Supercontinuum radiation source and associated metrology devices
A supercontinuum radiation source including a modulator being operable to modulate pump laser radiation including a train of radiation pulses to provide modulated pump laser radiation, the modulation being such to selectively provide a burst of the pulses; and a hollow-core photonic crystal fiber being operable to receive the modulated pump laser radiation and excite a working medium contained within the hollow-core photonic crystal fiber so as to generate supercontinuum radiation.
1. A radiation source comprising:
a modulator configured to modulate pump laser radiation comprising radiation pulses to provide modulated pump laser radiation, the modulation being such to provide a first plurality of pulses and second plurality of pulses wherein a temporal delay between the first and second plurality of pulses is longer than a temporal delay between successive individual pulses within the first or second plurality of pulses; and
a hollow-core photonic crystal fiber configured to receive the modulated pump laser radiation having the first and second plurality of pulses and excite a working medium contained within the hollow-core photonic crystal fiber so as to generate broadband radiation.
2. The radiation source as claimed in claim 1 , wherein a period between successive individual pulses of the radiation pulses prior to modulation is the same as a period between successive individual pulses of the first or second plurality of pulses of the modulated pump laser radiation.
3. The radiation source as claimed in claim 1 , wherein the modulation is such that the temporal delay between the first and second plurality of pulses is over 2 times greater than a temporal delay between successive individual pump pulses within the first or second plurality of pulses.
4. The radiation source as claimed in claim 3 , configured so that the number of pump pulses per the first and second plurality of pulses and the temporal delay between the first and second plurality of pulses is controllable.
5. The radiation source as claimed in claim 1 , wherein the modulator is configured to provide one or more intermediate pulses between the first and second plurality of pulses and/or provide a variable length of each the first or second plurality of pulses.
6. The radiation source as claimed in claim 5 , wherein one or more parameters of the one or more intermediate pulses and/or variable length is optimized for high uniformity of average output power of the radiation source over a time period of less than 60 seconds.
7. The radiation source as claimed in claim 5 , wherein one or more parameters of the one or more intermediate pulses and/or variable length is optimized for high uniformity of average output power of the radiation source over a time period of less than 1 second.
8. The radiation source as claimed in claim 1 , wherein the broadband radiation comprises a wavelength range of 200 nm to 2000 nm, or a sub-range of at least 400 nm within this range.
9. A metrology device comprising:
the radiation source of claim 1 ;
a substrate support configured to support a substrate;
an optical system configured to direct the broadband radiation from the radiation source to the substrate; and
a detector configured to detect broadband radiation redirected by the substrate.
10. The metrology device as claimed in claim 9 , further comprising a processor configured to synchronize generation of the first and second plurality of pulses with performance of a measurement by the metrology device.
11. The metrology device as claimed in claim 9 , wherein the metrology device is operable as a scatterometer metrology apparatus.
12. The metrology device as claimed in claim 9 , wherein the metrology device is operable as a level sensor or an alignment sensor.
13. A radiation source comprising:
a modulator configured to modulate pulsed pump laser radiation having a repetition rate to provide modulated pump laser radiation, the modulator configured to introduce a temporal delay between pulses in the pulsed pump laser radiation different than a temporal delay of the repetition rate between successive pulses of the pump laser radiation; and
a hollow-core photonic crystal fiber configured to receive the modulated pump laser radiation and excite a working medium contained within the hollow-core photonic crystal fiber so as to generate broadband radiation.
14. The radiation source as claimed in claim 13 , wherein the broadband radiation comprises a wavelength range of at least 400 nm within the range of 200 nm to 2000 nm.
15. A metrology device comprising:
the radiation source of claim 13 ;
a substrate support configured to support a substrate;
an optical system configured to direct the broadband radiation from the radiation source to the substrate; and
a detector configured to detect broadband radiation redirected by the substrate.
16. The metrology device as claimed in claim 15 , wherein the metrology device is operable as a level sensor or an alignment sensor.
17. A radiation source comprising:
a modulator configured to modulate pulsed pump laser radiation having a repetition rate to provide modulated pump laser radiation;
a hollow-core photonic crystal fiber configured to receive the modulated pump laser radiation and excite a working medium contained within the hollow-core photonic crystal fiber so as to generate broadband radiation; and
a processor configured to cause the modulator to introduce a temporal delay between pulses in the pulsed pump laser radiation different than a temporal delay of the repetition rate between successive pulses of the pump laser radiation in synchronization with performance of a measurement by a metrology device using the broadband radiation.
18. The radiation source as claimed in claim 17 , wherein the broadband radiation comprises a wavelength range of at least 400 nm within the range of 200 nm to 2000 nm.
19. A metrology device comprising:
the radiation source of claim 17 ;
a substrate support configured to support a substrate;
an optical system configured to direct the broadband radiation from the radiation source to the substrate; and
a detector configured to detect broadband radiation redirected by the substrate.
20. The metrology device as claimed in claim 19 , wherein the metrology device is operable as a level sensor or an alignment sensor.