Design and analysis of piezoelectric MEMS micro-speaker based on scandium-doped AlN thin film

Abstract

Piezoelectric MEMS microspeakers are promising candidates for miniaturized speakers, such as for in-ear applications. Using lead-free scandium doped aluminium nitride (ScAlN) thin film instead of lead zirconium titanate helps these speakers to be environmental friendly, CMOS compatible and potentially more linear. The piezoelectric coefficient of ScAlN is higher than undoped AlN, which leads to improved performance of MEMS actuators including speaker chips. The design of piezoelectric MEMS ScAlN speaker based on four triangular cantilevers is proposed. The design in this work has been verified by finite element method simulation. The displacement and sound pressure level are 39 μm and 56 dB, respectively. This MEMS loudspeaker has small size and simple structure. The model opens the door also to further optimization for higher energy efficiency and higher acoustic performance based on lead-free ScAlN thin film.