The Acoustic Pressure Enhancement of Piezoelectric Micro-Machined Ultrasonic Transducer

Abstract

Miniaturization and integration are the biggest advantages of film Piezoelectric Micro-machined Ultrasonic Transducer (PMUT). However the small size also limits the application of film transducer in high power field. In order to replace traditional bulk material transducer with PMUT in some special applications, the vibration sensitivity and acoustic pressure of the transducer need to be improved. This paper proposes a novel PMUT structure with concentric circle and ring electrodes. We use 2nm PZT (lead zirconate titanate) film to fabricate PMUT array. Based on the piezoelectric theory and processing methods of Micro Electro-Mechanical System (MEMS), some simulations and experimental validations are carried out to verify the proposed transducer structure. With differential voltage input, the vibration sensitivity is better than 13nm/V in the air. After device packaging, the sound pressure generated by the PMUT is up to 580kPa at the position 2mm away from the vibrating surface underwater.