Effects of temperature coefficient of surface tension on oxygen transport in a small silicon Cz furnace

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.