Evaluation of the Initial Oxidation of Heavily Phosphorus Doped Silicon Surfaces Using Angle Dependent XPS and AFM

The room temperature oxidation of heavily P-doped Si (100) prepared by HF-treatment has been monitored for a period of about one year, using angle dependent x-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). Right after HF-treatment, the P/Si atomic ratio increased with decreasing the photoelectron take-off angle, which implies that the more segregated-P existed in near the top surface region. In case of the heavily P-doped sample, the chemical composition of the growing oxide films showed that not the Si4+ but Si3+ state was dominant component until the oxide thickness went up to over 1.5 nm, while the Si4+ was the major species for the moderately doped Si (100), except the oxide thickness was less than 0.5 nm. In contrast to the smooth AFM image of moderately doped Si (100) surface, the heavily P-doped Si (100) showed very unique geometrical pattern.