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
2001-06-22
2003-04-15
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
C430S905000, C430S914000, C430S921000
Reexamination Certificate
active
06548220
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a chemical amplifying type positive resist composition for use in the fine processing of a semiconductor.
In general, a lithography process using a resist composition is adopted for the fine processing of a semiconductor. In lithography,the shorter the exposure light wavelength is, the more the resolution can be higher in principle, as shown by Rayleigh's formula for diffraction limited. Exposure light sources for lithography used for manufacturing a semiconductor, such as a g-line with a wavelength of 436 nm, an i-line with a wavelength of 365 nm, a KrF excimer laser with a wavelength of 248 nm, and an ArF excimer laser with a wavelength of 193 nm have been adopted. Thus, the wavelength thereof has been reduced year by year. A F2 excimer laser with a wavelength of 157 nm is regarded as being promising as the next-generation exposure light source. Thereafter, a soft X-ray (EUV) with a wavelength of not more than 13 nm is proposed as a light source.
Since a light source having a shorter wavelength than that of a g-line or an i-line, such as an excimer laser, has low illumination intensity, the sensitivity of a resist is required to be increased. For this reason, there is used a so-called chemical amplifying type resist containing a resin having a group utilizing the catalytic action of an acid which is generated through light exposure, and is cleaved by the acid.
However, with a chemical amplifying type resist composition known in the art, the line edge roughness, i.e., the smoothness of the pattern side wall is deteriorated due to the occurrence of a standing wave, or the like. As a result, there occurs a problem that the uniformity of the line width is deteriorated.
An object of the present invention is to provide a chemical amplifying type positive resist composition which comprises a resin component and an acid generator; is suitable for excimer laser lithography using an ArF excimer laser, a KrF excimer laser, or the like; is excellent in various resist performances such as sensitivity and resolution; and provides a particularly improved line edge roughness.
The present inventors have already found and proposed the following fact. Namely, by using at least one onium salt selected from triphenylsulfonium salt and diphenyliodonium salt, and a perfluoroalkylsulfonate salt of 2-oxosulfonium such as cyclohexylmethyl(2-oxosulufonium)perfluoroalkyl sulfonate in combination as an acid generator, the resolution is improved, and the profile on a basic substrate or a low reflectance substrate is also improved (Japanese Patent Application No.2000-060057). Thereafter, they have found that this combination system is also capable of improving the line edge roughness, and further conducted a study thereon. As a result, they have found that by using a specific sulfonium salt in place of the perfluoroalkylsulfonate salt of 2-oxosulfonium in the combination, it is possible to improve the line edge roughness. Thus, they have completed the present invention.
SUMMARY OF THE INVENTION
The present invention provides a practically excellent chemical amplifying type positive resist composition which comprises:
(A) an acid generator containing (a) a sulfonium salt represented by the following formula (I);
wherein Q
1
and Q
2
each independently represent a straight chain or branched alkyl group having from 1 to 6 carbon atoms or a cycloalkyl group having from 3 to 10 carbon atoms, or Q
1
and Q
2
form, together with a sulfur atom to which Q
1
and Q
2
are adjacent, heteroalicyclic group which may further contain an oxygen atom and a sulfur atom; Q
3
represents a hydrogen atom, Q
4
represents a straight chain or branched alkyl group having from 1 to 6 carbon atoms or a cycloalkyl group having from 3 to 10 carbon atoms, or Q
3
and Q
4
form, together with a CHC(O) group to which Q
3
and Q
4
are adjacent, a 2-oxocycloalkyl group; and Q
5
SO
3
−
represents an organosulfonate ion, provided that when Q
5
represents a perfluoroalkyl group having from 1 to 8 carbon atoms, there is excluded the case where Q
1
represents a straight chain or branched alkyl group having from 1 to 6 carbon atoms, Q
2
represents a straight chain or branched alkyl group having from 1 to 6 carbon atoms, or a cycloalkyl group having from 3 to 10 carbon atoms, and Q
3
and Q
4
represent, together with their adjacent CHC(O) group, a 2-oxocycloalkyl group, and (b) at least one onium salt selected from a triphenylsulfonium salt represented by the following formula (IIa), and a diphenyliodonium salt represented by the following formula
wherein P
1
to P
5
each independently represent hydrogen, a hydroxyl group, an alkyl group having from 1 to 6 carbon atoms, or an alkoxy group having from 1 to 6 carbon atoms; and P
6
SO
3
31
and P
7
SO
3
−
each independently represent an organosulfonate ion; and
(B) a resin which has a polymerization unit having a group unstable against an acid, and is alkali-insoluble or -slightly soluble itself, but is converted to alkali-soluble by the action of an acid.
Further, the present invention also provides a sulfonium salt represented by the following formula (Ia):
wherein Q
6
represents a perfluoroalkyl group having from 1 to 8 carbon atoms, an alkyl group having from 1 to 8 carbon atoms, an aromatic group having from 6 to 12 carbon atoms or a camphor group; when Q
6
represents a perfluoroalkyl group having from 1 to 8 carbon atoms, Q
1
and Q
2
each independently represent a straight chain or branched alkyl group having from 1 to 6 carbon atoms or a cycloalkyl group having from 3 to 10 carbon atoms, or Q
1
and Q
2
form, together with a sulfur atom to which Q
1
and Q
2
are adjacent, heteroalicyclic group which may further contain an oxygen atom and a sulfur atom, Q
3
represents a hydrogen atom, Q
4
represents a straight chain or branched alkyl group having from 1 to 6 carbon atoms or a cycloalkyl group having from 3 to 10 carbon atoms; when Q
6
represents an alkyl group having from 1 to 8 carbon atoms, an aromatic group having from 6 to 12 carbon atoms or a camphor group, Q
1
and Q
2
each independently represent a straight chain or branched alkyl group having from 1 to 6 carbon atoms or a cycloalkyl group having from 3 to 10 carbon atoms, or Q
1
and Q
2
form, together with a sulfur atom to which Q
1
and Q
2
are adjacent, a heteroalicyclic group which may further contain an oxygen atom and a sulfur atom, Q
3
represents a hydrogen atom, and Q
4
represents a straight chain or branched alkyl group having from 1 to 6 carbon atoms or a cycloalkyl group having from 3 to 10 carbon atoms, or Q
3
and Q
4
form, together with their adjacent CHC(O) group, a 2-oxocycloalkyl group.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An acid generator to be used for a chemical amplifying type resist composition is decomposed to generate an acid by allowing a radiation such as light or an electron beam to act upon the substance itself or a resist composition containing the substance. In the composition of the present invention, as such an acid generator, a sulfonium salt represented by the formula (I), and at least one onium salt selected from a triphenylsulfonium salt represented by the formula (IIa), and a diphenyliodonium salt represented by the formula (IIb) are used in combination.
In the formula (I), Q
1
and Q
2
may be each independently an alkyl group having from 1 to 6 carbon atoms, or a cycloalkyl group having from 3 to 10 carbon atoms, and when they each have 3 or more carbon atoms, they may be strait-chain, or branched. Specific examples of an alkyl group and a cycloalkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, tert-butyl group, pentyl group, hexyl group, and cyclohexyl group. Further, examples of the heteroalicyclic group formed by Q
1
and Q
2
together with their adjacent sulfur atom include ethylene sulfide, trimethylene sulfide, tetrahydrothiophene, tetrahydrothiopyran, thioxane, dithiane, tetrahydrothiophen-3-one, and tetrahydrothiopyran-4-one
Kamabuchi Akira
Oohashi Kenji
Uetani Yasunori
Ashton Rosemary
Birch & Stewart Kolasch & Birch, LLP
Sumitomo Chemical Company Limited
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