The kinetics and mechanism of the anodic dissolution of phosphorus-containing copper in bright copper plating electrolytes

Abstract

The effect of the crystal grain size and the type of intergrain boundaries of phosphorus-containing polycrystalline copper anodes on anodic dissolution in bright copper-plating electrolytes (B-72-11 formulation) were investigated. A temperature-kinetic analysis of the anodic dissolution mechanism was carried out. It was confirmed that slime is formed when phosphorus-free copper dissolves, whereas a black anodic film is produced by the dissolution of phosphorus-containing copper anodes and very little slime is formed. The anodic dissolution of phosphorus-containing copper is under electrochemical control and depends on the average size of the crystal grains or the type of intergrain boundaries. The electrochemical limitations of the process are least for anodes with equilibrium intergrain boundaries. The initiation of the black anodic film displays a critical character. During its growth the film enhances anodic dissolution, and any increase in the rate of the process depends on the crystal structure of the anode, the anodic potential and the temperature of the electrolyte. The addition of phosphorus as an alloying element during the manufacture of the anodes results in the elimination of the possibility of grain boundary concentration and the alteration of the anodic dissolution mechanism. It also binds the cuprous ions into compounds that are part of the black anodic film, so that the anodic dissolution is slime free.