Design and Fabrication of a Piezoelectric Bimorph Microphone with High Reliability and Dynamic Range Based on Al_0.8Sc_0.2N

With the development of technology, MEMS microphones, which are small-sized and highly uniform, have been applied extensively. To improve their reliability in extreme environment and overcome the constraints of traditional microphones, this article presents a piezoelectric bimorph MEMS microphone using ${\mathrm{Al}}_{0.8}{\mathrm{Sc}}_{0.2}\mathrm{N}$. In the article, the high robustness of piezoelectric microphones and the reasons for choosing ${\mathrm{Al}}_{0.8}{\mathrm{Sc}}_{0.2}\mathrm{N}$ as piezoelectric materials are described. The sensitivity of an ${\mathrm{Al}}_{0.8}{\mathrm{Sc}}_{0.2}\mathrm{N}$-based piezoelectric bimorph compared with the traditional structure are revealed through FEA. Subsequently, a lumped element microphone model is constructed and all noise sources are evaluated comprehensively. The difference in output noise caused by different structures is calculated. The designed piezoelectric microphone, which comprises eight triangular cantilever beams, was fabricated on a chip with an area of 900 $\mu$m × 900 $\mathrm{\mu }$m. The sensitivity of the designed microphone achieves 1.68 mV/Pa, with a noise floor of −110 dBA and SNR of 54.5 dB. The acoustic overload point of the microphone stands at 147 dB SPL, and following the impact test, the survival rate was 100%. Compared to traditional MEMS microphones, the microphone achieves a dynamic range of 107.5 dB.