Atomic redistribution of implanted Fe and associated defects around moving SiO₂/Si interfaces

The behaviour of Fe atoms at the Si/SiO₂ interface, as a modelisation of an involuntary Fe contamination before or during the oxidation process has been studied in Fe-implanted wafers. As-implanted and oxidized wafers were characterized by SIMS, APT, HR-TEM and STEM-HAADF. Successive steps of Fe segregation, iron-silicide precipitation and dissolution were identified. As expected for such a temperature range, the iron-silicide precipitates adopt the FeSi₂ structure. Fe enriched phases were also identified in an advanced step of precipitation. Dynamic mechanisms are proposed, taking into account the competitive oxidizing of precipitates and silicon matrix, to understand the different steps and precipitation phases observed in the samples during the non-equilibrium conditions due to the oxide layer growth. The correlation between the formation of characteristic pyramidal defects at the SiO₂/Si interface and the presence of the Fe-rich precipitates is explained. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)