Extreme ultraviolet light source apparatus and method of generating ultraviolet light

An extreme ultraviolet light source apparatus, which is to generate an extreme ultraviolet light by irradiating a target with a main pulse laser light after irradiating the target with a prepulse laser light, the extreme ultraviolet light source apparatus comprising:

• a prepulse laser light source configured for generating a pre-plasma by irradiating the target with the prepulse laser light while a part of the target remains;
• a main pulse laser light source configured for generating the extreme ultraviolet light by irradiating the pre-plasma with the main pulse laser light;
• a light source configured for illuminating the pre-plasma generated by irradiating the target with the prepulse laser light;
• a camera configured for imaging the pre-plasma illuminated by the light source;
• an analyzer configured for analyzing an image of the pre-plasma imaged by the camera;
• and
• a controller configured for controlling a focus position of the main pulse laser light based on an analysis of the analyzer.

A method of generating an extreme ultraviolet light by irradiating a target with a main pulse laser light after irradiating the target with a prepulse laser light, comprising the steps of:

• emitting from a prepulse laser light source the prepulse laser light for irradiating the target with the prepulse laser light in order to generate a pre-plasma while a part of the target remains;
• illuminating, by a light source, the pre-plasma generated by irradiating the target with the prepulse laser light;
• imaging, by a camera, the pre-plasma illuminated by the light source;
• analyzing, by a analyzer, an image of the pre-plasma imaged by the camera;
• controlling, by a controller, a focus position of the main pulse laser light based on an analysis of the analyzer, and
• emitting from a main pulse laser light source the main pulse laser light for irradiating the pre-plasma with the main pulse laser light in order to generate an extreme ultraviolet light, the pre-plasma being irradiated with the main pulse laser light according to the focus position controlled by a controller.

An extreme ultraviolet light source apparatus for generating an extreme ultraviolet light by irradiating a target with a main pulse laser light after irradiating the target with a prepulse laser light, the extreme ultraviolet light source apparatus comprising:

• a prepulse laser light source configured for generating a pre-plasma by irradiating the target with the prepulse laser light while a part of the target remains;
• a main pulse laser light source configured for generating the extreme ultraviolet light by irradiating the pre-plasma with the main pulse laser light;
• a first camera configured for imaging the target before being irradiated with the prepulse laser light;
• a first analyzer configured for analyzing an image of the target imaged by the first camera;
• a second camera configured for imaging the pre-plasma generated by irradiating the target with the prepulse laser light;
• a second analyzer configured for analyzing an image of the pre-plasma imaged by the second camera;
• and
• a controller configured for controlling a focus position of the prepulse pulse laser light based on an analysis of the first analyzer, and focus position of the main pulse laser light based on an analysis of the second analyzer.