Scan projection optical lithography onto cylindrically curved convex and concave surfaces with inhomogeneous curvature radii

摘要

A novel exposure method was developed to print patterns onto cylindrically curved convex and concave surfaces with inhomogeneous curvature radii. This technology is effective to print patterns with widths of 20-100 μm onto curved components of various electro mechanical devices such as curved displays. Considering the productivity, lens projection optical lithography using regular flat reticles was adopted. If an object with a cylindrically curved surface is horizontally placed below a projection lens, the distance between a surface ridge line and the lens becomes constant Accordingly, patterns in a narrow slit area on the flat reticle can be sharply imaged around the ridge line. In addition, patterns can be replicated all over the curved object surface by synchronously scanning the reticle and the object, if the distance between the lens and the object ridge line is kept constant. Patterning feasibility was demonstrated using a handmade exposure system. Convex rules shortly cut in 30 mm length were used as specimens, and patterns were printed onto the convex and concave surfaces. The curvature radius was 15 mm at the center and infinite at both sides where the surfaces were flat. Resolution limit was found to be better than 15μm and width homogeneity of less than ±3% was obtained for various 100-μm patterns on all over the curved surfaces in the exposure area of 18 x 10 mm. It was verified that the novel exposure method was feasible.