Containerless' Solidification of Silicon by High-Purity Electromagnetic Techniques

Electromagnetic or cold-crucible melt confinement utilizes an array of water-cooled copper fingers to contain an inductively heated silicon melt. Biot/Savart-law forces between high-frequency currents induced in the fingers and in the liquid silicon cause the melt to be pushed away from the fingers so that minimal interaction takes place and the technique is essentially containerless.Dislocation-free Si single crystals can be grown, and the process is also useful for consolidation and purification of scrap silicon into either long ingots or chunks for reuse in conventional growth processes. Three variants of electromagnetic solidification are described, and laboratory-scale experimental results are presented. These are dislocation-free Czochralski growth, multicrystallinedirectional solidification, and semicontinuous casting of multicrystalline ingots. Calculations of the expected concentration profiles for impurities with various segregation and evaporation coefficients are also presented.