Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2000-11-28
2003-06-24
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
Reexamination Certificate
active
06583854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the manufacture of large scale display devices, and more particularly, the manufacture of large scale display devices by the stepping and scanning projection of images from a mask onto a plate.
2. Description of the Related Art
In recent years, there have been advances in the enlargement of the picture surface of display devices (made with glass plates) with a built-in liquid crystal display device or plasma display device. Mass produced articles having a display region of about 30-40 inches are being produced, with a future prospect of 60-inch wall mount type display devices having a width to height (aspect) ratios of 16:9. Further, for the production of printed circuit boards (ceramic plate, epoxy plate, high-molecular film sheet, and the like) of mother boards or CPU sub-boards used in electrical products to mount larger electronic devices, there is a need to both make the line width of the wiring patterns finer in order to increase the mounting density, and enlarge the boards.
Generally, photolithography is used to manufacture the fine circuit patterns for the display cells or wiring used for display panels, and is also used to manufacture the printed circuit boards used for electrical devices. The central role in the photolithography process is the need for an accurate exposure device to transfer an image of the circuit pattern on a mask to a resist (i.e., a plate coated with a substrate of uniform thickness on a glass plate or printed circuit board).
Conventional solutions using various exposure devices and exposure procedures have developed to transfer large circuit pattern structures onto glass plates or printed circuit boards. Among these solutions, picture surface stitch exposure methods have attracted attention. For these methods, the circuit patterns from the mask are joined on the substrate.
One such picture surface stitch exposure method is described in Japanese Unexamined Patent Publication JP-A-S62-145730 (U.S. Pat. No. 4,748,478). According to this method, a projection exposure device (stepper) is equipped with a high resolution projection lens, a mask (reticle) is divided into multiple circuit pattern regions, and a plate (substrate) to be exposed is on a stage. The projection exposure device moves/steps the stage to join the projected circuit pattern images on the substrate.
A similar known stepper type of exposure method is disclosed in JP-A-H1-161243 (U.S. Pat. No. 4,769,680). This method uses two high resolution projection lenses at fixed intervals. These lenses simultaneously expose the circuit pattern of masks installed in the respective projection lenses onto the plate, and join each respective projected image to the two circuit patterns on the preceding exposed substrate.
However, when forming large circuit pattern regions, such as those used for a display device, it is necessary to join images of multiple circuit patterns on a substrate. To accomplish this, methods, such as that disclosed in WO 95/16276, JP-A-H9-1909624 (U.S. Pat. No. 5,888,676), use stitch portions of respective circuit pattern images to make continuous boundaries (straight lines, polygonal lines, wavy lines, rectangles and the like). However, when there is a large difference in contrast of the stitch portions, this results in this boundary being visually observed, which is a disadvantage of this method.
For example, when exposing two respective circuit pattern images to be adjacently stitched onto a substrate using conventional methods, the gate width and the like of transistors used for driving color elements formed in the circuit pattern regions (display regions) differ minutely in the circuit patterns. This difference is due to residual alignment errors, residual focus errors, exposure amount control accuracy, and even differences in the drive voltage. This difference causes the transparency of the liquid crystal pixels to differ slightly in the resulting display regions.
To solve this problem, a method of gradation of the boundary line of the stitch portion has been developed as disclosed in JP-A-H6-324474. According to this method, a predetermined width in the stitch portion of the display portion is set within the circuit pattern, and the width is divided in a random stepping-stone form of interfitting relationship. By this method, without making a clear boundary line in the stitch portion, the combination of the fine pattern having a predetermined width and granularized as a whole is joined in an interfitting state.
The manufacture of circuit devices and display devices having display regions is possible by the various stitch exposure methods of the prior art. However, when taking the cycle time into account, they are not practical stitch exposure methods. For a liquid crystal device, because repeated stitch exposure of the mask pattern is possible in order to expose a display device, it is not necessary to change the mask frequently. However, when exposing the peripheral circuit portions of the display region (end portion pattern), the mask pattern must be frequently changed, and this changeover time increases the overall manufacturing time.
Of course, if the whole of the display region and the peripheral circuit portions are placed, unaltered, on one large mask that is larger than the external dimensions of the display device, it is possible to form the whole circuit pattern for the display device on the substrate without either exchanging the mask and stitch exposure. Nevertheless, in order to manufacture a device that has a size of 30-60 inches, a mask of the same size is necessary, and this makes the production of the mask difficult. In addition, as the size of the exposure device increases, the production of the mask becomes worse, particularly the mask stage unit.
SUMMARY OF THE INVENTION
Consequently, the present invention has as its object to provide a method of manufacturing a large circuit device or display device without a pronounced stitch mark by processing the arrangement or configuration of circuit patterns formed in a mask.
Another object of the present invention is to provide a method of manufacturing a large size circuit device or display device, while reducing the number of masks which are necessary during mask exposure.
Yet another object of the invention is to obtain a large size display device based on performing a smaller number of scans using a scanning exposure device.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In an embodiment of the present invention, a method of manufacture of a circuit device comprises exposing the substrate while causing the relative positional relationship of the mask and plate to change so that circuit pattern regions on the mask are transferred with mutual stitching onto the plate for use in circuit device formation, and within the peripheral region of the circuit pattern region of the mask, respectively formed pattern counterparts of a pair of stitch regions (SA
1
, SSA
2
) are facing each other in the direction in which the relative positional arrangement is changed so as to form a mutually complementary interfitting relationship after exposure, and exposing the substrate while the relative changing positional arrangement to transfer both sides or one side of the pair of stitch regions on the mask and causing them to join in an interfitting state with the similar stitch region of the circuit pattern region periphery already transferred onto the plate.
In another embodiment of the present invention, within the pair of stitch regions the stitch regions comprise a repetitively formed fine pattern structure at predetermined intervals with respect to the direction in which the relative positional relationship is caused to change.
In another embodiment of the present invention, the configuration or arrangement of respectively formed pattern counterparts of the pair of stitch regions ar
Hazama Junji
Kiuchi Tohru
Adams Russell
Esplin D. Ben
Nikon Corporation
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