| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 96 === 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.
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