A Hybrid Piezoelectric–Capacitive MEMS Microphone With Peripheral Electrostatic Transduction

This work proposes a piezoelectric –capacitive dual-mode micro-electromechanical system (MEMS) microphone with peripheral electrostatic transduction. Finite element analysis is used to investigate the contribution of the peripheral electrode configuration to the response characteristics of the proposed piezoelectric–capacitive MEMS microphone (PCMM). Piezoelectric transduction is achieved using a conventional piezoelectric stack with multiple layers. The capacitive transduction part is implemented through a peripheral electrode formed by the overlapping circumferential region between the silicon substrate and the device layer. The proposed PCMM shows a measured sensitivity of −51.1 dB (1 V/Pa) and a signal-to-noise ratio (SNR) of 49.6 dB at 1 kHz (1 Pa) for the piezoelectric part, and −51.3 and 68.9 dB at 1 kHz, respectively, for the capacitive part. Through the integration of dual outputs from the above two modes, the hybrid mode achieves measured sensitivities and SNR of −45.3 dB (1 V/Pa) and 55.3 dB (1 kHz). The A-weighted SNR in the piezoelectric, capacitive, and hybrid modes is 10.53, 30.58, and 16.27 dB(A), respectively. At 145.6-dB SPL, the hybrid mode shows lower total harmonic distortion (THD) (1.7%) than the piezoelectric (2.6%) and capacitive (2.3%) modes.