Polarization Independent Interferometer

摘要

Apparatus, systems, and methods are used for detecting the alignment of a feature on a substrate using a polarization independent interferometer. The apparatus, system, and methods include optical elements that receive light that has diffracted or scattered from a mark on a substrate. The optical elements may split the diffracted light into multiple subbeams of light which are detected by one or more detectors. The diffracted light may be combined optically or during processing after detection. The system may determine alignment and/or overlay based on the received diffracted light having any polarization angle or state.

主权项

1. A lithographic apparatus comprising:
an illumination system configured to condition a radiation beam; a substrate table configured to hold a substrate, the substrate comprising a mark; a projection system configured to project the radiation beam onto the substrate; and an optical system configured to receive a diffracted or scattered radiation beam from the mark along an optical path passing through the optical system and to output first and second beams, the optical system comprising:
an interferometeric sub-system located along the optical path and comprising a beam splitter configured to split the diffracted or scattered radiation beam to form the first and second beams, anda detector sub-system configured to detect respective first and second alignment signals containing information on a position of the mark based on the first and second beams.