Direct observation by X-ray radiography of convection of molten silicon in the Czochralski growth method

Convection of molten silicon during Czochralski single crystal growth was directly observed using X-ray radiography. The melt flow pattern was monitored using a tracer method. The tracer, whose density and wettability were adjusted to that of the molten silicon, was developed. The observed convection of the molten silicon in the crucible was not only steady but also transient, and not axisymmetric but asymmetric. This asymmetry is attributed to the asymmetric temperature distribution within the crucible. The flow velocity of the molten silicon in the 75 mm diameter crucible was 10 to 20 mm/s.