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
2001-03-06
2003-06-10
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, C430S909000, C430S910000, C430S914000, C430S945000
Reexamination Certificate
active
06576398
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to pattern formation material and method. More particularly, it relates to a pattern formation method employed for forming a resist pattern, used for forming a semiconductor device or a semiconductor integrated circuit on a semiconductor substrate, by using exposing light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band, and a pattern formation material used in the same.
Currently, in fabrication of a mass storage semiconductor integrated circuit, such as a 64 Mbit dynamic random access memory (RAM) and a logic device or a system LSI with a 0.25 &mgr;m through 0.15 &mgr;m rule, a resist pattern is formed by using a chemically amplified resist material including a polyhydroxystyrene derivative and an acid generator as principal constituents with KrF excimer laser (of a wavelength of a 248 nm band) used as exposing light.
Moreover, for fabrication of a 256 Mbit DRAM, a 1 Gbit DRAM or a system LSI with a 0.15 &mgr;m through 0.13 &mgr;m rule, 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.
The resist material including a polyhydroxystyrene derivative as a principal constituent has high absorbance against light of a wavelength of a 193 nm band because of an aromatic ring included therein. Therefore, exposing light of a 193 nm band cannot uniformly reach the bottom of a resist film, and hence, a pattern cannot be formed in a good shape. Accordingly, the resist material including a polyhydroxystyrene derivative as a principal constituent cannot be used when the ArF excimer laser is used as the exposing light.
Therefore, a chemically amplified resist material including, as a principal constituent, a polyacrylic acid derivative or a polycycloolefin derivative having no aromatic ring is used when the ArF excimer laser is used as the exposing light.
On the other hand, as exposing light for a pattern formation method capable of coping with high resolution, X rays, an electron beam (EB) and the like are being examined.
When the X rays are used as the exposing light, however, there are a large number of problems in the exposure system and preparation of a mask. Also, when the EB is used as the exposing light, the throughput is disadvantageously low, and hence, the EB is not suitable to mass production. Thus, neither the X rays nor the EB is preferred as the exposing light.
Accordingly, in order to form a resist pattern finer than 0.10 &mgr;m, it is necessary to use exposing light of a wavelength shorter than that of the ArF excimer laser, such as Xe
2
laser (of a wavelength of a 172 nm band), F
2
laser (of a wavelength of a 157 nm band), Kr
2
laser (of a wavelength of a 146 nm band), ArKr laser (of a wavelength of 134 nm band), Ar
2
laser (of a wavelength of a 126 nm band) and soft-X rays (of a wavelength of a 13, 11 or 5 nm band). In other words, a resist pattern is required to be formed by using exposing light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band.
Therefore, the present inventors have formed resist patterns by conducting pattern exposure using F
2
laser (of a wavelength of a 157 nm band) on resist films formed from conventionally known chemically amplified resist materials respectively including a polyhydroxystyrene derivative represented by Chemical Formula A, a polyacrylic acid derivative represented by Chemical Formula B and a polycycloolefin derivative represented by Chemical Formula C.
Now, a pattern formation method using any of the aforementioned conventional chemically amplified resist materials and problems of the method will be described with reference to
FIGS. 2A through 2D
.
First, as is shown in
FIG. 2A
, the chemically amplified resist material is applied on a semiconductor substrate
1
by spin coating and the resultant substrate is heated, thereby forming a resist film
2
with a thickness of 0.3 &mgr;m. Then, as is shown in
FIG. 2B
, the resist film
2
is subjected to pattern exposure by irradiating with a F
2
laser beam
4
through a mask
3
. In this manner, an acid is generated from the acid generator in an exposed portion
2
a
of the resist film
2
but no acid is generated in an unexposed portion
2
b
of the resist film
2
.
Then, as is shown in
FIG. 2C
, the semiconductor substrate
1
is heated with a hot plate at, for example, 100° C. for 60 seconds.
Next, the resist film
2
is developed with an alkaline developer, thereby forming a resist pattern
5
.
However, as is shown in
FIG. 2D
, the resist pattern
5
has a defective pattern shape, and much scum remains on the semiconductor substrate
1
. Such problems occur not only in using the F
2
laser as the exposing light but also in using another light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band.
Accordingly, a resist pattern cannot be practically formed by irradiating a resist film formed from any of the aforementioned chemically amplified resist materials with light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band.
SUMMARY OF THE INVENTION
In consideration of the aforementioned conventional problems, an object of the invention is forming a resist pattern in a good pattern shape with minimally producing scum by using exposing light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band.
The present inventors have studied the causes of the conventional problems occurring in using the aforementioned conventional chemically amplified resist materials, and have found the following:
First, the conventional chemically amplified resist materials have high absorbance against light of a wavelength of a 1 nm through 180 nm band. For example, a resist film formed from the chemically amplified resist material including a polyhydroxystyrene derivative as a principal constituent and having a thickness of 100 nm has transmittance of 20% at most against the F
2
laser (of a wavelength of a 157 nm band). Therefore, various examination has been made on means for improving the transmittance of a chemically amplified resist material against light of a wavelength of a 1 nm through 180 nm band. As a result, the transmittance of a chemically amplified resist material against light of a wavelength of a 1 nm through 180 nm band can be improved by introducing a unit of a polymer having a cyano group (—C≡N) on its side chain into a base polymer of the chemically amplified resist material.
Furthermore, when the aforementioned chemically amplified resist materials, particularly the resist material including a polyhydroxystyrene derivative, are irradiated with light of a wavelength of a 1 nm through 180 nm band, a reaction is caused regardless of the function of an acid, so that a hydrogen atom bonded to carbon located at the &agr;-position of the principal chain of the polymer can be released and that polymer radicals from which the hydrogen atoms are released can bond to each other to be crosslinked. As a result, the solubility of an exposed portion of the resist film in a developer is degraded. Therefore, means for preventing the crosslinking reaction of the principal chains of the polymer of the chemically amplified resist material has been variously studied. As a result, it has been found that the crosslinking reaction of the principal chains can be avoided by substituting an alkyl group or a chlorine atom for a hydrogen atom located at the &agr;-position of the principal chain of the polymer.
Moreover, when a cyano group is introduced to a side chain of the polymer, the cyano group interacts with a hydroxyl group based on a hydrogen bond. Therefore, the dry etching resistance and the heat resistance of the resist film can be improved, and an unexposed portion of the resist film can be more effectively prevented from dissolving in a developer, so as to improve the contrast between the exposed portion and the unexposed portion.
The present invention was devised on the basis of the aforem
Kishimura Shinji
Sasago Masaru
Shirai Masamitsu
Tsunooka Masahiro
Ashton Rosemary
Lee Sin J.
Matsushita Electric - Industrial Co., Ltd.
Nixon & Peabody LLP
Studebaker Donald R.
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