AlN Piezoelectric Micromachined Ultrasonic Transducer Array Monolithically Fabricated on Top of Pre-Processed CMOS Substrates

Abstract

This paper presents a 6×6 AlN piezoelectric micromachined ultrasonic transducers (PMUT) array with competitive performance as an actuator and as sensor compared with other devices using the AlN as piezoelectric material. The novelty is that the AlN-PMUT is fabricated over pre-processed CMOS wafers allowing compactness, better signal processing and higher fill factor (not limited by wafer bonding) than reported. The squared PMUT array achieves acoustic sensitivities as actuator of 130 Pa·mm·V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> (one row) and sensor of 5.9 V/MPa in fluorinert at 3 MHz with a fill factor of 50%. The 6x6 array with circular PMUT achieves a 65% fill factor.