Patent ID: 7434590

Claim:
A wafer holder for holding a semiconductor wafer by fluid pressure bias when processing the wafer in a processing chamber with a high pressure fluid, the wafer holder comprising: a platen disk having a backside, a frontside, and a wafer supporting surface on the frontside thereof, the disk having passages therein communicating with the wafer supporting surface, the passages being located such that, when fluid at a pressure lower than that of the high pressure fluid is applied therethrough to the backside of a wafer supported on the wafer supporting surface, the high pressure fluid in the chamber holds the wafer for processing against the wafer supporting surface; and a pressure plate below the platen disk and having a body sufficiently rigid to resist deformation when subjected to the high pressure fluid, said pressure plate having a cavity therein having the platen disk therein, the cavity being sufficiently larger than the platen disk and forming a gap between the disk and the pressure plate to allow the high pressure fluid therein; said gap communicating the high pressure of the high pressure fluid against the backside of said platen disk and thereby substantially isolating said platen disk from a substantial pressure gradient between the frontside and backside thereof.