Correcting device to compensate for polarization distribution perturbations and projection objective for microlithography

Abstract

Disclosed is a corrective device for compensating disturbances of polarization distribution across the cross-section of a light beam (10). Said corrective device comprises a corrective member (18; 118) encompassing two double-refractive corrective elements (20, 22; 120a, 120b, 122; 220; 222; 320, 322) with two substantially parallel surfaces (24, 26; 126, 127). The thickness (d) of the corrective element (22, 122, 222) is essentially constant between said surfaces (26; 126, 127). At least one of the surfaces (24, 26, 126, 127) of at least one of the corrective elements (20, 22, 120a, 120b, 122, 220, 222, 320, 322) is refinished in such a way that local irregularities in thickness Δd are created by means of which the disturbances of polarization distribution are at least nearly compensated. The arrangement, thickness (d), and double-refractory properties of the corrective elements (20, 22; 120a, 120b, 122; 220; 222; 320, 322) are selected such that the double-refractive effects thereof mutually cancel each other if the local irregularities in thickness Δd are not taken into consideration. The inventive corrective device influences polarization only at points where disturbances are to be compensated.

Dependencies are inferred from the claim text.