Dependence of Interface State Density on Silicon Thermal Oxidation Process Variables

The structural or intrinsic type of interface state charge, related to thermal oxidation and annealing processes, has been characterized with respect to silicon thermal oxidation variables using quasistatic C‐V techniques. Those variables include oxidation ambient ( , , ), annealing/cooling ambient ( , , Ar), oxidation temperature (800°–1200°C), silicon type (p‐ and n‐type), and orientation [(111) and (100)]. Oxides (1200–2200Å thick) annealed and cooled from any oxidation temperature in nitrogen or argon exhibit large interface state densities as oxidized. However after a low temperature hydrogen anneal these densities are lower than those of comparable oxygen‐cooled oxides. Interface state densities of oxides cooled in oxygen vary inversely with oxidation temperature before and after postmetallization anneals. This temperature relationship is very similar to that reported previously for oxide fixed charge and helps to substantiate a model based on a common origin of interface states and oxide fixed charge.