Out-of-plane CMOS-MEMS Resonator with Electrostatic Driving and Piezoresistive Sensing

In this paper, a prestress vertical comb drive resonator with piezoresisted sensor is developed. The proposed resonator consists of a set of comb fingers fabricated along the composite beam. One end of the composite beam is clamped to the anchor, whereas the other end is elevated vertically by the residual stress. The actuation occurs when the electrostatic force, induced by the fringe effect, pulls the composite beam downward to the substrate. The piezoresistor is designed to sense the vertical vibration frequency of the resonator. The device is fabricated through a standard 0.35μm 2P4M CMOS-MEMS process. The measurement results indicated that the resonant frequency of the device is 14.5 kHz, and the quality factor is about 36.