Oxygen precipitation in conventional and nitrogen co-doped heavily phosphorus (P)-doped Czochralski silicon (CZ-Si) crystal subjected to various high-temperature annealing in the range of 1000-1150 degrees C was comparatively investigated. It was revealed that oxygen precipitates hardly generated in conventional heavily P-cloped CZ-Si; while they remarkably generated in the nitrogen co-doped one. Moreover, nitrogen doping could enhance oxygen precipitation during the prolonged annealing with a rapid thermal process (RTP) pre-treatment. but it has neglectable influence on oxygen precipitation for short-time annealing. It was believed that nitrogen co-doped heavily P-doped CZ-Si possesses nitrogen-related complexes that act as heterogeneous nuclei for super-saturated interstitial oxygen and then enhanced oxygen precipitation. Finally, it was found that nitrogen doping could hardly enhance oxygen precipitation in heavily P-doped CZ-Si at 1200 degrees C. (C) 2009 Elsevier B.V. All rights reserved.