Low- and high-frequency pulse current and pulse reverse plating of copper

A model for galvanostatic pulse plating via pulse current (PC) and pulse reverse (PR) modes has been developed and compared with experimentally obtained electrode responses during copper deposition from a CuSO4-H2SO4 solution onto a rotating disk electrode. In addition to all forms of mass transport, electrode kinetics, and homogeneous reactions, the model incorporates capacitance effects due to double-layer charging and adsorption of an intermediate. Two important modifications from our previous model have been made: fully transient rather than steady-state electrode kinetics and a series rather than parallel connection between the adsorption pseudocapacitance and faradaic reactions. The model provides excellent quantitative agreement with the experimental results for both PR and PC plating for the entire range of conditions studied and shows considerable improvement over the previous version, particularly for PR plating. Fitting the model to some of the experimental data reveals that the double-layer capacity varies inversely with the square root of frequency for pulses of 500 Hz or more. Electrode responses do not totally become dc-like at frequencies as high as 50 kHz. Furthermore, at high enough frequencies (greater than or equal to5 kHz) during PR plating, the electrode potentials do not rise above the open-circuit potential during the reverse-time, indicating that copper dissolution does not occur and leading to a response similar to that observed during high-frequency PC plating. (C) 2003 The Electrochemical Society.