Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
1999-08-23
2001-03-27
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
Reexamination Certificate
active
06207328
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor process, and more particularly, to a method of forming a phase shift mask for the semiconductor wafer.
2. Description of the Prior Art
In order to define the circuit of the integrated circuits in a semiconductor process, the designed pattern is initially formed on the mask and then transferred onto the semiconductor wafer by lithography process. A prior art phase shift mask comprises a flat glass substrate, a phase shifter layer, and a chromium (Cr) layer with the pattern on it. The pattern on the Cr layer is formed by the exposure and the development processes. When transferring the pattern of the phase shift mask onto the semiconductor wafer, the phase shifter layer can generate 180° phase shift angle for the light penetrating through, which can reduce the pattern boundary vibration so as to accurately transfer the pattern onto the semiconductor wafer.
Please refer to
FIG. 1
to FIG.
4
.
FIG. 1
to
FIG. 4
are schematic diagrams of a prior art method of forming a phase shift mask
20
. A prior art method of forming a phase shift mask
20
is performed on a mask substrate
10
made of quartz. According to the designed pattern, the mask substrate
10
comprises a predetermined region A and a predetermined region B. When forming the phase shift mask
20
, a phase shifter layer
12
and a shield layer
14
are subsequently formed on the mask substrate
10
. Next, a first lithography process is performed to form a first photo-resist layer
16
on the surface of the predetermined region A of the mask substrate
10
, as shown in FIG.
1
. Then, a first etching process is performed to vertically remove the shield layer
14
not covered by the first photo-resist layer
16
, and then remove the first photo-resist layer
16
completely, as shown in FIG.
2
. And next, a second lithography process is performed to form a second photo-resist layer
18
on the surface of the predetermined region B of the mask substrate
10
, as shown in FIG.
3
. Then, a second etching process is performed to vertically remove the phase shifter layer
12
not covered by the second photo-resist layer
18
, and then the second photo-resist layer is completely removed, as shown in
FIG. 4
, so as to complete the phase shift mask
20
.
The prior art method of forming the phase shift mask
20
has to perform the first lithography process to form the first photo-resist layer
16
and remove the shield layer
14
surrounding the predetermined region A, and then perform the second lithography process to form the second photo-resist layer
18
and remove the phase shifter layer
12
surrounding the predetermined region B. Since the prior art method has to repeat the lithography process, the alignment accuracy of the pattern finally formed on the phase mask
20
may be reduced which may affect the quality of the subsequent semiconductor process. Besides, repeating the lithography process may raise the processing cost, and reduce the profit of the semiconductor product.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide a method of forming a phase shift mask to solve the above mentioned problem.
In a preferred embodiment, the present invention relates to a method of forming a phase shift mask on a mask substrate comprising:
sequentially forming a phase shifter layer and a shield layer on the mask substrate;
forming a photo-resist layer on a predetermined region of the shield layer, the periphery of the photo-resist layer comprising at least one vertical side-wall;
forming a deposition layer uniformly on the photo-resist layer and the shield layer surrounding the photo-resist layer;
silylanizing the deposition layer;
performing an anisotropic etching process to remove the deposition layer on top of the photo-resist layer and the shield layer surrounding the photo-resist layer, and to partially remove the deposition layer covered on the vertical side-wall of the photo-resist layer so as to form a spacer on the vertical side wall of the photo-resist layer;
vertically removing the shield layer and the phase shifter layer not covered by the photo-resist layer and the spacer, and vertically removing the spacer and the shield layer under the spacer; and
removing the photo-resist layer completely to complete the phase shift mask.
It is an advantage of the present invention that it can increase the alignment accuracy of the pattern formed on the phase shift mask and reduce the processing cost.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.
REFERENCES:
patent: 5637425 (1997-06-01), Lee et al.
Hsu Winston
Rosasco S.
United Microelectronics Corp.
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