Patent ID: 7491118

Claim:
A chemical mechanical polishing apparatus comprising: a platen; a polishing pad affixed to a surface of the platen; and a polishing head configured to retain and rotate a wafer while pressing a surface of the rotating wafer against the polishing pad, wherein the platen and the polishing head interoperate such that the rotating wafer moves in a loop across a surface of the pad, wherein the polishing head comprises a retaining ring that retains an edge of the wafer and that extends flush with the surface of the wafer and wherein a first portion of the polishing pad that engages the retaining ring of the polishing head proximate an innermost portion of the loop provides less rigidity than a second portion of the polishing pad that engages an entire surface of the wafer, wherein the polishing pad and the platen interoperate to provide a cushion where the polishing pad engages the retaining ring of the polishing head, wherein the cushion comprises an airspace bounded by the pad and/or the platen, wherein the airspace comprises a recess in the pad and/or a recess in the platen, wherein the pad comprises: a first resilient layer having the recess therein; and a second resilient layer interposed between the first resilient layer and the surface of the platen and less rigid than the first resilient layer and wherein the second resilient layer has an opening therethrough between the recess of the first resilient layer and the surface of the platen.