Patent ID: 8021215

Claim:
A carrier head for chemical mechanical polishing of a substrate on a polishing pad, comprising: a base; an annular retaining ring having an inner surface configured to circumferentially surround an edge of the substrate to retain the substrate, an outer surface, and a lower surface configured to contact the polishing pad, the lower surface of the retaining ring having a plurality of grooves extending from the inner surface of the retaining ring to the outer surface of the retaining ring; and a carrier ring having an inner surface circumferentially surrounding the retaining ring, an outer surface, and a lower surface configured to contact the polishing pad, the lower surface of the carrier ring having a plurality of grooves extending from the inner surface of the carrier ring to the outer surface of the carrier ring, wherein the plurality of grooves in the lower surface of the carrier ring are wider than the plurality of grooves in the lower surface of the retaining ring; and a substrate backing member having a substrate mounting surface.