RELAY LENS USED IN AN ILLUMINATION SYSTEM OF A LITHOGRAPHY SYSTEM

摘要

A relay lens used in an illumination system of a lithography system is provided to reduce a manufacturing cost by reducing the number of optical elements used therein. A first lens group(204) includes three lenses for reducing numerical apertures of received beams of radiation. The three lenses include at least two aspheric surfaces. A second lens group(208) includes at least one lens for receiving the beams of radiation from the first lens group and controlling characteristics of the beams of radiation in a pupil plane. A third lens group(212) includes a single lens for receiving the beams of radiation from the second lens group and controlling field characteristics of the beams of radiation in a patterning device plane. The single lens has a single refractive index. An aperture stop(206) is positioned between the first and second lens groups. A fold mirror(210) is positioned between the second and third lens groups.