Abstract
HfO2, due to its high □ value, is the leading candidate as a gate dielectric for SiO2 in the Si technology, which with the rapid shrinkage of its transistor feature size has forced the SiO2 gate oxide thickness to reduce to 1.0nm, the quantum tunneling limit. There are three known structures of HfO2: monoclinic, cubic, and tetragonal with the dielectric constants being ~20, ~30, and ~70, respectively, as obtained from the first-principles calculation. The common structure of HfO2 thin films from sputtering, atomic layer deposition, and MBE is monoclinic phase. Moreover, the MBE oxide films are epitaxially grown on GaAs with four domains and atomically sharp interface without any interfacial layer.In this work, HfO2 doped with Y2O3 have been grown on various semiconductors substrates, such as GaAs (100) and Si (111) etc., in a multi-chamber MBE system with electron beam evaporation from two separate charges of HfO2 and Y2O3. The oxide films were found to grow epitaxially on the semiconductors, again with very sharp interfaces. Furthermore, the structure of the oxide films was found to change from the monoclinic phase with a low dielectric constant to the cubic phase with a dielectric constant above 30. The structure transformation of HfO2 by doping yttrium increases the dielectric constant of it. The structural characteristics of these thin oxide films were studied using high-resolution x-ray diffraction conducted at BL17B1 wiggler beamline in Taiwan’s National Synchrotron Radiation Research Center.