Patent ID: 8551247

Claim:
A method for applying a time-varying magnetic field to counteract a buoyancy force caused by a buoyancy cell present in a semiconductor melt from which a monocrystalline ingot is grown according to a Czochralski process, the ingot being grown on a seed crystal pulled from the semiconductor melt, said method comprising: determining the buoyancy force caused by the buoyancy cell in the semiconductor melt; determining a direction and a magnitude of a pumping force to counteract the buoyancy force; determining one of a phase relationship between an upper coil alternating current (I UAC ) and a lower coil alternating current (I LAC ), a magnitude of I UAC , and a magnitude of I LAC that will generate a time varying magnetic field that will produce the pumping force that opposes the direction of the buoyancy force in the semiconductor melt; supplying the upper coil with I UAC and supplying the lower coil with I LAC to generate the defined time-varying magnetic field, wherein the time-varying magnetic field generates the pumping force in the semiconductor melt; and applying the generated time-varying magnetic field to counteract the buoyancy force in the semiconductor melt to produce a melt-solid interface shape that is concave relative to the ingot, wherein the ingot has a diameter of at least two hundred millimeters.