以低壓化學氣相沉積法ＴＥＯＳ製成之薄閘極氧化層之研究

Abstract

在本論文中，我們研究了藉由煉解ＴＥＯＳ製成的化學氣相沈積之二氧化 矽薄膜。在Ｎ２Ｏ環境下進行沈積後退火（ＰＤＡ）的二種結構：直接退 火之薄膜和疊型結構，皆被討論。在不同的溫度和加入ＴＣＡ下，以Ｏ２ 退火所產生的ＴＥＯＳ氧化層亦被研討。以Ｎ２Ｏ和Ｏ２來做ＰＤＡ，皆 能降低在剛沈積ＴＥＯＳ膜所見之直接穿隧電流。以Ｎ２Ｏ退火後之ＴＥ ＯＳ氧化層皆比以Ｏ２來退火之氧化層顯現較小的平能帶電壓。對以Ｎ２ Ｏ來做退火處理之ＴＥＯＳ膜，在電流注入後所能產生之最小界面陷阱密 度，最佳化的組合為６６Ａ之ＴＥＯＳ膜加上１０分鐘的ＰＤＡ。我們發 現所有的ＴＥＯＳ氧化層之中，最佳之ＴＤＤＢ特性為１００Ａ的ＴＥＯ Ｓ膜加上９２５Ｃ在Ｏ２環境下１５分鐘的退火處理。我們將此現象歸因 於沈積之氧化膜上半部的良好復原，這可由與熱氧化層相當的複晶矽與氧 化層界面位障高看出。電荷捕捉中心落在靠近複晶矽閘極處，顯示了ＴＥ ＯＳ膜的上半部需要良好之再結構，物理上的解釋在文中亦有提及。 In this thesis, we study the CVD SiO2 films formed by the pyrolysis of the tetraethylorthosilicate(TEOS) . Two different structures, the direct annealed thin films and the stacked structures, with the post-deposition-anneal (PDA) in the N2O ambient are discussed. The O2 annealed TEOS oxides prepared at different annealing temperature and with the addition of the TCA species are also studied. The additional PDA seems to reduce the direct tunneling current of the as-deposited TEOS films for both the N2O and O2 cases. The N2O annealed TEOS films all show the less flat-band voltage shift (ΔVFB) than the O2 annealed ones The optimal combination of the TEOS film with the N2O annealng process for the less interface state genetrated was found to be the 66A with the 10 minute PDA. The best TDDB performance is found to be the TEOS films 100A with the 15 minute annealed in the 925C O2 ambient. We contribute this phenomenon to the well- healing on the upper part of the deposited films for the equal value of the effective barrier height with the thermal oxide at the poly-silicon/oxide interface. The charge trapping centroid located near the poly- Si gate shows the upper part of the TEOS film needs well- restructuring. Physical explanations are given.