Abstract
This study presents a 2-in-1 MEMS audio transducer that monolithically integrates a MEMS microphone and a MEMS microspeaker within a 2.5mm×5mm footprint. Utilizing a PZT on SOI process platform, the design features three key aspects: (1) It leverages piezoelectric materials for both sensing and actuation in a single device. This architecture is particularly beneficial for compact applications like true wireless stereo (TWS); (2) The precision of microfabrication ensures phase consistency, enhancing the audio algorithms accuracy; (3) The PZT thickness is optimized based on a comprehensive evaluation of performance. The microphone structure is refined with a 44% PZT coverage ratio to maximize output energy. Measurements in an anechoic box show a 45.3 dB SNR at 1kHz and a 350Hz low cut-off frequency with a typical back volume of 3.5mm ×2.6mm×1mm. For the microspeaker, standard ear simulator tests demonstrate a 72.5dB SPL at 1kHz under a 0.707Vrms driving signal.