Patent ID: 7894040

Claim:
A lithographic apparatus, comprising: an illumination system configured to condition a beam of radiation; a support structure configured to hold a patterning device, the patterning device configured to impart the beam with a pattern in its cross-section; a substrate table configured to hold a substrate; a projection system configured to project the patterned beam onto a target portion of the substrate; and a liquid supply system configured to fill a space between the projection system and the substrate with a liquid, the liquid comprising an aqueous solution of an alkali metal halide, wherein the liquid supply system comprises: a mixer configured to mix at least a first component with a second component to form the liquid before supply to the space; a controller configured to control a physical property of the liquid by controlling the amount of the first and/or second component used to form the liquid; and a measuring device configured to measure a property of the liquid and to make feedback available to the controller, wherein the controller is configured to control the physical property of the liquid based on the feedback.