A high performance mixed micromachined differential resonant accelerometer

The vacuum packaged differential resonant accelerometer (DRXL) using gap sensitive electrostatic change effect is proposed by using the reverse surface micromachining (RSM) process based on the single crystal silicon. The differential frequency output is achieved by subtracting the resonant frequency between the two independent resonators, which has advantages with the wide input range and the good linearity. But the resonant accelerometer is fabricated using the epi-polysilicon surface micromachining process in the previous work. The residual and shear stress of the polysilicon result in the mismatch of the mechanical resonant frequency. The mismatch of the resonant frequency may demolish the advantages of the differential scheme because of the mechanical resonance characteristics. So, the single-crystal silicon was chosen for the accelerometer structure material because it has better mechanical properties than the polysilicon. The fabricated resonant accelerometer shows the nominal frequency of 6928 Hz and the sensitivity is about 10Hz in the ±10 G range. The bandwidth is more than 100 Hz.