Anomalous depth profile of implanted fluorine ions in SiO 2/Si

Abstract

Fluorine ions have been implanted into SiO 2/Si with an energy of 30 keV at doses of 0.5 and 1 × 10 17 ions/cm 2. Depth profiles of fluorine have been studied by X-ray photoelectron spectroscopy (XPS) for both as-implanted and annealed samples. It was found that depth profiles of fluorine in SiO 2/Si did not agree with the predicted Gaussian profiles and showed an enhancement of fluorine concentration in SiO 2 region for as-implanted samples. It is thought that anomalous depth profiles may be due to rather high diffusion coefficient in Si than that in SiO 2 as a result of fluorine implantation. After annealing at 700 ∘C for 30 min, fluorine concentrations considerably decreased in Si region compared with in SiO 2 region. It could be considered that the oxide layers prevent the fluorine diffusion and the fluorine is trapped at around the SiO 2/Si interface.