Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2001-05-23
2003-08-05
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S112000, C700S116000
Reexamination Certificate
active
06604011
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to an original chuck for holding an original such as a reticle, for example. Such an original chuck is usable, for example, in an exposure apparatus for transferring a pattern of an original such as a reticle onto a substrate such as a wafer, in a photolithographic process for the manufacture of semiconductor integrated circuits, liquid crystal substrates, or image pickup devices (CCDs), for example.
Exposure apparatuses such as described above are an apparatus in which an original such as a reticle being attracted by an original chuck, for holding the original, is illuminated and in which a pattern formed on the original is projected on a substrate such as a wafer, by a projection optical system and in a reduced scale, whereby the pattern of the original is transferred to the substrate. The original such as a reticle is conveyed to and placed on the original chuck by means of an original conveying system. Then, the original is attracted to an attracting face of original attracting and holding means, provided on the top face of the original chuck.
Generally, original chucks such as described above have a structure as shown in
FIGS. 10A-10C
. More specifically, an original chuck
51
includes a main chucking body
52
which has four attracting and holding portions
53
(
53
a
-
53
d
) disposed in relation to four corners of an original R. As shown in
FIG. 10C
, each attracting and holding portion
53
includes a holding pillar
54
which has formed on its top end face a planar original attracting face
56
having a certain area and being formed with an attracting groove
55
. The attracting groove
55
is communicated with a vacuum source, not shown, through an attracting bore
57
. With this structure, the original chuck
51
functions to vacuum-attract and hold the four corners of the original R (at the bottom face thereof) as the same is placed on the original attracting faces
56
of the four attracting and holding portions
53
.
However, it is very difficult to make all four of the original attracting faces
56
, for attracting the original R, completely on the same plane. Practically, in many cases, these original attracting faces
56
are inclined differently or they have different heights, such that they are not placed exactly on the same plane. If, for example, an original attracting face
56
is inclined such as depicted by a broken line in
FIG. 10C
, the original R follows the tilt surface shape of this attracting face
56
, and therefore it is attracted and held in such a tilted state.
In this manner, the original R may be deformed, such as depicted in
FIGS. 11A-11D
, for example, in accordance with the state of the original attracting faces
56
of the attracting and holding portions
53
. For example, as shown in
FIG. 11A
, it may be distorted and protruded downwardly, or, to the contrary, it may be distorted and protruded upwardly as shown in FIG.
11
B. Alternatively, it may be deformed into an S-shape as shown in FIG.
11
C. The deformation shown in
FIG. 11A
may occur when the attracting faces at the opposite sides are tilted inwardly downwardly. The deformation shown in
FIG. 11B
may occur when the attracting faces at the opposite sides are tilted inwardly upwardly. The deformation shown in
FIG. 11C
may occur when one attracting face is tilted inwardly downwardly, while the other attracting face is tilted inwardly upwardly.
The result shown in
FIG. 11D
may occur when the original attracting faces
56
a
and
56
d
of the attracting and holding portions
53
a
and
53
d
are taller than the original attracting faces
56
b
and
56
c
of the other attracting and holding portions
53
b
and
53
c
. As shown, the portions of the original adjacent to the original attracting faces
56
a
and
56
d
are distorted upwardly. Deformation as shown in
FIG. 11D
which is attributable to differences in height of the original attracting faces
56
may be disregarded if, for example, the number of the original attracting portions is made three. However, when the shape of the original and the exposure pattern placement area are taken into consideration, holding a substrate such as a wafer at three equiangular positions on the same circumference about the center, where deformation due to the weight thereof hardly occurs, is impossible.
Anyway, the tendency and the magnitude of deformation of the original R are variable in dependence upon the shape of the original attracting faces or the difference in height of the original attracting faces. In accordance with the tendency and the amount of deformation, distortion may occur in the pattern of the original R such as, for example, shown in
FIGS. 12A-12D
, which correspond to the cases of
FIGS. 11A-11D
, respectively. In
FIGS. 12A-12D
, the orientation and size of each arrow depicts a shift of a pattern at each grid point of an idealistic grid (grid without distortion), shown by broken lines. As a result, the pattern formed on the original R which is being distorted as described is transferred to a substrate such as a wafer. Namely, the transferred pattern is undesirably being distorted.
Generally, a semiconductor device is produced by accumulating circuit patterns of plural layers on a substrate such as a wafer, in a predetermined positional relation. In recent semiconductor manufacturing factories, for higher throughput (the number of wafers processed per unit time), in many cases, the exposure process is performed in accordance with a mix and match method in which different exposure apparatuses are used for different layers on the substrate. Here, the surface shapes of original attracting faces of original chucks in these exposure apparatuses may have different tendencies and, therefore, patterns transferred to the substrate such as a wafer may involve different distortions. This causes a problem of an error with respect to the pattern overlay or pattern junction.
The error may be tolerable, conventionally. Recently, however, the precision required for exposure apparatuses becomes higher and higher. It becomes very important to prevent deformation of an original resulting from the surface shape of attracting faces of an original chuck or from the difference in height of the attracting faces, thereby to reduce distortion of a pattern of the original or distortion of a pattern transferred to a substrate such as a wafer.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide an original chuck, by which deformation of an original such as a reticle when the same is attracted and held by the chuck can be prevented, such that distortion of a pattern of the original or distortion of a pattern transferred to a substrate such as a wafer can be reduced.
It is another object of the present invention to provide an exposure apparatus having an original chuck such as described above.
It is a further object of the present invention to provide a semiconductor device manufacturing method using an exposure apparatus such as described above.
In accordance with an aspect of the present invention, there is provided an original chuck having an attracting and holding portion for holding an original, characterized in that said attracting and holding portion has a contact member to be brought into contact with the original, wherein said contact member has a spherical shape.
In one preferred form of this aspect of the present invention, said attracting and holding portion may have an attracting pad for surrounding said contact member, said attracting pad being made of an elastic material and being effective to attract the original.
In accordance with another aspect of the present invention, there is provided an original chuck having a plurality of attracting and holding portions for holding an original, characterized in that at least one of said attracting and holding portions has an adjusting mechanism for providing adjustment in a vertical direction.
In one preferred form of this aspect of the present invention, said adjusting mechanism may in
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Picard Leo
Swindell Walter Russell
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