Photocopying – Projection printing and copying cameras – Illumination systems or details
Reexamination Certificate
2000-11-28
2003-04-29
Fuller, Rodney (Department: 2851)
Photocopying
Projection printing and copying cameras
Illumination systems or details
C355S053000, C355S066000, C355S077000
Reexamination Certificate
active
06556278
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure apparatus, and more particularly to a scanning projection exposure apparatus which performs exposure while moving a first object and a second object.
2. Related Background Art
Liquid crystal display panels are frequently used these days as a display device for word processors, personal computers, televisions, etc. A liquid crystal display panel is fabricated by patterning of transparent thin-film electrodes in a desired shape on a glass substrate by the photolithography technique. As an apparatus for the lithography a mirror projection type aligner is used for exposure-printing an original pattern formed on a mask onto a photoresist layer on a glass substrate through a projection optical system.
FIG.
1
and
FIG. 2
are drawings to show the structure of a conventional mirror projection type aligner.
FIG. 1
is a perspective view to show the overall structure of the aligner and
FIG. 2
is a lens cross-sectional view to show the structure of a projection optical system in the aligner.
In
FIG. 1
, an illumination optical system not shown illuminates a mask
71
c
in an arcuate illumination field
72
a.
An optical path of light from the illumination field
72
a
is deflected 90° by a First reflecting surface
73
a
of a trapezoid mirror
73
, as shown in
FIG. 2
, and the thus deflected light advances via a concave mirror
74
and a convex mirror
75
and then is reflected again by the concave mirror
74
. The optical path of the light reflected by the concave mirror
74
is deflected 90° by a second reflecting surface
73
b
of the trapezoid mirror. Then an image of the mask
71
c
or an image
72
b
of the illumination field
72
a
is formed on a plate
76
.
The aligner as shown performs the so-called scanning exposure while moving the plate
76
and the mask
71
c
in the X direction in the drawings, whereby a circuit pattern on the mask
71
c
is transferred onto a selected region on the plate
76
.
There is a recent demand to increase the size of liquid crystal display panels. With such a demand to increase the size, the above-described aligner is also desired to enlarge the exposure area.
In order to meet the demand to enlarge the exposure area, the conventional exposure apparatus as described above employed a method of exposure with exposure area as divided into pieces. Specifically, as shown in
FIG. 1
, an exposure area on the plate
76
is divided into four regions of
76
a
to
76
d,
and with scanning exposure of mask
71
a
and region
76
a
a circuit pattern of mask
71
a
is transferred onto the region
76
a.
In the next place, the mask
71
a
is exchanged for another mask
71
b
and the plate
76
is moved stepwise in the XY plane in
FIG. 1
before a region
76
b
comes to coincide with the exposure area of the projection optical system. With scanning exposure of mask
71
b
and region
76
b,
a circuit pattern of mask
71
b
is then transferred onto the region
76
b.
After that, the same step is repeated for masks
71
c
and
71
d
and regions
76
c
and
76
d,
whereby circuit patterns of masks
71
c
and
71
d
are transferred onto corresponding regions
76
c
and
76
d.
In such exposure with divided exposure area, the multiple scanning exposure steps must be taken for a single exposure area, which decreases the throughput (an exposed substrate amount per unit time). Further, in case of the partition exposure, there are seams or stitches between two adjacent exposure regions and, therefore, the stitching accuracy must be enhanced. Because of this requirement, the method had such disadvantages that the magnification error of projection optical system must be decreased as close to 0 as possible, that the alignment accuracy must be greatly improved, and that the production cost of the apparatus is increased.
On the other hand, it can be conceivable that the scale of projection optical system is increased for full scanning exposure of a single large exposure area instead of the partition exposure. In order to increase the scale of projection optical system, however, large-scale optical elements must be produced with very high accuracy, which results in increasing the production cost and the size of apparatus. Also, there was a disadvantage that the size increase of projection optical system caused an increase in aberrations or a decrease in imaging performance.
SUMMARY OF THE INVENTION
The present invention has been accomplished taking the above problems into consideration and an object of the present invention is to provide an exposure apparatus which can realize full scanning exposure of a large exposure area with excellent imaging performance and without lowering the throughput.
The above object and other objects will be further apparent form the following description.
Provided according to the present invention is an exposure apparatus for, while moving a first object and a second object in a certain moving direction, effecting projection exposure of an image of said first object onto said second object, comprising a first projection optical system for forming a real-size erect image of said first object on said second object, which is telecentric at least on an image side, a second projection optical system for forming a real-size erect image of said first object on said second object, which is telecentric at least on the image side and which is disposed next to said first projection optical system, a first field stop for limiting an exposure region to be formed on said second object by said first projection optical system, within a certain shape, and a second field stop for limiting an exposure region to be formed on said second object by said second projection optical system, within a certain shape, wherein a sum of a length along said moving direction, of the first exposure region limited by said first field stop and a length along said moving direction, of the second exposure region limited by said second field stop is constant over a direction perpendicular to said moving direction.
In the present invention, a scanning exposure apparatus performs such projection exposure that a real-size erect image (which is an image with positive horizontal and vertical lateral magnifications) of a circuit pattern formed on a mask as a first object is transferred through a plurality of projection optical systems onto a plate as a second object. A plurality of exposure regions formed on the plate through the respective projection optical systems are so arranged that a sum of lengths along the scanning direction is constant over the direction perpendicular to the scanning direction, that is, that an amount of exposure light becomes constant over the entire surface of plate.
Since the plurality of projection optical systems are so arranged that the sum of widths of exposure regions along the scanning direction is constant over the direction perpendicular to the scanning direction, single scan exposure can achieve a large exposure area on the whole even with compact projection optical systems and small exposure regions formed thereby.
Also, since each projection optical system is compact, scanning exposure can be made while minimizing occurrence of aberrations and keeping excellent imaging performance.
In case that each projection optical system is composed of two partial optical systems and that each exposure region formed on the plate is defined by the shape of an aperture in a field stop located at a position where an intermediate image of mask pattern is formed through a first partial optical system, a preferable arrangement is such that edges of the aperture are triangular and overlap with triangular edges of adjacent apertures in the scanning direction.
In case that the partial optical systems are Dyson optical systems, the center portion of each aperture excluding the both edges thereof is preferably defined by two straight lines. In case that the partial optical systems are Offner optical systems, the center portion is preferably defined by two arcs or by two
Chiba Hiroshi
Kato Kinya
Kato Masaki
Kumazawa Masato
Shirasu Hiroshi
Fuller Rodney
Nikon Corporation
Oliff & Berridg,e PLC
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