Preparation of 6N grade silicon ingot by combined purification processes from waste silicon cutting sludge

Abstract

Abstract This study is aimed at fabricating ultrahigh-purity silicon ingots from silicon cutting sludge – a byproduct of the ingot for solar cells cutting process. Firstly, silicon powder from the silicon cutting sludge was recovered by 1st purification, such as ultrasonication, centrifugation, and acid treatment before preparation of the silicon ingots. After the 1st purification, the silicon cutting sludge yielded silicon powder with a purity of 99.7612 %. The 1st-purified silicon powder was subjected to 2nd purification – 3 cycles hydrogen plasma arc melting (HPAM), resulting in ultrahigh-purity silicon ingot with a purity of 99.9999 %. HPAM has been verified to be an effective process for removal of B and P – the major impurities of silicon for semiconductors and solar cells – to levels of total ≤ 0.3 ppm.