Patent ID: 8393936

Claim:
A method of planarizing a substrate by chemical mechanical polishing (CMP), the method comprising planarizing the substrate while retained in a polishing head including a retaining ring, the retaining ring having an outer surface and an inner surface such that a width from the inner surface to the outer surface in a radial direction varies in an amount sufficient to substantially reduce an edge effect by causing an edge polishing profile to shift back and forth toward a center of the substrate as the width varies during chemical mechanical polishing, wherein: the outer surface has an annular shape with a feature selected from the group consisting of at least one projection, at least one recession, and a combination thereof; the width varies from about 2% to about 50% with respect to an average width; the inner surface has an annular shape with at least one recession; the outer surface has an annular shape with at least one projection; and the at least one recession on the inner surface is radially aligned with the at least one projection on the outer surface.