Electroplating method for coating a substrate surface with a metal

Method of coating a surface of a substrate with a seed copper layer by electroplating, wherein said surface is a copper diffusion barrier layer, the method comprising:

• a cold entry step during which the surface to be coated is brought into contact with an electroplating bath while the surface is not under electrical bias;
• a step of forming the seed copper layer during which the surface to be coated is in contact with the electroplating bath and is subjected to electrical bias for a time long enough to form the seed copper layer with a thickness of no more than 40 nm;
• and
• a hot exit step during which the surface is separated from the electroplating bath under electrical bias of the same sign and substantially the same electric potential level as the electrical bias during the forming of the seed copper layer;
• wherein the electroplating bath comprises, in solution in a solvent:
• copper sulphate, with a concentration of between 0.4 and 18 mM;
• and
• a copper complexing agent which is a mixture of pyridine and 2,2′-bipyridine;
• the copper sulphate/complexing agent molar ratio being between 0.2 and 0.6;
• and
• the pH of the electroplating bath being between 3.5 and 6.5.