Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-05-31
2001-06-05
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S056000, C525S057000, C525S132000, C525S133000, C525S191000, C525S328800, C528S104000, C528S129000
Reexamination Certificate
active
06242533
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novolak type phenol resin, in particular to a novolak type phenol resin for resists suitable for use in forming resist patterns.
This application is based on Japanese Patent Application No. Hei 11-158798, the contents of which are incorporated herein by reference.
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 novolak type 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 polycondensation of a compound (A) represented by the following general formula (I) and compound (B) represented by the following general formula (II) solely or as mixtures with a vinyl phenol or polyvinylphenol (C) can give rise to a phenol resin for resists that combine good resolution, sensitivity, and heat resistance, thus accomplishing the present invention.
That is, the novolak type phenol resin of the present invention is a novolak type phenol resin obtained by reacting at least two components, i.e., a vinyl phenol having a vinyl group and a phenolic hydroxyl group or a polyvinylphenol, which is a polymer of the vinyl phenol, and a compound (A) represented by the following general formula (I) in a ratio of 1 to 40 moles of the compound (A) to 100 moles of the vinylphenol or 100 moles of vinylphenol unit in the polyvinylphenol 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
independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, or an aralkyl group).
The novolak type phenol resin of the present invention is also a novolak type phenol resin obtained by reacting at least two components, i.e., a vinyl phenol having a vinyl group and a phenolic hydroxyl group or a polyvinylphenol, which is a polymer of the vinyl phenol, and a compound (A) represented by the following general formula (II) in a ratio of 1 to 40 moles of the compound (B) to 100 moles of the vinylphenol or 100 moles of vinylphenol unit in the polyvinylphenol in the presence of an acid and having a weight average molecular weight of 2,000 to 20,000
(wherein R
5
and R
6
independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, or an aralkyl group).
The novolak type phenol resin of the present invention is also a novolak type phenol resin obtained by reacting at least three components, i.e., a vinyl phenol having a vinyl group and a phenolic hydroxyl group or a polyvinylphenol, which is a polymer of the vinyl phenol, a compound (A) represented by the above general formula (I), and a compound (B) represented by the above general formula (II) in a ratio of 1 to 40 moles of the sum of the compound (A) and compound (B) to 100 moles of the vinylphenol or 100 moles of vinylphenol unit in the polyvinylphenol in the presence of an acid and having a weight average molecular weight of 2,000 to 20,000.
Such novolak type phenol resins can provide pattern shape, heat resistance, resolution, and sensitivity in resists for lithography, etc. and are useful as a light-sensitive resin such as a resist or as a resin precursor for obtaining the light-sensitive resin. Use of the novolak type 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 formulae (I) and (II), the alkyl groups in the substituents R
1
to R
6
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 butyl group, a 2-ethylhexyl group, a cyclohexyl group, etc.
The alkoxy groups in the substituents R
1
to R
6
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 butoxy group, etc.
The aryl groups in the substituents R
1
to R
6
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
6
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, etc.
Those preferred as the compound (A) represented by the above general formula (I) include ones in which at least two of R
1
R
2
, R
3
, and R
4
are each an alkyl group having 1 or more and 4 or less carbon atoms and the remaining ones being hydrogen atoms. As such compound (A), mention may be made of, for example, methylenebisphenols having a hydroxymethyl group at the 2- or 6-position with respect to the phenolic hydroxyl group, such as 4,4′-methylenebis(2-hydroxymethyl-3,6-dimethylphenol, 2,2′-methylenebis(6-hydroxymethyl-4-methylphenol).
Those preferred as the compound (B) represented by the above general formula (II) include ones in which one or two of R
5
and R
6
are each an alkyl group having 1 or more and 4 or less carbon atoms and the remaining ones being hydrogen atoms. As such a compound (B), dihydroxymethylphenol having a hydroxymethyl group at the ortho position with respect to the phenolic hydroxyl group are particularly preferred and mention may be made of, for example, 2,6-hydroxymethyl-4-methylphenol.
The compound (A) and/or compound (B) are reacted (condensed) with the vinylphenol, preferably polyvinylphenol (C), which is a polymer of the vinylphenol. The vinylphenol is a monomer having a vinyl group (preferably, CH
2
═CH—, CH
2
═C(CH
3
)—) and a phenolic hydroxyl group. As the vinylphenol, the ones having a vinyl group at the para-position with respect to the phenolic hydroxyl group, represented by the following general formula (III) are preferred
(wherein R
7
is a hydrogen atom or a methyl group, R
8
, R
9
, R
10
, and R
11
, 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
Kitano Satoru
Kurimoto Yoshiaki
Maruyama Katsuhiro
Yoshida Satoru
Yoshitomo Akira
Burns Doane , Swecker, Mathis LLP
Gun Ei Chemical Industry Co., Ltd.
Truong Duc
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