Modeling and Simulation of Aluminium Nitride-Based Piezoelectric Micromachined Ultrasonic Transducer for Ultrasound Imaging

In this work, a PMUT based on Pt/AlN/Pt/TiO2/SiO2/Si structure with square suspended membrane is proposed and modeled by performing finite element method (FEM) software COMSOL. The vibration mode, resonant frequency and effective electro-mechanical coupling coefficient (keff2) of the proposed AlN-based PMUT are analyzed. It is shown that the (0,1) resonant mode of PMUT reaches up to 25.73 MHz when the AlN thickness is 1μm. Moreover, the influences on the sensitivity of geometric parameters, i.e., the side length and thickness of top electrode, and the thickness of AlN thin film, are investigated. Maximum transmitting and receiving sensitivity of 32.79 pm/V and 0.478mV/kPa, respectively, are obtainable with optimum geometric parameters. Investigation results demonstrate that by optimizing the structure of the proposed AlN-based PMUT, keff2 and sensitivity are significantly improved, which is beneficial for meets the requirement for application of high resolution ultrasound imaging.