Harald Schmidt

Outplating of metallic contaminants on silicon wafers from diluted acid solutions

The outplating behaviour of Fe and Cu was investigated for diluted solutions of HCl and HNO 3 . The deposition of the metallic contaminants was found to be strongly dependent on the type of surface that is exposed to the contaminated solution. Cu deposits heavily on bare silicon surfaces, whereas only low levels of Fe deposition are observed. On the other hand, on thermal oxide surfaces, the levels of deposited Fe are consistently higher than the Cu ones. The acid used appears to have no major impact on the deposition process. The pH of the solutions has a major effect on the Cu deposition and a minor effect on the Fe case.