Patent ID: 9271381
Filing Date: 2016-02-23
CPC Classification: G03F,H05G

Claim Text:
1. A system for producing EUV light, comprising: a material delivery system for producing a stream of material droplets; a laser system for producing a drive laser beam, the drive laser beam is configured to irradiate the material droplets at an irradiation point, wherein the laser system operates in the No Master Oscillator (NOMO) mode that is configured to cause the drive laser beam to pulse on every droplet in the stream of material droplets; a monitoring system for monitoring at least one of drive laser beam reflection from the drive laser beam and EUV radiation pulses, the monitoring system producing a detector signal responsive to the monitoring of the drive laser beam reflection if the reflection from the drive laser beam is monitored or responsive to the monitoring of the EUV radiation pulses if the EUV radiation pulses are monitored, the detector signal being a pulse train wherein the stream of material droplets comprise of main droplets having a first droplet size and satellite droplets having a second droplet size smaller than the first droplet size, and wherein the material delivery system comprises arrangement to modulate a disturbance signal configured to produce the stream of material droplets at a predefined rate and wherein the main droplets represent droplets formed at the predefined rate and the satellite droplets represent droplets formed at a rate different from the predefined rate; and arrangement for analyzing the detector signal to ascertain whether there exists at least one of extra pulses outside of the envelope of pulses that correspond with the irradiation of the main droplets and extra signal peaks outside of the envelope of signal peaks that correspond with the irradiation of the main droplets.