Purification of phosphoric acid from waste acid mixture using melt crystallization

摘要

Spent etchant was the corrosive effluent coming from the etching process of the semiconductor. This waste solution consisted of H{sub}3PO{sub}4, HNO{sub}3 and CH{sub}3COOH and contained the various toxic metallic impurities due to the reaction between acid and metallic element of semiconductor board, that was composed of several metallic film as gate electrode using Al, Al-Ta, poly-Si and SiN{sub}x. In this work, the recovery of phosphoric acid was conducted using crystallization. The quantity of metallic impurities of purified phosphoric acid was significantly decreased to 1/10,000 times as small as initial content of crude etchant and concentration, 90%.