Copper electroplating method

A method for copper electroplating comprising, in this order, the steps of

• (i) providing a substrate comprising blind micro vias and a patterned resist layer having openings for trench formation and an aqueous acidic copper electrolyte comprising a leveler additive wherein the leveler additive is selected from the group consisting of ureylene polymers, aminocarboxylic acids functionalized with polyalkylene glycol residues, aminocarboxylic acids functionalized with polyalkylene imine residues, aminocarboxylic acids functionalized with polyvinyl alcohol residues, peptides functionalized with polyalkylene glycol residues, peptides functionalized with polyalkylene imine residues and peptides functionalized with polyvinyl alcohol residues,
• (ii) operating said substrate as a cathode which is in contact with at least one anode and contacting said substrate with said aqueous acidic copper electrolyte, and,
• (iii) applying to the substrate an electrical current, comprising at least one current pulse cycle consisting of one forward current pulse and one reverse current pulse and wherein the fraction of reverse charge to the forward charge applied to said substrate in said at least one current pulse cycle ranges from 0.1 to 5%,
• wherein
• the duration of the forward current pulse in said at least one current pulse cycle ranges from 10 to 1000 ms,
• the duration of the reverse current pulse in said at least one current pulse cycle ranges from 0.05 to 1 ms, and
• the current density of the reverse current pulse in said at least one current cycle ranges from 20 to 100 A/dm2,
• wherein the applying fills the blind micro vias with copper and forms copper trenches having a rectangular cross-sectional shape.