Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2000-07-27
2003-09-16
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
Reexamination Certificate
active
06620557
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a photo-mask and a photo-mask pair, and more particularly to a photo-mask and a photo-mask pair improved so as to enhance an ability of ensuring dimension accuracy. The present invention further relates to a semiconductor device formed to use such a photo-mask and to a method of manufacturing such a semiconductor device.
2. Description of the Background Art
FIGS. 21A
to
21
F illustrate a cross-sectional view showing a method of manufacturing a semiconductor device using a conventional photo-mask, in particular, a process of forming an etching pattern of SiO
2
film.
Referring to
FIG. 21A
, a SiO
2
film
52
is formed on a silicon substrate
51
.
Referring to
FIG. 21B
, a photo-resist
53
is formed on SiO
2
film
52
.
Referring to
FIG. 21C
, photo-resist
53
is selectively irradiated with UV rays using a photo-mask
54
to form a potential image in photo-resist
53
.
Referring to
FIG. 21D
, photo-resist
53
is developed to form a resist pattern
55
.
Referring to
FIG. 21E
, SiO
2
film
52
is etched using resist pattern
55
as a mask.
Referring to
FIGS. 21E and 21F
, photo-resist pattern
55
is removed so that a pattern
56
of the SiO
2
film remains on silicon semiconductor substrate
51
.
FIG. 22
is a cross-sectional view of a photo-mask. Referring to
FIG. 22
, a light-shielding pattern
57
formed of a metal film, oxide, nitride, sulfide, or fluoride of Cr, Mo, Zr, Ta, W or the like and a compound thereof is provided on a glass substrate
58
. Light-shielding pattern
57
has a film thickness of approximately 100 to approximately 170 nm. Such a photo-mask is provided, in addition to an actual pattern, with a monitor mark for ensuring the dimension of the actual pattern. The monitor mark is also formed of the metal film or the metal compound film described above.
FIG. 23
is a plan view of a conventional photo-mask.
A mask pattern region
2
is formed on a photo-mask
1
. A semiconductor element chip region
3
is provided in mask pattern region
2
. Memory cell region
3
a
(a high-density portion) is provided in semiconductor element chip region
3
. Semiconductor element chip region
3
is provided with an element pattern
5
for a high-density portion (such as a memory cell) and an element pattern
6
for a low-density portion (such as a low-density logic portion). Monitor mark
4
is provided at each of the four corners of mask pattern region
2
. Monitor mark
4
is also provided at a middle point of a long side of mask pattern region
2
.
Examples of conventional monitor marks are shown in
FIGS. 24A and 24B
.
FIG. 24A
is an example of a monitor mark formed with interconnections (hereinafter referred to as “interconnection type”).
FIG. 24
B shows a typical interconnection type element pattern in the actual pattern. The interconnection type monitor mark shown in
FIG. 24A
is configured to ensure the dimension of the interconnection type element pattern shown in FIG.
24
B. The arrows in
FIGS. 24A and 24B
point the position where the dimension is measured.
FIGS. 25A and 25B
are plan views of conventional monitor marks formed with holes (hereinafter referred to as “hole type”).
FIG. 25A
shows an example of a hole type monitor mark and
FIG. 25B
shows a typical hole type element pattern in the actual pattern. The hole type monitor mark shown in
FIG. 25A
is for ensuring the dimension of the hole type element pattern shown in FIG.
25
B.
FIG. 26
shows an example of a conventional cross mark for measuring registration accuracy.
In
FIGS. 24A through 26
, the portion designated by reference number
7
denotes an outer frame of the monitor mark and the portion designated by reference number
8
denotes a pattern region for which the element dimension is monitored. A cross pattern for registration accuracy measurement is designated by reference number
9
.
Thus, the conventional monitor mark was formed to have a pattern shape of simple cross, line and space, rectangle or the like, which is simply designed to represent the pattern of the semiconductor element.
However, since a semiconductor element has been required to have improved function and performance, a system LSI in which a memory element and a logic element are mounted with high density has come to be designed along with size reduction of the pattern, thereby complicating the photo-mask used for manufacturing of these elements. In particular, the memory element pattern having higher density and smaller size and the logic element pattern having a large difference between coarse portion and dense portion of the pattern are arranged on the same photo-mask. Further, as a pattern is reduced in size, an error between the pattern dimension and the design dimension abruptly increases if the pattern has coarse and dense portions. Thus, it has been difficult for the simple pattern for monitoring dimension as shown in
FIGS. 24A
,
24
B,
25
A,
25
B and
26
to represent the actual element pattern. It has therefore been difficult to ensure the photo-mask dimension with high accuracy. An example of the error is shown in Table 1.
TABLE 1
LINE TYPE (&mgr;m)
HOLE TYPE - X/Y (&mgr;m)
Design
Measured
Design
Measured
value
value
Error
value
value
Error
Monitor mark
1.20
1.21
0.01
1.20/1.20
1.21/1.21
0.01/−0.10
Memory cell portion element pattern
1.00
0.97
−0.03
0.80/2.20
0.85/2.14
0.05/−0.06
Logic portion element pattern
1.40
1.37
−0.03
1.50/1.50
1.55/1.55
0.05/0.05
In the conventional monitor mark, each element pattern was required to be individually measured in a process of manufacturing a photo-mask. However, such individual measurement of each element pattern takes too much effort, so that a method of making the mask with low cost and short delivery period has been desired.
SUMMARY OF THE INVENTION
The present invention is made to solve the problems described above, and an object of the invention is to provide a photo-mask improved to ensure the photo-mask dimension with high accuracy.
An another object of the invention is to provide photo-mask improved such that the photo-mask can be manufactured with low cost and short delivery period.
A further object of the invention is to provide a photo-mask pair, which enables efficient manufacturing of a semiconductor device.
A still further object of the invention is to provide a semiconductor device manufactured using such a photo-mask.
Another object of the invention is to provide a method of manufacturing the semiconductor device using such a photo-mask.
The photo-mask according to the first aspect includes a substrate. The substrate is provided with an actual pattern thereon. A monitor mark for ensuring the dimension of the actual pattern is provided on the substrate. The monitor mark is provided with a coarse pattern and a high-density pattern formed to have a density higher than the coarse pattern.
According to the invention, the monitor mark is provided with the coarse pattern and the high-density pattern formed to have a density higher than the coarse pattern, so that the dimension of the coarse portion of the actual pattern can be ensured and the dimension of the high-density portion of the actual pattern can also be ensured.
In the photo-mask according to the second aspect, the monitor mark is further provided with a cross pattern for registration accuracy measurement having a pair of arms crossing each other.
According to the invention, even the registration accuracy can be ensured. In the photo-mask according to the third aspect, the coarse pattern and the high-density pattern are each provided remote from a scanning region of the cross pattern.
According to the invention, the coarse pattern and the high-density pattern will not interrupt the scanning of the cross pattern.
In the photo-mask according to the fourth aspect, the monitor mark includes an outer frame pattern enclosing the coarse pattern and the high-density pattern. The outer frame pattern is formed wide enough to be visually recognizable through a microscope.
Accor
Hosono Kunihiro
Mori Masayoshi
Huff Mark F.
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Mohamedulla Saleha R.
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