Patent ID: 8759949

Claim:
An integrated circuit structure comprising: a semiconductor substrate comprising a front side and a backside; a transistor at the front side of the semiconductor substrate; a conductive via penetrating the semiconductor substrate, the conductive via comprising a back end extending to the backside of the semiconductor substrate; a redistribution line (RDL) on the backside of the semiconductor substrate and electrically connected to the back end of the conductive via, wherein the RDL is closer to the backside of the semiconductor substrate than to the front side of the semiconductor substrate; a passivation layer over the RDL, with an opening in the passivation layer, wherein a portion of the RDL is exposed through the opening; a copper pillar having a portion in the opening and electrically connected to the RDL; and a metal finish comprising a metal selected from the group consisting essentially of nickel, gold, palladium, and combinations thereof, wherein the metal finish comprises a top portion over the copper pillar and sidewall portions on sidewalls of the copper pillar.