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
1999-12-23
2004-03-02
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
Reexamination Certificate
active
06699635
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive photosensitive composition used in a production process of semiconductor devices, such as IC, production of circuit substrates for liquid crystal, thermal head and the like, and other photo-fabrication processes. To mention in detail, the invention is concerned with a positive photosensitive composition suitable for the cases wherein far ultraviolet rays having wavelengths of 250 nm or shorter are used as exposure light.
BACKGROUND OF THE INVENTION
The compositions containing alkali-soluble resins and naphthoquinonediazide compounds as photosensitive material are generally used as positive photoresist compositions. For instance, the combinations of phenol resins of novolak type with naphthoquinonediazido-substituted compounds are disclosed in U.S. Pat. Nos. 3,666,473, 4,115,128 and 4,173,470. And L. F. Thompson,
Introduction to Microlithography,
No.2, 19, pp. 112-121, ACS Publisher, describes as the most typical compositions the combinations of cresol-formaldehyde novolak resin with trihydroxybenzophenone-1,2-naphthoquinone-diazidosulfonates.
In the positive photoresist constituted basically of a novolak resin and a naphthoquinonediazide compound, the novolak resin ensures high resistance to plasma etching, and the naphtoquinonediazide compound functions as a dissolution inhibitor. And the naphtoquinonediazide has a characteristic that it yields carboxylic acid when irradiated with light, thereby losing its dissolution-inhibiting ability to raise the solubility of the novolak resin in alkali.
From such points of view, a number of positive photoresists comprising novolak resins and photosensitive materials of naphthoquinonediazide type have so far been developed and put to practical use. As to the processing of fine patterns the minimum line width of which is at the level of 0.8-2 &mgr;m, those photoresists have achieved satisfactory results.
However, the integration degree of integrated semiconductors kept on getting higher, and the production of semiconductor substrates for VLSI and the like has come to necessitate the processing of superfine line patterns having the width on the level of half micron.
As one of means to obtain finer patterns, it is known to use an exposure light of shorter wavelengths for the resist pattern formation. This can be explained by the following Rayleigh's equation for resolution (line width) of an optical system:
R=k·&lgr;/NA
wherein &lgr; is the wavelength of exposure light, NA is the aperture number of the lens and k is a process constant. From this equation, it is understand that the high resolution, or the reduction in the value of R, can be achieved by shortening the wavelength &lgr; of exposure light.
For instance, in the production of DRAM having an integration degree up to 64 Mega-bit, the i-line (365 nm) of a high-pressure mercury lamp has so far been used as exposure light. In the process of mass-producing 256 Mega-bit DRAM, the use of KrF excimer laser beam (248 nm) as exposure light has been examined in the place of i-line. Further, the sources for exposure light of shorter wavelengths have been investigated for the purpose of producing DRAM with an integration degree of 1 Giga-bit or above, and thereby the utilization of ArF excimer laser (193 nm), F
2
excimer laser (157 nm), X-rays and electron beams has been considered effective (Takumi Ueno et al.,
Short
-
wavelength Photoresist Materials—Micro
-
lithography for ULSI,
Bunshin Shuppan (1988)).
When the conventional resist constituted of a novolak resin and a quinonediazide compound is used for the pattern formation utilizing far ultraviolet or excimer laser lithography, it is difficult for the light to reach the depths of the resist because both novolak resin and naphthoquinonediazide have strong absorption in the far ultraviolet region. As a result, the resist sensitivity is low and the pattern obtained has a tapered profile.
As a measure to solve those problems, the chemically amplified resist compositions are disclosed in, e.g., U.S. Pat. No. 4,491,638 and European Patent No. 249, 139. The positive resist compositions of chemical amplification type are pattern-forming materials of the type which produce acids in the irradiated area when irradiated with actinic rays such as far ultraviolet rays. And the reaction catalyzed by such acids makes a difference between the solubility of the irradiated area in a developer and that of the unirradiated areas, thereby forming a pattern on a substrate.
Examples of positive resist of chemical amplification type include the compositions comprising the combinations of compounds of producing acids by photolysis with the acetal or O,N-acetal compounds (JP-A-48-89003, wherein the term “JP-A” means an “unexamined published Japanese patent application”), those with the orthoester or amidoacetal compounds (JP-A-51-120714), those with the polymers containing acetal or ketal groups in the main chain (JP-A-53-133429), those with the enol ether compounds (JP-A-55-12995), those with the N-acyliminocarbonic acid compounds (JP-A-55-126236), those with the polymers containing orthoester groups in the main chain (JP-A-56-17345), those with the tertiary alkyl ester compounds (JP-A-60-3625), those with silyl ester compounds (JP-A-60-10247) and those with the silyl ether compounds (JP-A-60-37549 and JP-A-60-121446). These compositions have high sensitivity because their quantum yields are greater than 1 in principle.
As examples of a positive resist composition of the type which decomposes on heating in the presence of an acid to become soluble in alkali, mention may be made of the compositions comprising the combinations of the compounds capable of producing acids by exposure as disclosed in JP-A-59-45439, JP-A-60-3625, JP-A-62-229242, JP-A-63-27829, JP-A-63-36240, JP-A-63-250642, JP-A-5-181279,
Polym. Eng. Sce.,
volume 23, page 1012 (1983),
ACS. Sym.,
volume 242, page 11 (1984),
Semiconductor World
1987, November issue, page 91,
Macromolecules,
volume 21, page 1475 (1988), and
SPIE,
volume 920, page 42 (1988), with tertiary or secondary carbon (e.g., t-butyl, 2-cyclohexenyl) esters or carbonic acid ester compounds, the combinations with the acetal compounds as disclosed in JP-A-4-219757, JP-A-5-249682 and JP-A-6-65332, and the combinations with the t-butyl ether compounds as disclosed in JP-A-4-211285 and JP-A-6-65333.
The resist compositions recited above contain as their main component a resin whose basic skeleton is poly(hydroxystyrene) showing small absorption at the wavelengths around 248 nm. When KrF excimer laser is used as exposure light source, therefore, those compositions can have high sensitivity and high resolution, and moreover they can form patterns of good quality. In other words, they can be superior in performance to conventional naphthoquinonediazide
ovolak resin resist.
However, in cases where the sources emitting light of further short wavelengths, such as ArF excimer laser (193 nm), are used for exposure, even the chemically amplified resist compositions recited above are inadequate since the compounds having aromatic groups essentially show strong absorption at wavelengths around 193 nm.
In addition, the use of poly(meth)acrylates showing weak absorption at wavelengths around 193 nm as resin component is described in
J. Vac. Sci. Technol.,
B9, 3357 (1991). However, such polymers have a drawback of being inferior to conventional phenol resins, wherein aromatic groups are present, in the resistance to dry etching generally carried out in the semiconductor production process.
On the other hand, it was reported in
Proc. of SPIE,
1672, 66 (1992) that the polymers containing alicyclic groups showed dry etching resistance equivalent to that of the polymers containing aromatic groups, and that weak absorption at wavelengths around 193 nm. As a result, the utilization of such polymers has come to be examined energetically in recent years. For instance, the polymers hitherto examined are those disclosed in JP-A-4-39665, JP-A-5-80515, JP-A-5-265212, J
Aoai Toshiaki
Kawabe Yasumasa
Kodama Kunihiko
Sato Kenichiro
Ashton Rosemary
Fuji Photo Film Co. , Ltd.
Sughrue & Mion, PLLC
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