Photocopying – Contact printing
Reexamination Certificate
2000-10-23
2002-10-01
Adams, Russell (Department: 2851)
Photocopying
Contact printing
C355S072000, C355S075000
Reexamination Certificate
active
06459474
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a contact exposure device used in contact exposure processes, especially a contact exposure device for exposing a mask pattern on a workpiece like a flexible printed circuit (FPC) having polyimide properties that is thin and prone to cracking. More specifically, the invention relates to a contact exposure device provided with an interval setting means that separates and mutually faces a mask and workpiece so as to have a preset contact-free interval when pressure between a mask and workpiece is reduced.
2. Description of Related Art
Exposure processes in which light passing through a mask is irradiated on a workpiece to expose a mask pattern on a workpiece are carried out to form various types of electronic devices on a workpiece in the production of various electrical components that require microsize processing, such as semiconductor devices, liquid crystal substrates, micro-machines, etc. Among aforementioned exposure methods, the contact exposure method is one that adheres a mask and workpiece and then copies a mask pattern onto the workpiece.
FIGS.
7
(
a
) &
7
(
b
) are diagrams showing the structure of a contact exposure device. The diagram shows the structure of a contact exposure device that adheres a mask and workpiece by applying force through decompression that pushes a photomask (hereinafter abbreviated mask M) and a workpiece W together, followed by exposure. FIG.
7
(
a
) is a top view while FIG.
7
(
b
) is a sectional view along line A—A of FIG.
7
(
a
).
In the diagram, positioning member
1
of mask M is mounted on a mask stage MS and an aperture
2
is formed in mask stage MS so that exposure light from a photo-irradiation unit (not shown) will be irradiated on workpiece W through mask M.
Mask M on which a mask pattern is formed is brought into contact with the positioning member
1
and is laid on aperture
2
of mask stage MS. A vacuum groove
3
extends about the periphery of aperture
2
of mask stage MS, and mask M is attached/held by vacuum that is provided to vacuum groove
3
from a vacuum source (not shown). In addition, a conduit
4
for depressurization of the space that is formed by photomask M, mask stage MS, workpiece W, workpiece stage WS and vacuum seal unit
6
is provided in the mask stage MS.
A groove
5
for drawing a vacuum to attach workpiece W is formed in workpiece stage WS and the workpiece W that is placed on the workpiece stage WS is attached/held on the workpiece stage WS by vacuum that is supplied to vacuum groove
5
from a vacuum source (not shown). Vacuum seal unit
6
comprises a sealing member formed, for example, from rubber, that is mounted about the periphery of workpiece stage WS and is useful for creating a vacuum state to adhere mask M to workpiece W.
In addition, the workpiece stage WS is attached to workpiece stage drive mechanism
8
via interval setting groove
7
. Workpiece stage drive mechanism
8
moves workpiece stage WS in the X direction (for example, left-right direction of FIG.
7
(
b
)), Y direction (for example, perpendicularly to the plane of paper in FIG.
7
(
b
)) and Z direction (up-down in FIG.
7
(
b
)), and rotates workpiece stage WS about an axis perpendicular to the plane of workpiece W. The shape of workpiece stage W is usually created to match the shape of workpiece W. It is round if the workpiece is round and aperture
2
also is polygonal if the workpiece is polygonal.
Exposure of workpiece W by the contact exposure device shown in of FIGS.
7
(
a
) &
7
(
b
) is explained below.
(1) Mask M is brought into contact with positioning member
1
and is placed on the mask stage MS. Next, a vacuum is supplied to vacuum groove
3
and the mask M is attached/held to the mask stage MS.
(2) Workpiece W is placed on the workpiece stage WS, a vacuum is supplied to the groove
5
from a vacuum source and workpiece W is attached/held on workpiece stage WS.
(3) Workpiece stage WS is raised by workpiece stage drive mechanism
8
and the workpiece W is brought into contact with mask M. Mask M and workpiece W are then positioned in parallel by interval setting groove
7
(consult the gazette of Japanese Kokai Publication Hei-7-74096 and corresponding U.S. Pat. No. 5,543,890 for parallel positioning of mask M and workpiece W).
(4) Following parallel positioning of mask M and workpiece W, the workpiece stage WS is lowered slightly and the gap between mask M and workpiece S is set to an alignment gap. An alignment mark inscribed on mask M and workpiece S is detected by an alignment microscope (not shown), and workpiece stage WS is moved in XY&thgr; directions the by workpiece stage drive mechanism
8
so that both alignment marks coincide, thereby completing alignment of mask M and workpiece W.
(5) Following completion of alignment, workpiece stage WS is elevated to bring mask M into contact with the workpiece W.
Here, mask M and workpiece W are merely brought into mutual contact. Mask M and workpiece W cannot be adhered along the entire surface if slight unevenness or warping are present on the mask M and workpiece W. Accordingly, unevenness may develop in the gap between mask M and workpiece W in some cases, as shown in an exaggerated manner in FIG.
8
.
When exposure is carried out in the aforementioned state, the exposure accuracy following exposure processing (pattern shape following developing) varies with the site of the exposure region. Thus, force is applied between mask M and workpiece W so as to push them together, as explained below, since mask M and workpiece W are adhered over the entire surface.
(6) Vacuum seal unit
6
mounted about the periphery of workpiece stage WS contacts the lower surface of mask stage MS when workpiece stage WS is raised and mask M is brought into contact workpiece W. A sealing space is created by mask M, mask stage MS, workpiece W, workpiece stage WS and vacuum seal unit
6
. A vacuum is supplied to conduit
4
mounted in mask stage MS in this state and the aforementioned sealing space is depressurized.
(7) Upon depressurization of the sealing space, mask M is pushed against workpiece W and mask M is adhered to workpiece W over the entire surface, as shown in FIG.
9
.
(8) Workpiece W is irradiated through mask M by a photo-irradiation unit with light containing exposure light while mask M is adhered to workpiece W as mentioned above to complete exposure.
In conventional contact exposure, as mentioned above, the space between mask M and workpiece W is depressurized, force is applied to mask M and the shape of mask M is altered so as to match the shape of the workpiece W. Workpiece W is then held between mask M and workpiece stage WS and adhered. However, if even a slight amount of dirt is present on workpiece stage WS in the aforementioned conventional example, the workpiece W would be deformed as shown in FIG.
10
. Accordingly, force would be concentrated at the section of contact between mask M and the deformed section of workpiece W when mask M is adhered to workpiece W, and the expensive mask M would be damaged. Exposure using a damaged mask would result in the copying of that damage directly to workpiece W, resulting in a defective product.
Furthermore, there is a danger of the workpiece W breaking since a concentrated force is applied even to deformed sections of workpiece W. In particular, thin workpieces W having thickness on the order of 100 to 50 &mgr;m, like flexible printed circuits (FPC) having polyimide properties, have come into use in recent years while a tendency to increased contact force between mask M and workpiece W has developed accompanying the demand for high resolution. This has increased the danger of breakage of the workpiece W.
Thus, the inventors have proposed a method of contact exposure which separates and mutually faces a mask and workpiece so that the two maintain a gap without contact upon depressurization of the space between mask and workpiece to a level of force that permits the desired contact force to be reached. The space between a mask and workp
Adams Russell
Nguyen Hung Henry
Nixon & Peabody LLP
Safran David S.
Ushiodenki Kabushiki Kaisha
LandOfFree
Contact exposure device provided with a mask and workpiece... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Contact exposure device provided with a mask and workpiece..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Contact exposure device provided with a mask and workpiece... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2956590