Sequential purification and crystal growth

Details Sequential purification and crystal growth Sequential purification and crystal growth

1978-07-18

1980-04-29

Peters, G. O.

Chemistry of inorganic compounds

Silicon or compound thereof

Elemental silicon

423350, 156617SP, 156 64, C01B 3302

Patent

active

042006210

ABSTRACT:
A combined method for purifying silicon and growing single crystals. A multiple step process is disclosed by which metallurgical grade silicon is purified and converted into a high quality monocrystalline silicon ingot. Each of the steps in the process is designed to remove specific impurities and thus improve the electrical quality of the silicon material. First, the insoluble slag and high segregation coefficient impurities are removed. Soluble impurities are then removed by a reactive gas step, and by a liquid-liquid extraction step using reactive metallic oxides or an oxide solvent. The remaining impurities are removed by segregation during freezing by pulling an ingot from a portion of the molten metallurgical grade silicon. The ingot so formed is then used to charge a second crystal puller. One or more of the previous purifying steps can then be repeated for the charge of the second crystal puller and an ingot of improved purity can be pulled from the melt of the second puller. In like manner, third and successive reiterations of the process can be used to obtain silicon of the desired purity and crystal quality.

REFERENCES:
patent: 2866701 (1958-12-01), Strauss
patent: 3012865 (1961-12-01), Pellin
patent: 4124410 (1978-11-01), Kotval et al.

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