Characterization of SOI MEMS capacitive accelerometer under varying acceleration shock pulse durations

In this work, the response of the z-axis differential capacitive MEMS accelerometer structure is studied under mechanical shock. The resonant frequency of the accelerometer is 9.12 kHz, and the corresponding time-period (T_n) is 0.11 ms. Simulation of the accelerometer structure under 30 g half-sine acceleration shocks of different durations (0.1–4 ms) revealed that the output amplitude attains the input acceleration shock value when the pulse duration (T) ≥ 0.9 ms. The simulated output time-lag over the input pulse is found to be around 0.2 ± 0.03 msec. The accelerometer showed higher rise-time (10−90 %) and fall-time (90−10 %) for the 0.1–0.5 ms shock pulse durations. The silicon-on-insulator (SOI) MEMS technology is employed to fabricate the accelerometer structure. The packaged accelerometer is tested under the 30 g half-sine acceleration shocks generated by an electrodynamic shaker. The measured output amplitude of the accelerometer achieved the input acceleration value when the shock pulse duration (T) ≥ 9T_n, and the measured time-lag varies from 0.05 to 0.3 msec. The measurement results showed that the output follows the input shock pulse when rise-time (t_r) ≥ T_n and fall-time (t_f) ≥ 2.7 T_n. The high value of pre-pulse noise is observed for the lower shock-pulse duration (≤ 0.5 ms), and the noise level (peak-to-peak) gets substantially minimized only when T ≥ 27 T_n.