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
2001-11-30
2004-06-15
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, C430S914000
Reexamination Certificate
active
06749989
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a novel chemical-amplification positive-working photoresist composition suitable for patterning light-exposure with light having a wavelength of 200 nm or shorter. More particularly, the invention relates to a chemical-amplification positive-working photoresist composition capable of giving a finely patterned resist layer with little line slimming.
It is an established formulation of chemical-amplification photoresist compositions that the composition is compounded with a resinous ingredient having high transparency to the KrF excimer laser beams of 248 nm wavelength such as a polyhydroxystyrene resin optionally substituted for the hydroxyl groups by acid-dissociable solubility-reducing groups.
Along with the trend in the technology of semiconductor devices toward more and more increased density of integration, however, the subject matter of development works relative to the photolithographic patterning technology is currently establishment of a patterning process by using ArF excimer laser beams of 193 nm wavelength. When the patterning exposure is conducted with such a short-wavelength light, the hydroxystyrene-based polymeric resinous ingredient compounded in the photoresist compositions can no longer be satisfactory because transparency of the resin to the 193 nm wavelength lights is not high enough due to the benzene rings contained in the polymeric molecular structure.
With an object to solve this problem, a great number of proposals are made for a chemical-amplification positive-working photoresist composition compounded with a polymer comprising the monomeric units of a (meth)acrylic acid ester having, in place of the benzene ring, an adamantyl ring as a part of the monomeric units constituting the polymeric structure (see Japanese Patent No. 2881969 and Japanese Patent Kokai 5-346668, 7-234511, 9-73173, 9-90637, 10-161313, 10-319595 and 11-12326).
A proposal was made recently in Japanese Patent Kokai 2000-137327 for a chemical-amplification positive-working photoresist composition suitable for patterning with ArF excimer laser beams or KrF excimer laser beams and capable of giving a finely patterned resist layer with excellent sensitivity and pattern resolution and exhibiting good adhesion to the substrate surface and high resistance against dry etching, in which the resinous ingredient is a copolymer of (meth)acrylonitrile and 3-hydroxy-1-adamantyl ester of (meth)acrylic acid.
In view of further narrowing of the design rule required in the modern manufacturing process of semiconductor devices, a pattern resolution not exceeding 150 nm or in the vicinity of 100 nm must be accomplished so that upgrading of the photoresist compositions is eagerly desired relative to the pattern resolution. In addition, a solution is desired for the problem of line slimming which is a phenomenon that slimming of the line width of a patterned resist layer proceeds during inspection of the resist pattern by using a scanning electron microscope (SEM). According to the report appearing in Journal of Photopolymer Science Technology, volume 13 (4), page 497 (2000), the mechanism leading to this phenomenon of line slimming is that the crosslinking reaction of the resinous ingredient in the line-patterned resist layer proceeds as promoted by the electron beam irradiation in the SEM.
While the influence of this line slimming on the photolithographic patterning process in the manufacture of semiconductor devices is increased so much as the fineness of the design rule therein is increased and solution of this problem is eagerly sought, none of the conventional chemical-amplification positive-working photoresist compositions can meet this requirement.
SUMMARY OF THE INVENTION
The present invention accordingly has an object, in view of the above described problems in the prior art, to provide a novel and improved chemical-amplification positive-working photoresist composition capable of giving a finely patterned photoresist layer with little line slimming by the patterning exposure to light of a 200 nm or shorter wavelength such as ArF excimer laser beams in addition to the excellent sensitivity and pattern resolution as well as good adhesion to the substrate surface and high resistance against dry etching.
Thus, the positive-working photoresist composition provided by the present invention comprises, as a uniform solution in an organic solvent:
(A) a resinous compound capable of being imparted with increased solubility in an aqueous alkaline solution by interaction with an acid;
(B) a radiation-sensitive acid generating compound capable of generating an acid by irradiation with a radiation;
(C) an organic solvent,
the component (A) being a copolymer consisting of the monomeric units of
(a1) 2-alkyl-2-adamantyl(meth)acrylate units,
(a2) (meth)acrylate ester units each having an acid-dissociable 2-oxooxapentyl group, and
(a3) 1-hydroxyadamantyl(meth)acrylate units, in a specified molar proportion.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The component (A) in the inventive photoresist composition is a resinous compound capable of being imparted with increased solubility in an aqueous alkaline solution when interacted with an acid. A typical resinous compound to meet this definition is a homopolymer of copolymer comprising the monomeric units derived from an acrylate or methacrylate ester substituted by acid-dissociable solubility-reducing groups. When interacted by an acid, the ester-forming groups in the monomeric units are dissociated to regenerate the carboxyl groups of the (meth)acrylic acid units so that the resin is imparted with increased alkali solubility.
The resinous compound as the component (A) in the inventive photoresist composition characteristically comprises three different types of the monomeric units including (a1) the monomeric units derived from a 2-alkyl-2-adamantyl(meth)acrylate, (a2) the monomeric units derived from a (meth)acrylate having a 2-oxooxapentyl group in the molecule and (a3) the monomeric units derived from 1-hydroxyadamantyl(meth)acrylate.
The monomeric units (a1) and (a2) in the resinous compound as the component (A) contribute to the improvement of the resist layer relative to sensitivity, pattern resolution, resistance against dry etching and adhesion to the substrate surface. The monomeric units (a3) as combined with the units (a1) and (a2) have an effect of decreasing the line slimming of the patterned resist layer.
The monomeric unit (a1) is represented by the general formula:
in which R
1
is a hydrogen atom or a methyl group and R
2
is an alkyl group having 1 to 4 carbon atoms such as methyl, ethyl and propyl groups. The acid-dissociability of the ester-forming adamantyl group is increased as the number of carbon atoms in the alkyl group R
2
is increased so that the sensitivity of the photoresist composition is increased. Since the 2-alkyladamantyl group is dissociated by interaction with an acid generated from the component (B) to regenerate the carboxyl group of the (meth)acrylic acid by irradiating the photoresist layer with a radiation, the resist layer is imparted with increased alkali-solubility in the exposed areas while the resist layer in the unexposed areas remains alkali-insoluble to retain excellent resistance against dry etching.
The monomeric unit (a2) of the second type is a (meth)acrylate ester unit represented by the general formula:
in which R
1
has the same meaning as defined above and of which the ester-forming group is a 2-oxooxapentyl group forming an ester linkage at the 4-position. The 2-oxooxapentyl group is also dissociable by interaction with an acid and behaves in a similar way to the above-described adamantyl groups in the exposed and unexposed areas of the photoresist layer. The 2-oxooxapentyl-containing monomeric units (a2) play a role to improve the sensitivity and pattern resolution of the photoresist layer along with the effect of increasing the adhesion of the resist layer to the substrate surface.
The monomeric unit (a3) of the third type is a unit
Fujimura Satoshi
Hada Hideo
Iwai Takeshi
Sasaki Kazuhito
Ashton Rosemary
Tokyo Ohka Kogyo Co. Ltd.
Wenderoth Lind & Ponack LLP
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