The present disclosure provides a chemical mechanical polishing system having a unitary platen. The platen includes one or more recesses within the platen to house various components for the polishing/planarization process. In one embodiment, the platen includes a first recess and a second recess. The first recess is located under the second recess. An end point detector is placed in the first recess and a detector cover may be placed in the second recess. A sealing mean is provided in a space between the end point detector and the detector cover to prevent any external or foreign materials from coming in contact with the end point detector. A fastener used for fastening the detector cover to the platen also provides addition protection to prevent foreign materials from coming in contact with components received in the recesses.