A high-Q magnetostatically-tunable all-silicon evanescent cavity resonator

We present, for the first time, an all-silicon magnetostatically-tunable evanescent-mode cavity resonator that is capable of analog tuning from 9.5 to 17 GHz (1:1.8) while maintaining a high unloaded quality factor (Q) of 650-950 (70-80% of the simulated results). The resonator is fabricated using silicon micromachining and is tuned by moving a gold-covered single-crystal silicon diaphragm over the capacitive post using magnetostatic actuation. The overall volume of the complete device is 600-mm³ including the tuning mechanism. Both the experimental and modeling results show that high-Q all-silicon tunable resonators can be achieved by minimizing the cavity-wall roughness and ensuring a highly conductive gold-gold thermocompression bonding between the diaphragm and cavity.