Oxidation-enhanced diffusion of ion-implanted boron in heavily phosphorus-doped silicon

Abstract

Oxidation-enhanced diffusion (OED) of ion-implanted boron in heavily phosphorus-doped silicon is studied by measuring boron depth profiles using secondary ion mass spectroscopy for phosphorus concentration from intrinsic conditions to 1.2×1020 cm−3. OED is observed for the whole phosphorus concentration range investigated in the present work. However, both the diffusion coefficient in N2 ambient DN and that in dry O2 ambient DO decrease with an increase in substrate phosphorus concentration in extrinsic conditions, i.e., for phosphorus concentration larger than the intrinsic carrier concentration. Diffusion coefficient increment due to OED ΔD(=DO−DN) decreases with an increase in phosphorus concentration. The decrease in ΔD with an increase in phosphorus concentration is attributed to a decrease in excess silicon interstitials due to recombination with acceptor-type vacancies.