本論文主要分析薄膜體聲波諧振器（Film Bulk Acoustic Wave Resonator, FBAR）的上電極型態和雜散模態之間的關係。製作的 FBAR 元件採用背向空腔架構，在矽基板上使用鉑作為下電極、氮化鋁作為壓電層、鋁作為上電極，最後將元件背部的矽基板蝕刻掉以釋放空腔。本研究中採用了反應式射頻磁控濺鍍方法來沉積氮化鋁壓電薄膜，使薄膜有高 C 軸優選取向，確保其具有良好的壓電特性，能夠在元件內部激發縱向聲波。首先透過製作 19600、14400、10000、6400μm² 四種不同正方形面積的上電極 FBAR 元件，量測的 S 參數結果中，19600、14400μm² 皆無觀察到額外的雜散模態，面積為 10000μm² 時，會觀察到明顯的雜散模態，因此將以面積 10000μm²做為後續實驗的參考依據。接著以相同條件下，製作圓形、五邊形兩種不同電極形狀的 FBAR 元件，在面積10000μm² 的形態下，量測的 S 參數結果中，並沒有觀察到明顯的雜散模態，這個結果顯示非正方形的上電極形態能夠抑制雜散模態的激發。當以相同的結構與材料製作FBAR 元件時，面積 10000μm²為是否觀察到明顯雜散模態的參考面積，若大於此參考面積，則三種形狀皆適用;若小於，則正方形不適合使用。

This thesis investigates the relationship between the top electrode configuration and spurious modes in Film Bulk Acoustic Wave Resonators (FBARs). The fabricated FBAR devices employ a back-etched cavity structure. The silicon substrate at the device's rear is etched to create a cavity release. Platinum is used as the bottom electrode on a silicon substrate, and aluminum nitride functions as the piezoelectric layer. For the deposition of the aluminum nitride piezoelectric thin film, reactive RF magnetron sputtering is used. Aluminum is then utilized as the top electrode. In the square FBAR device with an area of 10,000 μm², the presence of spurious modes is observed, and this area serves as a reference for detecting their occurrence. No spurious modes are observed when the shape is adjusted to circular and pentagonal with an area of 10,000 μm². Hence, non-square shapes contribute to the suppression of spurious modes.

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