A novel differential capacitive-sensing dual-axis accelerometer design using pendulum-proofmass, gimbal-springs, and harm vertical-combs

This study presents a novel dual-axis capacitive-type accelerometer design consists of a pendulum-proofmass (bulk Si), a gimbal-spring (poly-Si film), and vertical-combs sensing electrodes. This design has three merits, (1) pendulum-proofmass to produce torque by in-plane acceleration (offset-axis inertial force), (2) gimbal-springs enable the detection of dual-axis accelerations, and (3) high-aspect-ratio-micromachined (HARM) vertical-combs as the differential sensing electrodes to detect angular motion. In short, applying the HARM vertical-combs for differential capacitive sensing to detect the offset-axis inertial force is firstly implemented in this work. Measurement results show that sensitivities (non-linearity) of etch direction are 2.44 mV/G (0.04%) of X-axis, and 51.99 mV/G (0.11%) of Y-axis (measurement range: 0.05 G~2G). The resolution is 50 mG for both axes. The cross-axis errors range from 0.005% to 11%.