Patent ID: 7903233
Filing Date: 2011-03-08
Classification: G03F

Abstract:
1. An apparatus comprising: a table by which a substrate is supported; a projection system configured to project a pattern onto the substrate, the projection system having a last optical element; an immersion element which maintains immersion liquid in a space between the substrate and the last optical element; a first seal positioned between the projection system and the immersion element, the first seal being arranged to substantially prevent flow of the immersion liquid through a gap between the projection system and the immersion element and to permit flow of a gas through the gap; and a second seal positioned between the projection system and the immersion element, the second seal being arranged to substantially prevent the flow of the immersion liquid through the gap and to permit the flow of the gas through the gap, wherein the first and second seal each are solid members; the first seal is arranged such that a first aperture is formed to allow the flow of the gas through the gap, the second seal is arranged such that a second aperture is formed to allow the flow of the gas through the gap, and the first aperture and the second aperture are offset circumferentially.