高介電係數金屬閘極金氧半場效電晶體之反置層等效電子遷移率衰減機制探討

Abstract

隨著金氧半電晶體的微縮演進，使得反置層二維電子受到更急遽的散射機制而導致等效電子遷移率衰減。我們藉由廣泛地比擬微觀計算與實驗數據，證實界面電偶極為導致金屬/氧化鉿(HfO2)/半導體場效電晶體電子遷移率衰減的主因。界面電偶極會引起臨界電壓偏移量增加，透過存在於高介電係數氧化層/界面層的固定電荷及金屬/高介電係數氧化層的電偶極相互補償，基於此補償機制，元件的淨臨界電壓偏移可被忽略。此外，我們探討高介電係數金屬閘極金氧半場效電晶體電子遷移率隨著通道長度微縮至14奈米衰減的成因，經由分析溫度趨勢，用實驗的方法證實當通度長度小於25奈米時，源極/汲極電漿子將更甚中性缺陷嚴重地劣化電晶體效能。

As the evolution of shrinking MOS transistors, inversion-layer 2D electrons underwent the drastic scattering processes, causing the effective mobility degradation. In this thesis, we probed that the mobility reduction at low inversion-layer densities in hafnium-based gate dielectrics MOSFETs is due to interface dipoles by means of extensive comparison between microscopic calculation and experimental data. The interface dipoles accompanied by a large threshold voltage shift could be compensated with a negative produced by fixed charges at the high-k/IL interface and dipoles at the metal gate/high-k interface. Consequently, the net in present sample is negligibly small thanks to the compensation action. In addition, on the high-k metal gate MOSFETs, mobility degradation with the decreasing channel lengths L down to 14nm has been examined by temperature dependent analysis. We have experimentally demonstrated that for the channel lengths less than 25 nm, the source and drain plasmons will dominate over neutral defects in degrading the device performance.