Extreme ultraviolet light source systems

An extreme ultraviolet light source system comprising:

• a chamber including a condensing mirror that is configured to reflect extreme ultraviolet light along an optical path;
• a blocking plate on the chamber and comprising an opening that is configured to pass the extreme ultraviolet light therethrough;
• a transparent cover replacement unit including a plurality of transparent covers on the blocking plate, the plurality of transparent covers including a first transparent cover covering the opening and a second transparent cover adjacent to the first transparent cover;
• a nozzle between the chamber and the blocking plate and comprising an end portion adjacent the opening, the nozzle being configured to spray a gas in a direction intersecting the optical path;
• an exhaust pipe between the chamber and the blocking plate and facing the end portion of the nozzle;
• a driving unit configured to move the plurality of transparent covers;
• and
• a control unit configured to control the driving unit to replace the first transparent cover with the second transparent cover,
• wherein the exhaust pipe includes a pressure sensor that is configured to measure an internal pressure of the exhaust pipe and configured to transmit the measured internal pressure to the control unit, and
• the control unit is configured to control the driving unit to replace the first transparent cover with the second transparent cover when the measured internal pressure is higher than a predetermined value.

An extreme ultraviolet light source system comprising:

• a chamber including a condensing mirror, that is configured to reflect extreme ultraviolet light along an optical path;
• a blocking plate on the chamber and comprising an opening that is configured to pass the extreme ultraviolet light therethrough;
• a transparent cover on the blocking plate and covering the opening, the blocking plate extending between the transparent cover and the chamber;
• a nozzle between the chamber and the blocking plate and comprising an end portion adjacent the opening, the end portion of the nozzle being configured to spray a first gas in a direction intersecting the optical path;
• and
• an exhaust pipe between the chamber and the blocking plate and facing the end portion of the nozzle,
• wherein an internal space of the chamber is configured to include a second gas, and
• a temperature of the first gas is lower than a temperature of the second gas.