Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
1997-09-19
2001-01-09
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C250S548000, C250S206000, C356S399000, C356S400000, C356S401000, C318S625000, C318S628000
Reexamination Certificate
active
06172738
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to a scanning exposure apparatus for use in the manufacture of semiconductor devices, for example, and a device manufacturing method using the same.
Scanning exposure apparatuses are known as apparatus having a projection system for transferring a portion of a pattern of a reticle or mask (original) onto a workpiece substrate such as a wafer, an illumination system having a light source, for illuminating a portion of the pattern of the reticle with rectangular or arcuate slit-like light, and a scanning mechanism for scanningly moving the reticle and the workpiece substrate relative to the slight-like light and the projection system at a predetermined speed ratio, thereby to transfer the pattern of the reticle onto the wafer.
FIG. 16
shows an example of a scanning exposure apparatus. As shown in
FIG. 16
, the apparatus includes an illumination system
132
for transforming exposure light from a light source such as a Hg lamp or a laser light source into slit-like light, and a projection system
133
for projecting a pattern of a reticle
101
illuminated with the slit-like light onto a wafer
134
in a reduced scale. The reticle
101
is placed on a reticle stage
135
and is vacuum attracted thereto. Mounted on the reticle stage
135
is a reflection mirror
137
with which the position of the reticle stage can be measured in association with a reticle position measurement laser interferometer
136
.
On the other hand, the wafer
134
is vacuum attracted to a wafer chuck
138
which is mounted on a wafer stage
139
. Also mounted on the wafer stage
139
is a bar mirror
140
with which the position of the wafer stage
139
can be measured in association with a wafer position measurement laser interferometer
141
.
Disposed above the reticle
101
is an alignment detecting system
142
for detecting relative position of the reticle
101
and the wafer
134
. After their relative portion is detected by this detecting system, the exposure apparatus operates to perform the scan exposure while keeping positional synchronism of the reticle
101
and the wafer
134
in association with the reticle position measurement laser interferometer
136
and the wafer position measurement laser interferometer
141
.
The exposure apparatus as a whole is supported by a major assembly frame
144
which is mounted on an anti-vibration table
145
. The reticle stage
135
moves along a structure
143
disposed on this frame
144
.
SUMMARY OF THE INVENTION
There are inconveniences in such a scanning exposure apparatus, to be described below, mainly because the reticle
101
is vacuum attracted to the reticle stage
135
.
First, the attracting force of vacuum attraction is proportional to the area of attraction. Thus, when the attraction area is small and if the acceleration in scanning drive is enlarged to obtain increased productivity, there will occur a slip between the reticle
101
and the reticle stage
135
. This is a limitation on the drive acceleration and, thus, to improvement of device productivity. In order to prevent the slip, the attraction area has to be enlarged. Then, however, the reticle pattern region is restricted or reticle conveyance becomes difficult.
More specifically, the force for holding the reticle at a constant position on the reticle stage is provided by a friction force between the reticle as attracted to the reticle stage by the vacuum attraction force and the peripheral portion of the aperture of the reticle stage. Therefore, if the acceleration force for accelerating the reticle stage in the scan direction or a direction opposite thereto is so large that the inertia of the reticle exceeds the above-described friction force, the reticle will shift relative to the reticle stage, causing degradation of the pattern transfer precision.
During the exposure process, the reticle stage is scanningly moved at a scan speed four or five times higher than the speed of the wafer stage. Thus, a large acceleration is applied to the reticle. Recently, increases in the scan speed of the reticle stage or wafer stage have been desired for enhanced productivity of the exposure apparatus. With increased scan speeds, an acceleration force of about 1-2 G will be applied to the reticle. It will be difficult to hold the reticle stably against the acceleration of over 1 G, only with the friction force provided by vacuum attraction. Particularly, there are alignment marks or the like in the peripheral portion of a reticle for alignment with a wafer, and it is not easy to enlarge the contact area between the reticle and the reticle stage to increase the friction force.
It is accordingly an object of the present invention to provide a stage device and/or an exposure apparatus using the same, by which positional deviation of a substrate such as a reticle during motion of a movable stage such as a reticle stage can be prevented.
In accordance with an aspect of the present invention, there is provided a scanning exposure apparatus, comprising: a projection optical system; a reticle stage for scanningly moving a reticle relative to said projection optical system; a wafer stage for scanningly moving a wafer relative to said projection optical system, in a timed relation with the reticle scan movement; and a holding mechanism for holding the reticle on said reticle stage during the reticle scan movement, said holding mechanism including a first mechanism for confining an end edge portion of the reticle and a second mechanism for pressing the reticle from above.
The projection optical system may comprise a reduction optical system for projecting a pattern of the reticle onto the wafer in a reduced scale of a predetermined magnification, and wherein said reticle stage and said wafer stage may move at a speed ratio corresponding to the predetermined magnification.
In accordance with another aspect of the present invention, there is provided a scanning exposure apparatus, comprising: a projection optical system; a reticle stage for scanningly moving a reticle relative to said projection optical system; a wafer stage for scanningly moving a wafer relative to said projection optical system, in a timed relation with the reticle scan movement; and a holding mechanism for holding the reticle on said reticle stage during reticle scan movement, said holding mechanism including means for substantially prohibiting slip displacement of the reticle attributable to acceleration.
In accordance with a further aspect of the present invention, there is provided a device manufacturing method for producing a device by use of a scanning exposure apparatus as recited above.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
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Inoue Mitsuru
Korenaga Nobushige
Adams Russell
Brown Khaled
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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