Patent ID: 8848162

Claim:
A apparatus apparatus, comprising: a projection system configured to project a patterned radiation beam onto a target portion of a substrate; a liquid supply system configured to provide a liquid to a space between the projection system and a substrate; a recycling system configured to collect liquid leaving the liquid supply system and to re-provide the liquid to the liquid supply system, the recycling system comprising a first liquid treatment unit configured to treat the liquid, the liquid being recycled from the liquid supply system through the recycling system back to the liquid supply system through a first recycling path; a controller configured to direct liquid from the liquid supply system through a second recycling path during idle time of the lithographic apparatus so that liquid is recycled back to the liquid supply system without passing through the first liquid treatment unit, wherein the recycling system includes a second liquid treatment unit arranged in parallel with the first liquid treatment unit, the second liquid treatment unit configured to treat a level or type of contaminant or both in the liquid that is different from a level or type of contaminant or both treated by the first liquid treatment unit.