Removal of Boron and Phosphorus from Silicon by Three-layer Refining
A new refining concept aims to remove both B and P simultaneously in silicon has been proposed in Si/Slag/Me(Me:Fe or Cu)system.Both liquid Si and liquid Fe/Cu phases are separated by the molten slag phase spontaneously based on their physicochemical properties.Equilibrium evaluations indicate that both the B and P,the most difficult impurities to be removed from ultra-pure silicon,can be redistributed to the slag and another metal phase.It is experimentally shown that the simultaneous removal of both B and P via a single metallurgical refining process is possible by three-layer refining.The metal phase plays an P impurity collector role in the system,but has little effect on B adsorptions.Liquid Fe works better than the molten Cu for P adsorptions.Addition of CaF2 to the binary CaO-SiO2 slag increase significantly the remove rates of B and P,due to CaF2 can reduce the viscosity of slag.Increasing temperature from 1 600 C to 1 700 C improves the B remove rate significantly,but has little effect on P remove.
three-phase distribution equilibriapolysiliconpurificationthermodynamic simulation
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