Patent ID: 7993498

Claim:
An apparatus comprising a conductive pad having a plurality of alternating cathodes and anodes each of which are configured as stripes above a surface of the conductive pad and extending from one edge to another edge of the conductive pad, and which are provided with a power source and a plurality of gaps each of which is between pairs of the plurality of alternating cathodes and anodes, the conductive pad being structured and configured to contact all metal islands on a surface of the wafer, and further comprising a plurality of non-conductive pads, each of which are in a respective one of the plurality of gaps, the plurality of non-conductive pads extending from one edge to another edge of the conductive pad, wherein: the stripes and non-conductive pads are parallel, the conductive pad is circular, each adjacent parallel stripe is of a different length, each adjacent parallel non-conductive pad is of a different length, and each adjoining parallel stripe and non-conductive pads are of a different length.