以溶膠-凝膠法製備鈦酸鍶鋇薄膜及其結構與電性分析

Abstract

本研究嘗試以溶膠-凝膠法在Pt/Ta/SiO2/Si(100)基板上製備(BaxSr1-x) TiO3薄膜，並在400 ~ 850℃之間進行熱處理，以XRD鑑定結晶相，以SEM、TEM觀察薄膜的微觀結構。(BaxSr1-x)TiO3的成相溫度為650℃，並且在500℃ ~ 600℃之間觀察到中間過渡相，經由電性量測的結果得知，當x = 0.7時，熱處理溫度為750℃ 1小時，可得最佳電性，介電常數為382，漏電流密度為1.16’10-6 A/cm2。添加Zr取代部分Ti可降低漏電流至4.29’10-7 A/cm2。本實驗亦以同樣溶膠-凝膠法的製程製備(BaxSr1-x)TiO3的粉末，用以觀察其前趨物的反應過程以及經過熱處理後的微觀結構發展，並且與薄膜做比較。利用TGA、DTA、FT-IR、XRD、TEM觀察粉末的反應與成相過程，由此得知在400℃熱處理後凝膠反應會完成，並且形成(Ba,Sr)CO3結晶相，在550℃時形成(BaxSr1-x)TiO3結晶相，並且兩種結晶相同時存在。

(BaxSr1-x)TiO3 thin films were deposited on Pt/Ta/SiO2/Si(100) substrate by sol-gel and spin coating methods and then annealed at temperature ranging from 400 to 850℃. The crystallization behavior and microstructural evolution of the films were investigated by XRD, SEM and TEM. The films crystallized to an intermediate phase between 500 ~ 600℃ and crystallized to cubic (BaxSr1-x)TiO3 phase above 650℃. The specimen with a composition of x = 0.7 had optimum electrical properties. A dielectric constant of 382 and leakage current density of 1.16’10-6 A/cm2 were measured for the (Ba0.7Sr0.3)TiO3 films after annealing at 750℃ for 1h. The addition of 10 % Zr would decrease the leakage current density to 4.29’10-7 A/cm2. For comparison, the reaction behavior of precursors and the microstructural evolution of the (BaxSr1-x)TiO3 powders prepared by sol-gel method were observed by TGA, DTA, FT-IR, XRD and TEM. The gel reaction completed after heating to 400℃, then an intermediate phase (Ba,Sr)CO3 was formed. The powders crystallized to (BaxSr1-x)TiO3 phase above 550℃ coexisting with (Ba,Sr)CO3.