Polarographic determination of metallic impurities on lapped silicon wafers

Abstract The method is based on the anodic oxidation of silicon layers in a 0.05 M KNO 3 -10% H 2 O-ethylene glycol electrolyte. The silicon oxide is completely dissolved with 0.1 M hydrofluoric acid, and then the appropriate supporting electrolyte is added. For copper, cadmium, and lead determinations, a 0.1 M citric acid-1 M nitric acid supporting electrolyte is used and differential pulse anodic stripping voltametry provides a detection limit of 0.5 ng ml −1 with a precision of ±5% (at 5 ng ml −1 ). For iron determination, a 0.1 M triethanolamine hydrochloride-0.1 M potassium bromate-0.1 M sodium hydroxide supporting electrolyte is used and differential pulse polarography provides a detection limit of 2 ng nm −1 with a precision of ±2% (at 5 ng ml −1 ). The results were confirmed by furnace atomic absorption spectrophotometry (FuAAS) by using the same oxide removal solution. FuAAS provides a detection limit of 1 ng ml −1 with a precision of ±10% (at 5 ng ml −1 ).