Extreme ultraviolet light source and positioning method of light focusing optical means

A light focusing optical means position adjusting method of an extreme ultraviolet light source apparatus including an extreme ultraviolet light source and a light focusing optical means that reflects and focuses light emitted from the light source, comprising the following steps of:

• a step of associating two or more pieces of Angular distribution property image data in which an illuminance distribution is uneven, with Angular distribution property image data in advance and obtaining a movement direction and an amount of movement for moving a position of the light focusing optical means when Angular distribution property image data exhibiting uneven illuminance distribution is obtained, to a position where Angular distribution property image data exhibiting uniform illuminance, is obtained;
• and
• a step of measuring a current Angular distribution property and thereby acquiring Angular distribution property image data;
• a step of comparing the obtained current Angular distribution property image data with two or more pieces of uneven Angular distribution property image data, which are acquired in advance, and selecting Angular distribution property image data that is the most closely matched in a shape of an Angular distribution property with the current Angular distribution property image data, from the two or more pieces of uneven Angular distribution property image data;
• and
• a step of moving the light focusing optical means based on the movement direction and the amount of movement of the light focusing optical means, associated with the selected Angular distribution property image data.

An extreme ultraviolet light source apparatus comprising:

• an extreme ultraviolet light source;
• a light focusing optical means, which reflects and focuses light emitted from the light source;
• a light focusing optical means moving unit, which moves the light focusing optical means;
• an angle distribution property measurement unit, which receives light reflected by the light focusing optical means, and which obtains angle distribution property image data;
• a control unit, which controls the light focusing optical means moving unit based on the angle distribution property image data, so as to move the light focusing optical means, wherein the control unit includes:
• a memory unit for storing two or more sets of data, each set comprising (i) given angle distribution property image data in which illuminance distribution measured in advance is uneven, and (ii) movement direction and amount data that are associated with the given angle distribution property image data, wherein the movement direction and amount data are used to move a position of the light focusing optical means when angle distribution property image data indicating uneven illuminance distribution is obtained, to a position where angle distribution property image data indicating uniform illuminance is obtained,
• a comparison and selection unit, which:
• compares current angle distribution property image data measured by the angle distribution property measurement unit with angle distribution property image data saved in the memory unit in which illuminance is uneven,
• selects angle distribution property image data saved in the memory unit that is the most closely matched in a shape of an angle distribution property to the current angle distribution property image data, and
• reads out the saved movement direction and amount data that are associated with the selected angle distribution property image data, and
• a light focusing optical means movement control unit which controls the light focusing optical means moving unit so as to move the light focusing optical means based on the saved movement direction and amount data read out by the comparison selection unit.