Confocal chromatic metrology for EUV source condition monitoring
AssigneeKLA Corporation
InventorsPatrick Tae, Caijun Su, Ravichandra Jagannath, Brian Ahr
Life of this patent
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Abstract
A light source includes a rotatable drum to be coated with xenon ice and illuminated by a laser beam to produce a plasma. The drum may also be translatable. The light source further includes a confocal chromatic sensor to measure distances from the confocal chromatic sensor to the rotatable drum. The confocal chromatic sensor may include a sensor head to focus light onto the rotatable drum and to detect reflected light from the rotatable drum. The sensor head and the rotatable drum may be disposed within a vacuum chamber.
Claims22
A light source, comprising:
- a rotatable drum to be coated with xenon (Xe) ice and illuminated by a laser beam to produce a plasma;
- a confocal chromatic sensor to measure distances from the confocal chromatic sensor to the rotatable drum;
- one or more processors;
- and
- memory storing one or more programs for execution by the one or more processors, the one or more programs comprising instructions for:
- detecting defects in the Xe ice on the rotatable drum using the confocal chromatic sensor when the rotatable drum is coated with the Xe ice;
- and
- shutting off the laser beam in response to detecting a defect in the Xe ice on the rotatable drum using the confocal chromatic sensor.
A light source, comprising:
- a rotatable drum to be coated with xenon (Xe) ice and illuminated by a laser beam to produce a plasma;
- a confocal chromatic sensor to measure distances from the confocal chromatic sensor to the rotatable drum;
- a motorized translation stage;
- one or more processors;
- and
- memory storing one or more programs for execution by the one or more processors, wherein:
- the confocal chromatic sensor comprises a sensor head mounted on the motorized translation stage;
- and
- the one or more programs comprise instructions for translating the motorized translation stage to align the sensor head with a laser spot at which the laser beam illuminates the Xe ice.
A method of operating a light source, comprising:
- rotating a drum;
- while rotating the drum, coating the drum with xenon (Xe) ice;
- while rotating the drum with the drum coated with the Xe ice, illuminating the drum with a laser beam to produce a plasma;
- while illuminating the drum with the laser beam, monitoring the drum using a confocal chromatic sensor to detect defects in the Xe ice on the drum;
- and
- in response to detecting a defect in the Xe ice on the drum, shutting off the laser beam.
Dependencies are inferred from the claim text.