Patent attributes
A metrology system may include an imaging sub-system to image a metrology target buried in a sample, where the sample is formed from bonded first and second substrates with a metrology target at the interface. The metrology system may further include an illumination sub-system with an illumination field stop and an illumination pupil, where the illumination field stop includes an aperture to provide that a projected size of the field-stop aperture on a measurement plane corresponding to the metrology target matches a field of view of the detector at the measurement plane, and where the illumination pupil includes a central obscuration to provide oblique illumination of the metrology target with angles greater than a cutoff angle selected to prevent illumination from the illumination source from reflecting off of the bottom surface of the sample and through the field of view of the detector at the measurement plane.
