Alignment measurement system

Abstract

A substrate alignment measurement system comprising: an illumination source configured to provide a pulsed radiation beam comprising alternating s and p polarized radiation pulses; a first optical module configured to direct the pulsed radiation beam towards an alignment mark on a substrate; a second optical module configured to receive diffracted radiation from the alignment mark, the second optical module comprising a delay loop configured to provide temporally separated s and p polarized sub-pulses from each received pulse of the diffracted radiation; and a detection system configured to receive the s and p polarized sub-pulses from the second optical module and provide an output indicative of the intensity of each sub-pulse.

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