Flow mode transition and its effects on crystal—melt interface shape and oxygen distribution for Czochralski-grown Si single crystals

Abstract

Flow visualization and crystal growth experiments confirm that the crystal—melt interface shape of the Czochralski-grown silicon crystal is changed by the flow-mode transition of molten silicon caused by the baroclinic instability. They also confirm that the oxygen distribution in the grown crystal is modified by the flow-mode transition. The flow visualization and crystal growth experiments were carried out under the same conditions. The shape of the crystal-melt interface was identified from the growth striation shape in the grown crystal by X-ray topography. The oxygen distribution in the grown crystal was studied using micro Fourier-transform infrared absorption spectroscopy. The crystal—melt interface was changed from a convex to a gull-winged shape by the transition from a non-axisymmetric flow with vortices to an axisymmetric flow. The oxygen distribution along the growth direction in the crystal grown under the axisymmetric flow was more homogeneous than that grown under the non-axisymmetric flow. Experimental results suggest that an inhomogeneous oxygen distribution could result from thermal asymmetry generated by rotating vortices in the non-axisymmetric flow.