經電漿處理之氧化鉿/氧化鋁/銻化鎵金氧半電容界面缺陷研究;Investigation on the Interfacial Traps of Plasma-Treated HfO2/Al2O3/GaSb MOS Capacitors

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Title:	經電漿處理之氧化鉿/氧化鋁/銻化鎵金氧半電容界面缺陷研究;Investigation on the Interfacial Traps of Plasma-Treated HfO2/Al2O3/GaSb MOS Capacitors
Authors:	蘇冠華;Su, Kuan-Hua
Contributors:	電機工程學系
Keywords:	銻化鎵;金氧半電容;電漿表面處理
Date:	2017-01-20
Issue Date:	2017-05-05 17:39:27 (UTC+8)
Publisher:	國立中央大學
Abstract:	互補式金氧半(CMOS)積體電路技術依摩爾定律發展至今已近極限，尋求具高載子遷移率之新穎材料以取代目前的矽已是大勢所趨。在眾多選項中，三五族化合物半導體是目前最受矚目的標的之一。銻化鎵材料具備窄能隙及高電洞遷移率的特性，使元件能於低電壓下提供高的導通電流，適合製作低功耗高效能互補式電晶體，惟其與高介電材料氧化層之界面存在許多缺陷，這些界面缺陷會造成嚴重的載子散射，降低導通電流，閘極的調控能力亦受影響。因此，如何改善界面缺陷是目前銻化鎵金氧半場效電晶體製作上首要的課題。本論文研究使用氫氣與氮氣電漿進行銻化鎵表面處理，在其上製作氧化鉿(3 nm)/氧化鋁(2 nm)/銻化鎵之金氧半電容，藉電容-電壓特性曲線探討經氣體電漿表面處理後之界面缺陷密度變化及成因。從實驗結果得知，氫氣電漿與表面產生的化學反應可有效去除原生氧化層，避免氧化銻所產生的漏電途徑，但仍有氧化鎵殘留的現象；於室溫下的電容調變率為30 %，價電帶附近之缺陷電荷密度以電導法計算可降低至4.74×1012 eV-1cm-2；氮氣電漿則會於氧化層/半導體界面形成氮化鎵層，使閘極氧化層之絕緣性提升。為了得到更低的界面缺陷密度，本論文提出接續式氫氣電漿與氮氣電漿進行表面處理，亦即先以氫氣電漿去除原生氧化銻，再利用氮氣電漿於銻化鎵表面形成氮化層披覆之方法，使電容調變率可以高達53 %，且於價電帶附近與能隙中間區之缺陷密度經電導法計算後改善至2×1012 eV-1cm-2，而以Terman method計算後之界面缺陷密度為7.5×1013 eV-1cm-2。本論文研究結果顯示，經氫氣電漿處理後接續氮氣電漿表面處理，能更有效地降低界面缺陷密度和解決費米能階釘札效應，此全球首創之表面處理技術將對未來銻化鎵金氧半場效電晶體的實用化有相當大的助益。 ;The development of current complementary metal-oxide-semiconductor (CMOS) integrated circuits, which follows Moore’s Law for decades, has approaching its fundamental limit. Pursuing a high mobility channel material to replace current Si-based material is inevitable and urgent. Among the candidates available, III-V compound semiconductors are the one that attracts many attentions from worldwide researchers. GaSb is a promising material for future p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) because of its narrow bandgap and high hole mobility that give rise to high drive current at low operating voltage. However, the presence of native oxide and interface traps at high-k/GaSb interface makes it difficult to modulate the channel by gate voltage. Improving GaSb MOS interface is thus the top priority. In this study, hydrogen plasma and nitrogen plasma surface treatment on GaSb were employed during the fabrication of HfO2(3nm)/Al2O3(2nm)/GaSb metal-oxide semiconductor capacitors (MOSCAPs). The MOSCAPs prepared by hydrogen plasma process only show capacitance modulation of 30 % with an interface trap density (Dit) 4.74×1012 eV-1cm-2 extracted by conductance method. The devices that were subject to nitrogen plasma treatment only have a nitridation interface layer, which improves gate leakage. For further improvement, hydrogen plasma treatment and nitrogen plasma treatment were sequentially used to fabricate GaSb MOCAPs. As a result, the capacitance modulation improves to 53% and the Dit near the valence band is reduced to 2×1012 eV-1cm-2 and 7×1013 eV-1cm-2 extracted by conductance method and Terman method, respectively. The result of this study is encouraging for the realization of high performance GaSb MOSFETs.
Appears in Collections:	[Graduate Institute of Electrical Engineering] Electronic Thesis & Dissertation

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