An oxygen reduction mechanism in heavily antimony-doped Czochralski silicon has been investigated. The deposits evaporated from heavily Sb-doped and lightly phosphorus-doped silicon melts have been analyzed by means of X-ray diffraction and X-ray photoelectron spectroscopy. It was found that the deposits evaporated from heavily Sb-doped Si melts consisted of elementary Sb, Si and amorphous Sb2O5, SiO2, while the deposits from lightly P-doped silicon only consisted of elementary Si and amorphous SiO2. Based on the experimental results and thermodynamic calculations, it is suggested that Sb can react with SiO in the crystal pullers thereby enhancing the evaporation of SiO from Si melts and causing a reduction of the oxygen concentration in heavily Sb-doped silicon crystals. (C) 2003 Elsevier Science B.V. All rights reserved.