A REAL-TIME SIMULATION OF POINT-DEFECT REACTIONS NEAR THE SOLID AND MELT INTERFACE OF A 200-MM DIAMETER CZOCHRALSKI SILICON CRYSTAL

A real-time simulation of the point-defect reactions near the solid and melt interface of a 200 mm diam Czochralski silicon crystal was performed. The results from the thermal stress calculation accounting f or the temperature dependence of the elastic modulus of silicon indicate that the thermal stresses in the vicinity near the solid and melt interface are far above the silicon yield strength. Therefore, it is suggested that the effect of thermal stresses on the point defect reactions in a growing crystal is negligible. In this work, the crystal cooling conditions are found to have a significant impact on the point defect reactions. Under f ast cooling conditions, the simulator predicts a supersaturation of vacancies in the vicinity near the solid and melt interface while the silicon interstitial concentration retained in the crystal grown under slow cooling conditions could increase significantly The present results also indicate that the point defect reactions near the solid-melt interface as well as at the crystal periphery are governed predominantly by a short-range pair recombination which is driven by the chemical potential of point defect saturation. The contribution of a long-range or up-hill diffusion, on the other hand, is considered to be negligible.