Method and lens arrangement to improve imaging performance of microlithography exposure tool

摘要

A technique for introducing variable phase delay across portions of a spatially coherent light beam, such as a laser, without changing the focal length of the portions of the beam. A fly's-eye lens array is utilized to distribute the light for a more uniform illumination, but different length air gaps are introduced in the lens elements to provide a variable delay of portions of the beam. In a second scheme, a set of prisms is positioned in the path of the laser beam, in which the shape of the prism introduces variable phase delay across the cross- section of the beam.