US Patent 11164307 Misregistration metrology by using fringe Moiré and optical Moiré effects

A metrology system and metrology methods are disclosed. The metrology system includes an illumination sub-system, a collection sub-system, a detector, and a controller. The controller is configured to receive an image of an overlay target on a sample, determine an apparent overlay between two working zones along a measurement direction based on the image, and calculate an overlay between the two sample layers by dividing the apparent overlay by a Moiré gain to compensate for Moiré interference.