Optimization of Silicon-Silicon Adhesive Wafer Bonding

Abstract

Optimization of bonding parameters to develop a low temperature adhesive wafer bonding process for silicon was studied. SU-8 was used as the adhesive. The Key Process Input Variables were soft bake temperature, UV exposure and bonding temperature. The soft bake temperatures were 70 oC, 90 oC and 95 oC. UV exposure energies were 50 mJ/cm2, 100 mJ/cm2 and 150 mJ/cm2 and bonding temperatures of 90 oC, 115 oC and 140 oC were studied to optimize the curing process. The quality of the bonds was determined by two Key Process Output Variables: the fraction of interfacial area in intimate contact, measured by void area, and the strength of the bond interaction, measured by tensile strength. A general linear statistical model was used to determine the impact of the KPIVs on the KPOVs. The optimum conditions are soft bake temperature: 90 oC, UV exposure: 100 mJ/cm2 and bonding temperature: 115 oC.