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
2000-08-23
2002-10-08
Baxter, Janet (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
C430S905000, C430S320000, C430S322000, C430S907000, C525S332300, C525S061000, C521S141000, C524S459000
Reexamination Certificate
active
06461789
ABSTRACT:
This invention relates to polymers useful as the base resin 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 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. As long as the inventor has confirmed, polyvinylphenol has a window for transmittance in proximity to 160 nm, so the absorption is somewhat improved, but far below the practical level, and reducing carbonyl and carbon-to-carbon double bonds is essential for insuring a transmittance. 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 of 157 nm, 146 nm and 126 nm, and useful as the base resin 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 poly(fluorinated vinyl alcohol), a resist material featuring transparency and alkali solubility is obtained.
Specifically, polyvinyl alcohol has relatively low absorption because of the absence of carbonyl group, and halogen substitution, especially fluorine substitution on polyvinyl alcohol is effective for improving transmittance to a practically acceptable level. Since the development step of photolithography generally involves applying alkaline water to a resist film by puddling or dipping, rinsing with pure water and spin drying, it is necessary to adjust the solubility of a polymer in alkali relatively high and the solubility in pure water relatively low. Since polyvinyl alcohol is so water soluble that it is used as the base polymer in resists adapted to water development, polyvinyl alcohol has a high possibility that it is dissolved not only upon alkali development, but also upon rinsing. Then it has been found desirable to fluorinate polyvinyl alcohol to increase the acidity of alcohol for increasing its solubility in alkali, thereby enlarging the difference from the solubility in water.
In a first aspect, the invention provides a polymer comprising recurring units of the following general formula (1):
wherein at least one of R
1,
R
2
and R
3
is fluorine or a trifluoromethyl group, and the remainder is hydrogen or a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms, R
4
is an acid labile group, k and m are numbers in the range of 0<k≦1, 0≦m<1 and k+m=1.
In a second aspect, the invention provides a polymer comprising recurring units of the following general formula (2):
wherein at least one of R
1,
R
2
and R
3
is fluorine or a trifluoromethyl group, and the remainder is hydrogen or a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms, R
4
is an acid labile group, R
5
is an acid stable group, k, m and n are numbers in the range of 0<k≦1, 0≦m<1, 0≦n<1 and k+m+n=1.
In a third aspect, the invention provides a resist composition comprising the polymer of the formula (1) or (2).
In a fourth aspect, the invention provides a chemical amplification positive resist composition comprising (A) the polymer of the formula (1) or (2), (B) an organic solvent, and (C) a photoacid generator.
In a fifth aspect, the invention provides a chemical amplification negative resist composition comprising (A) the polymer of the formula (1) or (2), (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 polymers are defined as comprising recurring units of the following general formula (1) or (2).
Herein at least one of R
1,
R
2
and R
3
is a fluorine atom or a trifluoromethyl group, and the remainder is a hydrogen atom or a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms, R
4
is an acid labile group, R
5
is an acid stable group, k, m and n are numbers in the range of 0<k≦1, 0≦m<1, 0≦n<1, and m+n=1 for formula (1) and m+n+k=1 for formula (2).
The straight, branched or cyclic alkyl groups are those of 1 to 20 carbon atoms, preferably 1 to 16 carbon atoms, and more preferably 1 to 12 carbon atoms, including methyl, ethyl, propyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, and n-octyl.
The acid labile group represented by R
4
is selected from a variety of such groups, preferably from among the groups of the following formulae (3) and (4), tertiary alkyl groups of the following formula (5), trialkylsilyl groups whose alkyl groups each have 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20 carbon atoms.
In formula (3), 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 (4). 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 (4), R
7
and R
8
are independently hydrogen or straight, branched or cycli
Harada Yuji
Hatakeyama Jun
Watanabe Jun
Baxter Janet
Clarke Yvette M.
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