Heating Effect on Photoresist in Spray Coating Technique for Three-Dimensional Lithography

Spray coating of the photoresist is a promising technique for realizing photolithography on three-dimensional structures, which is frequently desired in the field of microelectromechanical systems. Revealing the technical performance and determining the optimum conditions are indispensable for making the process reliable. The conditions required for obtaining a uniform resist thickness over the anisotropically wet etched deep cavity are examined. The sample temperature and the power density required for heating the sample are found to have a significant effect. At the optimized conditions, a uniform resist film is obtained over the cavity (with an average thickness of 1.5 µm on the top, slanting, and bottom flat regions, and 2.4 and 2.7 µm on the convex and concave corners, respectively).