Fully differential CMOS-MEMS z-axis accelerometer with torsional structures and planar comb fingers

摘要

Fully differential z-axis acceleration sensing often requiresncomplicated multiwafer bonding processes. We present an integratednfully differential complementary metal-oxide semiconductor–micro-nelectromechanical systems u0001CMOS-MEMSu0002 z-axis accelerometer utiliz-ning planar comb fingers and a pair of single-crystal silicon u0001SCSu0002 tor-nsional springs. The sidewall capacitors formed by multiple CMOS inter-nconnect metal layers are exploited for fully differential displacementnsensing with a common-centroid wiring configuration. Single crystal sili-ncon is used throughout the device to form robust microstructures. A deepnreactive ion etching u0001DRIEu0002–based microfabrication process with largenprocessing tolerance has been developed to allow monolithic integrationnof CMOS circuitry with sensor structures and high fabrication yield. Withnan on-chip low-power, low-noise, dual-chopper amplifier that has a mea-nsured 44.5-dB gain and 1-mW power consumption, the fabricated inte-ngrated z-axis accelerometer demonstrates a sensitivity of 250 mV/g andnan overall noise floor of 110 u0001g/ u0001Hz