Effect of Crucible Rotational Velocity on Physical Field Distribution in 18-inch Czochralski Monocrystalline Silicon Melts

Using COMSOL Multiphysics simulation software, the optimal distance between the middle guide ring of the magnet and the free surface under an applied CUSP magnetic field was analyzed. Simulations were conducted to predict the distribution of the flow field, oxygen impurity concentration field, and thermal field during the growth process of an I8-inch solar-grade Czochralski monocrystalline silicon under different crucible rotation speeds. When the optimal distance is 90mm, the asymmetric CUSP magnetic field can generate a larger magnetic field strength in the main convective region, weakening the main convection and making the thermal distribution of the molten silicon more uniform. Meanwhile, the crucible rotational velocity significantly impacts the spatial distribution of the physical fields within the molten silicon. With the increase in crucible rotational velocity, melt oxygen impurity content in the region below the crystal first rises and then falls under the combined action of the melt thermal field and flow field. When the crucible rotational velocity reaches 11 revolutions per minute(rpm), the convection form that is generated is conducive to the volatilization of oxygen impurities from the free surface, resulting in a lower average oxygen impurities content near the solid-liquid interface.