Control of Oxygen-Atom Transport in Silicon Melt during Crystal Growth by Electromagnetic Force

Abstract

A novel method for the control of oxygen-atoms transport in silicon melt during crystal growth, using an electromagnetic force (EMF) to rotate the melt without crucible rotation, has been developed. We have named this technique, the electromagnetic Czochralski (EMCZ) method. An EMF in the azimuthal direction is generated in the melt by the interaction between an electric current (1) through the melt in the radial direction and a vertical magnetic field (B). The effectiveness of this method was confirmed by numerical simulation based on the finite element method. The rotation rate (ω m ) of the silicon melt is continuously changed from 0 to over 105 rpm under I = 0 to 8 A and B = 0 to 0.1 T. Thirty-mm-diameter silicon single crystals free of dislocations could be grown under several conditions. The oxygen concentration in the crystals was continuously changed from 1.1 × 10 -3 to 11.4 × 10 -3 mass% (1 × 10 17 to 1 × 10 18 atoms/cm 3 ) by applying an electromagnetic force in order to increase the melt rotation. Homogeneous oxygen distributions in the radial directions were achieved. The continuous change in oxygen concentration and the homogenization of the oxygen distribution along the radial direction are attributed to the control of the diffusion-boundary-layer at both the melt/crucible and crystal/melt interface by forced flow caused by the EMF. This new method could he useful for the growth of the large-diameter silicon crystals with a homogeneous distribution of oxygen.