Abstract
在今日金氧半(MOS) 元件製程中，因為離子佈植技術廣泛被使用於臨限電壓(threshold voltage)校正 。不均勻雜質分佈引起額外的內建電場和內建電壓會對理想平帶電壓(flat-band voltage) 模型造成相當的影響。本論文中我們考慮不均勻雜質分佈的元件和低溫下雜質的不完全離子化效應(Freeze-out effect) ，而提出一個修正平常帶電壓模型。此外由實驗中獲得平帶電壓的方法也會因為不均勻雜質分佈而變得非常困難。本論文中我們對曾經發表過平帶電壓實驗方法作一個廣泛優缺點比較，並對低溫下各方法適用性做一個討論。最後我們認為盡管對不均勻雜質分佈元件，修正的低溫平帶電容 (flat-band capacitance)方法仍可以在低溫到室溫（77-300oK）被有效使用。實驗結果中平帶電壓和溫度變化的關係和修正平帶電壓模型相當吻合，在n-type MOS電容中，平帶電壓的溫度係數大約是+1mV/℃，並且實驗結果顯示： 從修正的平帶電壓模型中推算的氧化層陷住電荷 ( effective oxide charge) 濃度值超過從理想平帶電壓公式中推算值大約 10~30﹪。除此之外，本論文討論目前廣泛應用於改善二氧化矽氧化的快速升溫製程技術( rapid thermal processing -RTP) ，發現經過升溫處理的MOS元件俱有較小的平帶電壓溫度係數 。我們並對不同 RTO ( rapid thermal oxidation ) 和RTA ( rapid thermal Ar/reanneal)製程條件在電氣特性和可靠度分析做一個廣泛研究比較，實驗結果顯示在（1100℃中NH3 回火60秒，隨後在1000℃中N2重新回火60秒）的製程條件中可以獲得最佳的MOS介電層。The classical derivation for the flat-band voltage of an MOSdevice, commonly used for non - implanting and ideal uniformsubstrate, is invalid in present day devices . Significanterror may be due to nonuniform doping and build - in field .We derive a modified model which considers both thenonuniformly doped substrate and the freeze - out effect tocompute the flat - band voltage at low temperatures. Goodagreement between experiment and theoretical result is observedover a wide range of temperature . The temperaturecoefficient of the flat - band voltage in n - type MOSC is dVfb/ dT = + 1mV / oC . The experimental results show that RTP (rapid thermal processing ) treated devices have lesstemperature dependent Vfb than pure oxide devices have. Wefound that the effective oxide charge derived with themodified model is 30% more than that derived from theclassical derivation . To extend this model and make acomprehensive study, the results of electrical characteristicsfor ONO (oxidation nitrided oxide) and ANO ( Ar/reannealingnitrided oxide ) structure are also presented . Resultsshow that reoxidzed / nitrided oxides (e.q., nitridation for60secs at high temperature of 1100oC and reoxidationin oxygen ambient at temperature of 1000oC for 60secs )have optimized electrical properties and leastreliability problems.