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
1999-09-09
2003-10-14
Baxter, Janet (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
C430S285100, C430S280100, C430S270100, C430S905000, C430S910000
Reexamination Certificate
active
06632586
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive resist composition for use in the production of a semiconductor such as IC, in the production of a circuit board such as liquid crystal and thermal head and in other photofabrication processes. More specifically, the present invention relates to a positive resist composition suitably employed in a case where a far ultraviolet ray of 220 nm or less is used as an exposure light source.
BACKGROUND OF THE INVENTION
A positive photoresist composition includes a composition comprising an alkali-soluble resin and a naphthoquinonediazide compound as a photosensitive material.
However, integrated circuits are being more and more intensified in the integration degree and the production of a semiconductor substrate such as VLSI requires working of an ultrafine pattern comprising lines having a width of a half micron or less.
According to one of known techniques for achieving miniaturization of a pattern, a resist pattern is formed using an exposure light source having a shorter wavelength. This technique can be described using the following Rayleigh's formula showing resolution R (line width) of an optical system:
R═k·&lgr;/NA
(wherein &lgr; is a wavelength of the exposure light source, NA is a numerical aperture of the lens and k is a process constant). As is apparent from the formula, higher resolution, namely, a smaller R value can be obtained by reducing the wavelength &lgr; of the exposure light source.
For example, in the production of a DRAM having an integration degree up to 64 M bits, the i-line (365 nm) of a high-pressure mercury lamp is used at present as the light source. In the mass production of 256 M bit DRAMs, use of a KrF excimer laser (248 nm) in place of the i-line has been studied. Further, for the purpose of producing DRAMs having an integration degree of 1 G bits or more, a light source having a further shorter wavelength has been investigated. To this effect, an ArF excimer laser (193 nm), an F
2
excimer laser (157 nm), an X ray, an electron beam and the like are considered to be effective (see, Takumi Ueno et al.,
Tanpacho Photoresist Zairyo—ULSI Ni Muketa Bisai Kako
—(Short Wavelength Photoresist Material—Fine Working Toward ULSI—), Bunshin Shuppan (1988)).
When a conventional resist comprising a novolak resin and a naphthoquinonediazide compound is used for the pattern formation by photolithography with a far ultraviolet ray or excimer laser beam, the novolak resin and naphthoquinonediazide compound exhibit strong absorption in the far ultraviolet region and the light scarcely reaches the bottom of resist. As a result, the resist has low sensitivity and only a tapered pattern can be obtained.
One of the techniques for solving this problem is a chemical amplification-type resist composition described in U.S. Pat. No. 4,491,628 and European Patent 249,139. The chemical amplification-type positive resist composition is a pattern formation material which generates an acid in the exposed area on irradiation of radiation such as a far ultraviolet ray and due to the reaction using the acid as a catalyst, differentiates solubility in a developing solution between the area irradiated with the active radiation and the non-irradiated area to form a pattern on a substrate.
Examples thereof include combinations of a compound capable of generating an acid by photolysis 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 ortho ester or amide acetal compound (JP-A-51-120714), with a polymer having an acetal or ketal group in the main chain (JP-A-53-133429), with an enol ether compound (JP-A-55-12995), with an N-acyliminocarbonic acid compound (JP-A-55-126236), with a polymer having an ortho ester group in the main chain (JP-A-56-17345), with a tertiary alkyl ester compound (JP-A-60-3625), with a silyl ester compound (JP-A-60-10247) or with a silyl ether compound (JP-A-60-37549 and JP-A-60-121446). These combinations in principle have a quantum yield exceeding 1 and therefore exhibit high photosensitivity.
A system which decomposes by heating in the presence of an acid and becomes soluble in alkali is also used and examples thereof include combinations of a compound capable of generating an acid on exposure with an ester or carbonic acid ester compound having a tertiary or secondary carbon (e.g., tert-butyl, or 2-cyclohexenyl) described, for example, 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
., Vol. 23, page 1012 (1983),
ACS. Sym
., Vol. 242, page 11 (1984),
Semiconductor World
, November, 1987, page 91
, Macromolecules
, Vol. 21, page 1475 (1988), and SPIE, Vol. 920, page 42 (1988), with an acetal compound described, for example, in JP-A-4-219757, JP-A-5-249682 and JP-A-6-65332, or with a tert-butyl ether compound described, for example, in JP-A-4-211258 and JP-A-6-65333.
Such systems are mainly composed of a resin having a basic skeleton of poly(hydroxystyrene) which has small absorption in the region around 248 nm and therefore, when the exposure light source is a KrF excimer laser, they have high sensitivity and high resolution and are capable of forming a good pattern. Thus they can form good systems as compared with conventional naphthoquinonediazide
ovolak resin systems.
However, when the light source has a still shorter wavelength, for example, when the exposure light source used is an ArF excimer laser (193 nm), the above-described chemical amplification systems are yet deficient because the compound having an aromatic group substantially has large absorption in the region of 193 nm. As a polymer having small absorption in the 193 nm region, the use of poly(meth)acrylate is described in
J. Vac. Sci. Technol
., B9, 3357 (1991). However, this polymer has a problem in that the resistance against dry etching which is commonly performed in the production process of semiconductors is low as compared with conventional phenol resins having aromatic groups.
In
Proc. of SPIE
, 1672, 66 (1922), it is reported that polymers having alicyclic groups exhibit the dry etching resistance on a level with the polymers having aromatic groups and at the same time, have small absorption in the 193 nm region. The use of these polymers has been aggressively studied in recent years. Specific examples thereof include the polymers described, for example, in JP-A-4-39665, JP-A-5-80515, JP-A-5-265212, JP-A-5-297591, JP-A-5-346668, JP-A-6-289615, JP-A-6-324494, JP-A-7-49568, JP-A-7-185046, JP-A-7-191463, JP-A-7-199467, JP-A-7-234511, JP-A-7-252324 and JP-A-8-259626. In the polymers having alicyclic groups described above, a carboxy group is used in place of a phenolic hydroxy group as the group of imparting solubility in an alkaline developing solution in order to reduce the absorption in the 193 nm region. However, since the carboxy group has large solubility in the developing solution, even the unexposed area dissolves at the development to cause a problem of decrease in film thickness, when developed with a developing solution hitherto used for resist materials (for example, a 2.38% aqueous solution of tetramethylammonium hydroxide).
In order to solve the problem, it is required to dilute the developing solution and decrease its concentration or to reduce the content of carboxy group in the polymer. However, when the concentration of developing solution decreases, reproducibility of the development becomes an issue. On the other hand, when the content of carboxy group in the polymer is reduced, the adhesion of polymer to a substrate disadvantageously deteriorate due to the increase in hydrophobic property of the polymer
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a positive resist composition suitable for using an exposure light source having a wavelength of 220 nm or less, particularly an ArF excimer laser beam (193 nm).
Another object of the present invention is to provide a p
Aoai Toshiaki
Sato Kenichiro
Baxter Janet
Lee Sin J.
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