Coding gray-tone mask for fabrication of microoptical elements
Su JQ., Yao J., Du JL., Zhang YX., Gao FH., Guo YK., Cui Z.
A new method was proposed to design coding gray-tone masks, based on modifying position and shape of cell on mask. Predistortion applied to modify mask was implemented by introducing this method according to the nonlinear effects in aerial image and resist development. Based on the theory of partial coherent light imaging and the resist development model, the intensity distribution through the coding gray-tone mask and the exposure of photoresist were simulated. The coding gray-tone mask was fabricated by electron beam exposure system, and the microlens array with continuous relief distribution on photoresist was obtained.