Electrical properties of ion beam sputtered and ion assisted SiO2, SiOxNy, and SiNx films on silicon

To develop methods for the formation of metal-insulator-semiconductor (MIS) devices at low temperature, thin SiO2, SiOXNY, and SiNX films were reactively sputtered onto nonheated silicon substrates using different sputtering and ion assist parameters. SiO2 was prepared by bombarding Si with Ar+ ions in Ar/O-2 ambient whereas SiOXNY and SiNX films were prepared by bombarding Si3N4 with N-2(+) ions in N-2/O-2 and Ar/N-2 ambients, respectively. In addition, 300 eV N-2(+) ion assistance was used during preparation of SiNX films to enhance film nitriding. The 100-300 eV Ar+ ion assistance was also used during preparation of SiO2 to investigate the electrical damage effects caused by energetic ion bombardment during sputtering of the insulator film. The bulk and interfacial electrical properties of these films, which were assessed from current-voltage and high-frequency capacitance-voltage (C-V) measurements on MIS structures, indicate that the Si native oxide and type of anneal play a key role in determining the final film-interface quality. SiOXNY sputtered films exhibit poorer C-V electrical characteristics with increasing nitrogen content resulting from the creation of positive fixed charge in the film and fast interfacial states. This damage can be suppressed using a native oxide but this increases the instability of the interface. Ion assistance of SiO? films increased the level of electrical damage to the film in the bulk and in the vicinity of the interface. The majority of this damage manifests itself as fixed charge and trapping states in the film rather than fast interfacial states and leads to lower breakdown voltages and higher dielectric constants. Drift behavior of these films suggest that, with a native oxide in place, the former type of ion bombardment induced damage can be eliminated by a forming gas anneal although some deterioration of the electrical bulk properties remains. (C) 1998 American Vacuum Society. [S0734-211X(98)00402-8].