Wafer-to-wafer transportable gold particle plug for spot vacuum sealing of MEMS

We have developed a spot vacuum sealing method utilizing conventional thermo-compression bonding at 160 °C with a transportable Au particle plug on a silicon through hole. The plug of which diameter is around 200 μm is composed of sub-micron-size Au particles and an Au thin film. The easy deformability of sintered Au particles leads to the hermeticity with changing the structure to closed pore state. The compliance with bond surface irregularity as well as the insensitivity to surface flatness are advantageous to hermetic sealing. From the deflection of Si diaphragms over the sealed cavity, the inside pressure was estimated below 100 Pa. The small leak rate of Kr-85 was below 4.7 × 10
^-12
Pa·m
³
/s detection limit, which was sufficient for the integration technology of MEMS.