Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-06-01
2001-04-03
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S212000, C528S218000, C525S191000, C525S132000, C525S219000, C430S170000, C430S270100, C430S909000
Reexamination Certificate
active
06211328
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phenol resin, in particular to a phenol resin for resists suitable for use in forming resist patterns.
2. Background Art
With the recent high degree of integration of integrated circuits, pattern formation at quarter micron levels has been desired. As a means for achieving downsizing of patterns, mention may be made of a method for shortening the wavelength of the light used. As such, in particular, use of a KrF excimer laser has enabled production of 64M DRAMs and 256M DRAMs and hence has been paid much attention.
Under the circumstances, there has been an increasing demand for resist materials for high resolution lithography and a resist material that shows good pattern formation ability and has improved heat resistance, resolution and sensitivity has been keenly desired.
In accordance with the downsizing of patterns, there has been a shift in the etching process of wafers from wet etching to dry etching. As a result resists are required such that the heat upon dry etching does not deform their patterns, and hence improvement in the heat resistance of resists has been demanded.
Resists must be transparent to the above light source, so mainly polyvinylphenols have been used. However, they are insufficient in pattern shape, resolution, developability, and film retention properties and modification of polyvinylphenols has heretofore been performed. Modification of polyvinylphenols by hydrogenation and modification by various types of copolymerization with styrene monomers, acrylic monomers, etc. have been carried out to promote functionalization of polyvinylphenols. However, in pattern formation at sub-quarter-micron levels, there has been found no resist material that simultaneously satisfies the requirements for good pattern shape, resolution, sensitivity, developability, film retention properties, and heat resistance.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a phenol resin that gives good pattern shape, heat resistance, resolution, and sensitivity simultaneously in resists for lithography, etc.
As a result of intensive research with a view to achieving the above object, the present inventors have found that condensation of a compound (A) represented by the following general formula (I) with a polymerizable phenol compound represented by the following general formula (II) or polyvinylphenol (B) that is a polymer of the polymerizable phenol compound can give rise to a phenol resin for resists that combines good pattern shape, resolution, sensitivity, developability, film retention properties, and heat resistance, thus accomplishing the present invention.
That is, the phenol resin of the present invention is a phenol resin obtained by reacting at least two components, i.e., a compound (A) represented by the following general formula (I) and a polymerizable phenol compound represented by the following general formula (II) or a polymer (B), which is a polymer of the polymerizable phenol compound, in a ratio of 1 to 50 moles of the compound (A) to 100 moles of the polymerizable phenol compound or 100 moles of structural unit of the polymerizable phenol compound contained in the polymer (B) in the presence of an acid and having a weight average molecular weight of 2,000 to 20,000
(wherein R
1
, R
2
, R
3
, and R
4
, which are the same or different, independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, a hydroxyl group or a halogen atom)
(wherein R
5
represents a hydrogen atom or a methyl group, R
6
, R
7
, R
8
, and R
9
, which are the same or different, independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, a hydroxyl group or a halogen atom, provided that at least one of R
7
and R
9
is a hydrogen atom).
Such a phenol resin can provide good pattern shape, heat resistance, resolution, and sensitivity in resists for lithography, etc. and is useful as a light-sensitive resin such as a resist or as a resin precursor for obtaining the light-sensitive resin. Use of the phenol resin of the present invention enables improvement in the properties of resists. The light-sensitive resin composition comprising the phenol resin of the present invention is excellent in the balance of various properties of resists.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the general formula representing the compound (A), the alkyl groups in the substituents R
1
to R
4
are preferably linear, branched or cyclic and have one or more and 10 or less carbon atoms. As such alkyl groups, mention may be made of, for example, a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a 2-ethylhexyl group, a cyclohexyl group, etc.
The alkoxy groups in the substituents R
1
to R
4
preferably have 1 or more and 4 or less carbon groups. As such alkoxy groups, mention may be made of, for example, a methoxy group, a propoxy group, a t-butoxy group, etc.
The aryl groups in the substituents R
1
to R
4
include preferably a phenyl group, a naphthyl group, a tolyl group, a cumyl group, etc.
The aralkyl groups in the substituents R
1
to R
4
preferably have 6 or more and 10 or less carbon atoms. As such aralkyl groups, mention may be made of, for example, a benzyl group, a phenethyl group, a 1-methyl-1-phenylethyl group, etc.
Those preferred as the compound (A) include ones in which R
1
R
2
, R
3
, and R
4
are each a hydrogen atom or an alkyl group. As such compounds (A), mention may be made of, for example, 4-hydroxymethylphenol, 4-hydroxymethyl-2-methylphenol, 4-hydroxymethyl-3-methylphenol, 4-hydroxymethyl-2-ethylphenol, 4-hydroxymethyl-3-ethylphenol, 4-hydroxymethyl-2-n-propylphenol, 4-hydroxymethyl-3-n-propylphenol, 4-hydroxymethyl-2-isopropylphenol, 4-hydroxymethyl-3-isopropylphenol, 4-hydroxymethyl-2-n-butylphenol, 4-hydroxymethyl-3-n-butylphenol, 4-hydroxymethyl-2-s-butylphenol, 4-hydroxymethyl-3-s-butylphenol, 4-hydroxymethyl-2-t-butylphenol, 4-hydroxymethyl-3-t-butylphenol, 4-hydroxymethyl-2,3-diemthylphenol, 4-hydroxymethyl-2,5-diemthylphenol, 4-hydroxymethyl-2,6-dimethylphenol, 4-hydroxymethyl-3,5-dimethylphenol, 4-hydroxymethyl-2-isopropyl-6-methylphenol, 4-hydroxymethyl-2-t-butyl-6-methylphenol, 4-hydroxymethyl-2,6-diisopropylphenol, 4-hydroxymethyl-2,6-di-t-butylphenol, 4-hydroxymethyl-2,3,5-trimethylphenol, 4-hydroxymethyl-2,3,6-trimethylphenol, etc.
Particularly preferred compounds (A) are those in which two or three out of R
1
to R
4
are alkyl groups and the remaining ones are hydrogen atoms. As such compounds (A), mention may be made of, for example, 4-hydroxymethyl-2-methylphenol, 4-hydroxymethyl-2,6-dimethylphenol, 4-hydroxymethyl-2,3,6-trimethylphenol, etc.
Other preferred compounds (A) include ones in which R
1
, R
2
, R
3
, and R
4
represent independently a hydrogen atom, an alkoxy group, a hydroxyl group or a halogen atom. As such compounds (A), mention may be made of, for example, 4-hydroxymethyl-2-methoxyphenol, 4-hydroxymethyl-3-methoxyphenol, 4-hydroxymethyl-2-hydroxyphenol, 4-hydroxymethyl-3-hydroxyphenol, 4-hydroxymethyl-2,6-difluorophenol, etc.
The polymerizable phenol compound to be condensed with the compound (A) and represented by the above general. formula (II) includes a vinylphenol compound and an isopropenylphenol compound.
The above vinylphenol compound is a compound that has a vinyl group (CH
2
═CH—) at the para-position with respect to the phenolic hydroxyl group.
AS the vinylphenol compound, the ones in which the substituents R
6
to R
9
in the above general formula (II) independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, a hydroxyl group or a halogen atom, provided that at least one of R
7
and R
9
is a hydrogen atom are preferred.
The alkyl groups in the substituents R
6
to R
9
are preferably linear, branched or cyclic and have one or more and 10 or less carbon atoms. As such alkyl groups, mention may be made of, for example, a methyl group, an ethyl group, an isopropyl group
Kitano Satoru
Kurimoto Yoshiaki
Maruyama Katsuhiro
Yoshida Satoru
Yoshitomo Akira
Burns Doane Swecker & Mathis L.L.P.
Gun Ei Chemical Industry Co., LTD
Truong Duc
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