The wafer support structure is used with a movable backplane having a curved upper surface which is moved between a wafer access position and a wafer process position to clamp a wafer against a clamping structure during processing. A guide ring surrounds the backplane and a floating ring is...http://www.google.de/patents/US5804042?utm_source=gb-gplus-sharePatent US5804042 - Wafer support structure for a wafer backplane with a curved surface
