- 學位論文
Investigation on oxygen-related stability and hot carrier stress for IGZO-TFTs
銦鎵鋅氧薄膜電晶體在氧氣下穩定度及熱載子壓下的研究
摘要
In the first part of my research, we tried to observe the influence of IGZO-TFT’s capacitance under oxygen atmosphere. Oxygen adsorption on back channel was one of the reasons which resulted in the capacitance windows. As oxygen differential pressure increases, the width of window also increases. In the second part of my research, we would like to know the impact of traditional hot carrier stress for IGZO-TFT in vacuum. The hot carrier stress in vacuum formed the interface traps near drain terminal which were donor-like states bellow intrinsic Fermi level and the whole oxide electron trappings. The donor-like states caused the off-state capacitance wholly lifted in gate-drain capacitance. The electron trapping in the oxide caused gate-drain capacitance parallel shifted to positive and made the threshold voltage in capacitance delayed. In the third part of my research, hot carrier stress in oxygen atmosphere formed the oxygen adsorption near drain terminal and the electron trapping on whole oxide. The electron concentration decreased and the IV Fermi level near drain terminal should align with all the other Fermi level so that the drain barrier became higher than original drain barrier. The gate-drain capacitance shifted greatly to positive because of the barrier which formed by the oxygen adsorption near drain terminal; two stage turn-on of gate-source capacitance resulted from source barrier and oxygen field induced barrier separately. The window of capacitance can confirm the barrier which oxygen molecular induced. In the last part of my research, hot carrier stress under 380K could descend the higher barrier formed by electron trapping.
並列摘要
在第一部分實驗中，我們要觀察IGZO-TFT在氧氣環境下的正反掃電容表現。 實驗結果發現:氧氣吸附在被通道是造成正反掃電容窗口的原因。 當氧氣分壓越大，正反掃電容的窗口將會越大。 在第二部分實驗中，我們要觀察IGZO-TFT真空下在傳統熱載子偏壓下的影響。 而實驗結果發現:1.熱載子的衝擊後會再靠近汲極端產生表面缺陷，該缺陷的生成位置在能帶中為費米能階底下的近似施體位階所提供。2.熱載子衝擊也會造成電子被缺陷補獲於閘極氧化層中。費米能階底下的近似施體位階將會導致電容值在關閉狀態下的抬昇。而電子被缺陷補獲於閘極氧化層中會導致電容值(Cgd)平行向右移動以及臨界電壓加大。 在第三部分實驗中，熱載子偏壓條件下並且置於氧氣環境之下。實驗結果發現氧氣會大量吸附在靠近汲極端以及電子被缺陷補獲於閘極氧化層中。氧氣的吸附會大量捕捉通道內的電子，使得費米能階下降，當費米能階重新對齊後會導致更高的汲極能障。當量測閘極對汲極電容時，電容會因為氧氣吸附於靠近汲極端所造成的能障而有大幅度的向右平行移動；當量測閘極對源極電容時，則會出現兩階段的導通。兩階段導通的原因在於:電子從源極提供載子進入通道，第一階段必須克服原本既有的源極能障，而第二階段必須克服因為氧氣吸附於靠近汲極端所造成的能障。氧氣產生的能障可以從正反掃電容來進一步驗證。 第四的部分的實驗，我們將熱載子偏壓的穩定度測試加上高溫環境。 而實驗結果發現:原本常溫下熱載子偏壓會造成的閘極氧化層捕獲電子會因為升溫加上熱載子偏壓產生的閘極氧化層捕獲電洞所中和。造成量測全通道電容時並沒有向右平移的狀態產生。
參考文獻
延伸閱讀
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