用N2O成長複晶矽氧化層的效應

Abstract

為了改善複晶矽氧化層的介電強度,我們嘗試用N2O去成長或氮化複 晶矽氧化層o 在非揮發性記憶元件的應用上,理想的複晶矽氧化層必 須在J-E特性上得到低漏電流與 高崩潰電場,而我們發現用N2O成長或 氮化的複晶矽氧化層在這方面都比用O2成長的要 好,這是因為氧化層 與下層的複晶矽介面附近有大量的氮嵌入氧化層中o 另外,跟用O2 成 長的複晶矽氧化層比起來,我們發現用N2O成長或氮化的複晶矽氧化層有較 大的崩潰 電荷,同時,氧化層中的電子捕捉也較少o 下層複晶矽的載子濃度對複晶矽氧化層的影響也在我們的研究範圍之中o 我們發 現雖然高濃度的下層複晶矽可以得到較平緩的介面,但是很不 幸的是,複晶矽氧化層的 成長過程中,下層複晶矽的高濃度載子向氧化 層擴散的情形很嚴重,這將會造成氧化層 介電強度的退化;至於如何在 這兩個效應中取得一個妥協,就必須視這層複晶矽氧化層 的用途而定 了o In this thesis, characteristics of N2O-grown polyoxides and N2O-nitrided polyoxides have been studied. When the top electrode was positively biased, the obtained polyoxides had a desirable polarity asymmetry of J-E characteristics, i.e., a lower leakage current and a higher breakdown electricfield than those of O2-grown polyoxides, which are ideal for the nonvolatile memory application. The asymmetry is due to the incorporation of nitrogen at bottom polyoxide/poly-Si interface which has been found in N2O-grown and N2O- nitrided gate oxides. Moreover, comparing to conventional polyoxides, the N2O-grown and N2O-nitrided polyoxides had a lower electron trapping rate and a larger charge-to-breakdown. Dopant concentration effects were also investigated in our study. We found that even if the heavily doped polyoxide had a smoother bottom polyoxide/poly-Si interface than the median doped polyoxide, the dopant outdiffusion effect degraded its dielectric strength. We must make a compromise between these two effects according to the application of the polyoxide film.