Calculation of Internal Gettering Sites after Double-Step and CMOS-Type Thermal Anneals

The formation of oxygen precipitates, determining the internal gettering of metal impurities in CZ-silicon, is studied during double-step and CMOS-type thermal anneals with our recently developed computer model. The model correctly predicts a number of experimental results on oxygen loss and the total concentration of precipitates after thermal anneals. It is found that in a double-step anneal variations of the oxygen solubility of only 20% can provide a potential explanation for the large scattering observed in experimental data. The simulations show that prolonged preannealing at 750°C reduces the sensitivity of the concentration of precipitates after a 1050°C growth anneal to variations in the cooling rate in crystal growth.