Mechanism of β-FeSi_2 precipitates growth-and-dissolution and pyramidal defects' formation during oxidation of Fe-contaminated silicon wafers

摘要

Fe-implanted Si-wafers have been oxidized at 900 ℃ and 1100 ℃ in order to investigate the behaviour of Fe atoms at the growing SiO_2/Si interface and the impact on the integrity of microelectronic devices of an involuntary Fe contamination before or during the oxidation process. As-implanted and oxidized wafers have been characterized using secondary ion mass spectroscopy, atom probe tomography, and high-resolution transmission electron microscopy. Experimental results were compared to calculated implantation profiles and simulated images. Successive steps of iron disili-cide precipitation and oxidation were evidenced during the silicon oxidation process. The formation of characteristic pyramidal-shaped defects, at the SiO_2/Si interface, was notably found to correlate with the presence of β-FeSi_2 precipitates. Taking into account the competitive oxidation of these precipitates and of the surrounding silicon matrix, dynamic mechanisms are proposed to model the observed microstructural evolution of the SiO_2/Si interface, during the growth of the silicon oxide layer.