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
1998-08-14
2001-05-22
Chu, John S. (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, C430S910000
Reexamination Certificate
active
06235446
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radiation sensitive resin composition and, more specifically, a radiation sensitive resin composition useful as a resist suitable for microfabrication using ultraviolet rays, far ultraviolet rays, X-rays, or various radioactive rays such as charged particle rays.
2. Description of the Background Art
In the field of microfabrication, typically in the manufacture of elements for integrated circuits, a rapidly progressing trend is to define design rules for the lithographic process with finer dimensions, with the aim of achieving higher degrees of circuit integration. Accordingly, development of a lithographic process that is capable of microfabrication with precision for a line width of 0.5 &mgr;m or less has been vigorously pursued in recent years.
However, drawing such a minute pattern as above with a high enough precision is very difficult with the conventional process based on visible rays (wavelength: 700-400 nm) or near ultraviolet rays (400-300 nm). For this reason, lithographic processes based on radiation with a shorter wavelength (300 nm or less) that is capable of achieving a greater focal depth and establishing finer design rules are being proposed.
As the lithographic processes using such short wavelength radiation, for example, methods based on a KrF excimer laser (wavelength: 248 nm), an ArF excimer laser (wavelength: 193 nm), X-rays such as synchrotron radiation, or charged particle radiation such as electron beams are being proposed. In addition, International Business Machines, Inc. (“IBM”) has proposed a “chemically amplified resist” as a high-resolution resist suitable for use with these short wavelength radioactive rays. Improvements in the chemically amplified resist are now being actively pursued.
With a chemically amplified resist, acid is generated when radioactive rays irradiate (a process hereinafter termed “exposure”) the photoacid generator contained in such a resist. The acid thus generated acts as a catalyst to trigger chemical reactions such as alteration of polarity, cleavage of chemical bonds, or crosslinking within the exposed part of the resist film. The resulting change in solubility characteristics of the exposed part to a developing solution can then be utilized to develop a pattern.
Among the existing chemically amplified resists, those known for relatively good resist performance include resists based on resins in which (1) an alkali affinitive group in the alkali soluble resin is protected by a t-butyl ester group or t-butoxycarbonyl group (see Japanese Patent Publication No. 27660/1990 or EP 102450 A) ; (2) an alkali affinitive group in the alkali soluble resin is protected by a ketal group (see Japanese Patent Application Laid-Open No. 140666/1995); and (3) an alkali affinitive group in the alkali soluble resin is protected by an acetal group (see Japanese Patent Application Laid-Open No. 161436/1990 and Japanese Patent Application Laid-Open No. 249682/1993).
However, it has been pointed out that each of these chemically amplified resists has a peculiar drawback, giving rise to various obstacles for actual application to microfabrication, particularly with a critical design dimension of 0.25 &mgr;m or less.
Specifically, various known chemically amplified resists have to be adopted in each narrowly defined use. Although good resolution with satisfactory appearance is generally available for line-and-space patterns or isolated patterns, resolution is often insufficient for contact holes. Further, popularization of multimedia information processing in recent years has necessitated that designs of semiconductor devices become more diversified. This, coupled with a requirement for a cost reduction to cope with the rapid price decrease in the marketplace, has created a strong demand for the development of a chemically amplified resist which is capable of resolving not only the usual line-and-space patterns but also isolated patterns as well as contact hole patterns with satisfactory appearance and therefore is useful in multiple applications.
The present invention has been made in consideration of the above circumstances and as a result of detailed research and examination applied to the constituents of the chemically amplified resists.
Accordingly, an object of the present invention is to provide a radiation sensitive resin composition suitable as a chemically amplified resist that has efficient response to various radioactive rays. Such a resist is capable of resolving any of line-and-space patterns, isolated patterns, and contact hole patterns with satisfactory appearance and resolution, and therefore is applicable to multiple uses.
SUMMARY OF THE INVENTION
According to the present invention, the above object can be achieved by a radiation sensitive resin composition comprising (A) a copolymer possessing three types of recurring units represented by the formulas (1), (2), and (3),
wherein R
1
indicates a hydrogen atom or methyl group,
wherein R
2
indicates a hydrogen atom or methyl group,
wherein R
3
indicates a hydrogen atom or methyl group, and R
4
, a monovalent group having an alicyclic structure containing 7 or more carbon atoms, the copolymer turning alkali soluble in the presence of acid, and (B) a photosensitive acid generator.
Other objects, features and advantages of the invention will hereinafter become more readily apparent from the following description.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
Copolymer (A)
The Copolymer (A) to be used in the present invention comprises a copolymer possessing three types of recurring units, i.e. a unit of the formula (1) given above (hereinafter referred to as “Recurring unit 1”), a unit of the formula (2) above (“Recurring unit 2”), and a unit of the formula (3) above (“Recurring unit 3”). The copolymer turns alkali soluble in the presence of acid.
The Recurring unit 1 may only comprise either a type wherein R
1
is a hydrogen atom or one wherein R
1
is a methyl group, or may also comprise a mixture of these unit types.
The percentage content of the Recurring unit 1 in the total recurring unit content in the Copolymer (A) usually is 10 to 75 mol %, preferably 20 to 70 mol %, and even more preferably, 40 to 70 mol %. If the above content is less than 10 mol %, the resist pattern is likely to peel off due to lack of adhesiveness to the substrate. If it is over 75 mol %, on the other hand, it will reduce the differential between the dissolution rates for the alkaline developing solution for the exposed part and unexposed part, thereby causing a declining trend in resolution.
Next, the Recurring unit 2 may only comprise either a type wherein R
2
is a hydrogen atom or one wherein R
2
is a methyl group, or may also comprise a mixture of these unit types.
The percentage content of the Recurring unit 2 in the total recurring unit content in the Copolymer (A) usually is 10 to 70 mol %, preferably 15 to 60 mol %, and even more preferably, 20 to 50 mol %. If the above content is less than 10 mol %, the dissolution rate of the exposed part to the alkaline developing solution could become too low, making the pattern formation insufficient. If it is over 70 mol %, on the other hand, the quantity of benzene rings in Copolymer (A) becomes insufficient, thereby causing a declining trend in dry etching resistance.
Next, the Recurring unit 3 may only comprise either a type wherein R
3
is a hydrogen atom or one wherein R
3
is methyl group, or may also comprise a mixture of these unit types.
Further, as R
4
in the Recurring unit 3 a monovalent group having an alicyclic structure containing 7 to 15 carbon atoms is preferred. As such a preferred monovalent group with an alicyclic structure, for example, groups represented by the following formulas (4) through (23) can be mentioned:
wherein R
5
indicates either a hydrogen atom or methyl group,
wherein R
6
indicates a hydrogen atom or methyl group, and R
7
, a hydrogen atom or hydroxymethyl group,
wherein R
8
and R
9
indicate a hydrog
Ikemura Toshiaki
Iwanaga Shin-ichiro
Kobayashi Eiichi
Tanabe Takayoshi
Chu John S.
JSR Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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