Numerical investigation of heat transport and fluid flow during the seeding process of oxide Czochralski crystal growth Part 2: rotating seed

In this paper, the role of seed rotation on the characteristics of the two-dimensional temperature and flow field in the oxide Czochralski crystal growth system has been studied numerically for the seeding process. Based on the finite element method, a set of two-dimensional quasi-steady state numerical simulations were carried out to analyze the seed-melt interface shape and heat transfer mechanism in a Czochralski furnace with different seed rotation rates: omega(seed) = 5-30 rpm. The results presented here demonstrate the important role played by the seed rotation for influencing the shape of the seed-melt interface during the seeding process. The seed-melt interface shape is quite sensitive to the convective heat transfer in the melt and gaseous domain. When the local flow close to the seed-melt interface is formed mainly due to the natural convection and the Marangoni effect, the interface becomes convex towards the melt. When the local flow under the seed-melt interface is of forced convection flow type (seed rotation), the interface becomes more concave towards the melt as the seed rotation rate (omega(seed)) is increased. A linear variation of the interface deflection with respect to the seed rotation rate has been found, too. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.