Enhanced and Retarded SiO sub(2) Growth on Thermally Oxidized Fe-Contaminated n-Type Si(001) Surfaces

At the beginning of the oxidation of Fe-contaminated n-type Si(001) surfaces, Fe reacted with oxygen (O sub(2)) on the silicon (Si) substrate to form Fe sub(2)O sub(3) and oxygen-induced point defects (emitted Si + vacancies). SiO sub(2) growth was mainly enhanced by catalytic action of Fe. At 650 [degrees]C, SiO sub(2) growth of the contaminated samples was faster than in reference samples rinsed in RCA solution during the first 60 min. However, it substantially slowed and became less than that of the reference samples. As the oxidation advanced, approximately half of the contaminated Fe atoms became concentrated close to the surface area of the SiO sub(2) film layer. This Fe sub(2)O sub(3)-rich SiO sub(2) layer acted as a diffusion barrier against oxygen species. The diffusion of oxygen atoms toward the SiO sub(2)/Si interface may have been reduced, and in turn, the emission of Si self-interstitials owing to oxidation-induced strain may have been decreased at the SiO sub(2)/Si interface, resulting in the retarded oxide growth. These results are evidence that emitted Si self-interstitials are oxidized not in the Fe sub(2)O sub(3)-rich SiO sub(2) layer, but at the SiO sub(2)/Si interface in accordance with a previously proposed model. A possible mechanism based on the interfacial Si emission model is discussed. The activation energies for the oxide growth are found to be in accord with the enhanced and reduced growths of the Fe-contaminated samples.