Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2000-11-01
2001-12-25
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
Reexamination Certificate
active
06333572
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a positioning apparatus for positioning a plate-shaped article such as a semiconductor wafer without contact with the article and an exposing apparatus having this positioning apparatus.
2. Related Background Art
For a photolithography process for manufacturing a semiconductor device, a liquid crystal display device, a thin-film magnetic head or the like, a projecting/exposing apparatus (a stepper or the like) for transferring a pattern of a reticle used as a mask onto each shot region on a wafer (or a glass plate or the like) used as a photosensitive substrate through a projection optical system and an exposing apparatus or the like using a proximity method for transferring the reticle pattern directly on the wafer have been heretofore used. Since such an exposing apparatus is required to position the wafer in an exposure position with high precision, the wafer is held on a wafer holder by a vacuum absorption or the like and this wafer holder is fixed on a wafer stage capable of being positioned with high precision or the wafer stage capable of roughly slightly moving.
FIG. 17
shows an example of the wafer stage of the prior-art exposing apparatus. Referring to
FIG. 12
, a Y stage
102
is placed on a wafer base
101
so that it may be driven in a Y-direction by a driving motor, and an X stage
103
is placed on the Y stage
102
so that it may be driven in an X-direction by the driving motor. Furthermore, a mounting support
104
is mounted on the X stage
103
, a wafer holder
105
is fixed on the mounting support
104
, and a wafer
106
is held on the wafer holder
105
by the vacuum absorption. Movable mirrors
107
,
108
for a laser interferometer are also fixed near the wafer holder
105
on the mounting support
104
so that they may be perpendicular to each other. In this case, the mounting support
104
can position the wafer
106
in a Z-direction and in a direction of rotation about an axis parallel to a Z-axis and can correct an inclined angle of the wafer
106
(that is, an angle of rotation about the axes parallel to an X-axis and a Y-axis).
When a deformation such as a local curvature is caused on the wafer, a reticle image is not transferred on the shot region near such a deformed region with high resolution. Therefore, proposed is the method in which many piezoelectric devices are buried in parallel in the wafer holder
105
and an amount of expansion/contraction (deformation) of these piezoelectric devices is partially controlled so as to thereby improve a flatness of the wafer held on the wafer holder
105
.
FIG. 18
shows an example of the prior-art wafer holder. In
FIG. 18
, many absorbing grooves
102
are formed on a contact surface of a front surface of a wafer holder
101
a
with a wafer W. Air or the like in the absorbing grooves
102
a
is evacuated through an exhaust path
103
a
in the wafer holder
101
, whereby the wafer W is absorbed/held on the front surface of the wafer holder
101
a
. On the other hand, when the thus absorbed/held wafer W is locally deformed (curved), the reticle image cannot be excellently exposed depending on the shot region on the wafer W.
As shown in
FIG. 19
, the wafer holder capable of correcting the flatness of the wafer is also proposed. In
FIG. 19
, a space is provided in a bottom portion of the exhaust path
103
a
in the wafer holder
101
a
, and many expandable/contractible piezoelectric devices
104
are attached in this space. Therefore, the amount of expansion/contraction (deformation) of the piezoelectric devices
104
a
is individually controlled so that the region on the front- surface of the wafer holder
101
a
on the piezoelectric devices
104
is deformed, whereby the flatness of the wafer W absorbed/held on the region can be improved.
FIG. 20
shows an example of the conventional wafer stage. In
FIG. 20
, a Y stage
106
is placed on a wafer base
105
a
so that it may be movable in the Y-direction, and an X stage
107
is placed on the Y stage
106
a
so that it may be movable in the X-direction. A slight moving stage
109
is also mounted in the X stage
107
a
by using four elastic hinges
108
A-
108
D as a guide so that it can be slightly moved in the X-direction by piezoelectric devices
111
,
112
. The wafer W is fixed on a mounting support
113
through the wafer holder
101
a
. Movable mirrors
116
X,
116
Y for the laser interferometer are also fixed near the wafer holder
101
. In this case, the X stage
107
and the Y stage
106
are operated as a rough moving stage so as to roughly position the wafer W. Then, the slight moving stage
109
and the mounting support
113
are slightly moved in the X-direction and the Y-direction, respectively, whereby the wafer W is positioned with high precision.
As described above, the wafer stage of the prior-art exposing apparatus is composed of various stages and the mounting support stacked on the wafer base. Positioning of the wafer on the mounting support is performed by, for example, the driving motor using a feed screw method or the like. As regards this fact, it has been recently needed to further improve the positioning precision of the wafer stage in response to a finer formation of the semiconductor device or the like. Moreover, since an improvement of throughput (productivity) is desired in the process of manufacturing the semiconductor device or the like, the improvement of a positioning speed of the wafer stage is also required.
Although the driving motor having a high power is needed in order to position the mounting support (wafer) at high speed with high precision by means of this conventional stacked-structure wafer stage, the use of such a driving motor causes an apparatus constitution to be large-sized and be heavy in weight. As a result, the positioning speed cannot be disadvantageously improved so much. Furthermore, if the high-power driving motor is used, the mounting support and the wafer are deformed due to heat by an influence of the heat generated by the driving motor, and thus there is a possibility that the positioning precision is deteriorated rather than improved.
In the prior art in which many piezoelectric devices are buried in the wafer holder in order to improve the local deformation of the wafer, it is also necessary to dispose many high-voltage wires for use in the piezoelectric devices in the wafer holder. Thus, the wafer holder is large-sized and the positioning speed is thus reduced, and a manufacturing cost is also disadvantageously increased.
In the above-described prior art, in case of the wafer holder of
FIG. 18
, the wafer W is held on the wafer holder
101
by the vacuum absorption. Thus, if a contaminant such as resist residue is put between the rear surface of the wafer W and the front surface of the wafer holder
101
, the wafer W is deformed due to the contaminant. As a result, there is a possibility that a yield of a semiconductor device to be finally manufactured is reduced. On the other hand, in case of the wafer holder of
FIG. 20
, the flatness of the wafer W is corrected by the expansion/contraction of many piezoelectric devices
104
in the wafer holder
101
. However, disadvantageously, since this method is required to arrange many high-voltage wires for the piezoelectric devices, the apparatus constitution is increased in size and complicated, which results in the higher cost.
Moreover, in the conventional wafer stage of
FIG. 20
, when the position of the image projected on the reticle matches to that of each shot region on the wafer, the wafer W is stepped at high speed through the X stage
107
and the Y stage
106
(the rough moving stage). Then, the slight moving stage
109
and the mounting support
113
are slightly moved through the piezoelectric devices
111
,
112
and
114
,
115
, whereby the wafer W is finally positioned. However, for a structure for adjusting the position by pushing/pulling the slight moving stage
109
and the mounting support
113
by the piezoelectric devices, the high-
Foley & Lardner
Jones Judson H.
Nikon Corporation
Ramirez Nestor
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