Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Electron beam imaging
Reexamination Certificate
2000-05-10
2003-06-10
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Electron beam imaging
C430S270100, C430S325000, C430S326000, C430S910000, C430S942000, C430S966000
Reexamination Certificate
active
06576400
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a positive-working radiation-sensitive composition which is used to produce semiconductor integrated circuits, masks for lithography and the like.
FIELD OF INVENTION
In recent years, in fields such as the production of semiconductor circuits and masks for lithography, in order to achieve ever finer patterns as densities of circuits are increased, still higher degrees of resolution have been demanded of the resist materials, and it has become necessary to be able to carry out sub-quarter micron (<0.25 &mgr;m) pattern processing at high sensitivity. With lithography of the kind carried out hitherto which employs radiation sources of comparatively long wavelength, such fine processing is difficult, and so lithography employing still shorter wavelength deep ultraviolet, X-rays or electron beams is being investigated, and resists suitable for such radiation sources are being demanded.
Recently, as known resist materials with the high sensitivity and high resolution for such radiation sources, chemically-amplified resists have been actively investigated. Chemically-amplified resists are resists employing a mechanism whereby an acid is generated in the exposed regions by the action of a photoacid generator and, by the catalytic action of this acid, the solubility of the exposed regions is altered. Amongst such chemically-amplified resists, as resin components for showing comparatively good resist properties there are already known resists employing resins where the groups with alkali affinity in an alkali-soluble resin are protected by a t-butyl ester group or t-butoxycarbonyl group (JP-B-2-27660), resins where protection is carried out in the same way with silyl groups (JP-B-3-44290), resins where protection is carried out in the same way with ketal groups (JP-A-7-140666), resins where protection is carried out in the same way with acetal groups (JP-A-2-161436 and JP-A-5-249682), and resins containing a (meth)acrylic acid component (JP-A-4-39665), etc. However, resolution and sensitivity have a mutually conflicting relationship, and there has been the disadvantage that, in obtaining the resolution to carry out sub-quarter micron pattern processing, the sensitivity is inadequate.
SUMMARY OF THE INVENTION
This invention relates to a positive-working radiation-sensitive composition which is characterized in that it is a positive-working radiation-sensitive composition containing
(1) polymer A, the solubility of which in aqueous alkali solution is increased by the action of acid (hereinafter referred to as polymer A), and/or
(2) alkali-soluble polymer B (hereinafter referred to as polymer B) and a compound which has the effect of suppressing the alkali solubility of said polymer and the suppression effect of which is lowered or eliminated by the action of acid (hereinafter referred to as dissolution inhibitor C), and
(3) a compound which generates acid by irradiation with radiation,
and the ease of occurrence of main chain scission of said polymer A and/or B by means of radiation is greater than that of polymethyl methacrylate.
DETAILED DESCRIPTION OF THE INVENTION
It has been discovered that, by means of the positive-working radiation-sensitive composition of the present invention which employs polymer where main chain scission readily occurs as a result of irradiation with radiation, there is obtained a synergistic effect between the chemical amplification mechanism and the main chain scission mechanism, and high resolution and high sensitivity can be realized. Below, the details are explained.
Polymer A employed in the positive-working radiation-sensitive composition of the present invention is a polymer which is normally insoluble or sparingly soluble in aqueous alkali solution, but by the action of acid its solubility in aqueous alkali solution is increased and it becomes soluble. Polymer B is a polymer which is soluble in aqueous alkali solution but, by the addition of dissolution inhibitor C, its solubility in aqueous alkali solution is reduced and, normally, it is insoluble or sparingly soluble. In addition to such solubility characteristics in terms of aqueous alkali solution, polymer A and B possess the characteristic that the ease of occurrence of main chain scission by means of radiation is greater than that of polymethyl methacrylate. Furthermore, polymer of main chain scission efficiency value Gs at least 2.5 is more favourably employed. More preferably, the Gs value is at least 3.0 and no more than 50. If the Gs value is less than 2.5, then adequate sensitivity and resolution are not obtained, while if the Gs value is greater than 50 the polymer stability is no longer adequate.
The Gs value expresses the number of main chain scissions per 100 eV irradiation energy of an electron beam of acceleration voltage 20 kV, and the following relation is established between the molecular weight of the polymer before and after irradiation.
1/
Mn*=
20,000
GsD/
100
eN
A
+1/
Mn
Here, D is the exposure dose (C/g) per 1 g of polymer; e is the charge on an electron; N
A
is Avogadro's number; Mn* is the number average molecular weight following exposure, as determined by GPC; and Mn is the number average molecular weight before exposure, as determined by GPC. From this formula, if 1/Mn*, which is the reciprocal of the molecular weight of the polymer following exposure as determined by GPC, is plotted against the exposure dose D, it is clear that the slope is 200 Gs/eN
A
, and so Gs can be calculated.
Polymer B employed in the present invention contains acidic functional groups which ordinarily manifest alkali solubility. As the acidic functional groups, there may be used phenolic hydroxyl groups, carboxyl groups, sulphoxy groups or the like. Polymer containing monomer units represented by general formula (1) may be cited as a particularly suitable example of polymer B (hereinafter these monomer units are simply referred to as monomer units B).
Here, R
1
represents a halogen atom or cyano group, and R
2
represents a hydrogen atom or a C
2
to C
12
organic group with an acidic functional group. As specific examples of the halogen atom represented by R
1
, there are the fluorine atom, chlorine atom and bromine atom. As specific examples of the organic group with an.acidic functional group, represented by R
2
, there are the carboxylmethyl group, p-hydroxyphenyl group, p-carboxyphenyl group and the like. As R
1
, a halogen atom is particularly preferably used.
Polymer A employed in the positive-working radiation-sensitive composition of the present invention can be obtained, for example, by replacing the hydrogen atoms of the acidic functional groups contained in aforesaid polymer B (the hydrogen atoms in the case where R
2
is hydrogen) by one or more type of acid labile group.
Examples of acid labile groups are the methoxymethyl group, methylthiomethyl group, ethoxymethyl group, ethylthiomethyl group, methoxyethoxymethyl, benzyloxymethyl group, benzylthiomethyl group, phenacyl group, bromophenacyl group, methoxyphenacyl group, methylthiophenacyl group, &agr;-methylphenacyl, cyclopropylmethyl group, benzyl group, diphenylmethyl group, triphenylmethyl group, bromobenzyl group, nitrobenzyl group, methoxybenzyl group, methylthiobenzyl group, ethoxybenzyl group, methoxycarbonylmethyl group, ethoxycarbonylmethyl group, n-propoxycarbonylmethyl group, isopropoxycarbonylmethyl group, n-butoxycarbonylmethyl group, t-butoxycarbonylmethyl group, propenyl group, 1-methoxyethyl group, 1-methylthioethyl group, 1,1-dimethoxyethyl group, 1-ethoxyethyl group, 1-ethylthioethyl group, 1,1-diethoxyethyl group, 1-phenoxyethyl group, 1-phenylthioethyl group, 1,1-diphenoxyethyl group, 1-benzyloxyethyl group, 1-benzylthioethyl group, 1-cyclopropylethyl group, 1-phenylethyl group, 1,1-diphenylethyl group, 1-methoxycarbonylethyl group, 1-ethoxycarbonylethyl group, 1-n-propoxycarbonylethyl group, 1-isopropoxycarbonylethyl group, 1-n-butoxycarbonylethyl group, 1-t-butoxycarbonylethyl group, isopropyl group, s-butyl group, t-butyl group, 1,1-dimeth
Chu John S.
Toray Industries Inc.
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