Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
2002-01-03
2004-06-22
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S313000, C430S311000, C430S270100, C430S907000, C430S967000
Reexamination Certificate
active
06753132
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pattern formation method and a pattern formation material, and more particularly, it relates to a pattern formation method 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 shorter than a 180 nm band and a pattern formation material used in the pattern formation method.
Currently, in fabrication of a mass storage semiconductor integrated circuit, such as a 64 Mbit dynamic random access memory (DRAM) 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 lasing 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 wavelength 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, an electron beam (EB) and the like are being examined.
When the EB is used as the exposing light, however, the throughput is disadvantageously low, and hence, the EB is not suitable to mass production.
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), soft-X rays (of a wavelength of a 13, 11 or 5 nm band) and hard-X rays (of a wavelength shorter than a 1 nm band). In other words, a resist pattern is required to be formed by using exposing light of a wavelength shorter than a 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.
Chemical Formula A:
Chemical Formula B:
Chemical Formula C:
Now, a method for forming a resist pattern by using any of the aforementioned conventional chemically amplified resist materials and problems arising in the conventional method will be described with reference to
FIGS. 2A through 2D
.
First, as shown in
FIG. 2A
, the chemically amplified resist material is applied on a semiconductor substrate
1
by spin coating and the resultant is heated, so as to form a resist film
2
with a thickness of 0.3 &mgr;m. Thereafter, as shown in
FIG. 2B
, the resist film
2
is irradiated with a F
2
laser beam
4
through a mask
3
for pattern exposure. Thus, an acid is generated from the acid generator in an exposed portion
2
a
of the resist film
2
while no acid is generated in an unexposed portion
2
b
of the resist film
2
.
Next, as shown in
FIG. 2C
, the semiconductor substrate
1
is heated with a hot plate at, for example, 100° C. for 60 seconds.
Then, the resist film
2
is developed with an alkaline developer, thereby forming a resist pattern
5
.
However, as shown in
FIG. 2D
, the resist pattern
5
cannot be formed in a good pattern shape, and there remains much scum on the semiconductor substrate
1
. Such problems occur not only in using the F
2
laser beam as the exposing light but also in using any of the other light of a wavelength shorter than a 180 nm band.
Accordingly, a resist pattern cannot be practically formed by irradiating a resist film made from any of the aforementioned chemically amplified resist materials with light of a wavelength shorter than a 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 by using exposing light of a wavelength shorter than a 180 nm band with minimally producing scum.
The present inventors have studied the causes of the conventional problems occurring in using the conventional chemically amplified resist materials and have found the following:
First, the chemically amplified resist materials have high absorbance against light of a wavelength shorter than a 180 nm band. For example, a resist film with a thickness of 100 nm made from the chemically amplified resist material including a polyhydroxystyrene derivative as a principal constituent has transmittance of 20% at most against a F
2
laser beam (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 shorter than a 180 nm band. As a result, it has been found that the transmittance of a chemically amplified resist material against light of a wavelength shorter than a 180 nm band can be improved when a unit of a polyhydroxystyrene derivative having hexafluoroisopropyl alcohol ((CF
3
)
2
C—OH) on its side chain is introduced into a base polymer.
Furthermore, when any of the aforementioned chemically amplified resist materials, particularly the resist material including a polyhydroxystyrene derivative, is irradiated with light of a wavelength shorter than a 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 á-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 a 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 á-position of the principal chain of the polymer.
Moreover, since the polymer has an aromatic ring on a side chain thereof, the dry etching resistance and the heat resistance of the resist film can be improved.
In addition, when hexafluoroisopropanol is introduced into an aromatic ring of the polyhydroxystyrene derivative, the transmittance against light of a wavelength shorter than a 180 nm band can be improved, and the solubility in a developer of a hydroxyl group from which a protecting group has been released can be improved. As a result, the contrast in the solubility between an exposed portion and an unexposed portion of the resist film can be improved.
The present invention was devised on the basis of the aforementioned findings, and specifically provides pat
Endo Masayuki
Kishimura Shinji
Sasago Masaru
Shirai Masamitsu
Tsunooka Masahiro
Chacko-Davis Daborah
Huff Mark F.
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