Investigation of performance dependence on transduction diaphragm design for piezoelectric micromachined ultrasonic transducers

Abstract

One of the most important performance metrics for piezoelectric micromachined ultrasonic transducers (PMUTs) is their transmitting sensitivity, which is significantly dependent on the design of the transduction diaphragm. In this work, a comprehensive comparison of transmission sensitivities for PMUTs with circular, square, and hexagonal transduction diaphragms are investigated through theoretical calculations, finite element analysis (FEA), as well as experimental verifications. Compared to the PMUTs with circular and square transduction diaphragms, PMUTs with hexagonal transduction diaphragm can achieve greater volume displacement and hence better transmitting sensitivity as a transmitter, due to their higher fill-factor and larger quality factor (Q). The measured average resonant volume displacement and Q of 15 fabricated PMUTs with hexagonal transduction diaphragm are 3.07 × 10−13 m3/V and 798, respectively. The transmitting sensitivity of the hexagonal PMUTs exceeds that of the circular PMUTs by over 15% and that of the square PMUTs by over 3.5%. This work highlights an effective and simple approach for PMUTs to achieve high transmitting sensitivity.