Patent ID: 7067048

Claim:
A method of electro-polishing a semiconductor wafer having copper thereon, said method comprising: providing an outer container having a drain, a drain pipe connected to the drain of the outer container, an inner tank disposed in the outer container, and a holding tank below the outer container, wherein the outer container gravity feeds into the holding tank through the drain and drain pipe, providing a pump between the holding tank and the inner tank, using the pump to pump an electrolyte polishing solution from the holding tank to the inner tank such that electrolyte polishing solution spills into the outer container, holding the semiconductor wafer in the inner tank such that the electrolyte polishing solution contacts the semiconductor wafer and removes copper from the semiconductor wafer; draining, via gravity feed, the electrolyte polishing solution through the drain of the outer container through the drain pipe and into said holding tank; using an electrode in the holding tank to remove copper atoms from the electrolyte polishing solution; and after using the electrode to remove copper atoms from the electrolyte polishing solution, using the pump which is provided between the holding tank and the inner tank to re-pump the electrolyte polishing solution directly into the inner tank for re-use.