Patent ID: 8465345

Claim:
A retaining ring of a carrier head of a polishing apparatus, comprising: an annular lower portion of a first material, the lower portion having a lower surface to contact a polishing pad and an upper surface, wherein the upper surface of the lower portion includes an upwardly projecting step positioned along an inner diameter of the lower portion, and wherein a remainder of the upper surface of the lower portion between the step and an outer diameter of the lower portion has no step of equal or greater height, and wherein the upper surface of the lower portion includes an upward projection that is shorter than the step; an annular upper portion of a different second material, the upper portion having a lower surface and an upper surface configured to attach to a base of a carrier head, wherein the lower surface of the upper portion includes a recess positioned along an inner diameter of the upper portion and the step fits into the recess, and wherein a remainder of the lower surface of the upper portion between the recess and an outer diameter of the upper portion is flat; and a bonding layer between the step and the recess.