Toward a Tunable AlN-Based Piezoelectric MEMS Microphone: Design, Characterization, and Analysis

• Published in: Journal of microelectromechanical systems Vol. 34; no. 4; pp. 432 - 442
• Main Authors: Zheng, Zhuoyue, Wu, Xinyu, Wang, Yuan, Luo, Huahuang, Ke, Qingqing, Wang, Chen, Kraft, Michael, Martins, Rui P., Mak, Pui In
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2025; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustics; Adaptive audio systems; Adaptive systems; Couplings; Electrodes; Equivalent circuits; Impedance; Microelectromechanical systems; microelectromechanical systems (MEMS); Micromechanical devices; Microphones; microphones piezoelectric; Piezoelectric effect; Piezoelectricity; Resonant frequencies; Resonant frequency; Sensitivity; Speech recognition; tunable performance; Tuning
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2025.3558897

This work introduces a novel tunable piezoelectric MEMS microphone, featuring a fully clamped membrane and dual-sensing electrodes. The device achieves a baseline sensitivity of -39.31 dB, with tunability enabled by a DC tuning mechanism. The key innovations of this subject include: 1) a discrete electrode design enabling simultaneous tuning of sensitivity and resonant frequency while preserving acoustic sensing functionality; 2) utilizing the reverse piezoelectric effect to achieve large tunable ranges with minimal tuning voltages; and 3) a cost-effective performance tuning methodology that eliminates the need for structural modifications; 4) ascertain the tuning mechanism. Furthermore, a refined equivalent circuit model provides insights into the electromechanical behavior of the device, enabling the optimization of tunable microphones and acoustic transducers. Experimental results demonstrate the tuning ability successfully. The acoustic experiment shows that the output amplitude can be changed by up to 182.18% under ±0.5 V DC tuning under 1 kHz acoustic input. The electrical experiment reveals a maximum resonant frequency change of 6.85% with ±10 V DC. The proposed microphone is a promising candidate to be employed in many next-generation audio applications, such as adaptive voice systems, AI-driven speech recognition, and noise cancellation.[2025-0005]