Patent ID: 9170500
Filing Date: 2015-10-27
Classification: G02B,G03F

Abstract:
1. A lithographic apparatus arranged to project a pattern from a patterning device onto a substrate and having an illumination system configured to condition a radiation beam and direct the radiation beam onto the patterning device, wherein the illumination system comprises: a first reflective component and a second reflective component, the first reflective component being arranged to direct radiation of the radiation beam onto the second reflective component and comprising a plurality of movable reflective elements, each movable reflective element being movable between at least a first position and a second position so as to change an illumination mode, and the second reflective component being associated with a pupil plane of the illumination system; and a control system arranged to set the plurality of movable reflective elements to respective desired positions in order to effect a desired illumination mode and further arranged, in the event that a first one of the movable reflective elements is defective and cannot be set to the respective desired position, to set a second one of the movable reflective elements to a corrective position, different than its desired position, to at least partially ameliorate a deleterious effect of the first one of the movable reflective elements, wherein the control system is arranged such that the second one of the movable reflective elements is a movable reflective element that in its desired position would direct radiation to a second point in the pupil plane that is opposite to a first point in the pupil plane to which radiation would have been directed by the first one of the movable reflective elements, and wherein the second point is opposite to the first point relative to an optical axis of the illumination system or relative to an imaginary line lying in the pupil plane and passing through the optical axis of the illumination system.