Patent ID: 7869002

Claim:
A method for reducing contamination in immersion lithography, the method comprising: retaining a semiconductor wafer on a support surface of a wafer chuck, the wafer chuck having a gap therein, the gap located adjacent an outer edge of the wafer, and the gap containing a volume of immersion lithography fluid therein; providing a fluid circulation path within the wafer chuck so as to facilitate the radial outward movement of the immersion lithography fluid in the gap, thereby maintaining a meniscus of the immersion lithography fluid at a selected height with respect to a top surface of the semiconductor wafer; introducing pressurized fluid through an inlet path included in the fluid circulation path, the inlet path in communication with the immersion lithography fluid in the gap; and removing excess fluid immersion lithography fluid from the gap through a return path included in the fluid circulation path, and wherein the chuck further comprises: a first fluid column, defined by the gap; a second fluid column, disposed radially outward with respect to the first fluid column; the second fluid column including the inlet path and the return path passing therethrough; and a passage configured for fluidly connecting the first and the second fluid columns; wherein the meniscus of the immersion lithography fluid is passively controlled through fluid level control within the second fluid column.