Iron diffusivity measurement with deep-level transient spectroscopy at room temperature

Abstract

Time dependence of iron interstitial concentration changes in p-type silicon wafers was measured with deep-level transient spectroscopy. A slab diffusion model was applied to the iron-to-FeB transformation in order to calculate the room temperature diffusion coefficient of iron. It was very close to the extrapolated value obtained from high temperature iron diffusivity and some room temperature diffusion data obtained by the electron paramagnetic resonance or by resistivity change measurements. The effects of oxygen and its precipitation on iron diffusion was considered, by comparing floating-zone wafers with Czochralski wafers of various oxygen contents. It was observed that these variables do not affect iron diffusivity at room temperature. It was also noted that there was no dependence of the substrate resistivity on the iron diffusivity at room temperature. From these results it is concluded that the apparent iron diffusion is mostly caused by the random walk of iron atoms.