Patent ID: 7714984
Filing Date: 2010-05-11
Classification: G03F

Abstract:
1. A method of correcting for pupil asymmetry in a lithography system, comprising: measuring a first pupil asymmetry of a uniformity profile of an illumination beam; determining positions of first and second attenuating elements of a plurality of attenuating elements arranged for compensating for the first pupil asymmetry, including moving the first attenuating element into the illumination beam, wherein the plurality of attenuating elements is located at a defocus position of the illumination beam; and moving the second attenuating element out of the illumination beam, the second attenuating element being located across the path of the illumination beam from the first attenuating element; wherein the first attenuating element and the second attenuating element are moved to positions that compensate for the first pupil asymmetry by introducing the second pupil asymmetry.