On the Performance Enhancement of Piezoelectric MEMS Microphone Using S-Shape Slit Design

This study demonstrates the piezoelectric MEMS microphone with S-shape slits on clamped-clamped diaphragm to reduce the influence of residual stress yet maintain a decent bandwidth. The proposed design has two major merits: (1) Compared with cantilever diaphragm: the structure with S-shape slits acting as the spring to reduce stress-induced bending to lower the acoustic short circuit, (2) Compared with the bridge (clamped-clamped) diaphragm w/o slits: S-shape slits could change the boundary conditions and reduce the resonance frequency to improve the signal-to-noise ratio (SNR) of the microphone. In short, the proposed S-shape slit design could improve the SNR without sacrificing the bandwidth of microphone. Measurements demonstrate an SNR improvement of 10 dB at 1 kHz compared to the bridge structure, reaching an SNR of 67.5 dB, furthermore, its bandwidth exhibit nearly 100 Hz improvement in low frequency response compare to the cantilever design.