GROWTH-RATE AND CHARACTERIZATION OF SILICON-OXIDE FILMS GROWN IN N2O ATMOSPHERE IN A RAPID THERMAL PROCESSOR

A rapid thermal oxidation process of silicon in N2O ambient was investigated using a commercially available reactor with a fixed wafer position and a gas flow parallel to the wafer surface. For such a configuration, thickness uniformities in the 2% range were obtained for the first time. The oxidation rate as a function of process temperature and time was investigated. A retardation in the N2O oxidation rate as compared to the oxidation in 02 ambient is explained by the formation of a nitrided interfacial layer. A comparison of experimental results with an oxidation model calculation shows that this interface can affect either the oxidant diffusivity through the oxide or the reaction rate at the silicon surface. Infrared spectra of nitrided oxide films reveal a regular arrangement in the Si-O network, similar to that of high quality thermally grown oxides. A vibrational contribution to that spectrum from a Si-O-N subnetwork is displayed. The accumulated charge to breakdown on metal-oxide-semiconductor capacitors as a function of the injected current density revealed different slopes for oxides either thermally grown or grown in N2O. Hence, the projected lifetime for devices with N2O grown oxide under low operating fields is extended by one order of magnitude in comparison with the thermal oxide.