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In order to understand the influence of crystal and crucible rotations on the silicon melt flow and oxygen transport in a small Czochralski (Cz) furnace, a set of global numerical simulations, based on the pseudo-steady and axisymmetric laminar flow model, was conducted using the finite-element method. The crystal rotation rates ranged from 0 to 20 rpm and the crucible rotation rates from 0 to −2.5 rpm. The model evaluated the effects of the thermocapillary force on the radial distributions of oxygen concentration and (Vs,n/Gn) at the melt/crystal interface, where Vs,n and Gn are the crystal pulling rate and temperature gradient in the direction normal to the melt/crystal interface, respectively. Simulation results indicate that the thermocapillary force causes significant changes in the flow pattern and temperature distribution in the melt but gives small effect on the oxygen concentration in the crystal in the case of a small Cz furnace without a gas guide. On the contrary, installation of a gas guide has a significant effect on the flow fields and the oxygen concentration in the grown crystal. [Copyright &y& Elsevier]

In order to understand the effects of temperature coefficient of surface tension (γT) on oxygen transport as well as on the heater power and the melt/crystal interface shape in a small silicon Czochralski furnace, a set of global numerical simulations is conducted using the finite-element method for a wide range of γT between 0 and 0.35×10−3 N/m K. The results for cases without rotations of crystal and crucible indicate that the larger Marangoni effect enhances a toroidal roll cell in the crucible and reduces the heater power and oxygen concentration in the crystal but makes the melt/crystal interface more convex toward melt. When the crystal and the crucible are rotating in counter directions, an upwelling flow near the axis from the bottom of the crucible takes important role in determining the radial distributions of oxygen concentration. γT gives significant effects on the flow pattern, oxygen concentration, heater power and interface shape. [Copyright &y& Elsevier]