Dome-shaped diaphragm microtransducers

We present a novel idea of using domeshaped diaphragms for piezoelectric microphones, pressure sensors, and microspeakers. Dome-shaped diaphragm microtransducers are built on a thin, dome-shaped, silicon-nitride diaphragm (a few pm thick and a few mm in radius) with electrodes and piezoelectric ZnO film. Dome-shaped diaphragm transducers possess unique features, not shared by flat diaphragm transducers, due to their threedimensional nature in structure. For instance a dome-shaped diaphragm microphone is capable of detecting the magnitude and the direction of an incoming acoustic wave, like human ears. We present our theoretical study for such microphone. Three major equations are developed for signal readouts on three different positions over a hemispherical surface of a dome microphone. Also we describe our fabricated dome-shaped diaphragm of low-stress silicon nitride (0.3 km thick and 1 mm in radius). Additionally, since mechanical resonant frequency of a dome-shaped diaphragm depends on static differential pressure, we describe piezoelectric pressure sensors (to sense static pressure) made with a dome diaphragm. Finally, we show that a dome diaphragm is much more effective in producing acoustic waves along radial direction than a planar diaphragm.