An Integrated Fully-Differential CMOS-MEMS Z-axis Accelerometer Utilizing a Torsional Suspension

This paper presents an integrated fully-differential CMOS-MEMS z-axis accelerometer utilizing a torsional sensing element. The sidewall capacitors formed by multiple CMOS interconnect metal layers are exploited for fully differential displacement sensing with a common-centroid wiring configuration. A deep reactive ion etching (DRIE) based micro-fabrication process with large processing tolerance has been developed to allow robust sensor structures and high fabrication yield. With a monolithically integrated low-power, low-noise, dual-chopper amplifier which has a measured 44.5 dB gain and 1 mW power consumption, the fabricated integrated z-axis accelerometer demonstrates a sensitivity of 320 mV/g and an overall noise floor of 110 mug/radicHz.