Patent ID: 8308931

Claim:
An apparatus for electroplating a layer of metal onto a work piece surface having edge regions around a center region, the apparatus comprising: (a) a plating chamber; (b) a work piece holder configured for holding the work piece in the plating chamber and rotating the work piece; (c) electrical contacts arranged to make electrical connection to the work piece at one or more locations on the edge regions, such that the work piece is configured to serve as a cathode; (d) an ionically resistive ionically permeable element having an ionically resistive body with a plurality of perforations made in the body such that the perforations do not form communicating channels within the body, wherein said perforations allow for transport of ions through the element, and wherein the element is positioned to have one surface facing the work piece surface, and located within about 5 mm of said work piece surface, when held in plating position by the work piece holder, during plating in the plating chamber, wherein substantially all perforations have a principal dimension or a diameter of the opening on the surface of the element facing the surface of the work piece of no greater than about 5 mm; and (e) a stationary segmented second cathode comprising segments configured to divert different amounts of ionic current from different azimuthal positions of the work piece.