MASS-TRANSPORT IN A CZOCHRALSKI CRYSTAL PULLER WITH AN AXIAL MAGNETIC-FIELD - MELT MOTION DUE TO CRYSTAL-GROWTH AND BUOYANCY

The mass transport of dopants and impurities in a silicon melt is considered for a Czochralski crystal puller with a uniform axial magnetic field. For magnetic field strengths 1 B0 5 T, the dominant flow fields are those driven by buoyancy and the growth of the crystal. The mass transport is intrinsically unsteady, and the concentration of a crystallizing particle depends on the entire history of the particle. The buoyancy driven flow provides a mechanism for the circulation of fluid particles. However, the character of the flow in the diffusion boundary layers and the convection dominated core depends on the competition between the crystal growth and buoyancy driven velocities, which in turn depends on the magnetic field strength and depth.