氧氣微波電漿表面處理對五氧化二鉭薄膜性質改進之研究

Abstract

本研究利用濺鍍(Sputtering)技術長成五氧化二鉭薄膜，探討氧 氣微波電漿表面改質技術(Oxygen Microwave Plasma Surface Treat- ment)對提升薄膜品質及電性的可行性。 X-光繞射與歐傑能譜儀的 分析結果顯示，微波電漿表面改質處 理技術能使濺鍍長成的薄膜化學計 量比(Stoichiometric Ratio)更接近 五氧化二鉭；掃描式電子顯微鏡、 原子力顯微鏡與穿透式電子顯微 鏡對表面及內部微結構的觀察顯示微波 電漿處理能引發再配列及 氧化現象使原來柱狀晶粒間空隙獲得填補，並 使薄膜的表面粗糙度 降低約6.6倍；結構的緻密化同時改善了五氧化二 鉭薄膜的電性， 使崩潰電壓(Breakdown Voltage)提升了1至3.5倍。但 微波電漿處理 僅對較厚的試片提供改善，對厚度小於10nm的薄膜則因引 入過多 的佈植缺陷而使結構與電性同時劣化。 In this work we studied the oxygen microwave plasma modification on structure and electrical properties of tantalum pentoxide (Ta2O5) films deposited by magnetron sputtering process. The x-ray and Auger electron spectroscopy analyses (AES) revealed that the [O]/[Ta] ratio of the films is much closer to exact stoichiometery after the application of plasma treatment. The surface roughness and the sizes of intergranular voids of plasma-treated Ta2O5 films were effectively reduced, as observed by scanning electron microscopy (SEM), atomic force micro-scopy (AFM) and cross- sectional transmission electron microscopy (XTEM). The plasma-induced structure densification was also beneficial to the electrical properties of Ta2O5 films whose breakdown voltages were improved up to 3.5 times, as indicated by current-voltage (I-V) measurement. However, plasma modification seemed to be effective to thicker Ta2O5 flims. For the Ta2O5 films of thickness less than 10nm, the plasma treatment would result too many implanted defects which deteriorate both structure and electrical properties of the films.