US Patent 7455571 Window polishing pad

A window polishing pad having a reduced stress pad window formed therein for performing optical end point detection are provided, wherein the window polishing pad comprises a pad window and a pressure relief channel, wherein the pressure relief channel extends to an outer periphery of the window polishing pad from a cavity formed behind the pad window when the window polishing pad is interfaced with a platen and wherein a membrane is provided over at least one of an inlet and an outlet of the pressure relief channel. Also disclosed are methods of making and of using the window polishing pads to polish a semiconductor wafer.