薄氧化層的電子特性

Abstract

本論文我們是研究n型金氧半場效電晶體在閘氧化層2-7nm反轉層時的電子 遷移率,藉由高解析度穿透式電子顯微鏡(Transmission Electron Microscopy,TEM)及量測金氧半場效電晶體的遷移率可以得到電子遷移率 與界面平坦度有直接的關係.我們藉由低壓氧化沉積系統的製程使能在管 內去除氧化層(Native Oxide)後再成長氧化層1.1和3.8nm,結果藉由穿透 式電子顯微鏡可發現氧化層及矽層間有原子層般的平坦界面.當氧化層增 至5.5nm時界面粗糙度僅增加1-2矽的原子層.因為氧化層的平坦界面及良 好厚度均勻性,故高電場電子遷移率及氧化層崩潰行為都有極大的改善.傳 統的氧化層界面較不平坦,故電子遷移率較低.而在超薄氧化層發現有遷移 率減低的現象,可能由閘極的庫倫散射所產生. We have studied the inversion layer mobility of n-MOSFET's with thin oxide of 2-7nm.Direct relationship of electron mobility tointerface roughness was obtained from the measured mobility of MOSFET'sand high-resolution TEM.By using low-pressure oxidation process with nativeoxide removed in-situ prior to oxidation, atomically smooth interface ofoxide/Si can be observed by high- resolutional TEM for oxide thicknessof 1.1 and 3.8nm.The roughness increased to 1-2 monolayers of Si in a 5.5nmoxide. Because of the smooth interface and good thickness uniformity ofoxide,both high-field electron mobility and oxide breakdown behaviorare much improved.Significant mobility improvement is obtained from theseoxides with smoother interface than that from conventional furnace oxidation.Mobility reduction in ultra-thin oxide was observed for the first time,which may be due to the remote Coulomb scattering from gate electrode.