Effects of different cusp magnetic ratios and crucible rotation conditions on oxygen transport and point defect formation during Cz silicon crystal growth

The effects of different crucible counter- and iso-rotation rates and cusp magnetic ratios (MRs) on the melt flow, temperature, oxygen content, and point defect formation during the growth of a 5-inch diameter silicon crystal are discussed numerically. In cases without a cusp magnetic field (CMF), the oxygen content gets smaller at a low crucible rotation speed than at a high one, for both counter- and iso-rotation conditions. This trend is reversed under a CMF. The flow field is controlled by the crucible rotation rate, the rotation direction between the crucible and the crystal, and the MR. Since the melt flow motion is retarded by the Lorentz force at a high MR, diffusion has a greater effect on oxygen transport in the bulk melt. It promotes the transport of oxygen atoms from the crucible wall towards the melt surface and the growth interface. The point defect density is quite dependent on the thermal field arising from changes in the growth interface shape. Microdefects in the silicon crystal can be reduced in density and enhanced in the radial uniformity using a high crucible iso-rotation rate and high unbalanced MR. A flatter shape of growth interface can be obtained under these growth conditions.