Abstract
This study realizes an improved signal-to-noise ratio (SNR) MEMS microphone based on piezoelectric sensing principle. In Fig. 1a, the proposed square-shaped and the reference 45-degree right triangle cantilever diaphragm (PZT/Silicon unimorph) arrays are designed and implemented for comparison. The proposed microphone has two merits, (1) enhance SNR by increasing sensitivity: with the same diaphragm area, the proposed square cantilever diaphragm design can provide larger stress and wider stress distribution than the reference type, as in Fig. 1b, which increase the sensitivity. Measurement shows the proposed microphone has a higher SNR of 70.1dB (at 1 kHz). As compared with the reference type, the proposed design has a 2.3dB SNR improvement (at 1 kHz). (2) prevent sensitivity loss at low frequency by reducing the gap between cantilever diaphragms: the proposed arrangement of cantilever diaphragms reduces the gap between the bent cantilever diaphragms (caused by residual stress, as in Fig. 1a) to prevent the low-frequency acoustic loss. Acoustic frequency response measurement shows successful prevention of sensitivity loss at low frequency.