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

摘要

Fully differential z-axis acceleration sensing often requires complicated multiwafer bonding processes. We present an integrated fully differential complementary metal-oxide semiconductor-micro- electromechanical systems (CMOS-MEMS) z-axis accelerometer utilizing planar comb fingers and a pair of single-crystal silicon (SCS) torsional springs. The sidewall capacitors formed by multiple CMOS interconnect metal layers are exploited for fully differential displacement sensing with a common-centroid wiring configuration. Single crystal silicon is used throughout the device to form robust microstructures. A deep reactive ion etching (DRIE)-based microfabrication process with large processing tolerance has been developed to allow monolithic integration of CMOS circuitry with sensor structures and high fabrication yield. With an on-chip low-power, low-noise, dual-chopper amplifier that has a measured 44.5-dB gain and 1 -mW power consumption, the fabricated integrated z-axis accelerometer demonstrates a sensitivity of 250 mV/g and an Overall noise floor of 110 μg//Hz.