INFLUENCES OF CU AND FE IMPURITIES ON OXYGEN PRECIPITATION IN CZOCHRALSKI-GROWN SILICON

Characteristics of oxygen precipitation in Czochralski-grown silicon ( CZ-Si) intentionally contaminated with Cu or Fe are investigated by me ans of Fourier-transform infrared spectroscopy (FTIR), transmission el ectron micros copy (TEM), electron-beam-induced-current (EBIC) mapping and etch pit observation. It is found that oxygen precipitation is no t influenced by the presence of Cu impurities, while it is enhanced si gnificantly by the presence of Fe impurities even if the concentration of Fe is much lower than that of Cu. Precipitations of supersaturated Cu and O impurities are found to proceed independently of each other in Si crystals. Oxygen precipitates in an Fe-contaminated specimen are much denser and smaller than those in a noncontaminated specimen. Fe impurities seem to react with minute Si oxide particles which are pres ent in as-grown CZ-Si crystals and reduce the nucleation barrier for o xygen precipitation.