Study and optimization of gas flow and temperature distribution in a Czochralski configuration

Abstract

The Czochralski (Cz) method has virtually dominated the entire production of bulk single crystals with high productivity. Since the Cz-grown crystals are cylindrical, axisymmetric hot zone arrangement is required for an ideally high-quality crystal growth. However, due to three-dimensional effects the flow pattern and temperature field are inevitably non-axisymmetric. The grown crystal suffers from many defects, among which macro-cracks and micro-dislocation are mainly related to inhomogeneous temperature distribution during the growth and cooling processes. The task of the paper is to investigate gas partition and temperature distribution in a Cz configuration, and to optimize the furnace design for the reduction of the three-dimensional effects. The general design is found to be unfavorable to obtain the desired temperature conditions. Several different types of the furnace designs, modified at the top part of the side insulation, are proposed for a comparative analysis. The optimized one is chosen for further study, and the results display the excellence of the proposed design in suppression of three-dimensional effects to achieve relatively axisymmetric flow pattern and temperature distribution for the possible minimization of thermal stress related crystal defects.