Parylene-diaphragm piezoelectric acoustic transducers

This paper reports the fabrication of piezoelectric acoustic transducers built on a 1.5 μm thick parylene (both flat 5,000×5,000 μm² square and dome-shaped 2,000 μm-radius diaphragm with circular clamped boundary on a silicon substrate) with electrodes and piezoelectric ZnO film. The main advantages of a parylene diaphragm for an acoustic transducer are its large elastic compliance and low residual stress. In fabricating the parylene-diaphragm (which has relatively low melting point) acoustic transducers, we use a silicon nitride layer as a temporary structural layer during high temperature process steps. The dome-shaped parylene-diaphragm transducers are reliably and reproducibly fabricated with a shadow mask technique with high-deposition-rate thermal Al evaporation