Extension of silicon emission model to silicon pillar oxidation

Abstract

Missing Si in the oxidation of Si pillar structures is investigated by extending the Si emission model to the oxidation of planar structures. The original Si emission model [H. Kageshima et al., Jpn. J. Appl. Phys. 38, L971 (1999)] assumes the emission of excess Si from the interface into the oxide during the oxidation process, the diffusion of the excess Si through the oxide, and the control of the oxidation rate by the concentration of remaining excess Si around the interface. By assuming the sublimation of the excess Si from the oxide surface in addition to the assumptions of the original Si emission model, the origin of the missing Si is consistently explained. It is suggested that the amount of the missing Si is enhanced by the geometrical effect of the pillar structure because the concentration of excess Si is inversely proportional to the radial position. This also suggests that the missing Si is inevitable for the thin pillar structures. Careful approaches to the oxidation process are recommended for pillar structures.