以電子迴旋共振電漿氧化加前置處理技術成長低溫二氧化矽之研究

Abstract

以低溫下成長極薄的高品質二氧化矽薄膜的技術，在未來次微米元件 的應用上是不可或缺的，而電子迴旋共振電漿氧化法是一個不錯的選擇。 本篇論文主旨在研究在室溫下以無偏電壓的電子迴旋共振氧電漿氧化矽基 板的技術；並且我們也在氧電漿氧化步驟前，在相同的腔體中施以一前置 電漿處理步驟，所使用之氣體為氬氣、氫氣、氮氣及氨氣。結果，發現有 前置電漿處理步驟的二氧化矽成長速度比較快，所以前置電漿處理步驟對 矽基板有表面清潔的效果。因此，兩種成長過程的二氧化矽成長機制是不 相同的。同時，我們也發現氧電漿的氧化速度是微波功率、電漿壓力、前 置電漿處理的時間及氧化時間的函數。 利用以鋁膜及複矽晶膜為閘極 的電晶體電容，分析電子迴旋共振電漿二氧化矽的電性。以鋁閘極電晶體 電容而言，閘極氧化層的崩潰電場在 10 - 14 MV /cm 之間，而界面缺陷 密度及氧化層的有效電荷密度可分別低至 6.2E+11eV－1cm－2及1.0E+12 cm－2。有前置電漿處理步驟的二氧化矽有較高的崩潰電場及較低的界面 缺陷密度和 氧化層的有效電荷密度。由此可知，有前置電漿處理步驟的 二氧化矽有較佳的電性。同時，我們也利用複矽晶閘極電晶體電容分析經 過一些熱處理後，此電子迴旋共振電漿二氧化矽的電性。閘極氧化層的崩 潰電場約在 13 MV /cm 左右，而界面缺陷密度及氧化層的有效電荷密度 可分別低至 6.0E+10 eV－1cm－2及5.0E+10 cm－2 。而且，在 200 mA / cm2 的固定電流密度的作用下，導至閘極氧化層崩潰的電荷密度可達到 9 Coul / cm2。因此，利用前置氮電漿及氨電漿處理步驟可以改善電子迴旋 共振電漿二氧化矽的品質。 A technique of growing a ultra thin SiO2 film of good quality at low temperature is indispensable for future submicron device applications .The electron cyclotron resonance ( ECR ) plasma oxidation can be a good choice to grow the SiO2 film at low temperature . We study the technique of oxidizing a Si substrate with ECR O2 plasma at room temperature under the floating bias condition . We also apply a in-situ plasma pretreatment step before ECR O2 plasma oxidation process .The pretreatment gases used in our studies are Ar , H2 , N2 and NH3 . The SiO2 film growth rate without plasma pretreatment step is lower than that with the plasma pretreatment step .The surface cleaning effect on the Si substrate is obtained by applying this plasma pretreatment step . Therefore , we can observe two kinds of growth mechanisms of the plasma SiO2 with and without plasma pretreatment steps . The ECR O2 plasma oxidation rate is observed as a function of the microwave power , plasma pressure , plasma pretreatment time and oxidation time . The Al gate and poly-Si gate MOS capacitors are used to analyzed the electrical properties of ECR SiO2 film . For the Al gate MOS capacitors , the breakdown field of the gate dielectrics is ranging on 10 - 14 MV / cm . The interface states densities and the effective oxide charge densities is reduced to 6.2E+11 eV -1cm -2 and 1.0E+12 cm -2 . Therefore , the samples with the plasma pretreatment step have the better electrical quality than the ones without this step . The poly-Si gate MOS capacitors are used to analyze the ECR SiO2 with applying some thermal treatments . The breakdown field of the gate dielectrics is about 13 MV / cm ,the interface states density and the effective oxide charge density can be reduced to 6.0E+10 eV -1cm -2 and 5.0E+10 . The charge- to-breakdown of the gate dielectrics can reach 9 Coul / cm2 under a 200 mA / cm2 constant current density stressing . Also the quality of the plasma grown SiO2 can be improved by applying the N2 and NH3 plasma pretreatment steps .