Patent ID: 8840446

Claim:
An inner ring of a carrier head of a polishing apparatus for holding a substrate during polishing, comprising: an annular body having an inner surface defining an inner diameter of the inner ring, the inner surface configured to circumferentially surround an edge of the substrate to retain the substrate during polishing, an annular lower surface configured to be brought into contact with a polishing pad, an annular upper surface, and an outer surface defining an outer diameter of the inner ring, wherein the inner surface includes a lower region adjacent to the annular lower surface that is a vertical cylindrical surface and an upper region that is a vertical cylindrical surface and has a first inner diameter greater than a second inner diameter of the lower region of the inner surface, and wherein the outer surface includes a lower region adjacent to the lower surface that is a vertical cylindrical surface, an upper region adjacent the upper surface that is a vertical cylindrical surface and has a first outer diameter that is greater than a second outer diameter of the lower region of the outer surface, an outwardly projecting lip between the lower region of the outer surface and the upper region of the outer surface, the lip including a horizontal lower surface and a sloped area connecting the lower region of the outer surface to the horizontal lower surface of the lip, and wherein the annular upper surface is wider than the annular lower surface.