Micromachined Tri-Axis Capacitive Accelerometer Based on the Single Mass

Abstract

A novel micromachined tri-axis capacitive accelerometer based on the single mass is proposed in this paper. The presented accelerometer contains a single proof mass acting as the sensitive element which is suspended by two flexible beams above the substrate, and an array of movable and fixed electrodes is utilized. To match the sensitivity design requirement, the differential capacitive detection is utilized, and the cross-sensitivity problem of three orthogonal axes is avoided ideally. The accelerometer structure is based on the EPI-poly process to realize the 18 microns thickness. Thus the detection capacitance, sensitivity and reliability are improved, the mechanical noise is decreased. To reduce the thermomechanical stress’ effect on the offset, a special anchor-middle structure is designed. Simulation results show that the offset is insensitive to the thermomechanical stresses and the sensor has a good consistency in three axes which has been validated by the testing results.