Patent ID: 8636879

Claim:
An electro chemical deposition system comprising: a workpiece holder disposed in an electro chemical deposition chamber and connected to a first voltage source; a bottom electrode disposed below the workpiece holder with the electro chemical deposition chamber, wherein the bottom electrode is connected to a second voltage source; at least one auxiliary electrode disposed in the electro chemical deposition chamber and comprising a plurality of openings disposed between the bottom electrode and the workpiece holder, wherein the auxiliary electrode is connected to at least one third voltage source, wherein the at least one auxiliary electrode has a convex shape such that a first nearest distance is less than a second nearest distance and a third nearest distance is more than a fourth nearest distance, wherein the first nearest distance is the nearest distance from a center portion of the at least one auxiliary electrode to the workpiece holder, wherein the second nearest distance is the nearest distance from an edge portion of the at least one auxiliary electrode to the workpiece holder, wherein the third nearest distance is the nearest distance from the center portion of the at least one auxiliary electrode to the bottom electrode, and wherein the fourth nearest distance is the nearest distance from the edge portion of the at least one auxiliary electrode to the bottom electrode; and a diffuser disposed between the workpiece holder and the bottom electrode, the diffuser configured to control electric field lines in the electro chemical deposition chamber, wherein the diffuser is separated physically from the at least one auxiliary electrode.