Iron accumulation at the Si-SiO2 interface and possible reduction of SiO2

Abstract

It has been found for the first time by the secondary ion mass spectroscopy in-depth profiling technique that iron atoms accumulated at the Si-SiO2 interface of oxidized silicon crystals where iron had been introduced by in-diffusion prior to the oxidation at 1000°C. The origin of iron accumulation is ascribed to iron precipitation from bulk silicon. It has also been found that iron atoms that in-diffuse through the bulk silicon from the lapped backside of a pre-oxidized sample were trapped and aggregated at the front Si-SiO2 interface. An interesting observation is that this in-diffusing iron also penetrated the oxide region from the interface, enhancing the Si+ ion yield. This strongly suggests that SiO2 is reduced by the presence of iron resulting in lower oxides, elemental Si, and/or Fe silicides.