Two-Dimensional Growth and Decomposition of Initial Thermal SiO2 Layer on Si(100)

The growth and decomposition kinetics of initial thermal oxide layers on Si(100) were investigated by in situ ultraviolet photoelectron spectroscopy (UPS). From a time evolution of the correlation between the amount of oxide and the clean area observed, it was found that the initial thermal oxidation as well as the decomposition proceed two-dimensionally with the formation of oxide islands until the clean surface is fully covered with oxides, after which the oxides grow deeply toward the substrate with a very slow oxidation rate. The oxide island thickness was evaluated from the X-ray photoelectron spectra of Si-2p to be 7.1 A. The two-dimensional oxidation, in which the oxide growth predominantly occurs at the periphery of oxide islands, means that adsorbed oxygen atoms migrate on the clean surface to be captured at the periphery of the oxide islands, resulting in the two-dimensional enlargement of islands, and be desorbed as SiO during the initial thermal oxidation.