Piezoelectric MEMS microphone

Abstract

Owing to the compact size, low power consumption, high signal-to-noise ratio, dustproof and waterproof properties, piezoelectric MEMS microphones have stood out from other conventional microphones throughout these years. Piezoelectricity allows acoustic pressure to stress the piezoelectric material and accumulate charges on the material surface to generate the electrical signal. The shape of a microphone can be a determining factor of affecting the sound recording performance. Previously, microphones with circular membranes have been studied. While, the sandwich-like design was discovered in the Vesper piezoelectric microphone, which is special (Figure A). Therefore, this project examines the performance of some modified designs with reference to the Vesper microphone, and the possible applications of the microphone. Aluminum nitride (AlN) is chosen as the piezoelectric material in this project, as the AlN film does not need to be compatible with the CMOS process. To illustrate the characteristics of the samples, three tasks including the simulation of the device, electrical measurement, and acoustic measurement have been conducted. The COMSOL Multiphysics was used for the simulation. The eigenfrequency of the device, displacement and electrical potential versus 1 Pa pressure analysis were determined. The simulation results supported the electrical and acoustic measurements for explaining the characteristics of the device.