Achieving of aluminum-aluminum wafer bonding at low temperature and pressure using Surface passivated technique

Micro-electro-mechanical systems (MEMS) device packaging has proven to be more costly and complex, and it has been a substantial barrier to the commercialization of MEMS. Because of the reason there is a huge requirement of vacuum seal packages for MEMS devices at low cost at low thermal budgets. In this work, we are proposing a method of developing direct aluminum-aluminum (Al-Al) wafer frame bonding using themo-compression bonding method. However, the formation of chemically stable surface oxide, immediately after exposed to ambient conditions, is a major inter-diffusion barrier for grain growth across the interface of bonding. To break this barrier requires high temperature (minimum of similar to 450 degrees C) and pressures, which may cause the some of the MEMS devices may damage or properties of CMOS devise may change. Therefore, we motivated towards the formation of direct Al-Al interconnect at the low temperature and pressures using surface passivation of another noble metal (Palladium (Pd)) for wafer level thigh seal encapsulation for MEMS. Here, we studied the effect of Pd on Al surface and optimization of minimum Pd thickness to protect the surface from oxidation. Based on AFM, XRD, C-SAM, SEM, EDX analysis, the role of Pd on Al Surface for hermetic sealing applications were discussed