Patent ID: 7070661

Claim:
An apparatus for supporting a thin, planar workpiece comprising; a plenum in fluid communication with a gas supply and comprising a workpiece support flange having an inner diameter slightly smaller than an outer diameter of the workpiece; an edge ring that movably rests on the support flange and contacts an outer edge of the workpiece and wherein the edge ring has an inner diameter slightly smaller than the outer diameter of the workpiece and an outer diameter slightly larger than an outer diameter of the workpiece and wherein when the workpiece is placed on the support flange an outer edge of the workpiece rests upon the edge ring; and wherein when a workpiece is placed on the support flange and gas is supplied to the plenum the edge ring is lifted by the gas in contact with the outer edge of the workpiece such that the inner diameter of the support flange coacts with an outer diameter of the edge ring to define a gas flow path through which the supplied gas flows when the edge ring and the workpiece is are lifted off the support flange.