Numerical analysis of stabilization techniques for oscillatory convective flow in Czochralski crystal growth

Results of numerical simulations of transient oscillatory flow in a Czochralski growth system are reported. A numerical analysis assuming axisymmetric flow and temperature fields in a cylindrical enclosure was performed in which the swirl component of velocity is included in the computation to account for rotational effects. Temperature and flow field oscillations were computed for natural and forced convection dominated flow regimes. Numerical predictions are in excellent agreement with previously reported experimental results. Computational results are presented which disclose relevant features of oscillatory flow and temperature fields. Parametric studies were carried out to evaluate the effects of crystal radius and melt depth variations on the oscillatory flow. It was shown that a non-oscillatory striation-free condition can be attained for certain flow conditions by reducing the radius fraction r(c)/R-c, and increasing the crucible aspect ratio R-c/H. The effects of a circular flat plate immersed in the melt were also evaluated for different vertical positions of the baffle. It was found that inserting a baffle with a radius slightly larger than the crystal radius at an appropriate vertical position can effectively attenuate the thermal fluctuations. (C) 2002 Elsevier Science B.V. All rights reserved.