Oxygen diffusion and reaction at annealed InSb MOS interfaces

We investigated the effects of heat treatments on the interfacial chemical and electronic properties of InSb metal-oxide-semiconductor (MOS) structures, prepared by wet anodization. Results of in-depth profiling of the heat-treated passivation films, using high-resolution Auger electron spectroscopy (AES), including line-shape analysis and deconvolution techniques, reveal important information on changes in the layers' structure and composition. Among the salient trends, we note that annealing at increasingly elevated temperatures monotonically enhances the extent of O in-diffusion, increases the width of the In-In oxide and Sb-Sb oxide interfaces, and changes their overlap and relative positions. The electrical features observed in the capacitance-voltage (C-V) curves, such as flat band voltage, hysteresis, and other deviations from the ideal C-V curves, are explained in terms of changes in surface states and charges. The effect of the heat treatments was noted by a marked decrease in the oxide trap and fast interface state densities, whereas the fixed oxide charge density increased. The significant dependence of all the features on the annealing temperatures facilitates the assignment of electrically active species to different spatial positions and oxidation states of In and Sb at the oxide layers and at their interfaces. The electrical properties of these MOS structures are shown to be considerably improved by annealing at relatively low temperatures (below 250°C).