Pendulum Type Accelerometers based on Thick Polysilicon Surface Micromachining

A capacitive accelerometer based on a pendulum structure made by surface micromachining of thick polysilicon layers suitable for open and closed-loop configurations is presented. Because of the small electrode gap dimensions viscous damping is expected to be an important factor in its behaviour. Finite element simulations have been performed to evaluate damping influence and the results confirm the feasibility of reducing the squeeze film damping effect by means of properly hole patterning the movable plate. The asymmetry of the pendulum structure causes an asymmetric damping value. This leads to a response function of the device with hysteresis behaviour, which was verified experimentally.