A novel micromachined differential resonant accelerometer with flexural mechanisms fabricated by SOI-MEMS technology

A novel micro-machined resonant accelerometer designed with differential structure is put forward. The device structure is a seismic mass supported by two flexural hinges and two vibrating beams, in which the hinges and the beams are doubly-clamped by the seismic mass and the substrate. Due to the different thickness of the hinges and the beams, the neutral axes of the hinges and the beams are not coplanar. Therefore, the beams encounter axial stress induced by the bending of the hinges when out-of-plane acceleration applied on the seismic mass, which will result in the change of the resonant frequency of the beams. Two vibrating beams are arranged symmetrically on both sides of the seismic mass to form the differential structure to improve the performance of the sensor. SOI-MEMS processes are adopted to achieve the complicated structure with different thickness simultaneously by three-step DRIE etching. Preliminary experiments show that the Q-factors of the two vibrating beams are about 400 in air and the differential sensitivity measured can reach 584 Hz/g.