What is Exposure?
Exposure is a module that simulates the physical phenomenon and chemical reaction of SU-8 photoresists during the exposure, PEB, and development process which are the focuses of UV lithography modeling.
It includes all steps of UV lithography modeling:
A. Inclined light intensity distribution modeling
B. Exposure modeling
C. PEB modeling
D. Development modeling
Exposure can predict the developed profiles of SU-8 photoresists. Also, it can analyze the intensity distribution impact on the developed profile of SU-8 photoresists.
Verified to ensure unparalleled accuracy
A series of experiments for inclined/multi-directional UV lithography of SU-8 photoresists have been performed to verify the Exposure module¡¯s accuracy. The following two cases will show the influence of substrate reflection on the oblique structures. SU-8 was coated on both silicon wafers and glass wafers with TiO2 film.
Case 1 . SU-8 structures on silicon wafers
Figure 1. Simulation and experimental results for SU-8 oblique pillar with weak reflection-induced structures on bare silicon wafer. 240 ¦̀m thickness SU-8 was exposed at a UV light intensity of 2.6 mW/cm2 for 380 s at 23.5¡ă.
Figure 2. Simulation and experimental results for SU-8 oblique pillar with strong reflection-induced structures due to prolonged exposure time. 140 ¦̀m thickness SU-8 was exposed at a UV light intensity of 2.6 mW/cm2 for 600 s at 23.5¡ă.
Case 2. SU-8 structures on TiO2 substrate
Figure 3. Simulation and experimental results for L-shape oblique SU-8 structure with no reflection-induced pattern
Figure 4. Simulation and experimental results for I-shape oblique SU-8 structure with no reflection-induced pattern