US Patent 7598503 Lithographic apparatus and cleaning method therefor

A lithographic apparatus is disclosed. The apparatus includes a source for supplying hydrogen radicals, a guide for use in conjunction with the source, for directing hydrogen radicals to an application surface to be targeted by the hydrogen radicals. The guide is provided with a coating having a hydrogen radical recombination constant of less than 0.2. In this way, the radicals can be transported with reduced losses and are able to better interact with remaining contaminants on application surfaces, such as mirror surfaces.