Drying and gas or vapor contact with solids – Apparatus – Sheet – web – or strand
Reexamination Certificate
2000-08-04
2002-11-19
Doerrler, William C. (Department: 3749)
Drying and gas or vapor contact with solids
Apparatus
Sheet, web, or strand
C034S060000, C034S218000, C034S220000, C034S224000, C034S232000, C034S221000, C428S403000, C428S426000, C428S620000, C428S627000
Reexamination Certificate
active
06481119
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method of forming a resist pattern, and more specifically, it relates to a method of forming a resist pattern employed for ion implantation. The present invention also relates to a method of manufacturing a semiconductor device including such a method of forming a resist pattern. The present invention further relates to an apparatus for removing an organic antireflection coating.
2. Description of the Prior Art
FIGS. 12
to
16
are sectional views of a semiconductor device showing parts of steps of a conventional method of manufacturing a semiconductor integrated circuit for illustrating a method of forming a resist pattern employed for ion implantation.
Referring to
FIG. 12
, a silicon substrate
102
formed with an isolation oxide film
101
is prepared.
Referring to
FIG. 13
, a photosensitive resist film
103
is formed on the silicon substrate
102
.
Referring to
FIG. 14
, the photosensitive resist film
103
is first exposed to exposure light
105
such as X-rays or ultraviolet rays through a mask pattern
104
.
Referring to
FIG. 15
, the exposed photosensitive resist film
103
is brought into contact with a developer
106
mainly composed of aqueous trimethylammonium hydride (TMAH) for removing the exposed part thereof, thereby obtaining a resist pattern
107
.
Referring to
FIG. 16
, ions are implanted into the silicon substrate
102
through the resist pattern
107
serving as a mask.
Conventional ion implantation is performed in the aforementioned manner. However, the shape or size of the formed resist pattern
107
is disadvantageously rendered abnormal depending on the shape of the underlayer or the relative positional relation between the underlayer and the mask.
Referring to
FIGS. 17A and 17B
, for example, part of exposure light
202
passing through a mask
201
strikes a tapered portion on the upper end of an isolation oxide film
203
to form reflected light
205
. The reflected light
205
disadvantageously exposes a part of a photosensitive resist film
206
located on an essentially unexposed region. As shown in
FIG. 17B
, therefore, a resist pattern
207
is formed in a shape different from a desired one. In other words, the size of the resist pattern
207
disadvantageously varies with the shape of the isolation oxide film
203
.
Referring to
FIGS. 18A and 18B
, the isolation oxide film
203
has high transmittance for the exposure light
202
. On the other hand, a silicon substrate
204
has high reflectivity with substantially no transmittance. Therefore, the exposure light
202
passing through the mask
201
is reflected by the uppermost surface and the bottom surface of the isolation oxide film
203
, to form reflected light components
211
and
212
. Combined light of the two reflected light components
211
and
212
sensitizes the photosensitive resist film
206
. The intensity of the combined light remarkably depends on the phase shift between the two reflected light components
211
and
212
. When the thickness of the isolation oxide film
203
fluctuates, therefore, the optical path length of the reflected light component
211
as well as the phase shift between the reflected light components
211
and
212
also change. Therefore, the intensity of the light exposing the photosensitive resist film
206
changes. Thus, the size of the formed resist pattern
207
also changes. In other words, the size of the resist pattern
207
disadvantageously varies with the thickness of the isolation oxide film
203
.
Referring to
FIGS. 19A and 19B
, reflected light
221
is generated due to multiple reflection in the isolation oxide film
203
when the bottom end portion of the isolation oxide film
203
is differentially tapered. The reflected light
221
disadvantageously sensitizes a part of the photosensitive resist
206
located on the essentially unexposed region. Therefore, the resist pattern
207
is finished in a shape different from the desired one. In other words, the resist pattern
207
disadvantageously varies with the shape of the isolation oxide film
203
.
In a step of forming such a resist pattern readily influenced by the underlayer, a photosensitive resist film containing a dye or an organic antireflection coating is generally employed.
The present invention is directed to a method of forming a resist pattern in an ion implantation step. A resist pattern formed according to the present invention is generally employed as a mask for implanted species, and hence the thickness of a photosensitive resist film is 2 to 6 &mgr;m, which is largest among those of resist films employed in general steps of forming a semiconductor integrated circuit.
FIG. 20
shows a sectional shape of a resist pattern
303
formed from a photosensitive resist film containing a dye.
The amount of energy of light received by the photosensitive resist film from exposure light is reduced in descending order from the uppermost layer to the lowermost layer of the resist film, and hence an end of the resist pattern
303
tends to be blind over edging as shown in
FIG. 20
, disadvantageously leading to reduction of dimensional accuracy.
FIG. 21
shows a sectional shape of a resist pattern
404
formed through an organic antireflection coating
403
. When employing the organic antireflection coating
403
, influence by an underlayer can be suppressed and hence the shape of the formed resist pattern
404
is stabilized. After formation of the resist pattern
404
, however, the organic antireflection coating
403
remains on the bottom of an opening
405
, which must essentially be subjected to ion implantation. The organic antireflection coating
403
remaining on the bottom of the opening
405
disadvantageously serves as a mask for ion implantation.
When performing ion implantation through the organic antireflection coating
403
, substances contained in the organic antireflection coating
403
are secondarily injected into a silicon substrate
401
, to disadvantageously contaminate the silicon substrate
401
.
In the ion implantation step for manufacturing a semiconductor integrated circuit, as hereinabove described, the quality of the underlayer for forming the resist pattern is generally optically heterogeneous as shown in each of
FIGS. 12
to
21
. Particularly in the device isolation step, the silicon substrate having high reflectance and the transparent isolation oxide film readily causing interference of light due to the thickness are alternately arranged while the resist pattern is formed with following the boundary between the silicon substrate region and the isolation oxide film region. Therefore, the aforementioned problems extremely readily arise. Under such circumstances, the antireflection coating is indispensable for suppressing influence by the underlayer, and a technique is required for exerting no bad influence on the silicon substrate.
SUMMARY OF THE INVENTION
The present invention has been proposed in order to solve the aforementioned problems, and an object thereof is to provide a method of forming a resist pattern, which is so improved as to exert no bad influence on a silicon substrate in ion implantation.
Another object of the present invention is to provide a method of manufacturing a semiconductor device including such a method of forming a resist pattern.
Still another object of the present invention is to provide an apparatus for removing an organic antireflection coating without exerting bad influence on a silicon substrate in ion implantation.
According to a first aspect of the present invention, a method of forming a resist pattern employed for ion implantation is provided. First, an organic antireflection coating is formed on a semiconductor substrate. A resist film is formed on the semiconductor substrate through the aforementioned organic antireflection coating. The aforementioned resist film is patterned for forming a resist pattern having an opening. A part of the aforementioned organic antireflection coating exposed on the bot
Doerrler William C.
Mitsubishi Denki & Kabushiki Kaisha
Shulman Mark
LandOfFree
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