Surface micromachined polysilicon accelerometer

A surfaced micromachined polysilicon accelerometer is designed and manufactured. The sensing element represents a differential capacitor comprised of three polysilicon layers. The structure is made such that the seismic mass (polysilicon layer 2) is movable while the other polysilicon layers (layers 1 and 3) are nonmovable (fixed). The seismic mass is centered between the two fixed layers, thereby creating a differential capacitance: the bottom capacitance being formed between polysilicon layers 1 and 2, and the top capacitance being formed between polysilicon layers 2 and 3. The sensitive axis of the structure is in the direction perpendicular to the surface of the substrate. The device can be used with a signal processing circuit configured as an open loop system to achieve a sensitivity of 0.35 mV/g/V.<>