Reliability performance of Au-Sn and Cu-Sn wafer level SLID bonds for MEMS

Wafer level Solid-Liquid Interdiffusion (SLID) bonding is used to encapsulate MEMS devices. The metals in SLID bonds can improve the reliability by absorbing mechanical and thermo-mechanical stresses. In this paper, the reliability of wafer level Au-Sn-(Ni) and Cu-Sn SLID bonds was systematically characterized and evaluated with shear/tensile tests, shear fatigue test, mixed flow gas (MFG) test, high temperature storage (HTS) test and thermal shock (TS) test. The failure modes and physical mechanisms were analyzed. Overall, the results demonstrated the high mechanical strength and reliability of SLID bonds. Utilizing the reliability results the design of seal bonds for MEMS encapsulation could be improved.