MELT MOTION IN THE FLOAT ZONE PROCESS WITH AN AXIAL MAGNETIC-FIELD

The motion of the molten silicon in the float-zone process is significantly affected by the electromagnetic (EM) body force and the Joule heat, generated by the distribution of the AC electric current density which is induced by a needle-ey induction coil. Melt motion driven by the EM body force, buoyancy, thermocapillarity, and crystal growth are divided into two major regions, the outer and the inner core regions, under the influence of a strong, axial magnetic field. The maximum flow velocities due to the various driving forces are calculated and are compared with each other in these two regions. For a crystal with a 76 mm diameter and a growth speeds of 2 to 4 mm/min, the crystal-growth driven flow is comparable to the buoyancy driven flow in the inner core region. In the outer core region, the mass transport near the free surface of the melt is determined by EM body force and thermocapillarity. Streamlines of the flow for each driving mechanism and combined flows are presented.