Fe-implanted Si-wafers have been oxidized at 900 °C and 1100 °C in order to investigate the behaviour of Fe atoms at the growing SiO2/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 disilicide precipitation and oxidation were evidenced during the silicon oxidation process. The formation of characteristic pyramidal-shaped defects, at the SiO2/Si interface, was notably found to correlate with the presence of β-FeSi2 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 SiO2/Si interface, during the growth of the silicon oxide layer.
The French Ministry of Industry has funded this work in the frame of the COMET project. (Industrial partners: ST Microelectronics, Lfoundry, Ion Beam Services, Rockwood, Biophy Research, TERA Environnement, VEGAtec).
I. INTRODUCTION II. MATERIALS AND METHODS III. EXPERIMENTAL RESULTS IV. DISCUSSION A. Volumic diffusion of Fe in Si during the oxidation process B. Precipitation of β-FeSi2 at the SiO2/Si interface C. Formation of the pyramidal defects and dissolution of the precipitates V. CONCLUSION