Illumination design for scanning microlithography systems

Abstract

In one embodiment, the illumination system for a scanner incorporates an excimer laser whose square beam is incident upon a two-dimensional array of lenses. The light exiting the array is made incident on a long focal length lens for creating nearly parallel rays. The combination of the array and the long focal length lens causes the resulting square beam at the focal plane of the long focal length lens to have a substantially uniform intensity across its area. An array of cylindrical lenses receives these nearly parallel rays. The light output of the cylindrical lens array is then made incident on a first positive lens whose focal length is longer than the distance between the cylindrical lens array and the first positive lens. A second positive lens is located of the focal plane of the first positive lens. This results in all light rays from the cylindrical lenses which have the same angle to be focused at the same point on the second positive lens. The light incident upon the second positive lens has a long vertical dimension and a short horizontal width dimension. The oblong beam is further adjusted and redirected as necessary to illuminate a reticle.

Dependencies are inferred from the claim text.