The present invention relates to a method of manufacturing a display unit, and particularly to a technique of forming a preferable pattern, giving consideration to deformation of a panel.
With regard to display units such as liquid crystal display units, there has been progress in miniaturization and larger sized panels, while pattern formation on panels of various materials is being studied. Consequently it has become impossible to ignore panel deformation such as that which occurs with shrinkage due to the effect of heat in the course of manufacture, for example. Conventionally, to cope with such panel deformation, there is known a technique in which deformation of a pattern in a lower layer is measured and an upper pattern is drawn to fit the deformation (see Patent Document 1). This technique employs direct exposure equipment without using a mask and tries to form the upper pattern to fit deformation faithfully even when the lower pattern has been deformed from a rectangle into a quadrilateral without having parallel sides. Further, with regard to exposure equipment that uses a mask, there is known a technique in which an alignment error or optical distortion is corrected for alignment with a substrate.
Patent Document 1: Japanese Unexamined Patent Application Laid-open No. 2001-142225
A liquid display panel is manufactured by overlaying a Thin Film Transistor (TFT) panel and a Color Filter (CF) panel. Generally, the TFT panel and the CF panel are produced through separate processes. The TFT panel has transistors, capacitor parts, circuits, and the like, on a glass panel. The transistors become switching elements; each of the capacitor parts stores electric charge and generates an electric field; and the circuits connect these transistors and capacitor parts. Further, the capacitor parts play a role as pixels that intercept or transmit light. Since the transistors and the circuits do not easily transmit light, they are thus often arranged around the pixels. The CF panel has red, blue and green color resist parts arranged at places corresponding to the pixels in the TFT panel. Further, the CF panel has a light shielding part called a Black Matrix (BM) arranged at places corresponding to the transistors and the circuits in the TFT panel. To overlay the TFT panel and the CF panel together, a circuit layer pattern, through which light is not easily transmitted, of the TFT panel is aligned with a BM pattern of the CF panel, when the TFT panel and the CF panel are stuck together. This is done to improve visibility and the like, since the circuit layer pattern and the BM pattern both do not easily transmit light. The circuit layer is formed using aluminum (Al) or the like.
Here, when overlaying accuracy or processing accuracy of the TFT panel or the CF panel is not enough, then the pixel parts of the TFT panel overlaps the BM part of the CF panel, and a good aperture rate cannot be obtained.
According to the above-described alignment method, an upper pattern is formed by exposure, following lower pattern deformation caused by distortion of the panel. Accordingly, repeated exposures of many layers cause a mechanical error or a position measurement error at the time of alignment in each layer, so that the degree of deformation of each pattern shape generally tends to increase. As the deformation increases, the fabrication accuracy of the TFT panel becomes worse, and pixels of the TFT panel overlap the BM part of the CF panel at the time of overlaying the CF panel and the TFT panel together.
Here, occurrence of the above-described overlap between the pixels of the TFT panel and the BM part of the CF panel can be reduced to some degree by designing the shape of the CF panel giving considering to the way in which the TFT panel is deformed. However, deformations of TFT panels are not uniform for all panels, and vary from panel to panel. Thus, when exposure is performed to follow deformation of each panel, a mechanical error or a position measurement error is caused at the time of alignment with a substrate layer, and pattern deformation of the TFT panel becomes larger as processes proceed. This leads to overlap between the pixels of the TFT panel and the BM part of the CF panel. Thus, it is necessary to take a countermeasure allowing a margin, such as by setting the width of the BM part wider at the time of design. This, however, becomes an undesirable element for product specifications such as aperture rate and the like.
Thus, to reduce variation in pattern shapes in a TFT panel, what is required is, not a simple exposure method that faithfully follows deformation of a pattern in a lower layer, but an exposure method that suppresses variation in pattern shapes at the time of exposure.
An object of the present invention is to provide an exposure method that suppresses variation in pattern shapes at the time of exposure.
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