Two-part retaining ring with interlock features

A retaining ring includes an annular lower portion and an annular upper portion. The annular lower portion has a main body with a bottom surface for contacting a polishing pad during polishing, an inner rim projecting upward from the main body, an outer rim projecting upward from the main body and separated from the inner rim by a gap, and a plurality of azimuthally separated interlock features positioned between the inner rim and the outer rim, each interlock feature projecting upwardly from the main body. The annular upper portion has a top surface and a bottom surface and a plurality of azimuthally separated recesses in the bottom surface, the recesses defining thin portions of the upper portion, the plurality of interlock features fitting into the plurality of recesses. The lower portion is a plastic and the upper portion is a material that is more rigid than the plastic.