The impurities incorporated in the electrodeposited 40 nm Cu lines as well as in blanket Cu films were studied. Two different levelers were used in the study. While the impurity in the blanket films were found highly dependent on the leveler and its concentration, the leveler had no impact on the impurity in the narrow lines. Furthermore, the concentrations of suppressor and chloride showed little to no impact on the impurity in the narrow lines. An increase of accelerator concentration resulted in higher S and Cl contents in the lines. The increase in S incorporation was also observed for blanket wafers plated with incremental concentrations of accelerator. In addition, the impurity in the narrow lines was also found to increase with the increase of the applied plating current density. A correlation between a slow Cu grain growth and high impurity content was established by using Cu blanket films plated with different leveler concentrations or Cu films ion-implanted with different doses of impurities. (C) 2014 The Electrochemical Society. All rights reserved.