Patent Number: 
Section: abstract

A method is described for generating EUV radiation, comprising the steps of generating a flow of a medium (39); transporting this medium through a source space (60) connected to a vacuum pump (75), and irradiating part of the medium with an intensive, pulsed laser beam (41) focused on said part of the medium, thus creating a plasma (47) which emits EUV radiation. In order to maintain a vacuum in the source space and to prevent elements of the medium, like vapor or elementary particles, from leaving the source space through apertures (63, 64) provided in the wall of the space for passing the laser beam and EUV radiation, the flow of medium is embedded in a flow of rare gas. The invention also describes an EUV radiation source unit for performing the method and the application of the method in the manufacture of devices like IC devices, and in a lithographic projection apparatus.