Wafer-Scale hermetically packaged MEMS switches with liquid gallium contacts

A wafer-scale hermetically packaged self-healing RF MEMS switch, which utilizes liquid gallium (Ga) contacts to take the place of the traditional solid metal contacts, is proposed in this paper. Liquid Ga contact switch features significantly improved power handling capability compared to conventional MEMS switches. The switch is driven by an electrostatic actuator, which includes upper electrodes on a silicon nitride bridge and lower electrodes on the substrate. Small liquid Ga droplets serve as a self-healing interface between the upper and lower contact electrodes. To minimize RF loss, a quartz wafer is used as the substrate material. To prevent oxidation of the liquid gallium, a hermetical packaging process with frit glass seal is used. A pyrex glass cap wafer is connected to the quartz device wafer by the frit glass seal. Finite element analysis is used to simulate the electro-thermal heating of the package. The measured package leakage rate is below 1 Torr/year.