隨著5G時代的來臨，表面聲波元件(SAW device)應用於通訊裝置中之濾波器需要朝向高頻段、寬頻寬與優良溫度頻率穩定性發展。以多層結構元件為研究方向，結合不同材料之優點來獲得元件性質的提升。本研究將以 ScAlN/metal/LiNbO3 之結構增進薄膜壓電性質之表現。鈮酸鋰基板具有高機電耦合係數(k2)以及良好的壓電性質，而氮化鈧鋁薄膜也因鈧的參雜使壓電係數 d33 大幅提昇，有利於元件之 k2 提升。而選擇對的金屬層加入能有效增進壓電性質之表現。 除此之外，金屬層的加入會造成不同的波速，可以使更多的聲波保留於元件傳遞的區域之間，使插入損失減少同時 k2 上升。
將不同的金屬層鋁、鈦、鉻、鉬以電子槍蒸鍍的方式沉積在鈮酸鋰基板上，再將氮化鈧鋁薄膜以反應式磁控濺鍍雙靶的方式沉積於金屬層上。為了提升氮化鈧鋁薄膜之壓電性質，則探討不同金屬及其厚度對於薄膜特性與壓電性質之影響。當氮化鈧鋁薄膜成長於60 nm的鈦金屬層時，其樣品達到最高的d33，提升原本的97%，此時壓電薄膜具有最大之拉伸應力與(002)面傾斜角，應為較大之傾斜角與應力造成較大的晶面扭曲和晶格不對稱，使得壓電係數有顯著的提升，表示此結構有利於應用在多層結構之表面聲波元件。

In this study, the structure of ScAlN/metal/LiNbO3 will be used to improve the piezoelectric properties. The lithium niobate substrate has a high electromechanical coupling system (k2) and good piezoelectric properties, and the scandium aluminum nitride film has also greatly improved the piezoelectric coefficient, which also improve the k2. The addition of the right metal layer can effectively improve the piezoelectric properties. In addition, the addition of the metal layer will result in different wave speeds, which can keep energy between the regions , reduces the insertion loss and increases k2.
Different metal layers of aluminum, titanium, chromium, and molybdenum are deposited on the lithium niobate substrate by electron gun evaporation, and then the scandium aluminum nitride film is deposited on the metal layer by reactive magnetron sputtering. In order to improve the piezoelectric properties of scandium aluminum nitride films, the effects of different metals and their thickness on the film properties and piezoelectric properties are discussed. When the scandium aluminum nitride film grows on the 60 nm titanium metal layer, the sample reaches the highest d33, which is an increase of 97%. At this time, the piezoelectric film has the maximum tensile stress and the (002) plane tilt angle, which may cause larger crystal plane distortion and lattice asymmetry, so that the piezoelectric coefficient is significantly improved, indicating that this structure is beneficial to the application of the surface acoustic wave device of the multilayer structure.

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