Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
1999-06-30
2002-04-30
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S055000
Reexamination Certificate
active
06381002
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The production of a semiconductor device, a printed board, a LCD and similar devices comprises an exposure process in which exposure light containing UV radiation is emitted via a mask onto a workpiece and thus a mask pattern is transferred to the workpiece. The invention relates to both a process for controlling a gap between the mask and the workpiece in a proximity exposure device and to a proximity exposure device.
2. Description of Related Art
The term “proximity exposure device” is generally defined as an exposure device in which a workpiece is located at a stipulated distance parallel to a mask. Exposure light is emitted via the mask and a mask pattern which has been formed on the mask is transferred to the workpiece. During exposure, there is therefore a need for a stipulated gap between the mask and the workpiece and for a parallel arrangement of the two to one another.
FIG. 5
schematically shows the basic arrangement of a proximity exposure device. In the figures, reference letter M indicates a mask on which a mask pattern is formed and which is held securely in a mask carrier MS by vacuum suction or other securing means. Above the mask carrier MS, there is a gap measurement means
1
which is driven up and down by means of a device
2
(the gap measurement means is described for example in Japanese patent application HEI 9-75564).
A workpiece carrier WS holds a workpiece W by vacuum suction or other securing means. The workpiece carrier part in which the workpiece carrier WS is located has the multistage arrangement described below. On the base plate BP, by means of a first movement device D
1
(hereinafter called “Z
1
-movement device”), there is a first carrier ZS (hereinafter called “Z-carrier ZS”). The workpiece carrier WS is located on the Z-carrier ZS by means of a second movement device D
2
(hereinafter called “Z
2
-movement device”). The Z
1
-movement device D
1
moves the Z-carrier ZS up and down.
A device for driving the Z-carrier ZS is described as follows. As is shown in
FIG. 5
, an intermediate movement carrier
11
is movably located over rolling components, such as balls or the like, on the base plate BP. The lower area of the Z-carrier ZS is provided with an obliquely running surface
12
at each of three locations (two of which are illustrated in FIG.
5
). The obliquely running surfaces
12
are seated via rolling components, such as balls
14
or the like, on obliquely running surfaces
13
with which the intermediate movement carrier
11
is provided at the three corresponding locations.
The Z-carrier ZS is furthermore located over a bearing
16
in a guide
15
which is located perpendicular to the base plate BP. The guide
15
controls the direction of motion in the X-direction and the Y-direction such that the Z-carrier ZS does not move in the X-Y direction when it moves in the Z-direction (X: for example to the right and left in the drawings, Y: the direction perpendicular to the page of the drawing). The guide
15
controls movement in the X-direction. In the direction sloped 90° in this respect, there is a guide which controls movement in the Y-direction.
When the intermediate movement carrier
11
is moved by a device
17
for driving the intermediate movement carrier on the base plate BP, the Z-carrier ZS moves along the obliquely running surfaces of the intermediate movement carrier
11
in the Z-direction. In doing so, the Z-carrier ZS moves only in the Z-direction because it is moving along the guide
15
. Therefore it does not move in the X-Y directions. Since the obliquely running surfaces have the same slope at these three locations, the Z-carrier ZS moves in the Z-direction while maintaining the horizontal position. The movement stroke of the Z-carrier ZS is usually 50 to 100 mm.
A stipulated gap can be set between the mask and the workpiece by the parallel movement of the Z-carrier ZS in the Z-direction in this way by means of the Z
1
-movement device D
1
. Only by vertical movement of the Z-carrier ZS is it however possible that the workpiece carrier WS is sloped with respect to the exposure device, the mask and the like. Since this slope cannot be corrected by the Z
1
-movement device D
1
, there is the Z
2
-movement device D
2
which moves the workpiece carrier WS back and forth and adjusts it. The workpiece carrier WS is supported, for example as in
FIG. 5
, by workpiece carrier support parts
20
at three points which each have one workpiece carrier support component
20
a
which can be moved in the Z-direction. The respective workpiece carrier support component
20
a
executes independent motion in the Z-direction by means of a drive part
20
b
. In this way, the workpiece carrier WS is moved back and forth, and the Z-carrier ZS is prevented from being sloped with reference to the exposure device, the mask and the like.
The workpiece carrier support component
20
a
of the respective workpiece carrier support part
20
is driven by means of the drive part
20
b
which has, for example, a servomotor. In this way, precision movement with high accuracy is achieved while the speed of movement is low. The stroke of movement of the respective workpiece carrier support component
20
a
is 1 to 2 mm.
The actuation of the device shown in
FIG. 5
is described as follows using
FIGS. 6 and 7
.
(1) To simplify transport of the workpiece W in and out the workpiece carrier WS is moved down. With consideration of the thickness of a workpiece transport finger
3
and the bending of the workpiece W, a distance of at least 50 mm is required between the mask M and the workpiece carrier WS.
(2) As is illustrated in
FIG. 6
, the workpiece W is held securely by the workpiece transport finger
3
and is transported on the workpiece carrier WS. In the workpiece carrier part, there are transfer pins
4
(not shown in
FIG. 5
) in order to transfer the workpiece W between the transport finger
3
and the workpiece carrier WS. The transport finger
3
is lowered, the workpiece W is transferred to the transfer pins
4
and the transport finger
3
is removed.
(3) As is shown in
FIG. 7
, the workpiece carrier WS is briefly raised by means of the Z
1
-movement device D
1
so that the distance between the workpiece W and the mask M is set to a stipulated exposure gap. By raising the workpiece carrier WS, the workpiece W is transferred to the workpiece carrier WS by means of the transfer pins
4
. The above described stipulated exposure gap will be different depending on the conditions of use, the exposure process, and the other factors. But there is usually a demand for an exposure gap of less than or equal to 100 microns because the exposure accuracy (resolution) becomes higher as the exposure gap is reduced.
(4) For a parallel arrangement of the mask M to the workpiece W, the distance between the mask M and the workpiece W is measured by means of the gap measurement means
1
shown in
FIG. 5
at several points (for example at three points). Based on these measured values, the workpiece carrier WS is moved back and forth and adjusted by means of the Z
2
-movement device D
2
so that the mask M and the workpiece W are located parallel to one another.
(5) After confirming the parallel arrangement of the mask M to the workpiece W by means of the gap measurement means
1
, the exposure light is emitted via the mask M and thus exposure is done.
(6) After completion of exposure, the workpiece carrier is lowered by means of the Z
1
-movement device D
1
. The workpiece W is then transferred to the transfer pins
4
. The transport finger
3
is inserted into the workpiece carrier part. The already treated workpiece is transferred from the transfer pins
4
to the transport finger
3
and transported away from the workpiece carrier part.
Recently there has been a trend for workpieces to become larger. Especially in the area of liquid crystal substrates, large substrates, measuring 550 mm×650 mm to 650 mm×830 mm, are becoming more important. Furthermore there is a growing demand for an expos
Adams Russell
Kim Peter B.
Nixon & Peabody LLP
Safran David S.
Ushiodenki Kabushiki Kaisha
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