Method and apparatus for electroplating a metal onto a substrate

A method for electroplating a metal onto a substrate (P), wherein said substrate (P) is a flat substrate having opposing first and second substrate surfaces (P1, P2), said method comprising:

• (a) providing said substrate (P), an electroplating apparatus (100, 200) comprising at least one counter electrode (120, 130;
• 220, 230), and an electroplating liquid (L);
• (b) bringing said substrate (P) with said opposing first and second substrate surfaces (P1, P2) and said at least one counter electrode (120, 130;
• 220, 230) into contact with said electroplating liquid (L);
• (c) electrically polarizing said first and second substrate surfaces (P1, P2) of said substrate (P) to effect metal deposition onto said first and second substrate surfaces (P1, P2) by feeding at least one first forward-reverse pulse current sequence each one being composed of successive first forward-reverse pulse periods to said first substrate surface (P1) and at least one second forward-reverse pulse current sequence each one being composed of successive second forward-reverse pulse periods to said second substrate surface (P2);
• (d) each one of said at least one first forward-reverse pulse current sequence at least comprising, in each one of first consecutive forward-reverse pulse periods, a first forward pulse generating a first cathodic current during a first forward pulse duration (tf1) at said first substrate surface (P1), said first forward pulse having a first forward pulse peak current (if1), and a first reverse pulse generating a first anodic current during a first reverse pulse duration (tr1) at said first substrate surface (P1), said first reverse pulse having a first reverse pulse peak current (ir1);
• and
• each one of said at least one second forward-reverse pulse current sequence at least comprising, in each one of consecutive second forward-reverse pulse periods, a second forward pulse generating a second cathodic current during a second forward pulse duration (tf2) at the second substrate surface (P2), said second forward pulse having a second forward pulse peak current (if2), and a second reverse pulse generating a second anodic current during a second reverse pulse duration (tr2) at the second substrate surface, said second reverse pulse having a second reverse pulse peak current (ir2);
• (e) wherein said first and second forward pulses are further superposed with a respective first or second superposing cathodic pulse having a respective first or second superposing cathodic pulse duration (tc1, tc2) which is shorter than said respective first or second forward pulse duration (tf1, tf2);
• and
• wherein a phase shift φr, between said first reverse pulse of said at least one first forward-reverse current sequence and said second superposing cathodic pulse of said at least one second forward-reverse current sequence is set to 0°±30°.