Photocopying – Projection printing and copying cameras – Methods
Reexamination Certificate
2000-06-23
2002-01-22
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Methods
C355S053000, C355S067000
Reexamination Certificate
active
06341011
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to industrial image exposure devices that are used in lithographic processes to expose images onto substrates such as during the manufacture of liquid crystal display panels, semiconductor elements, etc.
2. Description of the Related Art
Industrial imaging devices such as image exposure devices are used to produce liquid crystal display panels, semiconductor elements, etc. For example, personal computers, laptop computers, word processors, televisions, and many other common devices include components that are manufactured, in part, by using image exposure devices. The manufacture of liquid crystal display panels, for example, has become increasingly reliant on image exposure devices and techniques. And, as such display panels have become more complex and intricate, so too have the manufacturing devices and processes associated with production of the same.
Liquid crystal display (LCD) panels often are produced, in part, by forming a conductive thin film electrode (e.g., of the Indium Tin Oxide (ITO) variety, etc.) on and affixing a liquid crystal molecular orientation element to a glass substrate and sealing that arrangement with a sealant or sealing member at the outer periphery of the substrate. Formation of ITO-type thin film electrodes and, in particular, complex LCD display segments have been achieved by imaging the same via lithographic image exposure devices and processes.
To perform such lithographic processes, a photolithographic image exposure device known as a “stepper” often is used. With a stepper, a desired pattern contained in a mask or on a reticle may be projected onto a substrate via a “step and repeat” exposure method. Depending on the nature of the pattern to be exposed (e.g., the number and complexity of the display units to be exposed, etc.), other patterning devices and techniques have been used (e.g., scanning exposure devices using mirror projection aligners and systems, etc.).
Despite their widespread use to produce LCDs, etc., stepper throughput efficiency has become problematic. That is, as LCD elements have increased in complexity, the number of devices that can be made via step and repeat techniques has decreased. And, when using mirror projection type systems, etc., problems also have been realized in terms of manufacturing relatively large mirrors and assemblies to expose enlarged masks. As such, mirror-type systems have resulted in relatively large scanning devices and stepper units.
To address efficiency and size problems associated with prior stepper units, some have proposed scanning type exposure devices for relatively large circuit pattern masks. One such device is disclosed in Japanese Laid-Open Patent Publication Hei 7-57986 (U.S. Pat. No. 5,729,331). Such a scanning type exposure device uses plural projection optical systems to simultaneously scan a mask and a photosensitive substrate. As such, scanning type exposure devices of the type disclosed in the aforementioned Japanese patent publication have led to increased device throughput efficiency and decreased stepper size.
An exemplary scanning type exposure device (of the type illustrated in the aforementioned Japanese patent publication) is shown in drawing figure (FIG.)
1
, which is attached to this document. In particular, the stepper unit exposure device shown in
FIG. 1
includes a mask table
122
and a plate table
123
which are supported on a carriage
112
. The carriage has a U-shaped cross-section. The mask and plate tables are supported opposite each other. A mask
113
and a plate
114
are respectively supported on tables
122
and
123
. A mask-side reference mark plate
130
is fixed to the end of the mask table
122
, and a plate-side reference mark plate
128
is fixed opposite to the mask-side reference mark plate
130
. Movement of the carriage
112
in the direction of arrow A, causes mask
113
and plate
114
to be scanned by an illuminating system
117
and a projection optical system
118
. A pattern is formed through mask
113
via illuminating light from illuminating system
117
. To expose plate
114
, the light that passes through mask
113
and which passes through projection optical system
118
becomes incident on plate
114
. In
FIG. 1
, actuators
124
a
-
124
c
control the position of the mask table during mask setup processes to ensure proper exposure.
The exposure device depicted in
FIG. 1
is further illustrated in and discussed with regard to
FIG. 2
which also is attached hereto. In particular, the projection optical system shown in
FIG. 1
is made up of seven optical modules
125
1
-
125
7
. Each optical module
125
has a trapezoidal exposure field that divides the pattern on mask
113
to be copied/projected onto plate
114
. Each optical module
125
has a mechanism
126
to adjust the position of the projected image. The trapezoidal regions PA
1
-PA
4
are projected by optical modules
125
1
-
125
4
while trapezoidal regions PA
5
-PA
7
are projected by optical modules
125
5
-
125
7
.
The trapezoidal regions are aligned in a direction (non-scanning direction) perpendicular to the scanning direction at a predetermined spacing. The ends (those portions shown by dashed lines in
FIG. 3
, which is attached hereto) of adjacent trapezoidal regions (for example, PA
1
and PA
5
, PA
5
and PA
2
, etc.), and the optical modules
125
1
-
125
7
are arranged such that they overlap by a predetermined amount in a non-scanning direction.
In mask-side reference mark plate
130
, and in plate-side reference mark plate
128
, as shown in
FIG. 3
, mask-side reference marks M
1
-M
8
, and plate-side reference marks P
1
-P
8
, are disposed such that the associated marks overlap. Such marks are located so as to correspond to the aforementioned overlap portions of the trapezoidal regions.
Calibration of the optical modules
125
1
-
125
7
is illustrated with regard
FIG. 4
, which also is attached hereto. As shown in
FIG. 4
, mask-side reference marks M
1
-M
8
are projected onto plate-side reference marks P
1
-P
8
via optical modules
125
1
-
125
7
. Because reference marks M
1
-M
8
and P
1
-P
8
are formed and disposed to overlap, when the same do not overlap (e.g., because of device movement or drive anomalies, etc.), the optical modules are considered to be the cause of such an anomaly and any resultant distortion. Consequently, the relative positions of the marks M
1
, M
2
projected by optical module
125
1
, and the plate-side reference marks P
1
, P
2
are photoelectrically detected by use of a sensor
132
(e.g., a TV camera, etc.). In turn, positional displacement data (dx
1
, dy
1
) between mark P
1
and the projected image of mark M
1
, and positional displacement data (dx
2
, dy
2
) between mark P
2
and the projected image of mark M
2
may be found and derived. With such displacement data (e.g., displacement measurement data, etc.), the particular adjustment mechanism
126
corresponding to optical module
125
1
may be used to adjust optical module
125
1
so that the respective positional displacement amounts become zero or tolerable.
Similarly, adjustment is performed relative to optical modules
125
2
-
125
7
such that corresponding mask-side reference marks (M
3
-M
8
) and plate-side reference marks (P
3
-P
8
) overlap. Furthermore, the adjustment of the optical modules
125
5
,
125
6
,
125
7
may be performed by moving carriage
112
, so that the reference marks enter the exposure fields of the optical modules
125
5
,
125
6
,
125
7
. Accordingly, adjustment is possible so that the seven optical modules are able to project the pattern on mask
113
accurately and within expected tolerances.
Although, prior exposure devices allow calibration of projected images and, in particular, calibration of projection optical systems to effect accurately projected design patterns, such calibration is performed by using mask-side reference marks disposed on a special mask-side reference mark plate which may be independent of the mask that is to be imaged and
Adams Russell
Erik B. Cherdak & Associates LLC
Nguyen Hung Henry
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