Abstract
A new concept of a projection exposure system is proposed. In the new system, a liquid crystal display (LCD) is used in place of a conventional reticle, and arbitrary patterns are introduced on the LCD by a computer keyboard. After investigating what types of LCDs are suitable, and what exposure contrast is obtained, a prototype test exposure bench is manufactured using a LCD panel that is detached from a notebook computer. The bench has a camera lens with F-numbers of 2.8–16 as a projection lens. The LCD dots are of size 263×263 µm2, and each dot includes red, green and blue filter cells. Patterns on the LCD are replicated onto the wafer on a scale of 1/14.3. It is clarified that a maximum contrast of 4.9 is obtained when blue and black designations are used as transparent and opaque cells respectively. Since color LCDs are composed by such red, green and blue cells, the transparent part cannot be stitched in the lateral direction. However, in the longitudinal direction, patterns are stitched quite smoothly, and quasi-arbitrary patterns are replicated successfully.
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