Electron stimulated oxidation of silicon surfaces

Abstract

Experimental evidence of electron stimulated oxidation (ESO) has been given for Si(111) 7×7 surface. In a first stage, the oxide thickness as a function of time shows a linear relationship; in a second stage, the growth rate quickly decreases and a pressure dependent saturation oxide thickness is reached. During the oxidation process an electrical potential does exist across the oxide, as is required in the Cabrera–Mott theory. The linear kinetics and the electrical potential are shown to be explicable in terms of a modified coupled-current approach based on the Cabrera–Mott theory, provided a semiphenomenological pressure dependent parameter is included. This represents a contribution of the surface reaction to the transport equation. The saturation has been explained as due to the decrease of the negative surface charge (donor levels) which produces a decrease of the electron current.