A high sensitivity MEMS gravimeter with electrically tunable stiffness

This paper reports on a high sensitivity capacitive micro-electromechanical systems (MEMS) gravimeter. The high sensitivity is achieved by the low resonant frequency structure and large sensing capacitance. An electrical tuning method was employed to reduce the stiffness. The resulting resonance frequency was as small as 1Hz. To attain the large capacitance, a through-silicon Deep- RIE method was applied to a 525 mu m thick silicon layer. A cascaded demodulation method is adopted in the readout circuit. This capacitive gravimeter demonstrated a sensitivity of 293 pF/g. The voltage sensitivity is 0.96 V/Gal. The gravimeter has a noise floor of 0.8 mu Gal/root Hz.