Oxygen Incorporation and Precipitation in Czochralski-Grown Silicon

Oxygen incorporation is examined for growth of large-diameter (80–130 mm) silicon single crystals by the Czochralski method. The primary growth parameters affecting the oxygen concentration in the crystals are shown to be the crystal-melt interface position within the hot zone and the rate of crucible rotation used. Tight control of the oxygen concentration [±1.5 parts per million atomic (ppma) in the range of 25–40 ppma (ASTM)] has been reproducibly attained by programmed variation of these growth parameters. The attainable oxygen concentrations may be extended over a wider range (20–45 ppma) through slight modifications of the hot zones. Wafers from the uniform-oxygen-concentration crystals are subjected to single-step and two-step annealing procedures (700–1100°C) for oxygen precipitation studies. The rate of precipitation is shown to depend on the initial oxygen content and on the number of initially unpopulated nucleation sites present.