a porous polishing pad for use chemical / mechanical planarization of semiconductor wafers is provided with a transparent section formed in a section of the porous polishing pad by direct injection of a polymeric material into a modified portion of the pad . the modified section may be either a low density area , or may be created by removing a complete vertical section of the pad . the injected polymer forms an integral window with the pad by flowing into the matrix of the pad at the pad / window interface . no additional reinforcement is required to hold the window in place ; however , adhesive and / or another impervious layer may be attached behind the window for additional support . in an alternative embodiment , a separate and distinct window - plug is inserted into a cutout section of the pad , and bonded to the pad by one or more binding film layers on the back , non - working surface of the pad .