Patent ID: 7540946

Claim:
A plating apparatus comprising: a power supply for generating a voltage between a pair of terminals; an anode connected to one of the terminals of the power supply; a main cathode connected to the other terminal of the power supply while in contact with a substrate; an auxiliary cathode connected to the other terminal of the power supply while out of contact with the substrate; a main resistance connected in series between the other terminal of the power supply and the main cathode; and an auxiliary resistance connected in series between the other terminal of the power supply and the auxiliary cathode; wherein the main cathode has an annular form and is in contact with a peripheral part of the substrate; wherein the auxiliary cathode has an annular form and opposes the main cathode; wherein an insulating layer is provided between the main and auxiliary cathodes; wherein an outer diameter of the auxiliary cathode is larger than an outer diameter of the main cathode; wherein the auxiliary cathode includes a protruding part projecting in a radial direction beyond an outer face of the main cathode, the insulating layer covering a portion of a surface of the protruding part, the insulating layer projecting from the auxiliary cathode in the radial direction beyond an outer face of the auxiliary cathode.