Contact UV Lithography Simulation for Thick SU-8 Photoresist

A two-dimensional (2D) simulator that integrates aerial image simulation two-dimensional (2D) simulator that integrates aerial image simulation module, exposure simulation module, post-exposure bake (PEB) simulation module and development simulation module is presented for the deep UV lithography of thick photoresists such as SU-8 photoresists. A method based on Fresnel diffraction is developed to simulate the UV light intensity distribution into the SU-8 Photoresists with the refraction, the absorbance of the SU-8 photoresists and the reflection of the wafer are efficiently considered. The development model considering both swell and depth-dependent dissolution rate, which is quite different from those models for the thin photoresists, is presented to obtain the final development profiles, combined with the 2-D dynamic cellular automata model for photoresist etching simulation. The simulation profiles have been found to be in good agreement with the experimental results.