Some Aspects of Mechanism of Electropolishing of Copper in Phosphoric Acid

摘要

In this study, electrochemical impedance spectroscopy (EIS) and electron spectroscopy for chemicalanalysis (ESCA) were used to investigate copper electropolishing in phosphoric acid. Theexperimental results indicate that a bright and smooth surface can be obtained using 85 wt%phosphoric acid at the applied potential, which leads to a limiting current. The surface treated using 30wt% phosphoric acid was not glossy, and conventional electropolishing models could not adequatelyexplain the results. Based on the results of EIS and ESCA analyses, a dual-layer model was proposedin this study. The two layers consist of a passive precipitate because of anodic polarization and adiffusion layer because of lack of water near the copper surface. Therefore, the dual layers limited themass transfer rate. In addition, the polymeric characteristic of concentrated phosphoric acid enhancedthe formation of dual layers, which significantly limited mass transfer and thus produced a glossysurface. Consequently, concentrated phosphoric acid demonstrates better electropolishing performancethan low-concentration phosphoric acid.