Device manufacturing method and computer program

A device manufacturing method using a lithographic apparatus having a localized immersion system for confining an immersion liquid to a space between a projection system and a substrate to be exposed by the projection system, the method including: predicting a set of first locations on the substrate having a risk of residual liquid from the immersion system when exposed using an initial route for a substrate to expose a plurality of fields thereon; determining a set of modifications to the initial route to reduce the risk of residual loss; test exposing at least one test substrate using the initial route; obtaining a set of second locations of defects in the exposed test substrate; selecting a subset of the set of modifications by comparing the first locations and the second locations; and exposing a plurality of production substrates using the initial route modified by the selected subset of modifications.