Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2001-02-08
2003-02-25
Nguyen, Henry Hung (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S072000, C355S075000, C356S399000
Reexamination Certificate
active
06525804
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to an exposure device that detects an alignment mark on a workpiece by a microscope, aligns a mask and workpiece and exposes a mask pattern on a workpiece. More specifically, an exposure device is provided which is adapted to move a mask without moving a workpiece and to search for a workpiece alignment mark if a workpiece alignment mark cannot be detected.
2. Description of Related Art
An exposure device is used in which a mask and workpiece are aligned to form various types of electronic devices on a workpiece, followed by exposing a pattern formed on a mask (mask pattern) onto a workpiece which is the processed material.
Aforementioned workpiece and mask are aligned by detection of a workpiece alignment mark (hereinafter abbreviated workpiece mark) formed on a workpiece and a mask alignment mark (hereinafter abbreviated mask mark) formed on a mask via an alignment microscope, followed by matching the spatial relationships of the two (for example, overlap). The workpiece mark and the mask mark are usually created at two locations and are aligned by moving the workpiece in the horizontal direction relative to the mask.
Available types of aforementioned exposure devices include an exposure device that exposes a mask pattern on a workpiece that had been divided into individual sheets (termed a sheet type exposure device) and an exposure device (termed a band-shaped workpiece exposure device) that sequentially exposes a mask pattern on a workpiece while moving a band-shaped film workpiece (band-shaped workpiece).
A conventional sheet type exposure device and a band-shaped workpiece exposure device are explained below.
(1) Sheet Type Exposure Device
FIG. 6
shows the outline structure of a sheet type exposure device.
As shown in that diagram, workpiece stage WS is laid on frame
1
so that it can move in the XY&thgr; directions (X would be the direction to the left/right in the diagram, Y would be the direction perpendicular to the plane of the paper, &thgr; would be rotation about an axis perpendicular to the XY plane) via workpiece stage movement mechanism
10
. Mask stage MS that holds mask M is mounted on frame
1
. Furthermore, alignment microscope
2
is mounted on frame
1
via an insertion, removal mechanism (not illustrated) during detection of an alignment mark.
Mask mark MAM and workpiece mark WAM are mounted at two locations on mask M and on workpiece W, respectively, and aforementioned mask mark MAM image and workpiece mark WAM image are received, after which mask M and workpiece W are aligned.
Photo-irradiation device
3
is mounted over alignment microscope
2
and mask stage MS, and light having exposure light is irradiated from photo-irradiation device
3
during exposure resulting in exposure of the mask pattern that had been formed on the mask on to the workpiece W.
Exposure processing using an exposure device with aforementioned structure is carried out as follows.
Mask mark MAM and workpiece mark WAM are detected by alignment microscope
2
when workpiece W is laid on workpiece stage WS. Workpiece stage WS is moved in the XY&thgr; direction by workpiece stage movement mechanism
10
so that the spatial relationships of the two coincide.
Light having exposure light is irradiated from photo-irradiation device
3
when alignment of mask M and workpiece W is completed. A mask pattern is projected, focused on workpiece W and exposure is completed.
If the conveyance precision of workpiece W is poor when detecting aforementioned workpiece mark WAM, the workpiece mark would not enter the field of alignment microscope
2
when workpiece W is laid on workpiece stage WS. In such a case, workpiece W (via workpiece stage WS) would be moved and the workpiece mark would be sought.
A method of moving a workpiece and of searching for a workpiece mark has been presented in the gazette of Japanese Kokai Publication Hei-10-22201, for example, in which nine regions of an alignment microscope are sequentially searched as a function of the field thereof in spiral fashion by moving a workpiece stage.
FIG. 7
shows an example of aforementioned spiral search procedure. Field AS of an alignment microscope is a 1.5 mm square, for example. The workpiece stage is moved in sequential spirals [1] to [8] centering on the alignment microscope in
FIG. 7
in a search until the workpiece mark is detected.
In this case, the workpiece stage is moved so that the regions SS of search would overlap to permit the workpiece mark to be detected even when it is at the boundary of field AS of the alignment microscope. The width of overlapping regions SS would be suitably set in conjunction with field AS of the alignment microscope. In aforementioned case, the width would be set at 800 to 500 &mgr;um, for example. If the workpiece mark is not detected in searches [1] to [8] in
FIG. 7
, an error would be concluded to have occurred in the operation of workpiece mark mounting itself and processing would be halted as an abnormality of an undetectable workpiece mark.
(2) Band-shaped Workpiece Exposure Device
A band-shaped workpiece would be a long film of organic material or a continuous, long workpiece of thin metal, for example. A band-shaped workpiece would be exposed by unwinding the workpiece from its roll, exposing it, and then rewinding it into a roll.
Thick workpieces (workpiece thickness t=150 &mgr;m or more, for example, workpieces exceeding 250 &mgr;m thickness are often used) or workpieces comprising resin film lined with copper foil (so-called stiff) workpieces have come into use recently as band-shaped workpieces.
There are cases in which the mask is moved without moving the workpiece to align a mask and workpiece when using such workpieces.
Otherwise, the righting moment of the workpiece acts in the opposing direction when attempting to move a workpiece if it is thick. Since great force must be applied by the workpiece stage to counter this righting moment, the workpiece stage movement mechanism must be enlarged and the overall device must be enlarged. Furthermore, the force holding the workpiece to the workpiece stage (for example, the force retaining a workpiece by vacuum adsorption) must also withstand the righting moment. Accordingly, the workpiece could shift from the workpiece stage and alignment would then be impossible. The mask should be moved to align the mask and the workpiece in the case of this band-shaped workpiece.
FIG. 8
shows a diagrammatic structural example of a band-shaped workpiece exposure device that moves a mask to complete alignment.
Workpiece stage WS is attached onto frame
1
as shown in the diagram, and drive roller DR to convey band-shaped workpiece Wb as well as squeeze roller SR, brake roller BR and guide rollers GR
1
, GR
2
are mounted on frame
1
.
Unexposed band-shaped workpiece Wb is wound about rewind roller R
1
and it is drawn out from rewind roller R
1
during exposure. The workpiece Wb is conveyed onto workpiece stage WS and each prescribed region (hereinafter abbreviated exposure region) on the band-shaped workpiece is exposed. The exposed band-shaped workpiece Wb is then rewound on take-up roller R
2
.
Alignment microscope
2
is mounted on frame
1
via an insertion, removal mechanism (not illustrated) during detection of each alignment mark. In addition, mask M is attached to mask stage MS. A workpiece stage movement mechanism is not mounted on workpiece stage WS to move workpiece stage WS since mask M is moved instead without moving band-shaped workpiece Wb in alignment in the case of this example. Instead, mask stage MS is attached to frame
1
via mask stage movement mechanism
4
and mask stage MS is moved in XY&thgr; directions.
Two mask marks MAM are formed on mask M and two workpiece marks WAM are formed in each exposure region of band-shaped workpiece Wb. Aforementioned mask mark MAM image and workpiece mark WAM image are received by alignment microscope
2
, and mask M is moved and aligned with band-shaped
Nguyen Henry Hung
Nixon & Peabody LLP
Safran David S.
Ushiodenki Kabushiki Kaisha
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