Inspection Method and Apparatus, Lithographic Apparatus, Lithographic Processing Cell, and Device Manufacturing Method to Measure a Property of a Substrate

摘要

A system is configured to measure two separately polarized beams upon diffraction from a substrate in order to determine properties of the substrate. Circularly or elliptically polarized light sources are passed via a fixed phase retarder in order to change the phase of one of two orthogonally polarized radiation beams with respect to the two beams. The relative phases of the two radiation beams and other features of the beams are measured in a detector to provide information on the properties of the substrate surface.