The study on the O2 plasma treatment for bonding of SU-8 layers

SU-8 is becoming increasingly important for fabrication of lab-on-a-chip devices due to its excellent chemical stability, mechanical, and optical properties. To form a complete SU-8 device, O-2 plasma-assisted thermal bonding has been used to bond SU-8 layers. O-2 plasma treatment is critical and has a significant influence on the fabrication quality of SU-8 devices. However, to the best of our knowledge, there is no work which analyzed O-2 plasma treating process for SU-8 material in depth and systematically. In this study, the influence of O-2 plasma treatment on the water contact angle and bonding strength for both un-crosslinked and crosslinked SU-8 layer was investigated in detail. The etching effect of SU-8 layer was also studied. The leakage test demonstrated that there is no gas leakage in the bonded SU-8 layer up to 0.65 Mpa which indicates the practicability of the proposed SU-8 bonding method.