Design and Modeling of a Dual-Driving PMUT with Increased Round-Trip Sensitivity

Piezoelectric micromachined ultrasonic transducers (PMUTs) are fabricated with Micro-Electro-Mechanical Systems (MEMS) processes. They have advantages such as high uniformity and density, high flexibility in array configuration, and compatibility with integrated circuits. However, the transmitting/receiving sensitivity and the bandwidth of PMUTs are usually lower than those of capacitive micromachined ultrasonic transducers (CMUTs) and conventional thickness mode transducers, which are vital for acoustical imaging resolution. This work presents a novel structure of piezoelectric micromachined ultrasonic transducer (PMUT) with dual piezoelectric driving at the device’s top surface, achieving better round-trip sensitivity while keeping cell size small compared with traditional PMUTs. Due to the high transmitting performance of the PZT film and the high receiving performance of the AlN film, the designed PMUT achieves ideal round-trip sensitivity-relative bandwidth product (Rt-SBW), which is 9.68dB higher than that of the optimized PZT-PMUT and 26.36dB higher than that of the optimized AlN-PMUT, greatly improving the pulse-echo imaging quality.