表面聲波元件是在壓電基板上利用聲電換能原理的特性,做各種訊號的處理。目前通訊元件有朝著高頻化的發展趨勢,而高頻表面聲波元件須具有高波速,高機電耦合係數,低插入損失等特性,經由壓電薄膜與不同基底材料或高聲速薄膜材料所組成之表面聲波元件不但可以提高表面聲波元件操作頻率以及增加機電耦合係數,因此在講求輕薄短小的行動通訊產品中已被大量使用 本研究在鈮酸鋰(LiNbO3)壓電基板上製作指叉狀換能器(IDT)完成後,使用電子束蒸鍍法(electron beam evaporation)成長氧化鋁(Al2O3)薄膜在鈮酸鋰(LiNbO3)表面聲波(SAW)元件的兩IDT電極上與兩IDT電極間的區域,比較在不同厚度的氧化鋁(Al2O3)薄膜之表面聲波元件頻率響應變化。研究結果顯示波速成功地隨著氧化鋁(Al2O3)薄膜厚度增加而由0 %提升至4.385% 。證實以電子束蒸鍍法成長高波速氧化鋁(Al2O3)薄膜可以提升表面聲波元件波速,降低成本並縮短製程時間,將來可以提供作為高頻表面聲波元件之製作。
Now communication elements are developing towards high frequency. SAW devices must have high velocity, high electromechanical coupling coefficient, low insertion loss. SAW devices composed of the piezoelectric thin film and different substrate materials or buffer layers can improve the operating frequency of SAW devices and the electromechanical coupling coefficient. Consequently, SAW devices have been widely applied in mobile communication due to their small size and light weight. This study is fabrication IDT on LiNbO3 piezoelectric substrate.We empoly electron beam evaporation to deposit Al2O3 thin film on LiNbO3 SAW device of over the IDT and between the IDT region.As compared with different thicknesses of Al2O3 thin film which frequency responses of SAW devices.Successfully, the phase velocity with Al2O3 thin film increased has been improved from 0 % to 4.385%.The electron beam evaporation to develop Al2O3 thin film with high velocity of wave has been proved to promote SAW velocity, lower the cost and shorten the time of production.The method is sure of producing high frequency SAW devices.