1. A method, comprising:forming a plurality of through holes in a substrate, the substrate comprising a plurality of metal layers separated by a plurality of insulating layers;
selectively etching the insulating layers in the through holes to form a plurality of copper lands and recesses between the copper lands;
exposing the substrate to a polymerization precursor mixture comprising an initiator and a monomer or oligomer whose polymerization is inhibited by copper to form a precursor layer in the recesses of the through holes;
polymerizing the precursor layer to form a polymer coating in the recesses of the through holes; and
washing the through holes with an organic solvent.