Dendritic Growth and Morphology Selection in Copper Electrodeposition from Acidic Sulfate Solutions Containing Chlorides

We investigate the morphology of Cu films electrodeposited onto silicon from an acidic sulfate electrolyte with the addition of a variable concentration of chloride anions. Addition of chloride increases grain size and the degree of grain faceting while decreasing the density of growth nuclei. Well-developed monocrystalline dendrites are formed in acidic sulfate solutions with high concentration of chloride. Dendrites form under growth conditions that either approach diffusion limitation, or occur within a potential range where different crystallographic faces exhibit a different potential dependence for chloride desorption. The presence of dendrites however is mainly related to the fact that the reduction route Cu2+ -> CuCl -> Cu becomes the rate-determining process in solutions with high chloride concentration; the rate of this reaction is largest at {110} planes, where the concentration of chloride anions is the highest, generating dendrites with branches along the {101} directions.