Patent ID: 8482718

Claim:
A lithographic apparatus arranged to transfer a pattern from a patterning device onto a substrate, wherein said apparatus is operable to measure at least one distortion selected from the group consisting of: third order distortions or image plane deviations of the patterning device, said apparatus comprising: a device for transmission detection; and a processor configured and arranged to model higher order distortions of the patterning device using signals received from the device for transmission 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 at least three sides of said perimeter and in the image field; wherein the alignment structures in the perimeter comprise gratings for measurement along an x-axis and gratings for measurement along a y-axis and alignment structures in the image field comprise a matrix of gratings disposed in scribe lines of the image field, the processor being further configured and arranged to perform a first reticle alignment using the alignment structures in the perimeter and to perform subsequent reticle alignments using the alignment structures in the scribe lines of the image field in conjunction with the alignment structures in the perimeter.