摘要 |
The invention relates to a lithographic apparatus arranged to transfer a pattern from a patterning device onto a substrate, wherein said apparatus is operable to measure higher-order distortions and/or image plane deviations of the patterning device, said apparatus comprising: a device for transmission image detection; and a processor configured and arranged to model higher-order distortions of the patterning device using signals received from the device for transmission image detection; wherein said patterning device has a main imaging field, and a perimeter and said apparatus is operable to model said higher-order distortions using signals resultant from alignment structures comprised in said perimeter and/or in the imaging field. |