ASML Holding N.V.
Position metrology apparatus and associated optical elements

Abstract:

Disclosed is a metrology apparatus comprising an optical element configured to receive at or near a pupil plane of the metrology apparatus, at least first radiation comprising a first higher diffracted order and second radiation comprising a zeroth order resulting from illumination of a metrology target with radiation; and to direct said first radiation and second radiation together in a first direction. The metrology apparatus is further configured to form at least a first image of a first interference pattern, the first interference pattern resulting from interference of said first radiation and second radiation at an image plane.