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
2000-12-21
2002-10-22
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, C430S921000
Reexamination Certificate
active
06468714
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radiation-sensitive resin composition, and more particularly to a negative radiation-sensitive resin composition useful as a chemically amplified resist suited for fine processing using radiations such as far-ultraviolet radiations, X-radiations and charged-particle radiations.
2. Description of the Prior Art
In the field of fine processing as typified by the fabrication of integrated-circuit devices, the size of processing in lithography is being rapidly made finer in order to achieve a higher degree of integration. In recent years, there is a demand for techniques that enable stable fine processing in a line width of 0.25 &mgr;m or smaller. Accordingly, resists used therein are also required to enable formation of fine patterns of 0.25 &mgr;m or finer in a high precision. From such a viewpoint, lithography that utilizes radiations having a shorter wavelength is studied.
As radiations having such a short wavelength, used are far-ultraviolet radiations of KrF excimer lasers (wavelength: 248 nm) and ArF excimer lasers (wavelength: 193 nm), X-radiations such as synchrotron radiations, and charged-particle radiations such as electron radiations. In recent years, various resists adaptable to such radiations are studied. As those which especially attract notice among such resists, what is called “chemically amplified resist” is known in which an acid is generated by irradiation with radiations (hereinafter “exposure”) and the reaction takes place to cause a chemical change in the solubility of the resist to a developing solution by the catalytic action of this acid.
Now, when integrated circuits are actually fabricated using resists, usually resist constituents such as a radiation-sensitive component and a film-forming resin component are dissolved in a solvent to prepare a resist solution, and the resist solution is coated on a substrate which is to be processed, to form a resist film. Thereafter, the resist film is exposed to light via a given mask and then developed to form a pattern suited for fine processing. The shape of cross sections of the pattern formed there (pattern cross-sectional shape) affects the precision of fine processing greatly, and a rectangular shape is considered preferable. Conventional chemically amplified negative resists, in which the pattern is formed by making cross-linking reaction proceed at exposed areas to lower the rate of dissolution of resist in developing solution in that area, have a disadvantage that the rate of dissolution of the resist in the developing solution does not contrast sufficiently between exposed areas and unexposed areas and hence a low resolution may result and the pattern may have not square but round top edges in its cross section. Moreover, the rate of dissolution of resist in developing solution can not sufficiently be lowered in the exposed area, bringing about difficulties that the pattern is swelled by the developing solution or formed serpentinely.
Japanese Laid-open Publication (Kokai) Nos. 1-293339 and 2-15270 disclose chemically amplified negative resist compositions making use of amino resins such as glycoluril resin as cross-linking agents. However, where cross-linking agents are merely selected, it has been difficult to form fine patterns of 0.25 &mgr;m or finer on a satisfactory level.
Meanwhile, Japanese Laid-open Publication (Kokai) No. 6-301200 discloses a chemically amplified negative resist composition making use of a cross-linking agent comprised of N-(alkoxymethyl)glycoluril compound. This composition, however, has had a problem that an aqueous 2.38% by weight tetramethylammonium hydroxide solution usually used as a developing solution in the fabrication of integrated-circuit devices is not applicable.
Japanese Laid-open Publication (Kokai) No. 5-34922 also discloses a proposal of a chemically amplified negative resist composition containing a partial hydrogenation phenolic resin and a glycoluril resin cross-linking agent whose mononuclear-structure proportion has been specified. However, in an attempt to form fine patters of 0.25 &mgr;m or finer by using this resist composition, it has been impossible to achieve any satisfactory performance. Also, if the mononuclear-structure proportion in the cross-linking agent used in the resist composition is too high, the resist may have a very high sensitivity. Such a resist may cause a great dimensional change of the pattern, with changes in exposure (quantity of light). This point rather comes into question in respect of processes for fabricating fine-pattern integrated-circuit devices.
In more recent years, as chemically amplified negative resist compositions improved especially in resolution, Japanese Laid-open Publication (Kokai) Nos. 7-120924, 7-311463, 8-44061 and so forth disclose compositions whose degree of dispersion of alkali-soluble resin has been specified. However, these resist compositions can also not yet be satisfactory in respect of the resolution, pattern cross-sectional shape and dimensional fidelity that are important as characteristics of usual negative resists.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a negative radiation-sensitive resin composition suitable as a chemically amplified negative resist, to which alkaline developing solutions having usual concentration are applicable and which can form, in usual line-and-space patterns, resist patterns having a rectangular cross-sectional shape in a high resolution and also has superior sensitivity, developability and dimensional fidelity.
According to the present invention, the above object can be achieved by a negative radiation-sensitive resin composition comprising:
(A) an alkali-soluble resin containing at least one copolymer selected from the group consisting of a hydroxystyrene/styrene copolymer having hydroxystyrene units in a content of from 65 to 90 mol % and a hydroxystyrene/&agr;-methylstyrene copolymer having hydroxystyrene units in a content of from 65 to 90 mol %;
(B) a radiation-sensitive acid-generating agent containing a hydroxyl group-containing onium salt compound; and
(C) a cross-linking agent containing an N-(alkoxymethyl)glycoluril compound.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below in detail.
(A) Alkali-soluble Resin
The alkali-soluble resin in the present invention comprises a resin containing as essential components at least one copolymer selected from the group consisting of a hydroxystyrene/styrene copolymer having hydroxystyrene units in a content of from 65 to 90 mol % and a hydroxystyrene/&agr;-methylstyrene copolymer having hydroxystyrene units in a content of from 65 to 90 mol % (these copolymers are hereinafter called “specific hydroxystyrene copolymer” generically). The hydroxystyrene units contained in this specific hydroxystyrene copolymer may preferably be in a content of from 70 to 90 mol %, and more preferably from 70 to 85 mol %. In this case, if the hydroxystyrene units in the hydroxystyrene/styrene copolymer and hydroxystyrene/&agr;-methylstyrene are in a content less than 65 mol %, the composition may have a low rate of dissolution in alkaline developing solutions to damage developability, resolution and so forth required as resists. If on the other hand they are in a content more than 90 mol %, a poor pattern cross-sectional shape may result.
The specific hydroxystyrene copolymer may also have a weight-average molecular weight (hereinafter “Mw”) of from 2,000 to 8,000, and preferably from 3,000 to 7,000, in terms of polystyrene as measured by gel permeation chromatography, and also a degree of dispersion of 1.8 or below, and preferably 1.5 or below, as defined by a ratio of Mw to number-average molecular weight (hereinafter “Mn”) in terms of polystyrene as measured by gel permeation chromatography, Mw/Mn. In this case, if the specific hydroxystyrene copolymer has an Mw less than 2,000, the composition tends to have low film-forming properties and have a low sensitivity as a resist. If on the othe
Kai Toshiyuki
Kusumoto Shirou
Ohta Yoshihisa
Wang Yong
Ashton Rosemary
JSR Corporation
Kelber Steven B.
Piper Rudnick LLP
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