High Q CMOS-MEMS resonators and its applications as RF tunable band-pass filters

Clamped-clamped beam resonators are designed and fabricated in a 0.35 mum CMOS commercial technology, using a simple one-step mask-less wet etching to release the MEMS structures. The resonator, with a 22 MHz resonance frequency shows a Q value of 227 and 4400, when measured at atmospheric pressure and vacuum, respectively. This resonator is used as the main building block for filtering application. Using parallel filtering and differential on-chip CMOS amplification, the RF-CMOS-MEMS system forms a tunable band-pass filter with programmable bandwidth (from 100 kHz to 200 kHz), stop band rejections of 30 dB and shape factors at -20 dB smaller than 3, providing comparable performance than other MEMS filters using specific technologies.