Design of a novel thin-film piezoelectric accelerometer

A novel piezoelectric thin-film accelerometer has been designed and its performance has been analysed. The piezoelectric thin film (PZT for example) is delineated into an array of pads to reduce the sensor capacitance. By filling the cavity around the PZT pads either with a polymer or a gas with controlled pressure, damping can be controlled. The piezoelectric thin-film material (i.e., pads) is clamped between a seismic mass and a base plate (silicon substrate). During acceleration in the axial direction the seismic mass exerts a force on the piezoelectric layer, resulting in the generation of a charge due to the piezoelectric effect. The induced charge is independent of the dimensions of the piezoelectric layer and hence of its tolerances. The generated charge is directly sensed by a charge-sensitive preamplifier that is implemented by CMOS technology on a tiny silicon chip. In principle, the proposed thin-film accelerometer can be integrated with the electronic readout and can be extended into an array of accelerometers. The dynamic response is presented and the trade-offs between several design considerations are discussed. For a specific design, a sensor sensitivity of 320 mV g(-1) and lower and upper cut-off frequencies of, respectively, 1 Hz and 0.2 MHz have been calculated. By using differential sensing, the proposed thin-film accelerometer can be further developed to include compensation for temperature and pyroelectric effects. In addition, self-test features based on the application of electrostatic forces are feasible but require more sophisticated signal processing.