Transport Processes in the Thermal Oxidation of Silicon

Previous experiments on the effect of an electric field on the oxidation rate of silicon are reconsidered. It is shown that such experiments do not in themselves prove that oxidation occurs by the diffusion of a charged species through the reaction layer, but may be analyzed in terms of an electrolytic process being superposed on the normal oxidation process. Supplementary data present in the literature are also insufficient to conclude whether a charged species is involved. A theoretical analysis of the transport processes to be expected when oxidation involves a charged diffusant shows that the rate of such a process may be predicted if the electronic conductivity of SiO 2 under the conditions of oxidation is known. Suitable experiments for determining this quantity are suggested.