Methods, electroplating solution, and apparatuses for electroplating copper into a surface of a partially fabricated semiconductor substrate are provided. Electroplating solutions include copper ions, suppressor additives, chloride ions, and alternative halide ions, which include bromide ions and/or iodide ions. The concentration of the alternative halide ions in the solution may be between about 0.25 ppm and 20 ppm. Addition of the alternative halide ions at certain concentrations improves suppression properties of the solution over a range of feature sizes without a need to change suppressors.