Low cross-axis sensitivity micro-gravity microelectromechanical system sandwich capacitance accelerometer

This Letter presents the design and implementation of a highly symmetric microelectromechanical system sandwich accelerometer using a double-device-layer silicon-on-insulator (D-SOI) wafer. The proof mass of though-wafer-thickness is suspended by eight L-shaped beams mirror-symmetrically. The suspension system provides flexible mechanical suspension without large chip area consumption. Therefore the accelerometer is immune from trade-off between sensing capacitance and structure flexibility. The sensing mode (first vibration mode) of the accelerometer is successfully decoupled from other variation modes that followed. Thereby, the accelerometer is insensitive to the lateral acceleration and the rotation disturbance. The symmetric beam-mass structure is fabricated from both sides of the D-SOI wafer symmetrically using a combination of anisotropic wet etching and dry etching process. The accelerometer has high opened-loop capacitance sensitivity of 55 pF/ 1 g. The closed-loop sensitivity is 1.096 v/g and the cross-axis sensitivity is 0.356 . The resolution of the accelerometer is 4.167 g/ Hz (0 200 Hz at 1 atm).