RF device package method using Au to Au direct bonding technology

This paper presents design, fabrication and evaluation of a wafer level MEMS (Micro Electro Mechanical System) encapsulation using an Au to Au direct bonding with wrinkle patterned layer. For the effective encapsulation, the optimal bonding condition, the bonding temperature 350 °C, the bonding pressure 58 MPa and the duration time 30 min, was developed and used in this paper. We briefly evaluated the bonding strength of test wafers after the bonding test. For RF (Radio Frequency) device packaging, we effectively interconnected Au CPW (Coplanar Waveguide) lines to feedthroughs and measured the RF characteristics. Measured insertion loss of the packaged CPW line was −0.11 dB at 2 GHz. The glass wafer having patterned Au sealing lines was also bonded and has been dipped in the acetone solution for 24 h to examine the leakage of bonding wafer. After 24 h dipping, any leakage point has not been observed at the sealing line and inside the cavity. These results showed that our Au to Au direct bonding method is very reliable and suitable for RF device packaging.