Compact electrode design for an in-plane accelerometer on SOI with refilled isolation trench

Abstract

A two-axis in-plane capacitive accelerometer containing a refilled isolation trench is fabricated in 50 µm silicon-on-insulator (SOI). In the accelerometer, each stationary electrode is split into two sub-stationary electrodes by the refilled isolation trench, and the two sub-stationary electrodes form a pair of differential capacitors with the adjacent movable electrodes. With this deployment, there is no necessity to keep a wide gap between the split stationary combs to avoid stiction, and the sensing electrodes are arranged compactly. Compared with a typical design without isolation trench across the stationary comb, the presented accelerometer allows more pairs of differential capacitors arranged in a given sensing area, and thus has higher capacitance sensitivity. Experimental results show that the capacitance sensitivity is 0.19 pF g−1 and nonlinearity is 0.4%. In addition, the overlap area-changed capacitor enables the accelerometer to reduce the damping coefficient and minimize the possibility of stiction.