One embodiment is a method for void-free metallic electrofilling inside openings, said method includes: providing a substrate with at least one opening, the substrate includes an electrically conductive surface, including inside the at least one opening; immersing the substrate in an electrolyte contained in an ECD cell, the ECD cell includes at least one anode and a cathode, the cathode includes at least a portion of the conductive surface, the electrolyte includes plating metallic ions and at least one inhibitor additive, said metallic ions and at least one inhibitor additive having concentrations; providing electrolyte agitation across the substrate surface; and applying electroplating current density to the substrate; wherein the agitation, the concentrations, and the electroplating current density are such to produce void-free metallic electrofilling of the at least one opening, and wherein a height of electrodeposited surface bumps, or transition steps or humps, or transition spikes, is less than 140 nm.