensitive acid-forming agent. 
The additives further include a halation-preventing agent consisting of an 
azo compound, an amine compound or the like; an adhering aid; a 
storage-stabilizer; a defoaming agent; etc. 
The composition of the present invention can be prepared by dissolving in a 
solvent the necessary amounts of the polymer (A), the radiation-sensitive 
acid-forming agent and optional components such as the component (C) and 
various additives. The solvent used in this case includes, for example, 
ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 
ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, 
diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 
diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, methyl 
Cellosolve acetate, ethyl Cellosolve acetate, propylene glycol monomethyl 
ether acetate, propylene glycol monoethyl ether acetate, propylene glycol 
monopropyl ether acetate, toluene, xylene, methyl ethyl ketone, 
cyclohexanone, methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, 
ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl 
hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, 3-methoxybutyl 
acetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutyl 
propionate, 3-methyl-3-methoxybutyl butyrate, ethyl acetate, butyl 
acetate, methyl acetoacetate, ethyl acetoacetate, methyl 
3-methoxypropionate, ethyl 3-ethoxypropionate, N-methylpyrrolidone, 
N,N-dimethylformamide, N,N-dimethylacetamide and the like. 
To the above solvent may be added, if necessary, a high-boiling solvent 
such as benzyl ethyl ether, dihexyl ether, diethylene glycol monomethyl 
ether, diethylene glycol monoethyl ether, acetonylacetone, isophorone, 
caproic acid, caprylic acid, 1-octanol, 1-nonanol, benzyl alcohol, benzyl 
acetate, ethyl benzoate, diethyl oxalate, diethyl maleate, 
.gamma.-butyrolactone, ethylene carbonate, propylene carbonate, phenyl 
Cellosolve acetate or the like. 
The composition of the present invention is coated in the form of the 
above-mentioned solution on a substrate such as silicon wafer or the like 
and dried to form a resist film. In this case, the coating on a substrate 
is conducted, for example, by dissolving the present composition in the 
above-mentioned solvent so that the solid content in the resulting 
solution becomes 5-50% by weight, filtering the solution, and coating the 
filtrate by spin-coating, flow-coating, roll-coating or the like. 
The resist film formed is partially irradiated with a radiation for forming 
a fine pattern. The radiation used is not critical; however, for example, 
ultraviolet rays (e.g. excimer laser), X-rays (e.g. synchrotron 
radiation), charged particle beams (e.g. electron beam) and the like are 
used depending upon the kind of the radiation-sensitive acid-forming agent 
used. Conditions for irradiating with the radiation, such as radiation 
dose and the like are appropriately determined depending upon the 
formulation of the composition prepared, the kinds of the additives used, 
etc. 
In the present invention, in order to enhance the apparent sensitivity of 
the resist film, it is appropriate to heat the resist film after the 
irradiation. The heating temperature may be varied depending upon the 
formulation of the composition prepared, the kinds of the additives used, 
etc., and preferably ranges from 30.degree. to 200.degree. C., more 
preferably from 50.degree. C. to 150.degree. C. 
As a developing solution used in the subsequent development, there may be 
used, in order to obtain a positive pattern, an aqueous alkaline solution 
prepared by dissolving in water sodium hydroxide, potassium hydroxide, 
sodium carbonate, sodium silicate, sodium metasilicate, ammonia water, 
ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, 
methyldiethylamine, dimethylethanolamine, triethanolamine, 
tetramethylammonium hydroxide, tetraethylammonium hydroxide, pyrrol, 
piperidine, 1,8-diazabicyclo[5.4.0]-7-undecene, 
1,5-diazabicyclo[4.3.0]-5-nonane or the like. 
The above alkaline solution as a developing solution may have added thereto 
a water-soluble organic solvent, for example, an alcohol such as methanol, 
ethanol or the like and a surface active agent in appropriate amounts. 
Also, chloroform, benzene or the like may be used as a developing solution. 
In this case, a negative pattern can be obtained. 
The radiation-sensitive composition of the present invention can be 
suitably used as a resist composition which enables reliable fine 
processing, which has high sensitivity and high resolution degree, and 
which is superior in dry etching resistance, developability, adhesiveness, 
heat resistance, yield of residual film thickness, etc. Further, the 
present radiation-sensitive composition can be effectively used as a 
resist for the production of integrated circuits which are presumed to 
become increasingly finer because the composition can respond to various 
radiations such as far-ultraviolet rays (e.g. excimer laser), X-rays (e.g. 
synchrotron radiation) and charged particle beams (e.g. electron beam).

The present invention is described below in more detail referring to 
Examples. However, the present invention is by no means restricted 
thereto. 
SYNTHESIS EXAMPLE 1 
In 1,000 g of dioxane was dissolved 200 g of a poly(styrene-maleic 
anhydride) (styrene:maleic anhydride=1:1 by mole). To the resulting 
solution was added 200 g of benzyl alcohol. The solution was heated at 
100.degree. C. for 4 hours with stirring, after which the solution was 
coagulated in hexane to obtain poly(styrene-monobenzyl maleate) [referred 
to hereinafter as polymer (1)]. By using phenol or benzylamine in place of 
the benzyl alcohol, there were obtained poly(styrene-monophenyl maleate) 
[referred to hereinafter as polymer (2)] and poly(styrene-maleic acid 
benzylamide) [referred to hereinafter as polymer (3)]. 
In 100 g of tetrahydrofuran was dissolved 30 g of the polymer (1) used as a 
raw material polymer, and 30 g of 3,4-dihydro-2H-pyran was added as a 
reaction reagent, after which reaction was conducted. The reaction mixture 
was coagulated in hexane to obtain a polymer (referred to hereinafter as 
polymer A). 
The same procedure as above was repeated, except that the above raw 
material polymer and reaction reagent were replaced with those shown in 
Table 1 (the respective amounts were not changed) to obtain polymers 
(referred to hereinafter as polymers B to I). 
TABLE 1 
__________________________________________________________________________ 
Proportion 
Raw Kind of substituent 
of 
Formed 
material 
Reaction in formula (1) formula (1) 
polymer 
polymer 
reagent R.sup.1 R.sup.2 
(mole %) 
Mw 
__________________________________________________________________________ 
A (1) Dihydropyran 
Tetrahydropyranyl 
Benzyloxy 
50 7,000 
B (1) Trimethylchlorosilane 
Trimethylsilyl 
Benzyloxy 
50 7,000 
C (1) Ethyl vinyl ether 
1-Ethoxyethyl 
Benzyloxy 
50 7,000 
D (2) Dihydropyran 
Tetrahydropyranyl 
Phenoxy 
50 7,000 
E (2) Trimethylchlorosilane 
Trimethylsilyl 
Phenoxy 
50 7,000 
F (2) Ethyl vinyl ether 
1-Ethoxyethyl 
Phenoxy 
50 7,000 
G (3) Dihydropyran 
Tetrahydropyranyl 
Benzylamino 
50 7,000 
H (3) Trimethylchlorosilane 
Trimethylsilyl 
Benzylamino 
50 7,000 
I (3) Ethyl vinyl ether 
1-Ethoxyethyl 
Benzylamino 
50 7,000 
__________________________________________________________________________ 
SYNTHETIC EXAMPLE 2 
In 1,000 g of an aqueous solution containing 15% by weight of potassium 
hydroxide was suspended 200 g of a poly(styrene-maleic anhydride) 
(styrene:maleic anhydride=1:1 by mole). The suspension was heated at 
80.degree. C. for 6 hours with stirring, and then subjected to coagulation 
in 20 liters of an aqueous 5% by weight hydrochloric acid solution to 
obtain a poly(styrene-maleic acid) [referred to hereinafter as polymer 
(4)]. The same procedure as above was repeated, except the above 
poly(styrene-maleic anhydride) was replaced with a poly(styrene-maleic 
anhydride) (styrene:maleic anhydride=2:1 by mole ) or a poly( 
styrene-maleic anhydride) (styrene:maleic anhydride=3:1 by mole) to obtain 
a polymer (styrene:maleic acid=2:1 by mole) [referred to hereinafter as 
polymer (5)] and a polymer (styrene:maleic acid=3:1 by mole) [referred to 
hereinafter as polymer (6)]. 
In 100 g of ethyl acetate was dissolved 15 g of the polymer (4) used as a 
raw material polymer, and 15 g of 3,4-dihydro-2H-pyran was added as a 
reaction reagent, after which reaction was conducted. The reaction mixture 
was coagulated in hexane to obtain a polymer (referred to hereinafter as 
polymer J). The same procedure as above was repeated, except that the 
above raw material polymer and reaction reagent were replaced with those 
shown in Table 2 (the respective amounts were not changed) to obtain 
polymers (referred to hereinafter as polymers K to O). 
TABLE 2 
__________________________________________________________________________ 
Proportion 
Raw Kind of substituent of 
Formed 
material 
Reaction in formula (1) formula (1) 
polymer 
polymer 
reagent R.sup.1 R.sup.2 (mole %) 
Mw 
__________________________________________________________________________ 
J (4) Dihydropyran 
Tetrahydropyranyl 
Tetrahydropyranyloxy 
50 7,000 
K (4) Trimethylchlorosilane 
Trimethylsilyl 
Trimethylsilyloxy 
50 7,000 
L (5) Dihydropyran 
Tetrahydropyranyl 
Tetrahydropyranyloxy 
33 8,000 
M (5) Trimethylchlorosilane 
Trimethylsilyl 
Trimethylsilyloxy 
33 8,000 
N (6) Dihydropyran 
Tetrahydropyranyl 
Tetrahydropyranyloxy 
25 11,000 
O (6) Trimethylchlorosilane 
Trimethylsilyl 
Trimethylsilyloxy 
25 11,000 
__________________________________________________________________________ 
SYNTHETIC EXAMPLE 3 
In 40 g of dioxane were dissolved 20 g of di-tert-butyl fumarate, 12 g of 
styrene and 1.9 g of azobisisobutyronitrile. The gas phase in the system 
was purged with nitrogen. Reaction was conducted at 70.degree. C. for 6 
hours with stirring. The reaction mixture was coagulated in methanol to 
obtain a polymer (referred to hereinafter as polymer P). 
TABLE 3 
______________________________________ 
Substituent in Proportion of 
Formed formula (1) formula (1) 
polymer R.sup.1 R.sup.2 (mole %) Mw 
______________________________________ 
P tert-Butyl 
tert-Butoxy 
50 10,000 
______________________________________ 
EXAMPLE 1 
In methyl 3-methoxypropionate were dissolved 20 g of the polymer A and 1 g 
of triphenylsulfonium trifluoromethanesulfonate as a radiation-sensitive 
acid-forming agent. The solution was filtered through a 0.2 .mu.m filter 
to obtain a composition solution. The composition solution was spin-coated 
on a silicon wafer. The coated silicon wafer was heated on a hot plate at 
100.degree. C. for 2 minutes to form a resist film of 1 .mu.m in thickness 
on the silicon wafer. 
A pattern mask was intimately contacted with the resist film. The resulting 
assembly was irradiated through the mask with an excimer laser at a dose 
of 20 mJ/cm.sup.2 using a KrF excimer laser generator (MBK-400TL-N 
manufactured by Admon Science Inc.). Then, the mask was separated from the 
film. The film was heated on a hot plate at 100.degree. C. for 2 minutes, 
developed with an aqueous solution containing 2.38% by weight of 
tetramethylammonium hydroxide for 60 seconds, and then rinsed with water 
for 30 seconds. As a result, a pattern of 0.4 .mu.m was obtained. Good 
results were also obtained in dry etching resistance, developability, 
adhesiveness, heat resistance, etc. 
EXAMPLES 2-16 
Preparation of composition solutions and formation of patterns were 
conducted in the same manner as in Example 1, except that the polymer A 
used in Example 1 was replaced with one of the polymers B to P, to obtain 
patterns of 0.4 .mu.m. Good results were also obtained in dry etching 
resistance, developability, adhesiveness, heat resistance, etc.