A novel CMOS out-of-plane accelerometer with fully differential gap-closing capacitance sensing electrodes

Abstract

This study presents a novel CMOS-MEMS out-of-plane linear accelerometer. This capacitance-type accelerometer contains specially designed gap-closing sensing electrode arrays with on-chip fully differential sensing circuits. Moreover, the comb-finger electrodes have the characteristics of the high fill factor and sub-micron gap to increase the sensing capacitance. Thus, the sensitivity and signal-to-noise ratio can be further improved. This study has established a post-CMOS wet-etching process to realize the accelerometer with sensing electrodes of the sub-micron gap in the out-of-plane direction. The present accelerometer has been demonstrated using the standard TSMC 2P4M process plus the post-release technique. The measurement results demonstrate that the accelerometer has a sensitivity of 1.14 mV g−1, and a nonlinearity of 3.4%.