Establishment of new method of crystal growth with well-controlled convection by electro-magnetic force

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Application of magnetic fields in silicon Czochralski (CZ) crystal growth is an effective method for controlling the shape of the melt-crystal interface and for controlling melt convection in a crucible and therefore for improving crystal quality. Such a method is more effective for crystals with large diameter, since flow in a crucible becomes unstable due to large mass of the melt in a crucible.A transverse magnetic field applied to silicon CZ growth processes (TMCZ) has great potential for controlling melt flow. The melt flow in a crucible and, hence, the global thermal field within the furnace are principally three-dimensional (3D) under the influence of a transverse magnetic field. Although there are many excellent published works on numerical modeling of TMCZ growth, these models are limited to the melt or to the melt and the crystal due to the requirement of large computer memory and the requirement of a long time for computation. However, since a TMCZ growth furnace is a highly … More nonlinear and conjugated system, 3D global modeling is obviously necessary. Liu and Kakimoto recently proposed a partial 3D global model that makes partial 3D global modeling feasible with moderate requirements of computer resources and computation time. We applied the newly developed code to the analysis of temperature distribution near the melt-crystal interface to clarify the temperature gradient in a crystal, which determines distribution of point defects and voids in a crystal.A partly three-dimensional (3D) global analysis was carried out numerically for a small silicon Czochralski furnace in a transverse magnetic field to clarify temperature distribution near a melt-crystal interface. The melt-crystal interface shape and the axial temperature gradients in solid and liquid near the interface were calculated as functions of the magnetic field intensity and the pulling rate of a crystal. It was found that the axial temperature gradient in the crystal increases with increase in the crystal-pulling rate and that in the melt decreases near the interface. With increase in intensity of the magnetic field, the axial temperature gradients in both crystal and melt increase. The influence of melt convection becomes smaller with increase in either the magnetic field intensity or the crystal-pulling rate. The melt-crystal interface moves upward with increase in either the ratio between crystal pulling rate and temperature gradient in the crystal or the intensity of the applied magnetic field. Less