Multiple electrode piezoelectric micromachined ultrasonic transducers

Piezoelectric micromachined ultrasonic transducers (pMUTs) with multiple electrodes were shown to have enhanced effective electromechanical coupling factors, about 211% larger than that of the state-of-the-art, single electrode design. In this work, a theoretical model of the electromechanical coupling is developed for the circular-shape, clamped unimorph pMUTs and validated with published experimental results on single electrode structures. A 4-electrode design with a 5 μm-thick poly-Si structural layer, 2 μm-thick PZT piezoelectric layer, and 135 μm in radius has an effective electromechanical coupling of 13.72%, which is 211% higher than that of a conventional single-electrode pMUT. As such, multiple electrode pMUTs could replace the state-of-art, single-electrode pMUTs for high electromechanical coupling in various ultrasonic transduction applications, such as gesture recognition and medical imaging.