以電子束蒸鍍沈積高介電材質氧化鈦在動態隨機存取記憶體電容器之研究

Abstract

在本論文中，我們先探討電極材料（包含鎢、氮化鎢、鉭、氮化鉭、鉬、 以及氮化鈦）對於氧化鈦薄膜漏電流的影響，並提出在高溫及低溫（攝氏 ８００度及４００度）製程中最適合用來做為電極的材料。實驗結果顯示 ，電極材料的功函數與漏電流的臨界電壓（１０Ｅ－６安培╱平方公分下 ）沒有明顯的關聯。 其次，我 們以氮化鉭上電極做電容討論後續加熱氧化退火製程對氧化鈦薄膜的影響 。這部分的實驗包含加熱氧化退火時應用的氣體、所採用的溫度、以及所 使用的時間。對於不同氣體加熱氧化退火後的氧化鈦薄膜電容，我們多研 究了其在不同量測溫度下漏電流的變化。另一方面，不同厚度的氧化鈦薄 膜及不同硼濃度基板的效應我們也加以研究。相對於爐管加熱氧化退火及 快速加熱氧化退火製程，我們驗証出快速加熱一氧化二氮退火製程是降低 氧化鈦薄膜漏電流最有效的方法。在未來的研究裡，我們需要找出快速加 熱一氧化二氮退火製程的最佳條件，來更進一步地改進氧化鈦電容的特性 。 In this work, the effects of electrode materials (W, WN, Ta, TaN, Mo, and TiN)on the leakage current of TiO2 films were studied. The optimum electrode materials for high- and low- temperature processes (800 ℃ and 400 ℃) are shown. No obvious correlation between ψms and Vcrit (voltage at 10E-6 A/ cm2)is found in our experimental results. We also discussed post-TiO2-deposition annealing effect using TaN top electrode. The effects of annealing ambient, annealing temperature, and annealing time are included. In annealing ambient effect, temperature dependence of leakage current was investigated. On the other hand, the effects of TiO2 film thickness and doping concentration of boron-doped substrate were analyzed. We have then demonstrated that rapid thermal N2O (RTN2O) annealing is the most effective method in suppressing leakage current of TiO2 films, compared with furnace O2 (FO) and rapid thermal O2 (RTO) annealing. For future studies, optimal process conditions of RTN2O annealing are required to further improve performance of TiO2 capacitors.