Study on the recycle of solar grade silicon from waste IC wafers

Abstract

The technology of recycling waste silicon wafers from IC industry which usually are highly doped was investigated in this paper. Two approaches were selected to remove the metal layers, intermediate layers and doping layers of the waste silicon wafers on the surface: sand-blasting and acid etching. After removing the impurities, the structure, electrical properties and impurities content were analysed through the SEM, resistance measurement and ICP-OES methods respectively. The results show that both two methods are effective to remove the impurities, however, the acid etching method is fit for both small pieces and large pieces of waste IC wafers, while sand-blasting is fit for the large waste silicon wafers. After removing, the impurities especially metal impurities are quite low enough, the recycled silicon wafers are still high B doped, if it used for PV, some measures such as by doping with high intrinsic silicon feedstock must be adopted.