分子束磊晶成長氧化鋁/氧化鉿高介電常數薄膜在鍺基板

Molecular Beam Epitaxy Grown Al2O3/HfO2 High-κ Dielectrics for Germanium

覃炳華(Bing-Hua Chin)

指導教授 ： 洪銘輝 ； 郭瑞年

國立清華大學/工學院/材料科學工程學系/碩士(2008年)

摘要

本實驗室使用分子束磊晶(MBE)的方法成長高介電常數氧化層氧化鋁/氧化鉿(Al2O3/HfO2)在鍺基板上，此氧化層與鍺基板的界面有良好的熱穩定性及其金氧半電容元件呈現優良的電性。經由高解析度穿透式電子顯微鏡(HRTEM)的分析，氧化鉿與鍺基板之間並無任何的界面層或鍺氧化物產生。利用臨場可調變角度式的X光光電子能譜儀(in situ AR-XPS)來檢測氧化鉿與鍺基板界面的熱穩定性及其價電帶的能階差值(valence band offset)為4.15~4.55± 0.2eV。探討氧化鋁/氧化鉿在鍺基板上所製作電容元件的熱穩定性及電性，當元件經過氮氣500oC 20分鐘的退火後，元件呈現良好的電容電壓曲線，在平帶電壓正負一伏特下(VFB ±1V)閘極到基板的漏電流密度為10-3~10-5 A/cm2。此元件的界面能量態密度(Dit)經Terman method計算約為1~5×1012 ev-1cm-2之間，等效氧化層厚度(CET)小於2奈米，氧化鉿層的介電常數值則高達18~20。本實驗證明了:鍺基板表面不需要任何的界面擴散阻擋層來保護，雖然在經過退火後氧化鉿與鍺基板界面有些微的反應產生，元件仍呈現良好的特性。氧化鋁/氧化鉿/鍺基板的結構能有效應用在金氧半場效電晶體的製作。

關鍵字

分子束磊晶 ； 氧化鋁/氧化鉿 ； 高介電常數 ； 鍺 ； 金氧半電容元件

並列摘要

Molecular beam epitaxy (MBE) grown high-k dielectric Al2O3/HfO2 on Ge substrate, without the assistance of interfacial barrier layer, has demonstrated excellent electrical properties and good thermal stability. In-situ MBE-Al2O3 was deposited on HfO2 as a cap layer for protection. An abrupt Al2O3/HfO2/Ge interface without any interfacial layer was revealed by high-resolution transmission electron microscope. The interface thermal stability and the valence band offset about 4.15~4.55± 0.2eV for the HfO2/Ge hetero-structure were studied by the in-situ Angle-resolved X-ray photoelectron spectroscopy (AR-XPS). Well-behaved capacitance-voltage (C-V) characteristics with CET smaller than 2nm, high k-value of about 18~20 for HfO2, Dit in the low range of 1012 cm-2eV-1 near the midgap, and a low leakage current density at VFB ±1V of 10-3~10-5 A/cm2 were obtained for a sample annealed at 500oC in N2 ambient for 20 min, which exhibit an absolutely outstanding thermal stability of the Al2O3/HfO2/Ge hetero-structure. Therefore, MBE grown Al2O3/HfO2 are the promising high-k dielectric to realize a high performance Ge MOSFET. In this work, we also prove that no interfacial barrier layer was needed in our approach, and a minor diffusion of Ge into the oxide layer has no significant influence on the electrical properties.

並列關鍵字

Molecular beam epitaxy ； Aluminum oxide ； Hafnium oxide ； High-k dielectric ； Germanium ； metal-oxide-semiconductor capacitors

參考文獻

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