A poly-Si based 2-axis differential capacitive-sensing accelerometer

This study reports the design and implementation of a 2-axis capacitive-type accelerometer design consists of a pendulum-proofmass (bulk Si), a gimbal-spring (poly-Si film), and vertical-comb 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 2-axis accelerations, and (3) high-aspect-ratio-micromachined (HARM) vertical-combs as the differential sensing electrodes to detect angular motion. In short, this study implements the HARM vertical-comb electrodes for differential capacitive sensing to detect the 2-axis in-plane accelerations. Measurement results show that sensitivities (non-linearity) of etch direction are 20.3mV/G (10.36%) of X-axis, and 17.67mV/G (4.25%) of Y-axis (measurement range: 0.05G~3G). The resolution is 50mG for both axes. The cross-axis errors range from 0.75% to 19.18%.