Natural and forced convection of molten silicon during Czochralski single crystal growth

Natural and/or forced convection of molten silicon during Czochralski single crystal growth was directly observed using X-ray radiography with solid tracers for various crystal and crucible rotation speeds, and temperature distribution in a crucible holder. Downflow attributed to natural convection in the center of a crucible which had been simulated by numerical calculation was scarcely observed with and without crucible rotation. Numerical simulation of the molten silicon was carried out by a packaged code of "FLUENT"; in the calculation, measured non-axisymmetric temperature distribution in a crucible holder was adopted. Unidirectional flow with and without crucible rotations can be qualitatively explained by the numerical simulation with non-axisymmetric temperature distribution in the crucible holder. The particle path attributed to natural convection near the solid-liquid interface was suppressed downward with increase in crystal rotation speed. The phenomena can be explained by a generation of forced convection beneath the rotating crystal.