Lithographic pre-alignment imaging sensor with build-in coaxial illumination

Abstract

A patterning device pre-alignment sensor system is disclosed. The system comprises at least one illumination source configured to provide an incident beam along a normal direction towards a patterning device. The system further comprises an object lens group channel along the normal direction configured to receive a 0th order refracted beam from the patterning device. The system further comprises a first light reflector configured to redirect the 0th order refracted beam to form a first retroreflected beam. The system further comprises a first image lens group channel configured to transmit the first retroreflected beam to a first light sensor. The first light sensor is configured to detect the first retroreflected beam to determine a location feature of the patterning device.

Dependencies are inferred from the claim text.