Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2000-09-08
2002-10-08
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S326000, C430S905000, C526S251000
Reexamination Certificate
active
06461790
ABSTRACT:
This invention relates to polymers useful as the base polymer in chemical amplification resist compositions suited for microfabrication. It also relates to chemical amplification resist compositions comprising the polymers, and a patterning process using the same.
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. No. 4,491,628 and U.S. Pat. No. 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 polymer having a high transmittance to vacuum ultraviolet radiation of up to 300 nm, especially an 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), and useful as the base polymer in a chemical amplification resist composition. Another object is to provide a chemical amplification resist composition comprising the polymer, and a patterning process using the same.
It has been found that using a resin based on fluorinated polyvinyl phenol comprising recurring units of the general formula (1) defined below, a resist material featuring transparency and alkali solubility is obtained.
As long as the inventor has confirmed, polyvinyl phenol has a window for absorption in proximity to 160 nm, so the transmittance is somewhat improved, but far below the practical level, and reducing carbonyl and carbon-to-carbon double bonds is essential for insuring a transmittance. However, as compared with acrylic resins, phenolic resins are good in etching resistance, alkali solubility, and substrate adhesion. Halogen substitution, especially fluorine substitution on phenolic resins is effective for improving the transmittance to a practically acceptable level by expanding the window.
In a first aspect, the invention provides a polymer comprising recurring units of the following general formula (1).
Herein R
1
is hydrogen, chlorine or a straight, branched or cyclic unsubstituted, fluorinated or chlorinated alkyl group of 1 to 20 carbon atoms, R
2
is an acid labile group, letters o, p, q, r, s, and t are numbers satisfying 0≦o<5, 0<p≦5, 0≦q<5, 0<r≦5, 0≦s ≦5, 0≦t≦5, 0≦o+q<5, 0<s+t≦5, 0<o+p+q≦5, and 0<o+q+r≦5, and letters k, m and n are numbers satisfying 0<k<1, 0≦m<1, 0≦n<1, and k+m+n=1.
In a second aspect, the invention provides a resist composition comprising the polymer of the formula (1).
In a third aspect, the invention provides a chemical amplification positive resist composition comprising (A) the polymer of the formula (1), (B) an organic solvent, and (C) a photoacid generator.
In a fourth aspect, the invention provides a chemical amplification negative resist composition comprising (A) the polymer of the formula (1), (B) an organic solvent, (C) a photoacid generator, and (D) a crosslinker.
The resist compositions may further include (E) a basic compound and/or (F) a dissolution inhibitor.
In a still further aspect, the invention provides a process for forming a pattern, comprising the steps of applying the resist composition onto a substrate to form a coating; heat treating the coating and exposing the coating to high energy radiation with a wavelength of up to 300 nm or electron beam through a photo-mask; optionally heat treating the exposed coating, and developing the coating with a developer.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Polymer
According to the invention, the polymer or high molecular weight compound is defined as comprising recurring units of the following general formula (1).
Herein R
1
is a hydrogen atom, a chlorine atom or a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms, which may be fluorinated or chlorinated, and R
2
is an acid labile group.
The straight, branched or cyclic alkyl groups represented by R
1
are those of 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, and more preferably 1 to 10 carbon atoms, including methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, and n-octyl. The fluorinated alkyl groups correspond to the foregoing alkyl groups in which some or all of the hydrogen atoms are substituted by fluorine atoms and include, for example, trifluoromethyl, 2,2,2-trifluoroethyl, 3,3,3-trifluoropropyl, and 1,1,2,3,3,3-hexafluoropropyl. The chlorinated alkyl groups correspond to the foregoing alkyl groups in which some or all of the hydrogen atoms are substituted by chlorine atoms and include, for example, chloromethyl.
The acid labile group represented by R
2
is selected from a variety of such groups, preferably from among the groups of the following formulae (2) and (3), tertiary alkyl groups with 4 to 40 carbon atoms of the following formula (4), trialkylsilyl groups whose alkyl groups each have 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20 carbon atoms.
In formula (2), R
6
is a tertiary alkyl group of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group whose alkyl groups each have 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms or a group of formula (3). Exemplary tertiary alkyl groups are tert-butyl, tert-amyl, 1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, and 2-methyl-2-adamantyl. Exemplary trialkylsilyl groups are trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl. Exemplary oxoalkyl groups are 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and 5-methyl-2-oxooxoran-5-yl. Letter “a” is an integer of 0 to 6.
In formula (3), R
7
and R
8
are independently hydrogen or straight, branched or cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl and n-octyl. R
9
is a monovalent hydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, which may have a hetero atom (e.g., oxygen atom), for example, straight, branched or cyclic alkyl groups, and such groups in which some hydrogen atoms ar
Harada Yuji
Hatakeyama Jun
Kishimura Shinji
Nakashima Mutsuo
Sasago Masaru
Chu John S.
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
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