Extreme ultraviolet radiation source and cleaning method thereof

An extreme ultraviolet radiation source, comprising:

• a vessel having a gas supply and a gas outlet;
• an optical collector disposed within the vessel and configured to collect and reflect extreme ultraviolet light produced in the vessel;
• a gas source coupled to the gas supply to provide a cleaning gas to clean a surface of the optical collector;
• a vacuum pump coupled to the gas outlet to discharge the cleaning gas out of the vessel;
• and
• a gas scrubber disposed within the vessel and on a flow path of the cleaning gas;
• wherein the gas scrubber is a ring structure comprising a plurality of ribs distributed along a circumference of the ring structure and a plurality of gas passages formed between the ribs, wherein a pitch formed between the ribs close to the gas outlet is smaller than a pitch formed between the ribs away from the gas outlet.

A method of cleaning an extreme ultraviolet radiation source, comprising:

• providing the extreme ultraviolet radiation source, which comprises a vessel having a gas supply for supplying a cleaning gas and a gas outlet for discharging the cleaning gas, an optical collector disposed within the vessel, and a gas scrubber disposed within the vessel and on a flow path of the cleaning gas;
• providing the cleaning gas into the vessel to clean a surface of the optical collector;
• and
• flowing the cleaning gas out of the vessel after the cleaning gas passes through the gas scrubber;
• wherein the gas scrubber has a plurality of gas passages to allow the cleaning gas to flow through, and the size of the gas passage close to the gas outlet is smaller than the size of the gas passage away from the gas outlet.