壓電式微機電麥克風擁有防水防塵與低功耗等適合未來物聯網語音辨識與控制應用的優勢，然而目前市面上的壓電式麥克風之訊雜比仍不及電容式微機電麥克風。本研究以提升微機電麥克風的訊雜比與改善低頻靈敏度損失為兩大目標，透過PZT壓電薄膜之SOI晶圓製程進行壓電式麥克風之設計與實現，提出不同於典型之懸臂樑結構作為麥克風之振膜，設計部分移除PZT壓電層的三角形PZT懸臂樑麥克風，以提高受聲壓時結構所產生之彎曲應力與輸出能量，藉以提升壓電式麥克風的訊雜比；再設計保留懸臂樑末端PZT作為支撐結構的雙曲形PZT懸臂樑麥克風，以抑制殘餘應力所造成的翹曲，在提升訊雜比的同時改善低頻靈敏度的損失。無響箱量測結果顯示，三角形PZT懸臂樑麥克風之訊雜比達到82.4dB，相比商用麥克風之三角形懸臂樑結構的72.6dB提升了9.8dB；雙曲型PZT懸臂樑麥克風之訊雜比達到81.7，提升了9.1dB，同時截止低頻則較三角形PZT懸臂樑降低了13Hz，成功改善了低頻靈敏度損失。

Piezoelectric MEMS microphones have advantages such as water/ dustproof and low power consumption which are suitable for applications in the Internet of Things. However, the signal-to-noise ratio (SNR) of the piezoelectric microphones are still not as good as that of the capacitive MEMS microphones. The 2 targets of this study are: First, to enhance the SNR of the piezoelectric microphones. Second, to improve the low-frequency sensitivity loss. By using the SOI wafer with PZT thin film processes, the designs of piezoelectric MEMS microphone are realized. This study has proposed several unconventional cantilever designs as the structure. The triangular PZT cantilever is designed to have the PZT piezoelectric layer be partially removed to increase the bending stress and output energy under sound pressure. Thereby increasing the signal-to-noise ratio. The dual-curved PZT cantilever is designed to retain the PZT at the tip of the cantilever as a supporting structure to suppress the warpage caused by residual stress. Therefore it can improve the low-frequency sensitivity loss while remaining the high SNR. Measurement results have shown that the SNR of the triangular PZT cantilever design is 82.4dB, which is 9.8dB higher than the triangle cantilever structure of the commercial microphone. The SNR of the dual-curved PZT cantilever design is 81.7dB, having an increase of 9.1dB. Moreover, the low cut-off frequency is 13Hz lower than that of the triangular PZT cantilever design, which means it successfully improves the low-frequency sensitivity loss.

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