IMAGING OPTICAL SYSTEM FOR MICROLITHOGRAPHY

摘要

An imaging optical system (10), in particular a projection objective, for microlithography, comprises optical elements (M1-M6) configured to guide electromagnetic radiation (19) with a wavelength ? in an imaging beam path for imaging an object field (13) into an image plane (14), and a pupil (24), having coordinates (p, q) which, together with the image field (16), having coordinates (x, y), of the optical system (10), spans an extended 4-dimensional pupil space, having coordinates (x, y, p, q) as a function of which a wavefront W(x, y, p, q) of the radiation (19) passing through the optical system is defined. At least a first of the optical elements (M1-M6) has a non-rotationally symmetrical surface (26) having a respective surface deviation in relation to every rotationally symmetrical surface (28), which two-dimensional surface has a difference between its greatest elevation and its deepest valley of at least ?. A sub-aperture ratio of the non- rotationally symmetrical surface deviates at every point (?1, O2) of the object field (13) by at least 0.01 from the sub-aperture ratio of every other surface of the optical elements, which is located in the imaging beam path, at the respective point (O1, O2) of the object field (13). Furthermore, the surface (26) of the first optical element (M4) is configured such that by displacing the first optical element relative to the other optical elements a change to the wavefront of the optical system (10) can be brought about which has a portion with at least 2-fold symmetry, the maximum value of the wavefront change in the extended 4- dimensional pupil space being at least 1 x 10-5 of the wavelength ?.