US Patent 7550070 Electrode and pad assembly for processing conductive layers

An electrode assembly includes a distribution plate having a plurality of grooves that communicate with openings in an overlying polishing pad layer. The grooves include end openings that allow for draining of process solution, both during processing and subsequent cleaning/rinsing of the pad. Drainage occurs continually during processing, cleaning and rinsing, and so is constricted through the end openings relative to the grooves, to prevent wastage. The end openings are sufficiently large, however, to substantially completely drain fluids from the grooves between steps without delaying robotic motions.