Troubleshooting on the sample preparation for SU-8 to SU-8 wafer level bonding

The present technical note reports troubleshooting on the sample preparation for SU-8 to SU8 wafer level bonding, using Microchem SU-8 2050 and SU-8 dry film (SUEX). The SU-8 film spin coated from Microchem SU-8 2050 viscous solution suffers from uneven surface and edge bead that lower the yield of wafer level bonding. On the other hand, although the SU-8 dry film does not show such problems, the partial delamination of the SU-8 film on the glass wafer, the proximity effect on the glass wafer, and the cracking in the SU-8 film are observed. These issues are shown to be solved by optimizing the UV light intensity and the baking temperature.