Lithographic apparatus with multiple alignment arrangements and alignment measuring method

摘要

A lithographic apparatus has a plurality of different alignment arrangements that are used to perform an alignment measurement on the same mark(s) by: detecting a first alignment mark located on an object and producing a first alignment signal by a first detector; detecting the first mark and producing a second alignment signal by a second detector using a different alignment measurement than the first detector; receiving the first alignment signal from the first detector; calculating a first position of the at least first mark based on the first alignment signal; receiving the second alignment signal from the second detector; calculating a further first position of the at least first mark based on the second alignment signal.