Patent ID: 8859070

Claim:
An elastic member for use in a substrate holding apparatus for holding a substrate with a retainer ring located around a periphery of the substrate, said elastic member comprising: an elastic membrane having a contact portion, a first peripheral wall portion, and a second peripheral wall portion; and a first reinforcing member having a higher rigidity than the elastic membrane and reinforcing substantially an entire area of the contact portion of the elastic membrane, wherein the contact portion of the elastic member has a contact portion for contact with the substrate, wherein the first peripheral wall portion of the elastic membrane is coupled to a peripheral end of the contact portion and extends upwardly, wherein the second peripheral wall portion of the elastic member is located on an inside of the first peripheral wall portion, is coupled to the contact portion and extends upwardly, wherein the second peripheral wall portion of the elastic member defines a first chamber on an outer side thereof and a second chamber on an inner side thereof, and wherein the first reinforcing member is embedded in substantially the entire area of the contact portion of the elastic membrane.