Study on AlN micromachined ultrasonic transducer array with beamforming

Abstract

This paper mainly shows piezoelectric micromachined ultrasonic transducer (PMUT) with beamforming. The square 3x3 AlN PMUT array structure was designed and fabricated, including a Si/SiO2/Mo/AlN/Mo multilayer film structure, and each AlN PMUT has a separate cavity. In order to characterize the performance of a single square AlN PMUT in the array structure, we set up a test platform that used a standard hydrophone to test the sound pressure in the silicon oil. We found that the sound pressure at 1cm from the sound source was up to 53.59Pa, which is consistent with the simulation results. In order to achieve getting strong acoustic waves in the air, a beamforming AlN PMUT array structure is proposed. The finite element analysis is used to compare the transmitted sound pressure characteristics of square AlN PMUT arrays with beamforming or no-beamforming. The output sound pressure of the square AlN PMUT array emitting in air is 0.25Pa from the sound source 1cm after applying the time delay signal, higher than 0.18Pa with no-beamforming.