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
1998-12-23
2002-04-30
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
C430S914000
Reexamination Certificate
active
06379860
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive photosensitive composition for use in the production of lithographic printing plates and semiconductors, e.g., ICs, and the production of circuit boards for liquid crystals, thermal heads, etc., and in other photofabrication processes.
BACKGROUND OF THE INVENTION
Positive photoresist compositions in use generally comprise an alkali-soluble resin and a naphthoquinonediazide compound as a photosensitive substance. For example, photoresist compositions comprising “a combination of a phenolic novolak resin and a naphthoquinonediazide substitution compound” are described in, e.g., U.S. Pat. Nos. 3,666,473, 4,115,128, and 4,173,470. Further, an example of the most typical composition comprising “a combination of a cresol-formaldehyde novolak resin and a trihydroxybenzophenone-1,2-naphthoquinonediazidesulfonic acid ester” is described in L. F. Thompson, “Introduction to Microlithography” (ACS Press, No.2, 19, pp.112-121).
In such a positive photoresist consisting basically of a novolak resin and a quinonediazide compound, the novolak resin imparts high plasma etching resistance and the naphthoquinonediazide compound functions as a dissolution inhibitive agent. The naphthoquinonediazide has the property of generating a carboxylic acid upon light irradiation to thereby lose its dissolution-inhibiting ability and enhance the alkali solubility of the novolak resin.
Many positive photoresists comprising a novolak resin and a photosensitive naphthoquinonediazide compound have been developed and put to practical use so far from the above-described standpoint. These photoresists have produced satisfactory results in the formation of resist patterns having line widths ranging about from 0.8 to 2 &mgr;m.
However, the degree of integration in integrated circuits is increasing more and more, and it has become necessary to form an ultrafine pattern having a line width of 0.5 &mgr;m or smaller in the production of semiconductor substrates for VLSIs and the like. For attaining the necessary resolution, the wavelengths used in illuminators for photolithography are decreasing more and more and, as a result, use of far ultraviolet rays and excimer laser beams (XeCl, KrF, ArF, etc.) has come to be investigated.
The prior art resists comprising a novolak and a naphthoquinonediazide compound are unsuitable for use in pattern formation by lithography using far ultraviolet rays or excimer laser beams, because the novolak and the naphthoquinonediazide show intense absorption in the far ultraviolet region to render the light less apt to reach the resist bottom. Thus, the resist has low sensitivity to give only a tapered pattern.
One means for eliminating the above problem is the chemical amplification type resist composition described in, e.g., U.S. Pat. No. 4,491,628 and European Patent 249,139. A chemical amplification type positive resist composition is a pattern-forming material in which an acid generates in exposed areas upon irradiation with a radiation such as far ultraviolet rays and this acid catalyzes a reaction that makes the areas irradiated with the actinic rays and the unirradiated areas to differ in solubility in a developing solution to thereby form a pattern on a substrate.
Examples thereof include combinations of a compound which generates an acid upon photodecomposition with an acetal or O,N-acetal compound (see JP-A-48-89003; the term “JP-A” as used herein means an “unexamined published Japanese patent application”), with an orthoester or amidoacetal compound (see JP-A-51-120714), with a polymer having acetal or ketal groups in the backbone (see JP-A-53-133429), with an enol ether compound (see JP-A-55-12995), with an N-acyliminocarbonic acid compound (see JP-A-55-126236), with a polymer having orthoester groups in the backbone (see JP-A-56-17345), with a tertiary alkyl ester compound (see JP-A-60-3625), with a silyl ester compound (see JP-A-60-10247), and with a silyl ether compound (see JP-A-60-37549 and JP-A-60-121446). These combinations show high photosensitivity since they have a quantum efficiency exceeding 1 because of their principle.
Another means for eliminating the problem described hereinabove is a system which is stable over long at room temperature but decomposes upon heating in the presence of an acid to become alkali-soluble. Examples thereof include systems comprising a combination of a compound which generates an acid upon exposure to light with an ester having a tertiary or secondary carbon (e.g., t-butyl or 2-cyclohexenyl) or with a carbonic ester compound, as described in, e.g., JP-A-59-45439, JP-A-60-3625, JP-A-62-229242, JP-A-63-27829, JP-A-63-36240, JP-A-63-250642
; Polym. Eng. Sce
., Vol.23, p.1012 (1983); ACS. Sym., Vol.242, p.11 (1984);
Semiconductor World
, November 1987 issue, p.91
; Macromolecules
, Vol.21, p.1475 (1988); and
SPIE
, Vol.920, p.42 (1988). Since these systems also have high sensitivity and show reduced absorption in the deep UV region as compared with the naphthoquinonediazide
ovolak resin systems, they can be effective systems for coping with the wavelength reduction in illuminators.
The chemical amplification type positive resists described above are roughly divided into three groups: three-component systems comprising an alkali-soluble resin, a compound which generates an acid upon exposure to, e.g., a radiation (photo-acid generator), and a dissolution inhibitive compound for the alkali-soluble resin which has acid-decomposable groups; two-component systems comprising a resin having groups which decompose upon reaction with an acid to become alkali-soluble (acid-decomposable groups) and a photo-acid generator; and 2.5-component systems comprising a resin having groups which decompose upon reaction with an acid to become alkali-soluble, a dissolution inhibitive compound, and a photo-acid generator.
In these two-component, 2.5-component, or three-component chemical amplification type positive resists, the photo-acid generator is caused to generate an acid by exposure to light and the resists are heat-treated and then developed in the presence of the acid to obtain a resist pattern.
Chemical amplification type resists are required to be satisfactory in solubility discrimination between nonimage areas and image areas and to have high resolution. However, conventional resists of the chemical amplification type are still insufficient and a further improvement in resolution is desired. Furthermore, problems concerning lithography defects and development defects are attracting attention as reported recently in, e.g., The Japan Society of Applied Physics. These defects considerably influence the process yield, and this influence becomes serious more and more as the pattern becomes finer. Such defects can be caused by various factors in a process, e.g., the presence of bubbles during development. However, considerable influences on the formation of development defects are exerted by resist compositions, specifically components thereof and impurities present therein. Consequently, resist compositions themselves should be improved.
According to the various patent documents mentioned above, the resin to be used is isolated as a powder from the reaction system. As a result, the resin obtained inevitably contains various impurities which cannot be completely removed by crystallization from water. In addition, since solvents miscible with water in any proportion have been ordinarily used for reactions, it has been impossible to use the technique of water washing extraction/vacuum distillation. Consequently, the prior art methods are insufficient from the standpoint of impurity removal and hence have produced results insufficient in resolution, especially in development defects.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a positive photoresist composition which shows improved discrimination between nonimage areas and image areas, has high sensitivity, high resolution, and high heat resistance, suffers little change in performance with the laps
Aoai Toshiaki
Fujimori Toru
Takata Yasunori
Tan Shiro
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