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
2000-06-13
2003-03-11
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
C430S326000, C430S905000, C430S910000
Reexamination Certificate
active
06531259
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pattern formation method for forming a resist pattern by irradiating a resist film with exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band, and a pattern formation material to be used in the same.
Currently, in fabrication of a large scale semiconductor integrated circuit, such as a 64 Mbit dynamic random access memory (DRAM), a logic device with a 0.25 &mgr;m through 0.18 &mgr;m rule and a system LSI including such a memory and a device, a resist pattern is formed by subjecting a chemically amplified resist including a polyhydroxystyrene derivative and an acid generator to pattern exposure using KrF excimer laser (of a wavelength of a 248 nm band).
Moreover, for fabrication of a large scale integrated circuit, such as a 256 Mbit DRAM and a 1 Gbit DRAM with a 0.15 &mgr;m through 0.13 &mgr;m rule and a system LSI including such a memory, a pattern formation method using, as exposing light, ArF excimer laser operated at a shorter wavelength (of a 193 nm band) than the KrF excimer laser is now under development.
In the chemically amplified resist including a polyhydroxystyrene derivative used in employing the KrF excimer laser, however, an aromatic ring included in the polyhydroxystyrene derivative has such high absorbance against light of a wavelength of a 193 nm band that the exposing light cannot uniformly reach the bottom of a resist film. Therefore, this chemically amplified resist cannot be suitably used when the ArF excimer laser is employed.
Therefore, a chemically amplified resist including a polyacrylic acid derivative having no aromatic ring is being studied as a resist to be used in employing the ArF excimer laser.
In order to form a pattern finer than 0.13 &mgr;m, however, it is necessary to use exposing light of a wavelength of a 1 through 180 nm band, namely, a wavelength shorter than that of the ArF excimer laser, such as Xe
2
excimer laser (of a wavelength of a 172 nm band), F
2
excimer laser (of a wavelength of a 157 nm band), Kr
2
excimer laser (of a wavelength of a 146 nm band), ArKr excimer laser (of a wavelength of a 134 nm band), Ar
2
excimer laser (of a wavelength of a 126 nm band) or soft-X rays (of a wavelength of a 13 nm, 11 nm or 5 nm band).
Therefore, the present inventors have formed resist patterns by conducting pattern exposure, using exposing light of a wavelength of a 1 through 180 nm band such as F
2
excimer laser, on resist films of known resist materials, specifically, a resist material including a polyhydroxystyrene derivative represented by Chemical Formula 1 and a resist material including a polyacrylic acid derivative.
Chemical Formula 1:
As a result, the resist pattern cannot be formed in a good pattern shape with a rectangular section and much scum (residue) remains on a substrate.
Accordingly, the conventional resist materials, namely, the resist materials used in employing KrF excimer laser or ArF excimer laser, cannot be used in a pattern formation method using exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band.
SUMMARY OF THE INVENTION
In consideration of the aforementioned conventional problem, an object of the invention is providing a pattern formation material and a pattern formation method for obtaining a resist pattern in a good shape by using exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band.
In order to achieve the object, the present inventors have variously examined the reason why a resist pattern has a defective sectional shape when formed from a conventional resist material, such as a resist material including a polyhydroxystyrene derivative as a main component, through pattern exposure using exposing light of a wavelength of a 1 through 180 nm band, resulting in finding the following: Since the exposing light of a wavelength of a 1 through 180 nm band has high energy, the polyhydroxystyrene derivative, that is, the main component of the resist material, is directly reacted with the exposing light. Therefore, hydrogen bonded to carbon located at the &agr;-position and constituting the main chain of the resist material is eliminated, so as to cause a crosslinking reaction for bonding polymer radicals from which hydrogen has been eliminated, which degrades the solubility of an exposed portion of the resist film in a developer.
Therefore, the inventors have variously studied on means for preventing the crosslinking reaction of the main chain of the resist material. As a result, it has been found that the crosslinking reaction of the main chain can be prevented by substituting an alkyl group for a hydrogen atom bonded to carbon located at the &agr;-position and constituting the main chain.
Furthermore, when an alkyl group is substituted for the hydrogen atom bonded to carbon located at the &agr;-position and constituting the main chain of the resist film, the main chain decomposes in an exposed portion of the resist film in development of the resist film with an alkaline developer. Moreover, it has been found that since the solubility of the exposed portion of the resist film in an alkaline developer can be thus improved, the dissolution contrast between an exposed portion and an unexposed portion can be improved so as to attain high resolution. The present invention was devised on the basis of these findings.
The first pattern formation material of this invention comprises a base polymer including a unit represented by the following General Formula 1:
General Formula 1:
wherein R
0
is an alkyl group; R
1
is a group that is decomposed through irradiation of light; R
3
and R
4
are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the first pattern formation material, an alkyl group is bonded to carbon located at the &agr;-position and constituting the main chain of the base polymer, and the alkyl group is never eliminated through irradiation of the exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band. Therefore, a crosslinking reaction of the main chain of the base polymer is never caused in an exposed portion of the resist film.
The second pattern formation material of this invention comprises a base polymer that includes a unit represented by the following General Formula 2 and is decomposed by an acid; and an acid generator for generating an acid through irradiation of light:
General Formula 2:
wherein R
0
is an alkyl group; R
2
is a group that is decomposed by an acid; and R
3
and R
4
are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the second pattern formation material, an alkyl group is bonded to carbon located at the &agr;-position and constituting the main chain of the base polymer, and the alkyl group is never eliminated through irradiation of the exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band. Therefore, the crosslinking reaction of the main chain of the base polymer is never caused in an exposed portion of the resist film.
The third pattern formation material of this invention comprises a base polymer including a first unit represented by the following General Formula 3 and a second unit represented by the following General Formula 4:
General Formula 3:
General Formula 4:
wherein R
0
is an alkyl group; R
1
is a group that is decomposed through irradiation of light; R
3
and R
4
are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon; at least one of R
5
and R
7
is an alkyl group and R
5
or R
7
that is not an alkyl group is hydrogen or a compound including hydrogen and carbon; and R
6
and R
8
are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the third pattern formation material, an alkyl group is bonded to carbon located at the &agr;-position and constituting the main chai
Katsuyama Akiko
Kishimura Shinji
Sasago Masaru
Ashton Rosemary
Nixon & Peabody LLP
Studebaker Donald R.
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