Positive type photosensitive resin composition

A photosensitive resin composition comprising a 1,2-quanonediazide compound and a copolymer consisting essentially of (A) a conjugated diolefinic compound, (B) a monoolefinically unsaturated compound and (C) an .alpha.,.beta.-ethylenically unsaturated carboxylic acid. Said composition can provide a positive type resist which is difficult to break and excellent in adhesion to a substrate.

This invention relates to a positive type photosensitive resin composition. 
More particularly, it relates to a photosensitive resin composition 
capable of providing a positive type resist difficult to break and 
excellent in adhesion to a substrate. 
With the development of photo-lithographic technique, the degree of 
integration of integral circuits has been made higher and at the present 
time, it comes to be required that a 2 .mu.m pattern size be reproduced 
when producing an integral circuit. Most of the resists used at present in 
this photo-lithographic technique are negative type resists obtained by 
adding a bisazide compound as a photo-crosslinking agent to a cyclized 
polyisoprene rubber. However, this type of resists are limited in 
resolution, so that it is difficult to resolve a 2 .mu.m pattern. 
It is positive type resist which can fulfil the above mentioned 
requirement. A positive type resist contains a 1,2-quinonediazide compound 
as a constituent. This compound absorbs ultraviolet rays upon exposure to 
light to form a ketene via a carbene as shown in the following scheme, and 
this ketene reacts with a slight quality of water present in the system to 
give indenecarboxylic acid, which is dissolved in an aqueous alkali 
solution used as a developing solution: 
##STR1## 
Said phenomenon is utilized in the positive type resist. 
Thus, an aqueous alkali solution is used as a developing solution in the 
case of a positive type resist, owing to which the resolution can be 
enhanced without swelling the resist. 
Such positive type resists can roughly be classified into (1) a mixture of 
a polymer soluble in an aqueous alkali solution and a 1,2-quinonediazide 
compound and (2) a polymer obtained by condensing the side chain of a 
polymer with a 1,2-quinonediazide compound. 
Most of the alkali-soluble polymers used in the class (1) are phenolic 
resins synthesized from phenol, cresol or the like and formaldehyde. 
Although the phenolic resins per se are soluble in an aqueous alkali 
solution, the 1,2-quinonediazide compound added thereto is insoluble at 
all in the aqueous alkali solution before exposure to light, so that a 
mixture of both is very difficult to dissolve in an aqueous alkali 
solution. The 1,2-quinonediazide compound in the part exposed to 
ultraviolet rays changes into indenecarboxylic acid as mentioned above, 
owing to which the mixture becomes soluble in an aqueous alkali solution. 
Thus, a positive pattern can be obtained. Accordingly, photosensitivity 
and developability can be controlled by varying the amount of 
1,2-quinonediazide compound added to the system. 
On the other hand, those belonging to the class (2) include, for example, a 
condensate of polyaminostyrene and 1,2-quinonediazide compound (Japanese 
Patent Publication No. 34,681/74) and a condensate of polyhydroxystyrene 
and a 1,2-quinonediazide compound (Japanese Patent Application Kokai 
(Laid-Open) No. 113,305/75). Since the polymer has previously been 
condensed in said class, their photosensitivity and developability are 
more difficult to control than in the class (1) where the 
1,2-quinonediazide compound is merely added. 
For this reason, most of the commercially available positive type resists 
are those belonging to the class (1) wherein a phenolic resin is mixed 
with a 1,2-quinonediazide compound. However, said phenolic resin type 
positive resist has some faults as compared with the negative type 
resists. 
One of the faults is the poor adhesion of the resists to a substrate such 
as silicon dioxide film or the like. Because of the poor adhesion, the 
developing solution permeates into the interface between the resist and 
the substrate in the course of development to cause peeling of the part 
which is to be left as a resist pattern. Even if said part can remain 
well, the subsequent wet etching process produces so great a side etch 
that the product is unusable as a resist. In order to eliminate this 
fault, a pretreatment for modifying the surface of the substrate is 
carried out by coating the substrate with a silylamine derivative such as 
hexamethyldisilazane and chloromethylsilane or the like. 
Further, there is another fault that the resist film is hard and brittle. 
Thus, when the resist layer is intimately contacted with a mask and 
exposed to light, the phenolic resin type positive resist is readily 
broken owing to its poor flexibility. When the mask is removed a part of 
the broken resist is attached to the mask to spot the same. When the 
spotted mask is reused next time, therefore, an insufficient exposure is 
caused at the spot portion to form areas impossible to develop with an 
aqueous alkali solution on the resist. 
The present inventors have conducted various studies on the above-mentioned 
problems to discover that all the above-mentioned problems can be solved 
by combining a 1,2-quinonediazide compound with a copolymer consisting 
essentially of a conjugated diolefinic compound, a monoolefinically 
unsaturated compound and an .alpha.,.beta.-ethylenically unsaturated 
carboxylic acid. It has also been found that said photosensitive resin 
composition has a high photosensitivity when the copolymer has a narrow 
composition distribution which has been produced so that the standard 
deviations in the proportions of individual comonomers copolymerized 
(copolymer composition) are 3 or less at any time in the process of 
polymerization reaction. 
According to this invention, there is provided a positive type 
photosensitive resin composition comprising a 1,2-quinonediazide compound 
and a copolymer consisting essentially of (A) a conjugated diolefinic 
compound, (B) a monoolefinically unsaturated compound and (C) an 
.alpha.,.beta.-ethylenically unsaturated carboxylic acid. 
If the positive type photosensitive resin composition of this invention is 
used, there can be obtained, owing to its quite excellent adhesion to a 
substrate a quite excellent positive type resist having an advantage that 
the resist pattern does not peel off in the course of development even if 
the substrate is not coated with a surface treating agent such as 
hexamethyldisilazane, the undercut after etching is very slight, and the 
breaking of the resist film and the adhesion of the resist film to a mask 
do not occur when it is exposed to light in contact with the mask. 
The conjugated diolefinic compound (A) plays an important role in the 
constitutive polymer in the positive type photosensitive resin composition 
of this invention. That is to say, a flexibility characteristic of rubber 
can be given to the copolymer, so that a flexibility becomes possessed by 
the resist, the problem of breaking occurring in phenolic resin type 
positive resists disappears, and the yield of product can be improved 
markedly. Further, a flexibility can be given to the resist, so that the 
adhesive force of the resist to a silicon dioxide film is enhanced. As a 
result, the adhesive force between the resist layer and the substrate can 
be increased without using any surface treating agent, so that the peeling 
of the resist film does not occur at all at the time of development with 
an aqueous alkali solution or etching with an aqueous hydrogen fluoride 
solution. 
As said conjugated diolefinic compound (A), there are preferably used 
1,3-butadiene, isoprene, chloroprene, dimethylbutadiene and the like. They 
may be used alone or in admixture of two or more. The proportion of the 
conjugated diolefinic compound in the copolymer is preferably 5-60 mole % 
and particularly preferably 10-40 mole %. 
If the proportion of the conjugated diolefinic compound in the copolymer is 
less than 5 mole %, the flexibility of the copolymer becomes so 
insufficient that the desired effect cannot be sufficiently obtained. If 
the proportion exceeds 60 mole %, the flexibility of the copolymer becomes 
so great as to cause a resist flow at the time of prebaking or post-baking 
and the hydrophobic property of the copolymer is increased to cause the 
decrease of the developability with an aqueous alkali solution. Therefore, 
these proportions are undesirable. 
By adding said monoolefinically unsaturated compound (B) to the copolymer, 
the mechanical properties of the copolymer can be controlled appropriately 
and the solubility of the copolymer in an aqueous alkali solution can be 
controlled delicately in relation to the .alpha., .beta.-ethylenically 
unsaturated carboxylic acid as mentioned hereinafter. 
As said monoolefinically unsaturated compound, there may be used alkyl 
methacrylates such as methyl methacrylate, ethyl methacrylate, n-butyl 
methacrylate, sec-butyl methacrylate, t-butyl methacrylate and the like; 
alkyl acrylates such as methyl acrylate, isopropyl acrylate and the like; 
cycloalkyl methacrylates such as cyclohexyl methacrylate, 
2-methylcyclohexyl methacrylate and the like; cycloalkyl acrylates such as 
cyclohexyl acrylate, 2-methylcyclohexyl acrylate and the like; aryl 
methacrylates such as phenyl methacrylate, benzyl methacrylate and the 
like; aryl acrylates such as phenyl acrylate, benzyl acrylate and the 
like; dialkyl esters of dicarboxylic acids such as diethyl maleate, 
diethyl fumarate, diethyl itaconate and the like; hydroxyalkyl acrylates 
or methacrylates such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl 
methacrylate and the like; styrene; styrene derivatives such as 
.alpha.-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 
vinyltoluene and p-methoxystyrene; acrylonitrile; methacrylonitrile; vinyl 
chloride; vinylidene chloride; acrylamide; methacrylamide; vinyl acetate; 
and the like. These compounds may be used alone or in admixture of two or 
more. If the effects of the monoolefinically unsaturated compound upon 
various properties of the copolymer are taken into consideration, the 
proportion of the compound in the copolymer is preferably 25-90 mole % and 
particularly preferably 35-80 mole %. 
If the proportion of the monoolefinically unsaturated compound in the 
copolymer is less than 25 mole %, the proportions of the other 
constituents in the copolymer, i.e., conjugated diolefinic compound and 
.alpha.,.beta.-ethylenically unsaturated carboxylic acid increase 
correspondingly, so that the mechanical properties and 
alkali-developability of the resist are difficult to control. If the 
proportion of the monoolefinically unsaturated compound exceeds 90 mole %, 
the proportion of .alpha.,.beta.-ethylenically unsaturated carboxylic acid 
decreases correspondingly, so that the solubility of the copolymer in an 
aqueous alkali solution decreases undesirably. 
The said .alpha.,.beta.-ethylenically unsaturated carboxylic acid (C) 
includes monocarboxylic acids such as acrylic acid, methacrylic acid, 
crotonic acid and the like; dicarboxylic acids such as maleic acid, 
fumaric acid, citraconic acid, mesaconic acid, itaconic acid and the like; 
acid anhydrides such as maleic anhydride, itaconic anhydride and the like; 
and monoesters of dicarboxylic acids such as monoethyl maleate, monoethyl 
fumarate, monoethyl itaconate and the like. These 
.alpha.,.beta.-ethylenically unsaturated carboxylic acids may be used 
alone or in admixture of two or more, and the proportion thereof in the 
copolymer is preferably 5-40 mole % and particularly preferably 10-25 mole 
%. If it is less than 5 mole %, the copolymer becomes difficult to 
dissolve in an aqueous alkali solution, so that undeveloped portions 
remain and a satisfactory resist pattern is difficult to make. If it 
exceeds 40 mole %, the solubility of the copolymer in an aqueous alkali 
solution becomes so high that it is difficult to prevent the dissolution 
of unexposed portions, even by the alkali-insolubilizing effect of the 
1,2-quinonediazide compound added. 
the conjugated diolefinic compound-containing copolymer of this invention 
is synthesized by a conventional radical solution polymerization method, 
radical emulsion polymerization method or the like. When it is synthesized 
by a radical emulsion polymerization method, the chain transfer to polymer 
takes place easily in the latter stage of polymerization and there is a 
tendency of forming a solvent-insoluble gel-like substance if the 
conversion is kept high. If the conversion is kept low in order to avoid 
the formation of a gel-like substance, the productivity drops, and hence, 
it is economically disadvantageous. 
On the other hand, when the copolymer is synthesized by a radical solution 
polymerization method, the monomer is diluted with a solvent, and 
therefore, the chain transfer to polymer in the latter stage of 
polymerization can be controlled and the polymerization can be allowed to 
proceed to a high polymerization conversion. Therefore, the radical 
solution polymerization method is excellent as a method of obtaining the 
copolymer used in this invention. The solvents usable in the radical 
solution polymerization method include alcohols such as methanol, ethanol 
and the like; ethers such as tetrahydrofuran and the like; glycol ethers 
such as ethylene glycol monomethyl ether and the like; Cellosolve esters 
such as methyl Cellosolve acetate, ethyl Cellosolve acetate and the like; 
aromatic hydrocarbons; ketones; esters; and the like. Depending on the 
object, a plurality of solvents may be used in admixture. Among these 
solvents, alcohols are particularly preferred. 
As the polymerization catalyst, conventional radical polymerization 
initiators may be used, for example, azo compounds such as 
2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 
2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) and the like; organic 
peroxides such as benzoyl peroxide, lauroyl peroxide, t-butyl 
peroxypivalate, 1,1-bis(t-butylperoxy)-cyclohexane and the like; and 
hydrogen peroxide. When a peroxide is used as a radical polymerization 
initiator, it may be used as a redox type initiator in combination with a 
reducing agent. 
The copolymer having a narrow composition distribution used for the purpose 
of enhancing the photosensitivity can be produced by portionwise or 
continuously adding the monomers to be copolymerized to the polymerization 
system in the above-mentioned radical solution polymerization method or 
radical emulsion polymerization method according to the respective 
reactivity ratios. That is to say, the composition distribution can be 
controlled by allowing a monomer or monomers having a lower reactivity 
ratio to be present in a high proportion in the early stage of 
polymerization and adding a monomer or monomers having a higher reactivity 
ratio to the system with the progress of polymerization. It is well-known 
that the reactivity ratio can be determined from Q value which is a 
characteristic value relating to resonance stability of monomer and e 
value which is a characteristic value relating to polarity of monomer, 
both being proposed by Alfrey-Price. As to equations for determining the 
composition of multi-component polymer formed at any instance by using 
these Q and e values, discussions are made in "High Polymers" Vol. XVIII, 
"Copolymerization" edited by G. E. Ham, pp. 30-37 (1964), John Wiley and 
Sons, Inc. and hence the determination method is well-known. 
A copolymer having a narrow composition distribution can also be produced 
by previously mixing the monomers to be copolymerized and adding the 
monomer mixture to the polymerization system at a rate lower than the 
polymerization velocity of the polymerization system, in the 
above-mentioned radical solution polymerization method, radical emulsion 
polymerization method, etc. In this case, the polymerization conversion is 
always close to 100% because the addition rate of the monomer mixture is 
lower than the polymerization velocity, and hence, the copolymer 
composition during the polymerization period can always be equalized to 
the composition ratio of the monomer mixture, whereby the copolymer 
composition can be narrowed. 
Copolymer composition distribution can be determined by measuring the 
standard deviations of the copolymerized proportions of individual 
copolymer components at any plural times during the polymerization 
reaction. By making the standard deviations 3 or less, preferably 2 or 
less, a photosensitive resin composition having a high photosensitivity 
can be obtained. 
Among the above-mentioned processes for producing a copolymer having a 
narrow composition distribution, particularly preferably is a process 
which comprises, in the radical solution polymerization method, 
portionwise or continuously adding the monomers to be copolymerized to the 
polymerization system according to the reactivities of the monomers. This 
process uses no emulsifier unlike the radical emulsion polymerization 
method, so that the copolymer obtained is not contaminated by impurities. 
Further, the period of time required for the production of a copolymer can 
be shortened as compared with the process using a monomer mixture formed 
by previously mixing the monomers to be copolymerized. 
The intrinsic viscosity [.eta.] of the copolymer used in this invention as 
measured in tetrahydrofuran at 30.degree. C. is 0.01-1 dl/g, preferably 
0.01-0.5 dl/g and more preferably 0.01-0.3 dl/g. 
If the intrinsic viscosity [72 ] exceeds 1 dl/g, the velocity of 
dissolution in an aqueous alkali solution becomes very low, so that the 
developing time becomes impractically long. If the intrinsic viscosity 
[.eta.] is less than 0.01 dl/g, the rate of dissolution in an aqueous 
alkali solution becomes so high that the yield of residual film thickness 
drops and the pattern-leaning phenomenon becomes remarkable. 
Since the degree of polymerization of the resultant copolymer is inversely 
proportional to the square root of the concentration of radical 
polymerization initiator, the intrinsic viscosity [.eta.] of the copolymer 
can be allowed to fall in the range of 0.01-1 dl/g by appropriately 
controlling the amount of the radical polymerization initiator added. 
Further, in order to adjust the intrinsic viscosity [.eta.] of the 
copolymer to 0.01-1 dl/g, a chain transfer agent conventionally used in 
polymerization systems, for example, a mercaptan such as 
n-dodecylmercaptan, t-dodecylmercaptan or the like or a halogenated 
compound such as carbon tetrachloride, carbon tetrabromide or the like, 
may be added to the polymerization system. 
The 1,2-quinonediazide compounds used in this invention include, for 
example, 1,2-benzoquinonediazidesulfonic acid esters, 
1,2-naphthoquinonediazidesulfonic acid esters, 
1,2-benzoquinonediazidesulfonic acid amides, 
1,2-naphthoquinonediazidesulfonic acid amides and the like, and known 
1,2-quinonediazide compounds may be used as they are. More specifically, 
the 1,2-quinonediazide compounds mentioned in J. Kosar, "Light-Sensitive 
Systems", 339-352 (1965), John Wiley and Sons, Inc. (New York) or W. S. De 
Forest, "Photoresist", 50 (1975), McGraw-Hill, Inc. (New York) may be 
used. That is, the said compounds include phenyl 
1,2-benzoquinonediazide-4-sulfonate, 
1,2,1',2'-di(benzoquinonediazide-4-sulfonyl)-dihydroxybiphenyl, 
1,2-benzoquinonediazide-4-(N-ethyl-N-.beta.-naphthyl)-sulfonamide, 
cyclohexyl 1,2-naphthoquinonediazide-5-sulfonate, 
1-(1,2-naphthoquinonediazide-5-sulfonyl)-3,5-dimethylpyrazole, 
4'-hydroxydiphenyl-4"-azo-.beta.-naphthol 
1,2-naphthoquinonediazide-5-sulfonate, 
N,N-di(1,2-naphtoquinonediazide-5-sulfonyl)-aniline, 
2'-(1,2-naphthoquinonediazide-5-sulfonyloxy)-1-hydroxyanthraquinone, 
2,4-dihydroxybenzophenone 1,2-naphthoquinonediazide-5-sulfonate, 
2,3,4-trihydroxybenzophenone 1,2-naphthoquinonediazide-5-sulfonate, a 
condensate of 2 moles of 1,2-naphthoquinonediazide-5-sulfonic acid 
chloride and 1 mole of 4,4'-diaminobenzophenone, a condensate of 2 moles 
of 1,2-naphthoquinonediazide-5-sulfonic acid chloride and 1 mole of 
4,4'-dihydroxy-1,1'-diphenylsulfone, a condensate of 1 mole of 
1,2-naphthoquinonediazide-5-sulfonic acid chloride and 1 mole of 
purporogallin, 1,2-naphthoquinonediazide-5-(N-dihydroabietyl)-sulfonamide 
and the like. The 1,2-quinonediazide compound mentioned in Japanese Patent 
Publication Nos. 1,935/62; 3,627/62; 13,109/62; 26,126/65; 3,801/65; 
5,604/70; 27,345/70 and 13,013/76 and Japanese Patent Application Kokai 
(Laid-Open) Nos. 96,575/73; 63,802/73 and 63,803/73, may also be used. 
These quinonediazide compounds are added preferably in an amount of 5-100 
parts by weight, particularly 1-50 parts by weight, per 100 parts by 
weight of the copolymer. If the amount is less than 5 parts by weight, the 
amount of a carboxylic acid which is formed upon absorption of light is 
too small to make different the solubilities of resist composition in an 
aqueous alkali solution before and after exposure to light, and hence the 
patterning becomes difficult. If it exceeds 100 parts by weight, the major 
part of the added 1,2-quinonediazide compound remains unchanged when 
exposed to light for a short period of time, so that the effect of the 
compound insolubilizing the rubber in an aqueous alkali solution is yet 
too high to develope an image. Further, if such a low molecular weight 
compound is added in a large amount, the film formability and the 
mechanical properties are deteriorated. Further, the alkali-insolubilizing 
effect, the solubility in an aqueous alkali solution of the carboxylic 
acid formed by exposure to light, the ability of the composition to form a 
resist film, the adhesion of the resist film to a substrate, and the like 
can be varied depending upon the kind of the 1,2-quinonediazide compound. 
The positive type photosensitive resin composition of this invention is 
used in the form of a solution in a solvent capable of dissolving the 
above-mentioned copolymer and 1,2-quinonediazide compound. Said solvent 
includes, for example, glycol ethers such as ethylene glycol monomethyl 
ether, ethylene glycol monoethyl ether and the like; Cellosolve esters 
such as methyl Cellosolve acetate, ethyl Cellosolve acetate and the like; 
aromatic hydrocarbons such as toluene, xylene and the like; ketones such 
as methyl ethyl ketone, cyclohexanone and the like; and esters such as 
ethyl acetate, butyl acetate and the like. 
These solvents may be used in admixture of several members, taking into 
consideration the solubilities of the above-mentioned copolymer and 
1,2-quinonediazide compound, as well as the evaporation rate of the 
solvent after the photosensitive resin composition is applied to a 
substrate and the effect of the coated film on the surface shape of the 
substrate. Further, if necessary, a storage stabilizer, a dyestuff, a 
pigment and the like may be added to this photosensitive resin 
composition. 
Furthermore, a polymer which is soluble in an aqueous alkali solution and 
compatible with the positive type photosensitive resin composition of this 
invention can be incorporated into the positive type photosensitive resin 
composition to enhance the mechanical strength of a resist film and 
improve the heat resistance thereof. Said polymer includes 
polyhydroxystyrene, polyaminostyrene, styrene-maleic anhydride copolymer 
resin and the like. However, it is impossible to mix a polymer insoluble 
in an aqueous alkali solution, because when a polymer insoluble in an 
aqueous alkali solution is present in a resist, the part in which the 
polymer is present remains undeveloped even when the 1,2-quinonediazide 
compound present in the composition has been converted into a carboxylic 
acid upon irradiation with a light and has become soluble in a developing 
solution consisting of an aqueous alkali solution, and the undeveloped 
part remains in a resist pattern, and an insoluble polymer dispersed in a 
developing solution attaches to the resist surface to cause unsatisfactory 
articles. 
As the developing solution for the positive type photosensitive resin 
composition of this invention, an aqueous solution of an inorganic alkali 
such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium 
silicate, sodium metasilicate, aqueous ammonia or the like or an aqueous 
solution of an organic alkali including primary amines such as ethylamine, 
n-propylamine and the like; secondary amines such as diethylamine, 
di-n-propylamine and the like; tertiary amines such as triethylamine, 
methyldiethylamine and the like; alcoholamines such as 
dimethylethanolamine, triethanolamine and the like; quaternary ammonium 
hydroxides such as tetramethylammonium hydroxide, tetraethylammonium 
hydroxide and the like; cyclic amines such as pyrrole, piperidine, 
1,8-diazabicyclo(5,4,0)-7-undecene, 1,5-diazabicyclo(4,3,0)-5-nonane and 
the like; and so on, as well as aqueous solutions obtained by adding an 
appropriate quantity of a water-soluble organic solvent such as an 
alcohol, for example, methanol, ethanol or the like, or a surfactant to 
the above-mentioned aqueous solution, can be used preferably. 
The positive type photosensitive resin composition of this invention is 
particularly useful as a material for integral circuit and also can be 
coated on a metallic support such as aluminum to be used for offset 
printing plate and for production of a mask.

This invention is not limited to the Examples. 
EXAMPLE 1 
After replacing the air in a pressure bottle having a capacity of 500 ml 
with dry nitrogen, 4.5 g of 2,2'-azobisisobutyronitrile, 150 g of 
methanol, 70 g of methyl methacrylate (MMA), 15 g of styrene (ST), 27 g of 
methacrylic acid (MAA) and 38 g of 1,3-butadiene (BD) were charged 
thereinto. After crown-capping the bottle, it was dipped in a 
polymerization bath controlled at a temperature of 70.degree. C. and 
reaction was effected for 20 hours while rotating the bottle. The contents 
were poured into petroleum ether to precipitate a copolymer. After 
recovering the copolymer, it was thoroughly washed with petroleum ether 
and dried for 15 hours in a hot-air vacuum drier controlled at a 
temperature of 50.degree. C. 
The composition of the copolymer thus obtained was 
BD/MMA/ST/MMA=35.5/37.8/11.2/15.5 mole %, and its intrinsic viscosity 
[.eta.] was 0.2 dl/g as measured at 30.degree. C. in tetrahydrofuran (all 
the intrinsic viscosities appearing hereinafter were measued under the 
same conditions as above). 
In 77.5 g of ethyl Cellosolve acetate were dissolved 19.5 g of the 
copolymer thus obtained and 3 g of 2,4-dihydroxybenzophenone 
1,2-naphthoquinonediazide-5-sulfonate, and then the solution was filtered 
through a millipore filter having a pore diameter of 0.45 .mu.m to obtain 
a positive type resist. 
This resist was coated onto a silicon dioxide film wafer by the use of a 
spinner and then prebaked for 30 minutes at 80.degree. C. in an oven to 
obtain a coating film having a film thickness of 1.2 .mu.m. A test pattern 
mask manufactured by Toppan Insatsu K.K. was intimately contacted with the 
wafer and irradiated for 15 seconds with ultraviolet rays having an 
intensity of 50 W/m.sup.2 at 365 nm. Then it was developed at 20.degree. 
C. for 40 seconds with 1.5% by weight aqueous solution of potassium 
hydroxide. Thus, it was found that a pattern having a line width of 0.7 
.mu.m could be resolved. 
After washing the pattern with water, it was etched, without drying, with 
an aqueous solution of hydrogen fluoride/ammonium fluoride as an etchant, 
whereby etching could be completed in a state almost substantially free 
from permeation. From this fact, it was confirmed that the adhesiveness of 
the positive type resist of this invention to a base board was excellent 
even if no adhesion promoter was used at all and no film-hardening 
treatment was carried out. 
After forming a coating film on a wafer and drying the film at 80.degree. 
C. for 30 minutes in an oven, the surface of the film was notched with a 
knife edge and observed by means of an optical microscope. As a result, no 
fine breaking nor scattering of the resist was observed at all. 
COMATIVE EXAMPLE 1 
A copolymer having a composition of MMA/MAA=82.5/17.5 mole % and an 
intrinsic viscosity [.eta.] of 0.15 dl/g was synthesized by the same 
procedure as in Example 1, and it was evaluated in the same manner as in 
Example 1. As a result, it was poor in adhesion to silicon wafer, and the 
pattern peeled off. 
COMATIVE EXAMPLE 2 
A copolymer of BD/ST=45/55 mole % having an instrinsic viscosity [.eta.] of 
0.25 dl/g was synthesized in the same manner as in Example 1, except that 
toluene was substituted for the solvent. Said copolymer was added 25% by 
weight to the MMA/MAA copolyemr of Comparative Example 1, and a positive 
type resist photosensitive solution was prepared from the resulting 
mixture according to Example 1 and evaluated, to find that the adhesion to 
a silicone wafer was somewhat improved, but the developability was bad and 
almost all patterns could not be developed. 
EXAMPLES 2-6 
The copolymers shown in Table 1 were synthesized by the same procedure as 
in Example 1, and evaluated in the same manner as in Example 1. 
TABLE 1 
__________________________________________________________________________ 
Example 
Copolymer composition [.eta.] 
Resolution 
Adhesion to 
No. (mole %) (dl/g) 
(.mu.m) 
silicon water 
__________________________________________________________________________ 
2 BD/EMA/MAA = 16.4/62.0/21.6 
0.23 
1.0 Excellent 
3 BD/n-BMA/MAA = 15.5/65.3/19.2 
0.25 
0.7 Excellent 
4 BD/MMA/AN/MAA = 27.3/31.8/22.8/18.1 
0.19 
0.9 Excellent 
5 BD/MMA/AA = 21.1/63.6/15.3 
0.16 
0.6 Excellent 
6 IP/MMA/MAA = 31.2/51.1/17.4 
0.18 
0.9 Excellent 
__________________________________________________________________________ 
Note:- 
EMA = ethyl methacrylate; 
nBMA = nbutyl methacrylate; 
AN = acrylonitrile; 
AA = acrylic acid; 
IP = isoprene. 
As shown in Table 1, all the samples exhibited a good resolution without 
peeling of the pattern from the wafer in the course of development, gave a 
small side etch at the time of etching, and were excellent in adhesion to 
wafer. When the resist surface was notched with knife edge, no fine 
breaking was observed at all. 
EXAMPLE 7 
After replacing the air in a pressure bottle having a capacity of 500 ml 
with nitrogen, 0.6 g of 2,2'-azobisisobutyronitrile, 147 g of methanol, 60 
g of MMA, 36 g of AA and 24 g of BD were charged thereinto. After 
crown-capping the bottle, it was dipped in a polymerization bath and 
reaction was effected at 70.degree. C. for 24 hours. The contents were 
poured into petroleum ether to precipitate and purify the product, after 
which it was heated and vacuum-dried at 40.degree. C. for 20 hours. The 
copolymer thus obtained had a composition of BD/MMA/AA=30.3/46.0/23.7 mole 
% and an intrinsic viscosity [.eta.] of 0.45 dl/g. 
In 85 g of ethyl Cellosolve acetate were dissolved 12.5 g of the 
above-mentioned copolymer and 2.5 g of p-tolyl 
1,2-naphthoquinonediazide-5-sulfonate, and then the solution was filtered 
through a millipore filter having a pore diameter of 0.45 .mu.m to produce 
a resist. The resist was coated onto a silicon dioxide film wafer by means 
of a spinner to obtain a resist layer having a film thickness of 0.9 
.mu.m. In the same manner as in Example 1, a test pattern manufactured by 
Toppan Insatsu K.K. was intimately contacted with the wafer and irradiated 
for 15 seconds with ultraviolet rays, after which the resulting image was 
developed at 20.degree. C. for 60 seconds in 1.5% by weight aqueous 
solution of potassium hydroxide. In the developed image, a line having a 
width of 1.5 .mu.m was resolved. No permeation occurred at the time of 
etching, and the resist was well bonded to the silicon wafer. When the 
resist surface was notched with a knife edge, no fine breaking was not 
found at all. 
EXAMPLE 8 
After completely replacing the air in an autoclave having a capacity of 100 
liters with nitrogen, 43 liters of methanol containing 680 g of 
2,2'-azobisisobutyronitrile (AIBN) dissolved therein was charged 
thereinto. Subsequently, 9.1 kg of ST, 5.7 kg of AN, 3.4 kg of MAA and 230 
g of t-dodecylmercaptan were charged into the autoclave, after which 1.8 
kg of BD was charged with gentle stirring. The polymerization was started 
at 70.degree. C. After one hour, there was started the continuous addition 
of BD at a rate of 400 g/hr and MAA at a rate of 230 g/hr while keeping 
the above-mentioned temperature. The period of continuous addition time 
was 5 hours for BD and 3 horus for MAA. After completion of the continuous 
addition of BD, the reaction was further continued for 10 hours. After the 
reaction, a part of the contents was taken out and poured into a large 
excess of petroleum ether to recover the copolymer. It was thoroughly 
washed with petroleum ether and heated and vacuum-dried at a constant 
temperature of 50.degree. C. for 15 hours to obtain the desired copolymer. 
Separately, the contents were portionwise sampled with a progress of 
reaction to measure the polymerization conversion, and, at the same time, 
the copolymer was recovered according to the above-mentioned procedure to 
examine the copolymer composition. 
The relations between polymerization conversion and copolymer composition 
are shown in FIG. 1, and the standard deviations of said composition are 
shown in Table 2. According to FIG. 1 or Table 2, it could be judged that 
the copolymer composition was changed only to a small extent even if the 
polymerization conversion changed, and the copolymer obtained in the 
present Example had a narrow composition distribution. 
In 180 g of ethyl Cellosolve acetate were dissolved 50 g of the copolymer 
having a narrow composition distribution and 10 g of 
2,4-dihydroxybenzophenone 1,2-naphthoquinonediazide-5-sulfonate, and then 
the solution was filtered through a millipore filter having a pore 
diameter of 0.45 .mu.m to prepare a photosensitive solution. This solution 
was coated on a silicon dioxide film on a silicon wafer by means of a 
spinner and then prebaked at 80.degree. C. for 30 minutes. A test pattern 
mask manufactured by Toppan Insatsu K.K. was intimately contacted with the 
wafer and irradiated for 8 seconds with ultraviolet rays having an 
intensity of 50 W/m.sup.2 at 365 nm. Thus, it was confirmed that a pattern 
having a width of 0.7 .mu.m could be resolved by a development at 
20.degree. C. for 40 seconds with a developing solution consisting of a 
mixture of 1.0 g of 1,8-diazabicyclo-(5,4,0)-7-undecene and 199 g of 
deionized water. 
When the developed pattern was wet-etched with an aqueous solution of 
hydrogen fluoride and ammonium fluoride without post-baking, substantially 
no permeation occurred, and it exhibited an excellent adhesion to the 
silicon wafer though no adhesion promoter was used. After forming a 
coating film on the wafer and prebaking it, the resist surface was notched 
with a knife edge and observed by means of an optical microscope. As a 
result, no fine breaking nor scattering of the resist was observed at all. 
EXAMPLE 9 
After charging 43 liters of methanol containing 680 g of AIBN, 9.1 kg of 
ST, 5.7 kg of AN, 4.1 kg of MAA and 230 g of t-dodecylmercaptan into an 
autoclave having a capacity of 100 liters, 3.8 kg of BD was charged 
thereinto with gentle stirring and polymerization reaction was carried out 
at 70.degree. C. for 20 hours. The relations between polymerization 
conversion and copolymer composition were as shown in FIG. 2, and the 
standard deviations of the composition were as shown in Table 2. By 
comparing them with those in FIG. 1, it was confirmed that the copolymer 
composition was uneven. 
After completion of the reaction, a copolymer was obtained in quite the 
same manner as in Example 8, and a photosensitive solution was prepared 
therefrom. This solution was coated on a silicon dioxide film on a silicon 
wafer by means of a spinner and then prebaked, after which a mask was 
intimately contacted therewith, and the resulting assembly was irradiated 
with ultraviolet rays for 8 seconds and developed with a developing 
solution containing 1,8-diazabicyclo(5,4,0)-7-undecene. However, a 0.7 
.mu.m pattern could not be resolved. It was confirmed that an irradiation 
with ultraviolet rays for 15 seconds was necessary for resolving the 0.7 
.mu.m pattern. Adhesiveness to silicon wafer and breaking of resist on the 
notched resist surface were, of course, similar to those in Example 8. 
EXAMPLE 10 
After completely replacing the air in an autoclave having a capacity of 100 
liters with nitrogen, 32 liters of methanol containing 1.3 kg of AIBN, 
19.7 kg of ST, 3.3 kg of MAA and 500 g of t-dodecylmercaptan were charged 
into the autoclave and then 3.3 kg of BD was charged thereinto with gentle 
stirring. The inner temperature was elevated to 70.degree. C. to start 
polymerization, one hour after which the addition of BD and MAA was 
started at a rate of 330 g/hr. After continuing the addition of these 
monomers over a period of 10 hours, the reaction was further continued for 
13 hours. In the course of the reaction, a small portion of the contents 
was sampled to measure the polymerization conversion and, at the same tme, 
the copolymer formed was recovered from the sample to examine the 
composition thereof. The results were as shown in FIG. 3 and Table 2, from 
which it was confirmed that a copolymer having a narrow composition 
distribution was formed. 
In quite the same manner as in Example 8, the copolymer produced was 
recovered, and a photosensitive solution was prepared therefrom, after 
which the period of ultraviolet ray-irradiation time necessary for 
resolving a 0.7 .mu.m pattern was determined. The result was 10 seconds. 
There were no problems at all regarding its adhesion to silicon wafer and 
breaking of resist on the resist surface. 
EXAMPLE 11 
In quite the same manner as in Example 10, 32 liters of methanol containing 
1.3 kg of AIBN was charged into an autoclave having a capacity of 100 
liters, after which 19.7 kg of ST, 6.6 kg of MAA, 500 g of 
t-dodecylmercaptan and 6.6 kg of BD were successively charged and the 
mixture was subjected to polymerization reaction at 70.degree. C. for 24 
hours. The relations between polymerization conversion and copolymer 
composition were as shown in FIG. 4 and Table 2. According to FIG. 4 or 
Table 2, it was confirmed that copolymers different in composition were 
formed with a progress of the polymerization. 
In quite the same manner as in Example 8, the copolymer was recovered and a 
photosensitive solution was prepared therefrom, and the period of 
ultraviolet ray-irradiation time necessary for resolving a 0.7 .mu.m 
pattern was determined. The result was 18 seconds. 
TABLE 2 
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Standard deviation of composition distribution 
in the copolymerization period 
Monomer 
component 
Example 8 Example 9 Example 10 
Example 11 
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BD 0.4 4.1 0.7 1.9 
ST 0.4 3.1 0.6 5.9 
AN 0.4 1.6 -- -- 
MAA 0.3 0.5 1.1 4.1 
______________________________________