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
2001-05-07
2002-06-18
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
C430S921000, C430S922000, C568S018000, C568S077000
Reexamination Certificate
active
06406830
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 and a novel compound usable as an acid generator in said resist composition.
In general, a lithography process using a resist composition has been adopted in the minute processing of a semiconductor. In 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 limited. 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, and some of resists for ArF excimer laser are being made practical.
A lens used in an ArF excimer laser exposure machine or an exposure machine using a light-source of shorter wave-length has a shorter lifetime as compared with lenses for conventional exposure light sources. Accordingly, the shorter time required for 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 due to exposure, and contains a resin having a group cleavable by the action of 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.
S. Takechi et al., Journal of Photopolymer Science and Technology, Vol. 9, No. 3, pages 475-487 (1996), and JP-A-9-73173 reported that, when a polymer or copolymer of 2-methyl-2-adamantyl methacrylate was used as the resin in a chemical amplifying type resist, 2-methyl-2-adamantyl was cleaved by the action of an acid to act as an positive type and a high dry etching resistance, a high resolution and a good adhesion to a substrate could be obtained. In addition, JP-A-10-274852 reported that the adhesion to a substrate was improved by using a resin having a butyrolactone residue in a part of polymerization units as the resin constituting a chemical amplification type positive resist composition. Further, JP-A-10-319595 described a resist composition containing a resin having a &ggr;-butyrolactone-3-yl residue as a protective group for carboxyl group.
On the other hand, since the chemical amplification type resists utilizes the action of an acid, a problem arises that profiles are liable to be bottom-tailed by deactivation of the acid when the substrate is of a basic nature. It is known that this problem can be resolved by adding a much amount of a basic quencher substance. Addition of a much amount of such quencher substance, however, results in decrease of the sensitivity of the resist. In addition, in ArF-exposure, a resist is often applied on a substrate having a low reflection such as an organic or inorganic anti-reflective layer. When such a substrate having a low reflection is used, the profile of the resist generally deteriorated in a taper shape due to light absorption, although dimension uniformity is effectively improved.
One possible mean for lowering the light absorption is to reduce the amount of the acid generator. In this case, however, the sensitivity is generally decreased. Another mean for lowering the light absorption is to use an aliphatic sulfonium salt having a high transparency such as those described in JP-A-7-25846, JP-A-7-28237, JP-A-7-92675and JP-A-8-27102. In the cases of these known aliphatic sulfonium salts, however, a sufficient resolution cannot be obtained and a problem that the profile on a basic substrate becomes bottom-tailed shape cannot be dissolved. Therefore, the chemical amplification type resists containing a conventional acid generator had a problem that performances, particularly the profile, are varied depending on the kind of the substrate.
An object of the present invention is to provide a chemical amplification type positive resist composition, which contains a resin component and an acid generator, which is suitable to use in excimer laser lithography with ArF, KrF or the like, particularly in lithography with a light having a wavelength of 220 nm or lower, for example, ArF excimer laser light, and which is superior in sensitivity and resolution confering a good profile.
Another object of the invention is to provide a compound useful as an acid generator in such a chemical amplification type positive resist composition.
The present inventors have found the fact that the transmittance and the resolution can be improved by using a combination of certain kinds of acid generators. Thus, the present invention has been completed.
SUMMARY OF THE INVENTION
The present invention provides a chemical amplifying type positive resist composition comprising an aliphatic sulfonium salt represented by the following formula (I):
wherein either Q
1
, Q
2
, Q
3
and Q
4
independently represent an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 10 carbon atoms, or Q
1
and Q
2
and/or Q
3
and Q
4
independently form, together with the adjacent sulfur atom, a heterocyclic group which has 2 to 8 carbon atoms and which may further have an oxygen atom or a sulfur atom, and m represents an integer of 1 to 8;
at least one onium salt selected from the group consisting of a triphenylsulfonium salt represented by the following formula (IIa) and a diphenyliodonium salt represented by the following formula (IIb):
wherein Q
5
, Q
6
, Q
7
, Q
8
and Q
9
independently represent a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and p and q represent integer of 1 to 8; and
a resin which contains a polymerization unit having a group unstable to an acid, and which is insoluble in alkali by itself but becomes soluble in alkali by the action of an acid.
The aliphatic sulfonium salt represented by the above formula (I) is a novel compound never described in literature. Therefore, the invention also provides the sulfonium compound represented by the above formula (I).
DETAILED DESCRIPTION OF THE INVENTION
The acid generator used in the chemical amplification type resist composition is a substance that decomposes to generate an acid by acting a radiation such as a light or an electronic ray on the substance itself or a resist composition containing the substance. In the resist composition of the invention, both of an aliphatic sulfonium salt represented by the above formula (I), and at least one onium salt selected from the group consisting of a triphenylsulfonium salt represented by the above formula (IIa) and a diphenyliodonium salt represented by the above formula (IIb). Such acid generators are used together.
In the formula (I), either Q
1
, Q
2
, Q
3
and Q
4
independently represent an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 10 carbon atoms. Alternatively, Q
1
, Q
2
and the sulfur atom bonding to them, and/or Q
3
, Q
4
and the sulfur atom bonding to them may form a heterocyclic group which has 2 to 8 carbon atoms and which may further have an oxygen atom or a sulfur atom. When the alkyl group has 3 or more carbon atoms, the group can be straight-chained or branched. Typical examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl, hexyl and the like. Typical examples of the cycloalkyl group include cyclopentyl, cyclohexyl, cycloheptyl and the like. Typical ex
Inoue Hiroki
Uetani Yasunori
Ashton Rosemary
Birch & Stewart Kolasch & Birch, LLP
Sumitomo Chemical Company Limited
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