濺鍍鈦酸鍶鋇薄膜的電學及微波性質研究

Abstract

本研究以物理氣相交流濺鍍法成長鈦酸鍶鋇薄膜，控制不同的成長條件，如溫度和成長時所通入氣體，以及經由不同的熱處理方法，比較不同成長條件之薄膜的電學及微波性質。以鈦酸鍶鋇薄膜製作MIS (metal-insulator-semiconductor) 的電容結構，然後量測其低頻的介電性質以及漏電流特性。此外也利用鈦酸鍶鋇薄膜製備共平面波導(coplanar waveguide)的傳輸線，經由微波的電路理論設計波導的線寬，並經由精確的微波校正方法，量測出薄膜的高頻性質，校正程序首先經由標準微波量測校正方法，校正探針端之前包括網路分析儀的系統誤差，此校正是以儀器提供的標準工具來達成，接著自行在晶片上設計校正圖案，這些圖案包括穿透(through)、反射(reflect)、線段(line)，並量測這些圖案的S參數，然後以穿透、反射、線段去埋藏法(TRL de-embedding method)來得到薄膜的微波性質，並比較低頻的電容量測和微波量測的結果，可得到鈦酸鍶鋇薄膜和界面層的介電常數，另外在共平面波導的信號及接地兩端加電壓，量測其相位移和插入損失對偏壓的關係，以研究薄膜和矽基板之間的界面性質。

BST (Ba1-xSrxTiO3) thin films have been demonstrated to be highly promising storage dielectrics in DRAM application and dielectric layer in microwave device at high frequency. We have developed a new method to investigate the dielectric and interface properties of BST thin films deposited on silicon substrate by using both CV and microwave measurement. In this work, the electrical and microwave properties of BST film deposited on silicon substrate at various substrate temperatures and their correlation with various OMR are studied. The MIS (metal-insulator-semiconductor) structures were fabricated to explore the low frequency dielectric properties of the BST thin films. The conductor/BST/silicon (high resistivity) substrate multilayer coplanar waveguide was fabricated to measure high frequency dielectric properties of BST thin films. Using network analyzer with conformal mapping technique, we can extract the dielectric parameters at microwave frequencies, and then dielectric constant of interface layer can be obtained. In addition, the properties of interface trap can be studied through the insertion loss vs. bias voltage characteristics measured by applying DC bias across the signal and ground line of the coplanar waveguide (CPW).