Device for characterizing a
mask for microlithography, with • at least one
light source (105, 405, 605) which emits coherent light; • an illumination
optics (110, 410, 610) which has a
zone plate (111, 411, 611) and generates a
diffraction-limited
light spot on the
mask (120, 320, 420, 620) from the coherent light of the at least one
light source (105, 405, 605) in a predetermined
diffraction order; • a scanning device via which a scanning movement of the
diffraction-limited
light spot relative to the
mask (120, 320, 420, 620) can be carried out; • a sensor unit (130, 430, 630); and • an evaluation unit for evaluating the light incident on the sensor unit (130, 430, 630) from the mask (120, 320, 420, 620); characterized in that the device is configured such that light emanating from the
zone plate (111, 411, 611) in a
diffraction order that does not correspond to the predetermined
diffraction order is eliminated by at least 90% from the useful beam path leading to the sensor unit (130, 430, 630); wherein the
zone plate (411, 511) is arranged in an off-axis configuration such that a beam bundle running from the
light source (405) to the zone plate (411, 511) only impinges on a partial area (512) of the optically
usable surface of the zone plate (411, 511).