US Patent 7128427 Method and apparatus for fluid handling in immersion lithography

Apparatus and method for a substantially distortion free immersion lithography is provided. The apparatus includes a lens element, an outlet for drawing immersion fluid towards the lens element, and a collector ring coupled to the central outlet for removing the immersion fluid. The method includes positioning a lens element relative to a wafer to provide a space between the lens element and wafer, introducing immersion fluid to that space, and drawing the immersion fluid from that space to minimize gas bubbles in the immersion fluid, and repeating the introducing and drawing steps to maintain the flow of the immersion fluid during a lithography process.