Three-dimensional simulation of the deep UV light intensity distribution in SU-8 photorsists

SU-8 photoresist is a chemically amplified negative resist used in MEMS to make microstructures with high aspect ratios. The simulation of the light intensity distribution in the SU-8 PR is very useful for us to give the final profile of the lithography and plan the experiments. Here, a simple estimation model of the simulation of the deep UV light intensity distribution is developed considering of the refraction caused by the step in the refraction index behind the mask, the absorbance in the SU-8 photoresist, and the reflection of the wafer on the basis of Fresnel-Kirchhoff diffraction equation. Based on the two-dimensional light intensity distribution in many studies, the three-dimensional result is given in this paper. It is successfully verified by experimental results, and the estimated and experimental results show similar trends. So the study demonstrates that the simulation is possible for the SU-8 photoresist