Abstract: A electrochemical deposition system which has a 3-D stacked architecture comprises a factory interface for receiving semiconductor wafers, a mainframe comprising a mainframe transfer robot and a plurality of wafer holder assemblies which disposed on the top thereof, a plurality of electroplating cells disposed within the mainframe, a plurality of cleaning cells disposed within the mainframe and located below the electroplating cells, a plurality of thermal treatment chambers disposed in between the mainframe and the factory interface, and a fluid distribution system fluidly connected to the electroplating cells and the cleaning cells, wherein the mainframe transfer robot transfers the semiconductor wafer from the factory interface and within the electroplating cells, the cleaning cells, and the thermal treatment chambers. As a result, the system of the present invention is expandable to accommodate newly-added processing units without overmuch increased footprint.