Resist compositions and patterning process

Details Resist compositions and patterning process Resist compositions and patterning process

2001-03-20

2003-04-01

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

C430S325000, C430S326000, C430S921000

Reexamination Certificate

active

06541179

ABSTRACT:

This invention relates to a resist composition comprising a specific sulfonium salt as the photoacid generator, for use with radiation having a wavelength of up to 200 nm, especially ArF excimer laser light, F
2
excimer laser light, EUV, x-ray and electron beam (EB), and a patterning process using the same.
BACKGROUND OF THE INVENTION
While a number of recent efforts are being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, deep-ultraviolet lithography is thought to hold particular promise as the next generation in microfabrication technology. In particular, photolithography using an ArF excimer laser as the light source is strongly desired to reach the practical level as the micropatterning technique capable of achieving a feature size of 0.2 &mgr;m or less.
In the photolithography using an ArF excimer laser (wavelength 193 nm) as the light source, a high sensitivity resist material capable of achieving a high resolution at a small dose of exposure is needed to prevent the degradation of precise and expensive optical system materials. Among several measures for providing a high sensitivity resist material, the most common is to select each component which is highly transparent at the wavelength of 193 nm. For example, polyacrylic acid and derivatives thereof, norbornenemaleic anhydride alternating copolymers, polynorbornene and metathesis ringopening polymers have been proposed as the base resin. This choice is effective in that the transparency of a resin alone is increased. However, the photoacid generator has the problem that increasing its transparency leads to a drop of acid generation efficiency, resulting in a low sensitivity or the lack of thermal stability and storage stability. There is available no photoacid generator which is practically acceptable.
For example, JP-A 7-25846, JP-A 7-28237 and JP-A 8-27102 disclose alkylsulfonium salts which are highly transparent, but unsatisfactory in acid generation efficiency and thermal stability. JP-A 10-319581 discloses alkylarylsulfonium salts which have a high sensitivity and a good balance of transparency and acid generation efficiency, but lack thermal stability and storage stability. Arylsulfonium salts, which are regarded effective in photolithography using a KrF excimer laser, are good in acid generation efficiency, thermal stability and storage stability, but very low transparent to ArF excimer laser light so that the pattern resulting from exposure and development is noticeably tapered. The lack of transparency can be compensated for by thinning the resist, but such a thin resist film is less resistant to etching. This is inadequate as the pattern forming process.
SUMMARY OF THE INVENTION
An object of the invention is to provide a highly resolvable resist composition comprising a photoacid generator having a high sensitivity to ArF excimer laser light as well as thermal stability and storage stability. Another object is to provide a patterning process using the resist composition.
It has been found that a sulfonium salt of the following general formula (1) has a high sensitivity to ArF excimer laser light as well as satisfactory thermal stability and storage stability and that a resist composition having the sulfonium salt blended therein has a high resolution and is fully suited for precise micropatterning.
The invention provides a resist composition comprising a base resin, a photoacid generator, and a solvent. The photoacid generator is a sulfonium salt of the following general formula (1).
Herein R
1
is a monovalent cyclic or bridgedring hydrocarbon group of 3 to 20 carbon atoms, R
2
is hydroxyl, nitro, halogen, or a straight, branched or cyclic monovalent hydrocarbon group of 1 to 15 carbon atoms which may contain an oxygen, nitrogen, sulfur or halogen atom, K
−
is a non-nucleophilic counter ion, x is equal to 1 or 2, and y is an integer of 0 to 3.
In one preferred embodiment, the base resin is a polymer having an alicyclic structure. The base resin is typically at least one polymer selected from the group consisting of polyacrylic acid and derivative thereof, a ternary or quaternary copolymer of a norbornene derivative-maleic anhydride alternating polymer and polyacrylic acid or derivative thereof, a ternary or quaternary copolymer of a tetracyclododecene derivativemaleic anhydride alternating polymer and polyacrylic acid or derivative thereof, a ternary or quaternary copolymer of a norbornene derivative-maleimide alternating polymer and polyacrylic acid or derivative thereof, a ternary or quaternary copolymer of a tetracyclododecene derivativemaleimide alternating polymer and polyacrylic acid or derivative thereof, polynorbornene, and metathesis ringopened polymer.
In a further preferred embodiment, the base resin is a polymer comprising recurring units of the following general formula (2) and having a weight average molecular weight of 1,000 to 500,000.
Herein R
001
is hydrogen, methyl or CH
2
CO
2
R
003
; R
002
is hydrogen, methyl or CO
2
R
003
; R
003
is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms; R
004
is hydrogen or a monovalent hydrocarbon group of 1 to 15 carbon atoms having a carboxyl or hydroxyl group; at least one of R
005
to R
008
represents a monovalent hydrocarbon group of 1 to 15 carbon atoms having a carboxyl or hydroxyl group while the remaining R's independently represent hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, R
005
to R
008
, taken together, may form a ring, and in that event, at least one of R
005
to R
008
is a divalent hydrocarbon group of 1 to 15 carbon atoms having a carboxyl or hydroxyl group while the remaining R's are independently single bonds or straight, branched or cyclic alkylene groups of 1 to 15 carbon atoms; R
009
is a monovalent hydrocarbon group of 3 to 15 carbon atoms containing a —CO
2
— partial structure; at least one of R
010
to R
013
is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a —CO
2
— partial structure, while the remaining R's are independently hydrogen or straight, branched or cyclic alkyl groups of 1 to 15 carbon atoms, R
010
to R
013
, taken together, may form a ring, and in that event, at least one of R
010
to R
013
is a divalent hydrocarbon group of 1 to 15 carbon atoms containing a —CO
2
— partial structure, while the remaining R's are independently single bonds or straight, branched or cyclic alkylene groups of 1 to 15 carbon atoms; R
014
is a polycyclic hydrocarbon group having 7 to 15 carbon atoms or an alkyl group containing a polycyclic hydrocarbon group; R
015
is an acid labile group; R
016
is a methylene group or oxygen atom; R
017
is a single bond or a straight, branched or cyclic alkylene group of 1 to 10 carbon atoms which may have a hetero atomcontaining substituent; R
018
is hydrogen or an alkyl group of 1 to 10 carbon atoms; k is equal to 0 or 1; a1, a2, a3, b1, b2, b3, c1, c2, c3, d1, d2, d3, and e are numbers from 0 to less than 1, satisfying a1+a2+a3+b1+b2+b3+c1+c2+c3+d1+d2+d3+e=1.
In another aspect, the invention provides a chemically amplified, positive resist composition comprising a photoacid generator of the general formula (1); a base resin as defined above which is substantially insoluble in a developer, but becomes soluble in the developer under the action of an acid; and a solvent. Preferably, the resist composition further includes a basic compound.
In a further aspect, the invention provides a chemically amplified, negative resist composition comprising a photoacid generator of the general formula (1); a crosslinker; a base resin as defined above which is soluble in a developer, but becomes insoluble in the developer after being crosslinked with the crosslinker under the action of an acid; and a solvent. Preferably, the negative resist composition further includes a basic compound.
In a still further aspect, the invention provides a process for forming a resist pattern

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