Patent ID: 7864291

Claim:
An exposure apparatus which has a projection optical system configured to project a pattern of a reticle onto a substrate, and exposes the substrate to light via the reticle and the projection optical system, with a space between the projection optical system and the substrate filled with liquid, said apparatus comprising: a supply nozzle configured to supply liquid to the space; a supply path configured to supply the liquid to said supply nozzle; a bypass which branches from said supply path; a supply control valve configured to change a flow rate of the liquid supplied from said supply path to said supply nozzle, to control the supply of the liquid to the space, while supplying liquid to said bypass; and a liquid quality sensor arranged in said bypass and configured to measure a purity of liquid in said bypass, wherein the supply of the liquid to the space is controlled based on a measurement result, obtained by said liquid quality sensor, of the quality of liquid that flows in the bypass, so that liquid having a purity satisfying a standard is supplied to the space.