초록 ▼

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 t

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.

대표청구항 ▼

A process for the sequential purification and crystal growth of silicon crystals from impure silicon which comprises the steps of: melting said impure silicon in a crucible to form a melt; removing insoluble impurities from said melt by rotating said crucible and said melt and directing a gas flow o

A process for the sequential purification and crystal growth of silicon crystals from impure silicon which comprises the steps of: melting said impure silicon in a crucible to form a melt; removing insoluble impurities from said melt by rotating said crucible and said melt and directing a gas flow onto a wall of said crucible, said rotating and said gas flow causing said insoluble impurities to coalesce on said melt, inserting a seed through said insoluble impurities to contact said melt, freezing a portion of said melt to said seed to trap said insoluble impurities, and withdrawing said seed, frozen melt and insoluble impurities; reacting a gas with said melt to remove soluble impurities from said melt; adding an oxide-slag forming compound to said melt to further remove soluble impurities; inserting a seed crystal into said melt and pulling an ingot from a portion of said melt; remelting said ingot to form a second melt; inserting a seed into said second melt and pulling a crystal therefrom.