Source of boron and phosphorus impurities in the silicon wiresawing slurry and their removal by acid leaching

Source of boron and phosphorus as the impurities in the silicon wiresawing slurry was clearly confirmed by systematical study on their elements content variation in the related materials in the cutting process. Extensive studies were concerned about the recovery of silicon particles in the wiresawing slurry. But there is little attention paid to the metal and nonmetal impurities in the slurry, especially for boron and phosphorus, which would affect the efficiency and reliability of the solar silicon cell. It was experimentally tested that for a typical steel sawing wire the boron content is about 4500 ppmw and phosphorus content is about 1000 ppmw, while in the other materials the content of the both impurities is very low. These impurities would be mixed with the silicon and silicon carbide particles after wiresawing cutting, instead of incorporating in the silicon crystal lattices. So conventional acid leaching was considered for using to effectively remove boron and phosphorus, and it was found that under optimal leaching conditions, the removal percentages of iron, boron and phosphorus were 95.50%, 82.95%, and 86.92%, respectively.