A Fully Differential CMOS–MEMS DETF Oxide Resonator With Q > 4800 and Positive TCF

A fully differential CMOS-MEMS double-ended tuning-fork (DETF) oxide resonator fabricated using a 0.18-μm CMOS process has been demonstrated with aQgreater than 4800 and more-than-20-dB stopband rejection at 10.4 MHz. The key to attaining such a performance attributes to the use of oxide structures with embedded metal electrodes, where SiO2offers aQenhancement (at least a 3-times-higherQ) as compared to other CMOS-MEMS-based composite resonators with similar structures and vibrating modes and where flexible electrical routing facilitates fully differential configuration to suppress capacitive feedthroughs. In addition, the resonators developed in this work possess a positive temperature coefficient of frequency (TCf) and mode-splitting capability, therefore indicating a great potential for temperature compensation and spurious-mode suppression, respectively. This technology paves a way to realize fully integrated CMOS-MEMS oscillators and filters which might benefit future single-chip transceivers for wireless communications.