Enhanced Boron Diffusion Through Thin Silicon Dioxide in a Wet Oxygen Atmosphere

Abstract

Boron diffusion through a 5 nm silicon dioxide film from heavily boron‐doped polysilicon was investigated at temperatures below 1000°C in nitrogen or a wet oxygen atmosphere. The boron concentration at the silicon substrate surface,Ns, which was enhanced by the boron penetration through the thin oxide film, was estimated from MOS‐CV curves. The boron diffusion coefficient in silicon dioxide, Dox, and boron concentration at the oxide surface, Nox, were calculated using Ns. It was observed that there is a limit to boron solubility in oxide. It was found, moreover, that the limit, as well as the boron diffusivity in oxide, is higher in wet oxygen than in nitrogen, which enables a large amount of boron to pass through the oxide.