Fabrication and characterization of gold-tin eutectic bonding for hermetic packaging of MEMS devices

This paper presents the fabrication of wafer-level hermetic encapsulation for MEMS devices using low-temperature (300°C) Au-Sn bonding together with their pre- and postbonding characterization. Thermal evaporation method was used for metallization which is easy and controllable method for low thickness metallization. In this respect, the current study represents preliminary characterization results of Au-Sn pre- and post-bonding with an average thickness of less than 1.5μm processed by thermal evaporation method. The real fabrication conditions for commercial sensor devices were simulated during the bonding trials. The optimum bonding was applied to sensor devices to ensure the reliability of the encapsulation. The average shear-strength upon constant strain rate of 0.5 mm.min-1 was found to be around 23 MPa which indicates a mechanically strong bonding for 1.5μm thick sealing rings.