Methods for measurement of rAIM

An overlay metrology system comprising:

• an illumination sub-system including one or more lenses configured to illuminate via oblique illumination an overlay target on a sample in accordance with a metrology recipe, wherein the overlay target includes one or more Moiré structures having directions of periodicity along one or more measurement directions, wherein an image is generated by illuminating the overlay target one or more oblique illumination beams, wherein a particular Moiré structure of the one or more Moiré structures comprises overlapping gratings with different pitches along a particular measurement direction, wherein a portion of the image associated with the particular Moiré structure is formed via Moiré diffraction orders from at least one of the one or more oblique illumination beams having an azimuth incidence direction orthogonal to the particular measurement direction;
• a collection sub-system including at least an objective lens configured to collect at least one Moiré diffraction order associated with diffraction of the one or more Moiré structures by the one or more oblique illumination beams;
• a detector configured to generate an image of the overlay target using illumination collected by the collection sub-system;
• and
• a controller communicatively coupled to the collection sub-system, the controller including one or more processors configured to execute program instructions causing the one or more processors to:
• receive the image of the overlay target;
• and
• determine overlay measurements associated with relative positions of sample layers along the one or more measurement directions based on the image of the overlay target.