Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2001-03-01
2003-05-27
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S030000, C430S296000, C430S942000
Reexamination Certificate
active
06569578
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method for forming a mask, and more particularly, the present invention relates to the method for forming the mask being utilized for lithography processes in semiconductor device fabrication.
This application is a counterpart of Japanese application Serial Number 58822/2000, filed Mar. 3, 2000, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
In general, as high integration advance, exposing technique has changed from exposing technique in a lump to electron beam exposing.
FIG. 1
is a plane-view showing a photo-mask according to a conventional art.
As shown in
FIG. 1
, a first region
200
shown with a slanting line in a photo-mask is not exposed. Since an area of exposure pattern
202
per unit area in a left side region of a broken line L-L′ is less than a half exposure area in the photo-mask, the exposure pattern
202
is defined as a small region. Since an area of exposure pattern
204
per unit area in a right side region of a broken line L-L′ exceeds a half of all exposure area, the exposure pattern
204
is defined as a large region.
FIG.
2
A-
FIG. 2E
are cross-sectional views showing a method for forming a mask using an electron beam exposure taken on line K-K′ of FIG.
1
.
As shown in
FIG. 2A
, a light-shielding layer
102
such as chrome is formed on a quartz substrate
100
. Then a positive-type resist film
104
a
having a thickness of 300-500 &mgr;m is formed on the light-shielding layer
102
.
As shown in
FIG. 2B
, the resist film
104
a
is exposed using electron beam exposure. Here, dosage of the electron beam exposure is 6-10 [&mgr;C/cm2]. Then, the exposed resist film
104
a
is developed. As a result, a resist pattern
104
b
is formed.
As shown in
FIG. 2C
, for removing resist remained on the light-shielding layer
102
, a slight etching process is carried out.
As shown in
FIG. 2D
, the light-shielding layer
102
is etched using the remained resist pattern
104
d
as a mask.
As shown in
FIG. 2E
, the remained resist pattern
104
d
is removed. Processes as described above form photo-mask.
In processes as described above, as shown in
FIG. 2A
, when small and large regions of the exposure pattern
204
are formed depending on location of region, an opening size difference causes such as sizes A and B shown in FIG.
2
B.
The opening size difference causes by fogging effect. The fogging effect has disclosed that “Shimomura, N., Ogasawara, M., Takamatsu. J., Yoshitake, S., Ooki, K., Nakayamada, N., Okabe, F., and Tojo, T.: “Reduction of fogging effect caused by scattered electrons in an electron beam system”, Part of the SPIE Symposium on Photomask and x-ray Mask Technology VI yokohama, Japan, September 1999, pp. 408-415”.
Since an opening size difference such as sizes A and B exists, the resist pattern
104
C if formed so that a size C of opening
107
is smaller than a size D of opening
108
, as shown in FIG.
2
C. Accordingly, as shown in
FIG. 2E
, an opening size F in the large region is formed larger than the designed size even if an opening size E in the small region is formed as designed.
It is desired to form opening size of the light-shielding layer
102
as designed without depending on the location of region formed resist pattern in the mask.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for forming a photo-mask that can form an opening dimension of the light-shielding layer pattern as designed without depending on the location of region formed resist pattern in the photo-mask.
According to one aspect of the present invention, for achieving the above object, there is provided A method for forming a mask comprising: forming a light-shielding layer on a substrate; forming a resist film having small and large regions on the light-shielding layer, the small and the large regions being defined as the exposed area; exposing the resist film with low dosage using electron beam exposure according to a predetermined pattern data; and forming a resist pattern having a first opening in the small region and a second opening in the large region by developing the exposed resist pattern; wherein the elevation angle of the first opening sidewall in the small region is smaller than an elevation angle of the second opening sidewall in the large region.
REFERENCES:
patent: 6379851 (2002-04-01), Innes
patent: 5-152200 (1993-06-01), None
patent: 10-221851 (1998-08-01), None
Kimura Yasuki
Nozaki Yuji
Oki Electric Industry Co. Ltd.
Volentine & Francos, PLLC
Young Christopher G.
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