Additive-assisted nucleation and growth by electrodeposition: II. Mathematical model and comparison with experimental data

The "island dynamics" numerical method was used to investigate kinetically limited nucleation and growth during copper electrodeposition in the presence of additives. The system geometry consisted of a metal substrate initially patterned with a square array of Cu seed clusters. The simulations used estimated values of the reaction rate constants associated with an additive system consisting of acid sulfate electrolyte containing " accelerator" and "suppressor" species. Numerical results were obtained for the probability distributions for nearest-neighbor distance and for distance of nuclei from the seed cluster, and were compared with comparable experimental data reported in Part I of this series. Numerical results were in qualitative agreement with experimental trends associated with variations in additive composition, array spacing, and applied potential. Conditions that favored formation of high nucleation density were high chloride (Cl^-) and high poly(ethylene glycol) (PEG) concentrations; in this case, it was found that 90% of the Au surface was covered by Cu upon passage of 0.1 mC/ cm ². Conditions that favored deposition onto pre-existing seed clusters were low (Cl-) concentration, moderate (PEG) concentration, and closely spaced clusters. The results reported here provide a foundation for developing improved parameter estimation procedures based on optimization methods.