Patent ID: 8253922

Claim:
An immersion lithography apparatus comprising: a lens assembly comprising an imaging lens; a wafer stage for retaining a wafer beneath the lens assembly, the wafer stage comprising a seal ring disposed on top of and substantially supported by a seal ring frame along a top edge of the wafer retained on the wafer stage such that the seal ring partially overlaps a top side of the wafer along an outside edge thereof; a fluid tank for retaining immersion fluid, the fluid tank situated with respect to the wafer stage for enabling full immersion of the wafer retained on the wafer stage in the immersion fluid; a trench disposed around the fluid tank proximate a top thereof for capturing immersion fluid overflowing from the fluid tank during operation via at least one overflow hole disposed in a wall of the fluid tank, wherein the wall of the fluid tank is configured so that it may be lowered with respect to the fluid tank to allow the immersion fluid to flow out of the fluid tank and into the trench; and a cover disposed over at least a portion of the fluid tank for providing a temperature-controlled, fluid-rich environment within the fluid tank.