Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-02-27
2001-08-28
Wilson, Donald R. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S173000, C525S328800
Reexamination Certificate
active
06281318
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a poly{1-(1-alkoxyalkoxy)-4-(1-methylethenyl)benzene} having a narrow molecular weight distribution, its preparation process, and a preparation process of poly(p-hydroxy-&agr;-methylstyrene) having a narrow molecular weight distribution [hereinafter referred to as “poly{4-(1-methylethenyl)phenol}”].
More specifically, the present invention relates to a poly{1-(1-alkoxyalkoxy)-4-(1-methylethenyl)benzene} having a narrow molecular weight distribution, for example, a poly{1-(1-alkoxyethoxy)-4-(1-methylethenyl)benzene} or a poly{1-(2-tetrahydrofuranyloxy)-4-(1-methylethenyl)benzene} which is useful as a chemical amplification type positive resist material, and a preparation process of the polymer from industrially easily available 4-(1-methylethenyl)phenol as a starting material.
In addition, the present invention relates to a preparation process, from the above-mentioned polymer as a starting material, of poly{4-(1-methylethenyl)phenol} having a narrow molecular weight distribution which is useful, for example, as a base polymer for a chemical amplification type positive resist material.
(2) Description of the Prior Art
Poly(p-hydroxystyrene) has been noticed as a base polymer for a lithography of a high resolution or for a resist material for use in LSIs, and many preparation processes regarding the polymer have been suggested (e.g., Japanese Patent Application Laid-open Nos. 44609/1982, 199705/1988, 32832/1994 and 1115/1993).
On the other hand, poly{4-(1-methylethenyl)phenol} is more useful as compared with poly(p-hydroxystyrene), because poly{4-(1-methylethenyl)phenol} is more improved by the effect of a methyl group on the &agr;-position than poly(p-hydroxystyrene) in performances such as a dissolution rate in a resist removal step with a release agent and a plasma resistance in a dry etching step which are required as the resist material applicable to a high integration. However, a polymerization method of poly{4-(1-methylethenyl)phenol} is limited by electronic and steric influences of the methyl group on the &agr;-position, and hence a preparation method of poly(p-hydroxystyrene) cannot directly be applied as it is.
In fact, the present inventors applied some of typical methods disclosed as the preparation method of poly(p-hydroxystyrene) to the preparation of poly{4-(1-methylethenyl)phenol}.
For example, in accordance with a method described in Japanese Patent Application Laid-open No. 32832/1994, an anionic polymerization of p-t-butoxycarbonyloxy-&agr;-methylstyrene was tried at −78° C. in the presence of n-butyl lithium as a polymerization initiator in tetrahydrofuran, but a reaction between a t-butoxycarbonyloxy group and n-butyl lithium predominantly occurred, so that the desired polymer could scarcely be obtained.
Furthermore, in accordance with a method described in Japanese Patent Application Laid-open No. 1115/1993, an anionic polymerization of p-tetrahydropyranyloxy-&agr;-methylstyrene was tried at −78° C. for 1 hour in the presence of n-butyl lithium as a polymerization initiator in tetrahydrofuran, but a polymerization reaction scarcely proceeded, so that the desired polymer could not be obtained.
However, there have been suggested some methods by which these difficulties can be solved and poly{4-(1-methylethenyl)phenol} can be manufactured.
Japanese Patent Application Laid-open No. 179204/1986 has disclosed a method which comprises subjecting an esterified compound of p-hydroxy-&agr;-methylstyrene to a cationic polymerization in the presence of antimony pentahalide as a catalyst to form a polymer, and then hydrolyzing the polymer to obtain poly{4-(1-methylethenyl)phenol}. In this cationic polymerization, however, methanol or water is used as a polymerization terminator, and therefore, a terminal of thus obtained poly{4-(1-methylethenyl)phenol} should be a methoxy group or a hydroxy group. As just described, the functional group naturally bonds to the polymer terminal, so that resistance to thermal decomposition deteriorates. For this reason, the thus obtained poly{4-(1-methylethenyl)phenol} is not preferable as a base polymer for a resist material which is required to be heated in a lithography step.
In Makromol. Chem., Macromol. Symp., Vol. 53, p. 139-149 (1992), there has been disclosed a method which comprises subjecting p-tert-butoxycarbonyloxy-&agr;-methylstyrene to a cationic polymerization in the presence of a boron trifluoride ether adduct as a catalyst in a sulfur dioxide solvent to form poly(p-tert-butoxycarbonyloxy-&agr;-methylstyrene), and then heating this compound at about 200° C. to obtain poly{4-(1-methylethenyl)phenol}.
However, since similarly utilizing the cationic polymerization, this method also has the same drawback as described above. In addition, the molecular weight distribution of the polymer obtained by this method is relatively broad, that is, 2.4 to 4.6, and it is not preferable as a resist material in this point.
Japanese Patent Application Laid-open No. 199705/1984 has disclosed a method which comprises reacting p-bromo-&agr;-methylstyrene with magnesium in an ether, further reacting it with peroxybenzoic acid 1,1-dimethylpropyl ester in tetrahydrofuran to obtain p-1,1-dimethylpropoxy-&agr;-methylstyrene, subjecting this compound to an anionic polymerization, and then carrying out an acid decomposition to obtain poly{4-(1-methylethenyl)phenol}. However, this method employs a Grignard reaction, and an equimolar or more magnesium is necessary, and the handling of secondarily produced magnesium bromide is troublesome. Accordingly, the disclosed method is not considered to be a practical method.
In Japanese Patent Application Laid-open No. 32819/1994, there has been disclosed a method which comprises subjecting methoxymethoxy-&agr;-methylstyrene to a living anionic polymerization, and then eliminating a methoxymethoxy group to obtain poly{4-(1-methylethenyl)phenol}. However, in this method, in order to synthesize methoxymethoxy-&agr;-methylstyrene which is a starting material, an expensive chloromethyl methyl ether is necessary. In addition, an equimolar alkali metal chloride is formed as a by-product, and hence the treatment of this by-product is also required. Accordingly, this method is not considered to be an industrial manufacturing method.
As described above, an efficient preparation method of poly{4-(1-methylethenyl)phenol} has not been present so far, and hence it has riot been industrially used.
On the other hand, a poly{1-(1-alkoxyalkoxy)-4-(1-methylethenyl)benzene} is considered to be useful as a chemical amplification type positive resist material having a high sensitivity, a high resolution and a high plasma resistance in a dry etching step.
As conventional techniques, typical preparation methods of only a related poly{1-(1-alkoxyethoxy)-4-ethenylbenzene} have been present as follows.
(1) A method which comprises reacting p-bromophenol with an alkyl vinyl ether to obtain a p-bromo(1-alkoxyethoxy)benzene, reacting this compound with metallic magnesium, carrying out a Grignard reaction between the reaction product and vinyl bromide in the presence of dichloro{1,2-bis(diphenylphosphino)ethane}nickel as a catalyst to obtain a p-(1-alkoxyethoxy)styrene, and then adding 2,2′-azobisisobutyronitrile as an initiator to the reaction system to carry out a radical polymerization, thereby preparing the desired product (Japanese Patent Application Laid-open Nos. 194842/1994 and 249682/1993).
(2) A method which comprises adding 2,2′-azobisisobutyronitrile as an initiator to p-tert-butoxystyrene to carry out a radical polymerization and to thereby obtain poly(p-tert-butoxystyrene), eliminating a tert-butoxy group by concentrated hydrochloric acid to obtain poly(p-hydroxystyrene), and then reacting this compoun
Fukuda Ritsuko
Hara Isao
Takao Toshiro
Yamamoto Yoshihiro
Burns Doane Swecker & Mathis L.L.P.
Mitsui Chemicals Inc.
Wilson Donald R.
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