Time dependence of the oxygen exchange O2⇆SiO2 at the SiO2-Si interface during dry thermal oxidation of silicon

During dry thermal oxidation of silicon oxygen exchange reactions may occur between oxygen molecules (O-2<->O-2, catalyzed by the SiO2) or between oxygen from the gas phase and the oxygen in SiO2 (O-2<->SiO2), both at the surface and at the Si-SiO2 interface. We found that the oxygen exchange rate at the Si-SiO2 interface is at least 25% of the oxygen uptake rate, requiring the movement of oxygen both from the surface to the interface, and from the interface to the surface. The oxygen exchange at the interface is further evidence in favor of the presence of a reactive interfacial layer between the growing oxide and the silicon substrate. (C) 1999 American Institute of Physics. [S0021-8979(99)08514-X].