PZT Micromachined Piezoelectric Ultrasonic Transducers with Good Coupling to Solids

Abstract

This paper presents PZT thick film based piezoelectric micromachined ultrasonic transducer (PMUT) and its arrays, showing high transmitting sensitivity in air and good coupling capability to solids. The PMUT is fabricated on a SOI substrate with sputtered PZT/Si diaphragm, and the top Si thickness is carefully designed in order to acquire enough coupling capability to solids. The obtained PMUT transmitter exhibits high sensitivity of 190 nm/V at resonant frequency of 0.887 MHz in air. And further thickness-measuring ability in solids is evaluated with one PMUT array with PZT diameter of 560 μm as transmitter providing 8 V pp input, and another single PMUT of identical frequency response as receiver showing 0.2 V pp output (after 20 times magnification), when the acoustic wave is transmitted through a 5 cm thick graphite plate. These PMUT with high sensitivity and good coupling capability to solids reveals high potential in structural detecting.