DC-50 GHz low-loss wafer-scale package for RF MEMS

This paper reports on the design and fabrication of wafer-scale packaging for RF MEMS devices. Coplanar waveguide (CPW) lines on a glass wafer are covered with a high resistivity silicon wafer using gold-to-gold thermo-compression bonding. Oxide is used as a dielectric interlayer for CPW feedthroughs underneath the gold sealing ring. The designed feedthrough has an insertion loss of 0.06-0.1 dB at 1-50 GHz with a return loss of < -35 dB (per transition). The gold sealing ring is connected to the CPW ground to achieve around 10 dB higher isolation. The whole package has a measured insertion loss of 0.2-0.5 dB and return loss of < -20 dB up to 50 GHz. The measured insertion loss at 1-2 GHz is 0.2 dB with return loss of < -30 dB.