Microscope for investigation of masks with different thickness, has illumination device, which has light source, and has illumination optical system that illuminates mask to be examined with illuminating radiation

摘要

The microscope has an illumination device (1), which has a light source (3) that emits illumination radiation. An illumination optical system (6,10) illuminates the mask to be examined with illuminating radiation (L1) and corrects for a predetermined mask thickness. A detection device (2) is provided for detection of illuminated mask (M). The spherical aberration of the microscope is corrected for a predetermined mask thickness. The microscope has a correction unit (17,18), which corrects the remaining part of the spherical aberration, which is caused in the illumination optical system.