Bimorph piezoelectric acoustic transducer

This paper describes a novel bimorph piezoelectric microphone built on a micromachined parylene diaphragm with two ZnO films of opposite c-axis orientations. Both the sensitivity and signal-to-noise ratio of the bimorph parylene-diaphragm microphone have been demonstrated to be much higher than those of a uni-morph piezoelectric microphone built on a silicon nitride diaphragm with similar structures. The bimorph microphone sensitivity is about 52 muV/mu bar, about 100 times higher than the uni-morph one. The piezoelectric bimorph microphone requires relatively simple fabrication steps with only four masks needed, all of which can be processed at a temperature lower than 250 degreesC (except the first step of silicon nitride deposition).