Patent attributes
An overlay metrology system may scan a sample including inverted Moiré structure pairs along a scan direction, include an illumination sub-system to illuminate first and second Moiré structures of one of an inverted Moiré structure pair with common mutually coherent illumination beam distributions, and include an objective lens to capture at least +/−1 diffraction orders from sample, where a first pupil plane includes overlapping distributions of the collected light with an interference pattern associated with relative wavefront tilt. The system may also include a diffractive element in the first pupil plane, where one diffraction order associated with the first Moiré structure and one diffraction order associated with the second Moiré structure overlap at a common overlap region in a field plane, and a collection field stop located in the field plane to pass light in the common overlap region and block remaining light and remove the relative wavefront tilt.
