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
2002-03-26
2004-12-28
Ashton, Rosemary (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
C430S910000
Reexamination Certificate
active
06835527
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a chemical amplifying type positive resist composition used in the minute processing of a semiconductor.
A lithography process using a resist composition has usually been adopted in the minute processing of a semiconductor. In the lithography, the resolution can be improved with a decrease in wavelength of exposure light in principle as expressed by the equation of Rayleigh's diffraction limit. A g-line with a wavelength of 436 nm, an i-line with a wavelength of 365 nm, and a KrF excimer laser with a wavelength of 248 nm have been adopted as exposure light sources for lithography used in the manufacture of a semiconductor. Thus, the wavelength has become shorter year by year. An ArF excimer laser having a wavelength of 193 nm is considered to be promising as a next-generation exposure light source.
A lens used in an ArF excimer laser exposure machine has a shorter lifetime as compared with lenses for conventional exposure light sources. Accordingly, the shorter time required or exposure to ArF excimer laser light is desirable. For this reason, it is necessary to enhance the sensitivity of a resist. Consequently, there has been used a so-called chemical amplifying type resist, which utilizes the catalytic action of an acid generated by exposure and contains a resin having a group cleavable by the acid.
It is known that, desirably, resins used in a resist for ArF excimer laser exposure have no aromatic ring in order to ensure the transmittance of the resist, but have an alicyclic ring in place of an aromatic ring In order to impart a dry etching resistance thereto. Various kinds of resins such as those described in Journal of Photopolymer Science and Technology, Vol. 9, No. 3, pages 387-398 (1996) by D. C. Hofer, are heretofore known as such resins.
As a resin used in a resist for ArF excimer laser exposure, a mutual copolymer composed of a polymerization unit of alicyclic olefin and a polymerization unit of an unsaturated dicarboxylic acid anhydride (T. I. Wallow et al., Proc. SPIE, vol. 2724, pp. 355-364 (1996)), a polymer having an alicyclic lactone structure unit (JP-A-2000-26446) and the like are known.
Conventionally, glycol ether esters, esters, ketones, cyclic esters and the like have been used as resist solvents. However, there is a problem that the solubility of the resins prepared by using a polymer having an alicyclic lactone structure unit In the conventional solvents is not satisfactory.
One object of the present invention is to provide a chemical amplification type positive resist composition comprising a resin component prepared by using a polymer having an alicyclic lactone structure unit and an acid generating agent which is particularly suitable for lithography using excimer lasers such as ArF and KrF, and has an excellent polymer dissolving capability.
The present inventers have conducted an extensive studies and have found that a solubility of the resin can be improved by using a specific amount of a specific solvent. The present invention has been accomplished based on this finding.
SUMMARY OF THE INVENTION
The present invention provides a resist composition comprising a resin having a alicyclic lactone structure unit that is insoluble in alkali by itself but becomes soluble due to the action of an acid, a solvent containing 2-heptanone and an acid generating agent, wherein a content of 2-heptanone in the solvent is in a weight ratio of from about 5 to about 95%.
DESCRIPTION OF EMBODIMENTS
Generally, a resist solution is prepared by dissolving each of the components consisting of a resin and an acid generating agent in a solvent, and the resist solution is then applied on a substrate such as a silicon wafer by a conventional method such as a spin coating. The solvent is required to dissolve each of the components, to attain a satisfactory drying rate and to supply an even and smooth coating after it is evaporated.
The resist composition of the present invention is characterized in that it contains 2-heptanoen as the specific solvent component, and a content of 2-heptanone in the solvent is in a weight-ratio of from about 5 to about 95%.
Other solvents such as esters, glycol ether esters, cyclic esters, ketones and the like may preferably be used since they will contribute to improve profiles Specific examples of the solvents include:
ethyl cellosolve acetate,
methyl cellosolve acetate,
propylene glycol monomethyl ether acetate,
methyl lactate,
butyl acetate,
amyl acetate,
ethyl pyruvate,
acetone,
methyl isobutyl ketone,
cyclohexanone and
ā-butylolactone,
As a specific example of a combination and a ratio of the above solvents, a combination of 2-heptanone and propylene glycol monomethyl ether acetate in a ratio of 5-95 wt. %:95-5 wt. % is preferable, since excellent dissolving properties as well as profile are expected by the combination.
It is also preferable to use a combination of 2-heptanone, propylene glycol monomethyl ether acetate and ā-butylolactone in a ratio of 10-85 wt. %:85-10 wt. %:1-10 wt. %, more preferably 19-75 wt. %:80-24 wt. %:1-10 wt. %, since excellent dissolving capability is expected.
The resin as a component of the positive resist composition of the present invention has an alicyclic lactone structure unit. The alicyclic lactone structure unit may preferably be selected from the group consisting of polymerization units represented by the following formulas (Ia) and (Ib)
wherein R
1
, R
2
, R
3
and R
4
each independently represent hydrogen or methyl, n represents an integer of 1-3, provided that when R
2
or R
4
is two or more, each of them may be same as or different from each other.
Specific examples of a monomer from which the polymerization units represented by the formulas (Ia) and (Ib) are derived include (meth)acrylic acid esters of alicyclic lactone having a hydroxyl group shown below and mixtures thereof, such as those shown below.
These esters can be prepared, for example by reacting a corresponding cyclic lactone having hydroxyl group with (meth)acrylic acids (e.g. JP2000-26446A).
The resin of the positive resist composition of the present invention is insoluble in alkali by itself but becomes soluble due to the action of an acid. Such a resin preferably contains a polymerization unit having a group de-blocked due to the action of an acid and becomes alkali-soluble due to the de-blockage is exemplified as the resin of the present invention.
Specific examples of the group de-blocked due to the action of an acid include various types of carboxylic acid esters, including: alkyl esters having about 1 to 6 carbons typified by tert-butyl ester: acetal esters such as methoxymethylester, ethoxymethylester, 1-ethoxyethyl ester, 1-isobutoxyethyl ester, 1-isopropoxyethyl ester, 1-ethoxypropyl ester, 1-(2-methoxyethoxy)ethyl ester, 1-(2-acetoxyethoxy)ethyl ester, 1-[2-(1-adamantyloxy)ethoxy]ethyl ester, 1-[2-(1-adamantanecarbonyloxy)ethoxy]ethyl ester, tetrahydro-2-furyl ester and tetrahydro-2-pyranyl ester, and alicyclic esters such as 2-alkyl-2-adamantyl, 1-(1-adamantyl)-1-alkylalkyl and isobornyl ester.
The monomer from which the polymerization unit having a carboxylic acid ester described above is derived may be an acrylic one such as methacrylic acid ester and acrylic acid ester, or an alicyclic monomer with a carboxylic ester group bound thereto, such as norbornene carboxylic acid ester. tricyclodecene carboxylic acid ester and tetracyclodecene carboxylic acid ester. Otherwise, it may be an ester formed by an alicyclic group of an alicyclic carboxylic acid ester and an acrylic acid or a methacrylic acid, as described in Iwasa et al., Journal of Photopolymer Science and Technology, Vol. 9, No. 3, pp. 447-456 (1996).
Among the monomers described above, one having a bulky group containing an alicyclic group such as 2-alkyl-2-adamantyl and1-(1-adamantyl)-1-alkylalkyl, as the group de-blocked due to the action of an acid, is preferably used because such a monomer exhibits excellent resolution. Examples of the monomer having a bulky
Moriuma Hiroshi
Takata Yoshiyuki
Ashton Rosemary
Birch & Stewart Kolasch & Birch, LLP
Sumitomo Chemical Company Limited
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