Zirconia grown by ultraviolet ozone oxidation on germanium(100) substrates

Growth of zirconia (ZrO2)-based gate dielectrics on germanium (Ge) substrates by oxidation using activated oxygen species produced by ultraviolet radiation (UV/ozone) is reported here. In this technique, a thin layer of zirconium (Zr) metal (10-30 Angstrom) is deposited by physical vapor deposition on Ge and subsequently oxidized in reactive oxygen. X-ray photoelectron spectroscopy (XPS) analysis indicates complete oxidation of the Zr metal. High resolution transmission electron microscopy (TEM) of UV-ozone oxidized ZrO2 on Ge indicates a sharp interface between the oxide and the substrate. However, conventional TEM is not well suited for identifying a Ge oxide layer in this system due to the closeness in atomic number of Zr and Ge. XPS spectra suggest the presence of a substoichiometric Ge oxide phase at the ZrO2/Ge interface. Depth profiling using angle-resolved XPS was performed on ZrO2/Ge gate stacks of varying oxide thickness. The results indicate that the amount of Ge oxide is dependent upon the ZrO2 overlayer thickness, suggesting that the interfacial layer can be controlled by the oxidation conditions. (C) 2004 American Institute of Physics.