微機電壓電式麥克風相較於電容式麥克風，擁有防水防塵與低功耗的優勢，然而受限於壓電材料本身的介電損失，使壓電式麥克風元件訊噪比較低，因此本研究將以訊噪比提升作為主要目標。首先將建立單壓電層懸臂式麥克風之解析模型，計算出能夠同時進行訊噪比與頻寬兩麥克風重要參數的性能指標－訊噪比與頻寬之乘積；並以此為設計基準進行下電極與PZT壓電材料層定義，提升元件的輸出能量並減少振膜之等效質量，使元件之訊噪比與頻寬得到上升。本研究以沉積PZT薄膜的SOI晶圓完成製程，完成後首先萃取使用之PZT各項參數，而後進行元件之聲學量測。結果顯示PZT/下電極定義後，其訊噪比於1 kHz下達到77.2 dB，且工作頻寬涵蓋至10 kHz，相比於未進行壓電材料與下電極定義的兩種不同長寬比的懸臂振膜，能在近乎等量的訊噪比下將頻寬提升兩倍；或是在相同的工作頻寬下提升4.6 dB的訊噪比輸出。另外，本研究額外透過給予壓電薄膜額外偏壓，減緩振膜殘餘應力翹曲，改善前後腔間孔隙造成的聲學短路，使訊噪比在1 kHz進一步提升了2.3 dB，更加改善元件性能。

Piezoelectric MEMS microphone features high environment tolerance, simple structure, and good linearity. Which provides a more reliable solution for a MEMS microphone. Unfortunately, due to relatively high noise floor by dielectric loss of piezoelectric material, Signal-to-noise ratio (SNR) of a piezoelectric microphone needs further improvement. This study starts with developing the theoretical solution of unimorph MEMS microphone. Then establish the figure-of-merit to estimate the trade-off between SNR and bandwidth (SNR×BW). Base on figure-of-merit, this study proposed a piezoelectric MEMS microphone with a partially removed PZT layer to increase the bandwidth without sacrificing SNR. Measurements demonstrate the SNR at 1 kHz up to 77.2 dB with bandwidth up to 10 kHz for the proposed design, Moreover, the proposed design has a 2.3 dB sensitivity enhancement after applying 10 V bias on PZT. Further, enhance the performance of unimporph MEMS microphone. Also, material properties of PZT used in this study have been well measured in this study.

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