氧化鋁/銻磷砷化銦金氧半電容元件特性改善與累積區頻散分析

Characteristic Improvement of Al2O3/InAsPSb Metal-Oxide-Semiconductor Capacitor and Analysis of Accumulation Frequency Dispersion

顏辰嘉(Chen-Jia Yan)

指導教授 ： 林浩雄

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201602180

摘要

本研究探討合成氣體與氮氣的金屬後退火對銻磷砷化銦原子層沈積二氧化鋁的氧化層固定電荷及其介面影響，欲改善半導體與氧化層的固定電荷及邊緣缺陷和費米能階釘札效應，提升電容隨電壓調變能力及降低累積區頻散。
首先，我們從電容對電壓曲線、平帶電壓VFB位置及元件漏電流分析合成氣體和純氮氣相同溫度的金屬後退火對銻磷砷化銦影響。結果顯示頻散、調變能力和延展特性差異不大，說明在有無氫環境皆能修補Al2O3/InAsPSb介面鍵結，改善費米能階釘札效應。平帶電壓VFB位置幾乎相同，推測氧化層固定電荷主要是受退火溫度影響與通入氣體環境無關。而漏電流在氮氣環境高於合成氣體環境107倍，氮氣保留下較多氧或鋁的空缺鍵。當施加偏壓時容易產生較大的漏電流。
由上述實驗我們可知合成氣體與氮氣相比，擁有漏電流較小的優勢，而在合成氣體環境下做不同溫度的金屬後退火。金屬後退火溫度低於250℃時，隨溫度增加，電容調變率、累積區頻散和磁滯平帶電壓差 獲得改善。推測是熱提供能量能修補Al2O3/InAsPSb介面鍵結、減少氧化層缺陷電荷和改善費米能階釘札效應。 而當退火溫度高於250℃環境，隨溫度增加，半導體介面的邊緣缺陷 (Border trap) 也隨之增加，電容調變率和累積區頻散特性將衰退，推測過量的熱能會使原本良好鍵結不穩定重新斷裂，其中磁滯平帶電壓差則保持不變。在漏電流部分，熱能則讓氧化層更加緊密使穿隧障壁減少，導致混合氣體環境溫度越高漏電流增加。
我們獲得以下結果：第一點，平帶電壓VFB隨溫度增加而平移接近理想，顯示氧化層固定電荷減少。第二點，電容對電壓曲線展延降低顯示介面電荷減少。第三點，累積區頻散減少及調變能力增加顯示介面特性的改善。

關鍵字

金氧半電容元件 ； 金屬後退火 ； 銻磷砷化銦 ； III-V族半導體

並列摘要

The research of the post metallization annealing in forming gas was performed to study the effect of fixed charge and its interface on InAsPSb with atomic layer deposition Al2O3 oxide. And it is not only to improve fixed charge and border trap of the metal-oxide-semiconductor and Fermi level pinning, but enhance the C-V modulation and reduce frequency dispersion in the accumulation. Three results were improved from experiment: (1) the trend of flatband voltage (VFB) shift with increasing temperature approaching ideal showed reduction of fixed charge on oxide layer, (2) The lower C-V stretch out presented reduction of interface charge, (3) the reduction of dispersion frequency and increment of Cmod indicated the improvement of interface characteristic.
The discussion of the effect of forming gas and N2 on the post metallization annealing for InAsPSb was conducted. The result showed that the difference of frequency dispersion, Cmod, C-V stretch out between old and new ones were small from analysis of capacitance-voltage curve, flatband voltage shift and leakage current of gate. It told that bonds were rearranged to fill vacancies on interface of Al2O3/InAsPSb to improve Fermi level pinning with almost the same flatband voltage in both oxygen and non-oxygen environment. It was found that fixed charged on oxide layer was mainly influenced by annealing temperature, not gas entering the environment. Leakage current was 107 higher in N2 environment than that in forming gas environment. N2 kept more oxygen and aluminum vacancies. When voltage bias was exerted, leakage current was easier to be generated in conductive filaments.
Different temperature of the post metallization annealing in forming gas was conducted. Cmod, frequency dispersion of accumulation capacitance and hysteresis flatband voltage difference ∆VFB were improved with increasing temperature in the environment of post metallization annealing temperature lower than 250℃, because thermal energy can rearrange bonds to fill vacancies on interface of Al2O3/InAsPSb, reduce defect of bonds on oxide layer and improve Fermi level pinning. When annealing temperature was higher than 250℃ and kept increased in environment, overheating can make stable bond become unstable and even broken again. The border trap on interface of semiconductor also increased. Cmod and frequency dispersion of accumulation capacitance decayed, while hysteresis flatband voltage difference kept the same. Higher thermal energy can densify oxide layer and reduce barrier of tunneling, but it led to increasing leakage current with higher temperature in the forming gas environment.

並列關鍵字

metal-oxide-semiconductor capacitor ； post metallization annealing ； InAsPSb ； III-V semiconductors

參考文獻

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