Novel enhancing impurities purification from silicon powder through metal-catalyzed chemical corrosion

Abstract

The preparation of solar-grade silicon (99.9999 wt%) with low-cost technology is facing challenges. In the present study, a novel metal-catalyzed chemical corrosion (MCCC) method on purifying industrial silicon powder, consisting of HF concentration, corroding temperature, H2O2 concentration and corroding duration were studied. The evolution of typical precipitates phases on the surface of silicon to each etchant were investigate before and after etching with/without MCCC via EPMA (electron probe micro analyzer) equipped with EDS (energy dispersive X-ray spectroscopy). The results showed that numerous microporous structures applied on the surface of silicon powder by MCCC are beneficial for the removal of impurities. After MCCC, the purity of silicon powder can be improved from 99.48 to 99.99 wt%, which is higher than 99.93 wt% obtained without MCCC. It was found that the removal reaction of boron and phosphorus by MCCC from industrial silicon powder in accordance well with the cracking shrinking kinetic model, which was confirmed to be controlled by both of interfacial transfer and diffusion through the product layer process. Furthermore, the chemical reaction mechanism of MCCC was revealed. The impurities deep removal under leaching step would greatly relieve successive impurities removal stress, even shorten the traditional metallurgical routes, which is of great significance to high-effective and clean produce solar grade silicon for industrial use.