Patent ID: 8208116

Claim:
An immersion lithography apparatus comprising: a lens assembly comprising an imaging lens; a wafer stage for retaining a wafer beneath the lens assembly and comprising a seal ring disposed around a bottom edge of a wafer retained on the wafer stage, wherein a top edge of the seal ring is substantially co-planar with and extends slightly above a bottom edge of the wafer when the wafer is secured to the wafer stage such that the edge of the wafer is sealed against fluid seepage under the wafer by the seal ring; 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 cover disposed over at least a portion of the fluid tank for providing a temperature-controlled, non-evaporating environment within the fluid tank; and at least one directional flow control fluid inlet surrounding the imaging lens for directing immersion fluid toward an edge of the wafer retained on the wafer stage closest to the imaging lens, the at least one directional flow control fluid inlet extending through the cover.