Fully Integrated Pitch-Matched AlScN PMUT-on-CMOS Array for High- Resolution Ultrasound Images

This article presents a fully integrated pitch-matched piezoelectric micromachined ultrasonic transducers (PMUTs)-on-CMOS array with high potential in catheter-based ultrasound imaging systems and capabilities to obtain resolutions under 100 \mu \text{m} . The system-on-chip (SoC) consists of {7} \times {7} AlScN PMUTs connected in a 1-D configuration where the six external rows are used to generate the acoustic pressure through three high-voltage (HV)-pulser CMOS circuits, and the central row is used to sense the incoming ultrasound wave which will be amplified by a low-noise amplifier (LNA) CMOS amplifier. The experimental verification in a liquid environment gave, as a first result, a peak frequency of 7.7 MHz with a normalized pressure (ST) of 1.98 \text{k}{\text {Pa}}_{\text {pp}} *mm* \text{V}^{-1} and receiving sensitivity (SR) of 3.3 V/MPa, respectively, competitive sensitivities in comparison to the state-of-the-art. In the second part, ultrasonic imaging for different wires with a minimum diameter of 25 \mu \text{m} was demonstrated as expected from numerical simulations. The system's performance for ultrasound images was evaluated considering the product of the area and the resolution at 1 mm, giving competitive values compared with other reported ultrasound systems for catheter-based medical ultrasound imaging and the only one providing monolithic integration with the CMOS front-end circuitry.