Bonded wafer metrology

Abstract

A metrology system may include a light source providing illumination, a single objective lens to direct the illumination to an overlay target with a top-substrate feature and a bottom-substrate feature and collect sample light from the overlay target, an adjustable illumination aperture stop to adjust an illumination numerical aperture, a detector configured to image the sample based on the sample light with both the top-substrate feature and the bottom-substrate feature within a field of view, and an adjustable collection aperture stop configured to adjust an imaging NA. The system may include a controller to receive a thickness of the top substrate, generate at least a portion of the metrology recipe defining imaging parameters providing a desired contrast, receive an image of the overlay target based on the metrology recipe, and generate an overlay measurement between the top substrate and the bottom substrate based on the image.

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