Edge load ring

An edge load ring (ELR) configured to fit inside a retaining ring of a chemical mechanical polishing (CMP) head, the ELR comprising:

• an annular body including:
• an inner surface having a step configured to retain the annular body within the polishing head;
• an outer surface opposite the inner surface, the outer surface having a diameter configured to slip inside the retaining ring;
• a bottom surface extending between the inner and outer surfaces, the bottom surface configured to contact a substrate disposed in the polishing head;
• an inner taper extending from the inner surface to the bottom surface;
• an outer taper extending from the outer surface to the bottom surface;
• and
• a venting feature extending between the inner and outer surfaces.

A polishing head, comprising:

• a housing;
• a retaining ring coupled to the housing;
• a membrane coupled to the housing inside the retaining ring, the membrane and the retaining ring forming a substrate-receiving pocket;
• and
• an edge load ring (ELR) disposed radially between the membrane and the retaining ring, the ELR including an annular body, the annular body having:
• an inner surface having a step configured to retain the annular body within the polishing head;
• an outer surface opposite the inner surface, the outer surface having a diameter configured to slip inside the retaining ring;
• a bottom surface extending between the inner and outer surfaces, the bottom surface configured to contact a substrate disposed in the substrate-receiving pocket, wherein the substrate extends radially to the retaining ring;
• and
• a venting feature extending between the inner and outer surfaces.