Selective Anodic Oxidation of Silicon in Oxygen Plasma

Plasma-enhanced oxidation process at low temperature was studied for the selective oxidation of silicon. Silicon dioxide films as thick as 1 μm were routinely obtained at the substrate temperature of 600°C. The oxidation was found to proceed through the motion of both oxygen and silicon ions and/or their vacancies under the electric field applied across the oxide. Aluminum oxide film was used as a mask for selective oxidation and very small lateral oxidation under the mask was found. Furthermore, no generation of dislocations was found at mask edges. The properties of the oxide were found comparable to those of thermally grown oxide. Electron-spin resonance measurements revealed one kind of defects in the oxide, which was attributed to the interface states by comparing with results obtained by measuring the capacitance-voltage characteristics. The morphology of the Si-SiO₂ interface, studied by transmission electron microscopy was not significantly different from that of thermally grown SiO₂-Si systems. Impurity redistribution in the substrate was not observed.