Patent ID: 8129700

Claim:
An optical element contamination preventing device for an extreme ultraviolet light source apparatus wherein a scattered material emitted together with extreme ultraviolet light from a first plasma generated by excitation of a target within a chamber by a laser beam is prevented from contaminating an optical element or an equipment having an optical element within the chamber, wherein at least a surface of the target is made of tin and the target has a tape-shape, a wire-shape, a plate-shape, a rod-shape or a ball-shape; a wavelength of the laser beam is CO 2 laser wavelength, and the laser is configured to reduce most of the scattered material to sub-nanometer size; the optical element comprises a collector mirror that reflects and collects the extreme ultraviolet light emitted from the plasma; the optical element comprises a laser window for guiding the laser beam into the chamber: wherein the device comprises; a plasma generating device for generating a second plasma for electrically charging the scattered material; a magnetic field generating device for applying a magnetic field to the electrically charged scattered material for deflecting the scattered material, thereby preventing the scattered material from reaching the optical element; and gasflow generating means for generating a gasflow in the vicinity of the optical element.