Styrene derivatives

Details Styrene derivatives Styrene derivatives

2000-09-07

2002-04-09

Padmanabhan, Sreeni (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S656000, C570S127000

Reexamination Certificate

active

06369279

ABSTRACT:

This invention relates to novel styrene derivatives which are useful monomers in preparing base polymers for use in chemically amplified resist compositions for microfabrication.
BACKGROUND OF THE INVENTION
In the drive for higher integration and operating speeds in LSI devices, the pattern rule is made drastically finer. The rapid advance toward finer pattern rules is grounded on the development of a projection lens with an increased NA, a resist material with improved performance, and exposure light of a shorter wavelength. In particular, the change-over from i-line (365 nm) to shorter wavelength KrF laser (248 nm) brought about a significant innovation, enabling mass-scale production of 0.18 micron rule devices. To the demand for a resist material with a higher resolution and sensitivity, acid-catalyzed chemical amplification positive working resist materials are effective as disclosed in U.S. Pat. Nos. 4,491,628 and 5,310,619 (JP-B 2-27660 and JP-A 63-27829). They now become predominant resist materials especially adapted for deep UV lithography.
Resist materials adapted for KrF excimer lasers enjoyed early use on the 0.3 micron process, went through the 0.25 micron rule, and currently entered the mass production phase on the 0.18 micron rule. Engineers have started investigation on the 0.15 micron rule, with the trend toward a finer pattern rule being accelerated. A wavelength change-over from KrF to shorter wavelength ArF laser (193 nm) is expected to enable miniaturization of the design rule to 0.13 &mgr;m or less. Since conventionally used novolac resins and polyvinylphenol resins have very strong absorption in proximity to 193 nm, they cannot be used as the base resin for resists. To ensure transparency and dry etching resistance, some engineers investigated acrylic and alicyclic (typically cycloolefin) resins as disclosed in JP-A 9-73173, JP-A 10-10739, JP-A 9-230595 and WO 97/33198. With respect to F
2
excimer laser (157 nm) which is expected to enable further miniaturization to 0.10 &mgr;m or less, more difficulty arises in insuring transparency because it was found that acrylic resins are not transmissive to light at all and those cycloolefin resins having carbonyl bonds have strong absorption.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel styrene derivative which is useful in the preparation of a base polymer for a chemical amplification resist composition having a high transmittance to vacuum ultraviolet radiation of up to 300 nm, especially F
2
excimer laser beam (157 nm), Kr
2
excimer laser beam (146 nm), KrAr excimer laser beam (134 nm) and Ar
2
excimer laser beam (126 nm).
It has been found that a novel styrene derivative of the following general formula (1) can be obtained by the method to be described later, and that using a resin based on a fluorinated polyhydroxystyrene obtained from the novel styrene derivative, a resist composition having transparency and alkali solubility is formulated.
As long as the inventor has confirmed, polyhydroxystyrene is somewhat improved in transmittance near 160 nm, but to an extent far below the practical level, and reducing carbonyl and carbon-to-carbon double bonds is essential for insuring a transmittance. However, phenols are good in etching resistance and alkali solubility, as compared with acrylic compounds. Further, halogen-substituted phenol polymers, and especially fluorine-substituted polymers obtained from the inventive styrene derivatives are improved in transmittance nearly to the practical level.
The invention provides a styrene derivative of the following general formula (1).
Herein R
1
is hydrogen, a straight, branched or cyclic, unsubstituted or fluoro-substituted alkyl group of 1 to 20 carbon atoms, chlorine atom, or trichloromethyl group, R
2
is a phenol protecting group, p, q and r are integers in the range of 0≦p<5, 0≦q<5, 0<r<5, and 0<p+q<5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In formula (1) representative of the novel styrene derivative according to the invention, R
1
is hydrogen, a straight, branched or cyclic, unsubstituted or fluoro-substituted alkyl group of 1 to 20 carbon atoms, chlorine atom, or trichloromethyl group. Examples of the straight, branched or cyclic C
1-20
alkyl group represented by R
1
include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, and n-octyl. The alkyl groups of 1 to 4 carbon atoms are preferred, with methyl being most preferred. The fluorinated alkyl groups are the foregoing alkyl groups in which some or all of the hydrogen atoms are replaced by fluorine atoms, for example, trifluoromethyl, 2,2,2-trifluoroethyl, 3,3,3-trifluoropropyl, and 1,1,2,3,3,3-hexafluoropropyl.
R
2
is a protective group on a phenol moiety, which is preferably selected from among methyl, vinyl, allyl, benzyl, and groups of the following general formulae (10), (11), (12), (13) and (14).
In formula (10), R
3
is a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms. R
4
and R
5
each are hydrogen, a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a hetero atom, R
6
is a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a hetero atom, aryl, aralkyl or oxoalkyl group, and a pair of R
4
and R
5
, a pair of R
4
and R
6
, or a pair of R
5
and R
6
, taken together, may form a cyclic structure of 3 to 12 carbon atoms. R
7
, R
8
and R
9
each are a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a hetero atom, aryl, aralkyl or oxoalkyl group, and a pair of R
7
and R
8
, a pair of R
7
and R
9
, or a pair of R
8
and R
9
, taken together, may form a cyclic structure of 3 to 12 carbon atoms. R
10
, R
11
and R
12
each are a straight or branched alkyl group of 1 to 4 carbon atoms. R
13
is a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain a hetero atom, aryl, aralkyl or oxoalkyl group, and “a” is an integer of 0 to 10.
Examples of the alkyl group represented by R
3
are the same as exemplified for R
1
. Alkyl groups of 1 to 4 carbon atoms are preferred, with methyl being most preferred. Illustrative examples of the group of formula (10) are acetyl, propionyl, butyryl and isobutyryl.
In formula (11), examples of the alkyl group represented by R
4
, R
5
and R
6
are the same as exemplified for R
1
. Alkyl groups of 1 to 8 carbon atoms, especially 1 to 6 carbon atoms are preferred. These alkyl groups may contain a hetero atom such as oxygen, sulfur, nitrogen or fluorine. Examples are alkyl groups which are separated by an oxygen atom, sulfur atom or NH group. Also included are alkyl groups in which some or all of the hydrogen atoms are replaced by fluorine atoms.
A pair of R
4
and R
5
, a pair of R
4
and R
6
, or a pair of R
5
and R
6
, taken together, may form a cyclic structure of 3 to 12 carbon atoms, especially 5 to 10 carbon atoms. Each of R
4
, R
5
and R
6
is an alkylene group that forms a cyclic structure having the desired number of carbon atoms, when they form a ring.
Illustrative examples of the group of formula (11) are straight or branched acetal groups such as methoxymethyl, methoxyethoxymethyl, 1-methoxyethyl, 1-ethoxyethyl, 1-n-propoxyethyl, 1-isopropoxyethyl, 1-n-butoxyethyl, 1-isobutoxyethyl, 1-sec-butoxyethyl, 1-tert-butoxyethyl, 1-tert-amyloxyethyl, 1-ethoxy-n-propyl, 1-cyclopentyloxyethyl, 1-cyclohexyloxyethyl, 1-methoxy-n-propyl, ethoxypropyl, 1-methoxy-1-methyl-ethyl, and 1-ethoxy-1-methyl-ethyl. These groups are shown by the following formulae.
Of the groups represented by formula (11), cyclic groups are, for example, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl, tetrahydropyran-2-yl and 2-methyltetrahydropyran-2-yl. Of the groups represented by formula (11), ethoxyethyl, butoxyethyl, and ethoxypropyl are preferred.
In formula (12), examples of the alkyl group represented by R
7
, R
8
and R
9
are the same as exemplified for R
1
. Alkyl groups of 1 to 8 carbon atoms, especially 1 to 6 carbon

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