The effect of oxidation on anomalous diffusion in silicon

Abstract The diffusion of impurities into silicon is usually carried out in the presence of an oxidizing environment and an oxide film is therefore formed on the surface of a silicon wafer during the diffusion process. The growth of this oxide takes place at the oxide-silicon interface and in order to accommodate the inward growing oxide, some of the material near the interface must be transported into the silicon matrix. This material flow will contain some impurity atoms and thus gives rise to an additional component in the impurity flux. The effect of this will be most apparent near the interface where the impurity concentration is greatest and gives rise to enhanced impurity diffusion. A model based on this effect has been analysed in detail and shown to account quantitatively for the anomalous profiles reported by other workers. For an interstitialcy diffusion mechanism an equation describing the profiles can be readily derived but it is necessary to treat the problem by irreversible thermodynamics a...