Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
1997-06-27
2001-06-05
Duda, Kathleen (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S395000, C430S950000
Reexamination Certificate
active
06242160
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a patterning method of a chemical amplification type resist film. More specifically, the invention relates to a patterning method of a chemical amplification type resist film for a far ultraviolet radiation, to be formed on an antireflection film.
2. Description of the Prior Art
In a lithographic process as one of a fabrication process of a semiconductor element, at first, a silicon oxide film, a BPSG film, a silicon nitride film, a polycrystalline silicon film, various silicide film, a metal film such as an aluminum or an aluminum alloy film and the like, are formed on a silicon substrate. Next, a resist film is applied on the film. The resist film is exposed in a desired pattern, and then developed. Subsequently, the film which should be patterned is etched with taking the resist film patterned into the desired pattern as a mask.
In such lithographic process, if the film to be patterned is the polycrystalline silicon film, the silicide film, the metal film such as aluminum or aluminum alloy film and the like, reflection of a light at an interface between the resist film and the film to be patterned becomes large. Accordingly, the shape of the pattern of the resist film after development is significantly degraded by reflection of the light. Therefore, in the prior art, in order to reduce reflection index at the interface between the film to be patterned and the resist film, various methods for forming an antireflection films between the resist film and the film to be patterned have been proposed (see Japanese Unexamined Patent Publications (Kokai) Nos. Showa 59-6540, Showa 62-46529 and Heisei 1-241125).
Hereinafter, a fabrication process of the semiconductor device disclosed in Japanese Unexamined Patent Publication No. Showa 59-6540 will be referred to as “first prior art”, an etching method of the film to be patterned disclosed in Japanese Unexamined Patent Publication No. Showa 62-46529 will be referred to as “second prior art”, and a fabrication process of the semiconductor device disclosed in Japanese Unexamined Patent Publication No. Heisei 1-241125 will be referred to as “third prior art”.
FIG. 1
is a section showing the fabrication process of the semiconductor device in the first prior art. An oxide layer
202
a
is formed on the surface of a semiconductor substrate
201
a
. A metal film (film to be patterned)
213
of 0.2 to 1 &mgr;m thick, is formed on the surface of the oxide layer
202
a
. Next, a layer semi-permeable to a light to be used in lithography, such as an antireflection film
221
a
of silicon nitride, for example, is grown on the surface of the metal film
213
by way of plasma excited vapor deposition (PECVD) method. Then, a resist film
231
a
is formed on the surface of the antireflection film
221
a.
Subsequently, above these, a photo-mask
261
formed with a desired pattern of light shielding layer
262
, is arranged. Next, a light beam
241
is irradiated on the resist film
231
a
from the upper side of the photo mask
261
. Then, the resist film
231
a
is exposed by a light
241
past through the photo mask
261
in the region where the light shielding layer
262
is not formed.
At this time, a part of the light inciding in the resist film
231
a
is reflected at the surface of the antireflection film
221
a
. The remaining light therefore which passes through the antireflection film
221
a
is reflected at the surface of the metal film
213
, and then discharged from the surface of the antireflection film
221
a
. In the first prior art, the antireflection film
221
a
is selected so that an intensity of discharged light (reflected light) becomes less than or equal to 30% relative to an intensity of an incident light. Thus, photo-sensitivity of the discharged light relative to the resist film
213
can be lowered to be ignorably low. Accordingly, by the antireflection film
221
a
, degradation of pattern of the resist film by the reflected light by the metal film
213
can be successfully prevented.
FIG. 2
is a section showing an etching method of the film to be patterned in the second prior art. At first, an oxide layer
202
b
and a polycrystalline silicon layer (film to be patterned)
214
are sequentially formed on the surface of the silicon substrate
201
b
. Next, an antireflection film
221
b
of silicon nitride is formed on the surface of the polycrystalline silicon layer. Then, a resist film
231
b
is deposit on the surface of the antireflection film
221
b
. Thereafter, the resist film
231
b
is selectively exposed by irradiating a light on the resist film
231
b
in the desired pattern.
In the second prior art, the material of the antireflection film is selected so that a refractive index n of the light in the antireflection film
221
b
becomes greater than a refractive index n, of the light in the resist film
231
b
and smaller than a refractive index n
2
of the light in the antireflection film
221
b
. The refractive index of the light is defined as, the reflected light by the antireflection film
221
b
and the polycrystalline silicon layer
214
is interfered by incident light to the antireflection film
221
b
. Thus, amplitude of the discharged light can be made smaller. Accordingly, similarly to the first prior art, degradation of the pattern shape of the resist film
231
b
by the reflected light by the polycrystalline silicon layer
214
, can be successfully prevented.
FIG. 3
is a section showing a fabrication process of the semiconductor device in the third prior art. At first, a field oxide layer
203
is selectively formed on the surface of a silicon substrate
201
c
. Then, a gate oxide layer
204
is formed on the surface of an element region defined by the field oxide layer
203
. Subsequently, on these surfaces, an undercoat layer (film to be patterned)
215
of tungsten silicide is formed. Then, an antireflection film
221
c
of silicon nitride is formed on the surface of the undercoat layer
215
. A resist film
231
c
is formed on the surface of the antireflection film
221
c
. Subsequently, similarly to the foregoing first and second prior arts, the resist film
231
c
is exposed by irradiating light on the resist film
231
c
in the desired shape.
In the third prior art, material of the undercoat layer
215
and the antireflection film
221
c
and thickness of the antireflection film
221
c
and so forth are selected so that an incident light to the antireflection film
221
c
and a reflected light from the antireflection film
221
c
and from the undercoat layer
215
cause interference to make the effective reflection index of the undercoat layer minimum. Accordingly, it can be successfully prevent degradation of the pattern shape of the resist film
231
c
by the reflected light.
On the other hand, the first to third prior art as set forth above, are directed to form a novolac type resist film to be used for a light (g ray) having a wavelength of 436 nm or a light (i ray) having a wavelength of 365 nm. This novolac type resist film shows color degradation property (bleaching characteristics).
However, a chemical amplification type resist film to be used for exposure by far ultraviolet radiation (KrF excimer laser or ArF excimer laser) having wavelength of 248 nm or 193 nm, in either positive type or negative type, generally does not have color degradation property. When the chemical amplification type resist film for far ultraviolet radiation is used, if a reflection index of the light at the interface between the resist film and the antireflection film is too low, degradation may be caused on the sectional configuration of the patterned resist film. Namely, if the resist film is the positive type, the sectional configuration of the patterned resist film becomes a tapered form or have non-uniformly spread baseboard portion. On the other hand, if the resist film is the negative type, the sectional configuration of the patterned resist film becomes a reversed taper form or is formed into a shape having non
Fukuzawa Shinichi
Kasama Kunihiko
Duda Kathleen
NEC Corporation
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