Low-temperature void-free wafer-level adhesive bonding for thin film transfer by nano-imprint resist

Experimental investigations using nano-imprint resist mr-i 9100M with various bonding parameters are performed to figure out the appropriate parameters for void-free adhesive bonding. In order to visualize the void formation at the bonding interface, glass wafer has been used to bond with silicon wafer. Based on the experimental results, it is found that the bonding pressure of 4.1 bar, pre-bake temperature of 100°C, pre-bake time between 5 minute and 10 minute and polymer thickness of 1.4 μm or more will achieve a void-free wafer-level bonding. The resulting bondings are void-free when the adhesive layers can be sacrificially removed in pure oxygen plasma without leaving any etching residues at the surfaces. It also demonstrates the mr-i 9100M are suitable adhesives for thin film transfer in hybrid integration of CMOS circuits and MEMS/MOMEMS devices.