CVS Control of Via Fill Acid Copper Electroplating Baths

Due to the increasing demands placed on acid copper plating solutions to perform via fill plating of blind micro vias, it is critical that the plating additives be monitored precisely. This paper presents electrochemical techniques for analyzing additives commonly used in via fill plating baths. The additives, commonly referred to as suppressor, brightener, and leveler, all need to be precisely monitored during the production process in order to achieve optimum via fill. Utilizing cyclic voltametric stripping (CVS), these additive types can be monitored with a single analytical instrument when the proper techniques are employed and the measurement procedures are optimized for each additive. The three primary additives can be independently analyzed by CVS, minimizing the influence of other components. The optimum procedure for brightener analysis requires sample dilution into a blank solution containing the suppressor. The authors also present new techniques for measuring the leveler concentration without interference from the brightener. Conditioning methods for the instrument are essential to ensure accurate results with CVS analysis. The findings underscore the importance of precise control over the additive package to avoid defects in the plated deposit.