The present disclosure relates to methods and solutions for growing metal charge-transfer salts on a metal surface, such as a metal layer at the bottom of a via hole. The method makes use of a solution comprising a salt additive. The temperature during growth is in the range of −100° C. to +100° C. The method allows controlled growth of the metal charge transfer salt inside via hole while limiting growth outside the via hole. The method further limits corrosion of the metallic connections at the bottom of the via hole.