Metrology system and lithographic system

Abstract

Disclosed is a metrology system comprising: a pre-alignment metrology tool operable to measure a plurality of targets on a substrate to obtain measurement data; and a processing unit. The processing unit is operable to: process said measurement data to determine for each target at least one position distribution which describes variation of said position value over at least part of said target; and determine a measurement correction from said at least one position distribution which corrects for within-target variation in each of said targets, said measurement correction for correcting measurements performed by an alignment sensor.

Dependencies are inferred from the claim text.