High fill factor piezoelectric micromachined ultrasonic transducers on transparent substrates

This study presents a high fill-factor array of aluminum nitride (AlN) piezoelectric micromachined ultrasonic transducers (PMUTs) fabricated on a transparent substrate. PMUTs with diameters ranging from 40 microns to 100 microns were fabricated, resulting in resonant frequencies from 3 MHz to 18 MHz in air. A high fill factor of 62% was achieved. Immersed pulse-echo experiments were conducted at 2.5 MHz.