Detection of an unstable additive breakdown product in a plating bath

摘要

The 3-mercaptopropylsulfonic acid (MPSA) breakdown product of the bis(sodiumsulfopropyl)disulfide (SPS) additive used in acid copper plating baths accelerates copper electrodeposition and can be detected by cyclic voltammetric stripping (CVS) analysis. In the presence of oxygen, MPSA decomposes rapidly in acid copper sulfate baths so that the CVS stripping peak area (A_r) decreases on successive cycles. The slope of a plot of A_r vs. CVS cycle number (or time) or logarithm of the CVS cycle number (or time) provides a measure of the initial MPSA concentration.