Microlens Lithography

The future demands for flat panel display (FPD) manufacturing is a resolution of 3-5 μm for large substrates of 550 × 650 mm2 size. Standard lithographic techniques, like wafer stepping or proximity printing can be used. Unfortunately, these methods have some severe drawbacks which significantly increase the fabrication costs. Using a wafer stepper, the small printing area will cause numerous exposure steps. The stepping has to be very accurate, because stitching errors can be easily seen in the display pattern. Using a proximity printer, the substrate is set some 20-50 μm behind the mask to achieve a resolution of 3-5 μm. This is not an easy task for large substrates. The costs for these highly planar substrates are immense. A direct contact may easily damage the expensive photomask.