Design of Piezoelectric Micromachined Ultrasonic Transducers Using High-Order Mode With High Performance and High Frequency

This work proposes the piezoelectric micromachined ultrasonic transducer (pMUT) design using high-order mode. Analytical models are established and used to estimate the performance of pMUT in ${n} ^{\text {th}}$ -order axisymmetric mode. To prove the concept, a comprehensive analysis is conducted on the $3^{\text {rd}}$ -order pMUT by finite element method (FEM). The analytical models give guidance for the design of electrode configuration and geometric dimensions, which are verified by FEM. With optimized electrode configuration and thickness, the proposed pMUT design shows extraordinary performance improvement in transmitting and round-trip sensitivity. Approximately $10.2\times $ and $4.12\times $ improvements in transmitting sensitivity and round-trip sensitivity have been achieved compared to the traditional $1^{\text {st}}$ -order pMUT in the same radius, while there is an $8.6\times $ improvement of the receiving voltage in the pulse-echo analysis. The high frequency, round-trip sensitivity, and directivity features of the proposed high-order pMUT design shown in FEM make it very promising for forming a high-frequency large-scale pMUT array.