Study on the effect of melt flow behavior on the uniformity of phosphorus doping during the growth of large-size n-type monocrystalline silicon by Czochralski method

The segregation effect of phosphorus during the Czochralski growth of large-size n-type monocrystalline silicon contributes to the poor uniformity of radial resistivitys which directly affects the local electrical properties of the photovoltaic device. In the current work, a two-dimensional unsteady model was adopted to investigate the numerical simulation of the growth process of 300 mm industrial Czochralski silicon single crystal. Combined with the fluid flow, heat transfer and mass transfer models, investigation on the distribution of phosphorus impurities at the crystal/melt interface was performed, moreover the contribution of melt circulation flow to the two-phase segregation of phosphorus impurities was also thoroughly studied. The experimental results indicate that, with the increase of the crystal rotation, the circulation in the melt at the solid-liquid interface increases simultaneously, and the phosphorus impurities tend to be more uniform. With increasing crucible rotation, the circulation in the melt at the solid-liquid interface becomes smaller and the phosphorus impurities tend to be uneven. The simulation results show that the optimum crucible speed is 5 rpm. The inhomogeneity of phosphorus impurities in the melt at the solid-liquid interface increases first and then decreases with the increase of the casting speed. The combination of high crystal rotation and low crucible rotation is beneficial for the radial distribution uniformity of phosphorus impurities in the crystal. The accuracy of the model is verified by combining with the experiments, which provides a theoretical basis for large scale industrial production.