Source material delivery system, EUV radiation system, lithographic apparatus, and methods thereof

A non-transitory computer readable medium having instructions stored thereon, that, when executed on a processor, cause the processor to perform operations, the operations comprising:

• receiving a detection signal from a detector of a source material delivery system, wherein the detection signal is associated with time intervals between crossings of coalesced droplets at the detector;
• measuring and tracking over time a variability of the time intervals;
• determining whether a discontinuity behavior in a coalescence length of the droplets occurs based on determining whether a current variability of the time intervals (1) exceeds a predetermined variability, or (2) exceeds a previous variability of the time intervals by a predetermined value;
• adjusting a parameter of an electrical signal supplied to an electromechanical element disposed on a nozzle of the source material delivery system based on the occurrence of the discontinuity behavior in the coalescence length of the droplets to thereby control an applied pressure to the nozzle;
• and
• mapping the discontinuity behavior as a function of (1) a relative phase between a first periodic waveform of the electrical signal and a second periodic waveform of the electrical signal and/or (2) an amplitude or an inverse amplitude of the first periodic waveform of the electrical signal by storing, upon determining that the discontinuity behavior is occurring, information representing that a discontinuity is occurring or has occurred at the then-current relative phase and/or the amplitude or inverse amplitude.

A source material delivery system comprising:

• a nozzle configured to eject initial droplets of a material;
• an electromechanical element disposed on the nozzle and configured to apply a pressure on the nozzle;
• a waveform generator electrically coupled to the electromechanical element, wherein the waveform generator is configured to generate an electrical signal supplied to the electromechanical element to control the applied pressure on the nozzle, the electrical signal comprises a first periodic waveform and a second periodic waveform, and the system is configured to generate coalesced droplets from a coalescing of the initial droplets based on the first and second periodic waveforms;
• a detector configured to generate a detection signal comprising information of time intervals between crossings of the coalesced droplets at the detector;
• and
• a processor configured to measure and track a variability of the time intervals over time, to determine whether a discontinuity behavior in a coalescence length of the droplets occurs by determining whether a current variability of the time intervals (1) exceeds a predetermined variability, or (2) exceeds a previous variability of the time intervals by a predetermined value, and to map the discontinuity behavior as a function of (1) a relative phase between the first periodic waveform and the second periodic waveform and/or (2) an amplitude or an inverse amplitude of the first periodic waveform by storing in a memory or memory device associated with the processor information representing that a discontinuity is occurring or has occurred at the then-current relative phase and/or the amplitude or inverse amplitude upon determining that the discontinuity behavior is occurring.