Measurement optical system for metrology inspection and method of measuring overlay using the same

Abstract

A measurement optical system and an overlay measurement method using the same are provided. The measurement optical system includes: a light source configured to emit infrared light; a light splitter configured to reflect, from the light source and to a subject, a first portion of the infrared light incident to the light splitter; a photodetector on a same optical axis as the light splitter and configured to receive a second portion of the infrared light reflected from the subject; a first lens optical system between the light splitter and the photodetector; and a second lens optical system between the first lens optical system and the photodetector, wherein the subject may include an alignment key on which a meta key is provided.

Dependencies are inferred from the claim text.