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
2001-06-27
2003-11-11
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, C430S907000, C430S910000, C430S914000, C430S326000
Reexamination Certificate
active
06645693
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resist composition and, more specifically, a chemical amplification type resist composition used for fine-processing of a semiconductor.
2. Description of the Related Art
A lithography process using a resist composition is usually adopted for fine-processing of a semiconductor, and in lithography, it is theoretically possible to improve resolution when the exposure wavelength is shorter, as demonstrated by the Rayleigh diffraction limit formula. Exposure light sources for lithography used for production of a semiconductor include g-line having a wavelength of 436 nm, i-line having a wavelength of 365 nm, KrF excimer laser having a wavelength of 248 nm and ArF excimer laser having a wavelength of 193 nm, the wavelength used becomes shorter gradually. In this regards, an F
2
excimer laser having a wavelength of 157 nm is regarded favorably as a next generation exposure light.
For KrF excimer laser exposure or ArF excimer laser exposure, a so-called “chemical amplification-type” resist utilizing a catalytic action of an acid generated by exposure is often used due to excellent sensitivity. Also for F
2
excimer laser exposure, there is a high possibility of use of a chemical amplification type resist from the standpoint of sensitivity.
Polyvinylphenol-based resins have been used as a resist for KrF excimer laser exposure. On the other hand, it is known that a resin having no aromatic ring for securing the transmittance of the resist and having an alicyclic ring instead of an aromatic ring for imparting dry etching-resistance is advantageous for use as a resist for ArF excimer laser exposure.
Various alicyclic resins are known such as those described in D. C. Hofer, Journal of Photopolymer Science and Technology, Vol. 9, No. 3, 387-398(1996). Further, S. Takechi et al., Journal of Photopolymer Science and Technology, Vol. 9, No. 3, 475-487 (1996) and JP-A No. 9-73173 disclose that when a polymer or copolymer of 2-methyl-2-adamantyl methacrylate is used as a resin in a chemical amplification type resist, 2-methyl-2-adamantyl dissociates by the action of an acid and acts in a positive manner, and high dry etching-resistance, high resolution and excellent adhesion to a substrate are obtained.
However, resins used in conventional resists for KrF excimer laser exposure and ArF excimer laser exposure do not have sufficient transmittance for light having a wavelength of 170 nm or less, for example, F
2
excimer laser having a wavelength of 157 nm. The low transmittance is disadvantageous with respect to various characteristics of the resist such as profile, contrast, sensitivity and the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a resist composition having excellent transmittance for light having a wavelength of 170 nm or less and, particularly, is suitable for F
2
excimer laser lithography.
This object and other objectives have been achieved by the present inventors who have found that the transmittance at an F
2
excimer laser wavelength of 157 nm, for example, can be improved by using a resin having a polymerization unit derived from a monomer as defined herein as the resin constituting a resist composition, and have completed the present invention.
Namely, the present invention provides a resist composition comprising a binder resin and a radiation-sensitive compound, wherein the binder resin is an alkali-soluble resin or becomes an alkali-soluble resin by the action of the radiation-sensitive compound after irradiation, and has a polymerization unit represented by the following formula (I):
wherein, R
1
represents a fluoroalkyl group having 1 to 12 carbon atoms and having at least one fluorine atom, and R
2
represents a hydrogen atom or an acyl group having 2 to 5 carbon atoms.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the present invention, a resin having a polymerization unit of the above-mentioned formula (I) is used as a binder resin. This resin is obtained, for example, by polymerization using a monomer of the following formula (VI):
wherein, R
1
is as defined above, and R
10
represents an acyl group having 2 to 5 carbon atoms.
The fluoroalkyl represented by R
1
in the formula (I) may be linear or it may be branched when 3 or more carbon atoms are contained therein. Compounds of formula (VI) in which R
1
represents a trifluoromethyl group are commercially available and are preferred for use in the present invention from the standpoint of industrial production of resins.
Raw material for polymer of formula (VI), in which R
10
represents an acetyl group, is commercially available and preferable from the standpoint of industrial production of resins.
The following unit (Ia) is formed by polymerization of a compound of the formula (VI):
where R
1
and R
10
are as defined above.
The unit (Ia) can be totally or partially converted, by decomposition of ester parts, into the following unit (Ib):
wherein, R
1
is as defined above.
The conversion from (Ia) into (Ib) can be conducted according to any suitable conventional method. For example, an alkali catalyst may be used in the presence of a lower alcohol, or heating may be utilized together with an acid catalyst in the presence of a lower alcohol, to achieve the conversion. Of course, other suitable methods will be apparent to one skilled in the art.
As specific examples of compounds of the formula (VI), the following compounds are exemplified.
1-(trifluoromethyl)vinyl acetate,
1-(difluoromethyl)vinyl acetate,
1-(fluoromethyl)vinyl acetate,
1-(2-trifluoroethyl)vinyl acetate,
1-(2,2,3,3,3-pentafluoropropyl)vinyl acetate,
1-(1-trifluoromethyl-2,2,2-trifluoroethyl)vinyl acetate,
1-(trifluoromethyl)vinyl propionate,
1-(difluoromethyl)vinyl propionate,
1-(fluoromethyl)vinyl propionate and the like.
Other suitable monomer compounds within the scope of Formula (VI) that may be used in the present invention will be apparent to one skilled in the art. The binder resin used in the present invention is alkali-soluble itself or undergoes a chemical change to become alkali-soluble by the action of a radiation-sensitive compound after irradiation.
The alkali-soluble portion of the binder resin used in the present invention can be a unit having a phenol, a unit having a (meth)acrylate with an alicyclic ring and carboxyl group on the alcohol side of the ester, a unit of an unsaturated carboxylic acid, or the like.
Specifically, alkali soluble portions of the binder resin may be a vinyl phenol, an isopropenylphenol, alicyclic esters of (meth)acrylic acid having a carboxyl group on the alicyclic ring, a (meth)acrylic acid unit, and the like. When such alkali-soluble portions are present in a relatively large amount, the resin itself becomes alkali-soluble. An alkali-insoluble portion may be present together with these portions. For example, resins in which hydroxyl groups of a vinylphenol or isopropenylphenyl are partially alkyl-etherified, resins obtained by copolymerization of vinylphenol or isopropenylphenol with other polymerizable unsaturated compounds, resins obtained by copolymerization of an alicyclic ester of (meth)acrylic acid with (meth)acrylic acid, polymer resins of a cycloolefin such as norbornene and the like, or derivatives thereof or copolymer resins of maleic anhydride, reins obtained by copolymerization with a compound produced by substituting part or all of hydrogen atoms in an alkyl ester of (meth)acrylic acid by fluorine atom, and the like, can be used as the resin which is alkali-soluble itself of the present invention provided they are totally alkali-soluble.
In the present invention, there may exist the above-described polymerization portion having an alkali-soluble group or polymerization portion having a group that undergoes a chemical change to become alkali-soluble by the action of a radiation-sensitive compound after irradiation of the binder resin, in addition to a polymerization unit of the above-mentioned formula (I).
Such a resin is produced usually by conducting, for exa
Hashimoto Kazuhiko
Miya Yoshiko
Baxter Janet
Lee Sin J.
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