No abstract

No abstract

Metal oxides such as zirconia and hafnia are being investigated as new materials for application as gate dielectrics in future complementary metal-oxide-semiconductor devices. In this paper, we present results on oxidation of metal films such as Zr, Hf, and Al by the ultraviolet ͑UV͒ ozone oxidation method. A nuclear reaction analysis technique, the 16 O͑d,␣) 14 N nuclear reaction, was used to quantify the oxygen concentration in the dielectric stacks. The method was found to be sensitive to monolayer levels of oxygen. It was found that the oxidation kinetics of the metals increased significantly due to the presence of UV light. The oxidation rate was also found to depend on the oxygen partial pressure. The oxidation rate of Zr was greater than that of Hf, while Al oxidized more slowly than Hf for the UV-ozone oxidation conditions investigated. Possible reasons for the observed oxidation behavior are discussed in detail.

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 Å) 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.