A Single-Chip AlScN PMUTs-on-CMOS Hydrophone

Abstract

This work presents a minute single-chip piezoelectric micromachined ultrasonic transducers (PMUTs)-on-complementary metal-oxide-semiconductor (CMOS)-based hydrophone with high receiving sensitivities and low noise. The system is based on three different Sc9.5% Al90.5% N PMUTs geometries: (a) square with an 80μm side, (b) rectangular with a dimension of 60 × 40μm, and (c) annular with an outer diameter of 80μm which allows to carry out acoustic measurements at very close distances from the transducer under test. Each device is monolithically integrated with a CMOS low noise amplifier (LNA) amplifier with a gain of 25 dB. The first hydrophone prototype was validated in water where two commercial hydrophones from ONDA (HGL-0085 and HNC-0200) were used as references. The experimental results give mean receiving sensitivities of-234 dB re 1 V/μPa (equivalent to 1.9 V/MPa),-234.6 dB re 1 V/μPa (equivalent to 1.86 V/MPa), and-238.3 dB re 1 V/μPa (equivalent to 1.22 V/MPa) for (a)-(c), respectively. These results demonstrate the high performance of the presented PMUTs-on-CMOS to be used in a miniaturized hydrophone for characterizing high-frequency ultrasound transducers.