Active spectral control of DUV light source

Abstract

According to aspects of an embodiment of the disclosed subject matter, a line narrowed high average power high pulse repetition laser micro-photolithography light source bandwidth control method and apparatus are disclosed which may comprise a bandwidth metrology module measuring the bandwidth of a laser output flight pulse beam pulse produced by the light source and providing a bandwidth measurement; a bandwidth error signal generator receiving the bandwidth measurement and a bandwidth setpoint and providing a bandwidth error signal; an active bandwidth controller providing a fine bandwidth correction actuator signal and a coarse bandwidth correction actuator signal responsive to the bandwidth error. The fine bandwidth correction actuator and the coarse bandwidth correction actuator each may induce a respective modification of the light source behavior that reduces bandwidth error. The coarse and fine bandwidth correction actuators each may comprise a plurality of bandwidth correction actuators.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a bandwidth control device E₉₅ sensitivity curve;

FIG. 2 shows as model of laser system operation on an idealized bandwidth control device curve, according to aspects of an embodiment of the disclosed subject matter;

FIG. 3 shows an illustrative E₉₅ response plot as the BCD position is varied, e.g., with time, according to aspects of an embodiment of the disclosed subject matter;

FIG. 4 shows an illustrative E₉₅ response plot for a change of E₉₅ setpoint using, e.g., the BCD as a control actuator, according to aspects of an embodiment of the disclosed subject matter;

FIG. 5 illustrates by way of example laser system operation curves for BCD positions (e.g., forwards and backwards trajectories), according to aspects of an embodiment of the disclosed subject matter;

FIG. 6 illustrates by way of example bandwidth variations with no bandwidth control, with passive control and the active control in addition, according to aspects of an embodiment of the disclosed subject matter;

FIG. 7 illustrates schematically and in block diagram form an active bandwidth control circuit according to aspects of an embodiment of the disclosed subject matter;

FIG. 8 illustrates disturbance types and time scales and magnitudes, according to aspects of an embodiment of the disclosed subject matter;

FIG. 9 illustrates an exemplary plot of changing e₉₅ bandwidth with change in fluorine gas content in a lasing chamber, according to aspects of an embodiment of the disclosed subject matter;

FIG. 10 illustrates an exemplary plot of bandwidth control according to aspects of an embodiment of the disclosed subject matter;

FIG. 11 illustrates an exemplary plot of the change of E₉₅ bandwidth with change in differential firing time between two chambers in a seed oscillator/amplifier gain medium laser system, according to aspects of an embodiment of the disclosed subject matter;

FIG. 12 illustrates an exemplary response of E₉₅ bandwidth with and without active bandwidth control according to aspects of an embodiment of the disclosed subject matter between gas refills, according to aspects of an embodiment of the disclosed subject matter;

FIG. 13 illustrates a control system error signal modification circuit for normalizing one laser parameter error signal to the effects of another laser parameter changing, according to aspects of an embodiment of the disclosed subject matter;

FIG. 14 illustrates schematically and in block diagram form a circuit for normalizing laser system parameter error signals in real time according to aspects of an embodiment of the disclosed subject matter;

FIG. 15 illustrates an exemplary plot of the normalization of raw data according to aspects of an embodiment of the disclosed subject matter, according to aspects of an embodiment of the disclosed subject matter;

FIG. 16 illustrates an exemplary trend curve for the change in dΔtMOPA/dF₂ over time, according to aspects of an embodiment of the disclosed subject matter;

FIG. 17 illustrates an exemplary trend curve for the change in dV/dF₂ over time, according to aspects of an embodiment of the disclosed subject matter; and,

FIG. 18 illustrates an exemplary trend curve for the change in dE_MO/dF₂ over time, according to aspects of an embodiment of the disclosed subject matter.

Claims

1. A line narrowed high average power high pulse repetition laser micro-photolithography light source bandwidth control system comprising: a bandwidth metrology module measuring the bandwidth of a laser output light pulse beam pulse produced by the light source and providing a bandwidth measurement;a bandwidth error signal generator receiving the bandwidth measurement and a bandwidth setpoint and providing a bandwidth error signal;an active bandwidth controller providing a fine bandwidth correction actuator signal and a coarse bandwidth correction actuator signal responsive to the bandwidth error.

2. The apparatus of claim 1 further comprising: the fine bandwidth correction actuator and the coarse bandwidth correction actuator each inducing a respective modification of the light source behavior that reduces bandwidth error.

3. The apparatus of claim 1 further comprising: the coarse and fine bandwidth correction actuators each comprising a plurality of bandwidth correction actuators.

4. The apparatus of claim 2 further comprising: the coarse and fine bandwidth correction actuators each comprising a plurality of bandwidth correction actuators.

5. The apparatus of claim 1 further comprising: the coarse bandwidth correction actuator targeting large amplitude disturbances occurring at low frequency and the fine bandwidth correction actuator targeting small amplitude disturbances occurring at high frequency.

6. The apparatus of claim 2 further comprising: the coarse bandwidth correction actuator targeting large amplitude disturbances occurring at low frequency and the fine bandwidth correction actuator targeting small amplitude disturbances occurring at high frequency.

7. The apparatus of claim 3 further comprising: the coarse bandwidth correction actuator targeting large amplitude disturbances occurring at low frequency and the fine bandwidth correction actuator targeting small amplitude disturbances occurring at high frequency.

8. The apparatus of claim 4 further comprising: the coarse bandwidth correction actuator targeting large amplitude disturbances occurring at low frequency and the fine bandwidth correction actuator targeting small amplitude disturbances occurring at high frequency.

9. The apparatus of claim 5 further comprising: the large amplitude disturbances comprising one or more of the group of large E95 setpoint changes, gas aging effects and the long timescale component of duty cycle setpoint changes, and the smaller amplitude disturbances comprising one or more of the group comprising laser system output pulse energy setpoint, and the fast component of duty cycle setpoint changes.

10. The apparatus of claim 6 further comprising: the large amplitude disturbances comprising one or more of the group of large E95 setpoint changes, gas aging effects and the long timescale component of duty cycle setpoint changes, and the smaller amplitude disturbances comprising one or more of the group comprising laser system output pulse energy setpoint, and the fast component of duty cycle setpoint changes.

11. The apparatus of claim 7 further comprising: the large amplitude disturbances comprising one or more of the group of large E95 setpoint changes, gas aging effects and the long timescale component of duty cycle setpoint changes, and the smaller amplitude disturbances comprising one or more of the group comprising laser system output pulse energy setpoint, and the fast component of duty cycle setpoint changes.

12. The apparatus of claim 8 further comprising: the large amplitude disturbances comprising one or more of the group of large E95 setpoint changes, gas aging effects and the long timescale component of duty cycle setpoint changes, and the smaller amplitude disturbances comprising one or more of the group comprising laser system output pulse energy setpoint, and the fast component of duty cycle setpoint changes.

13. The apparatus of claim 5 further comprising: fine actuator control output trends towards a minimum or maximum value;coarse actuator control applies corrective action in such a way as to move the fine actuator back towards a centered value.

14. The apparatus of claim 6 further comprising: fine actuator control output trends towards a minimum or maximum value;coarse actuator control applies corrective action in such a way as to move the fine actuator back towards a centered value.

15. The apparatus of claim 7 further comprising: fine actuator control output trends towards a minimum or maximum value;coarse actuator control applies corrective action in such a way as to move the fine actuator back towards a centered value.

16. The apparatus of claim 8 further comprising: fine actuator control output trends towards a minimum or maximum value;coarse actuator control applies corrective action in such a way as to move the fine actuator back towards a centered value.

17. The apparatus of claim 9 further comprising: fine actuator control output trends towards a minimum or maximum value;coarse actuator control applies corrective action in such a way as to move the fine actuator back towards a centered value.

18. The apparatus of claim 10 further comprising: fine actuator control output trends towards a minimum or maximum value;coarse actuator control applies corrective action in such a way as to move the fine actuator back towards a centered value.

19. The apparatus of claim 11 further comprising: fine actuator control output trends towards a minimum or maximum value;coarse actuator control applies corrective action in such a way as to move the fine actuator back towards a centered value.

20. The apparatus of claim 12 further comprising: fine actuator control output trends towards a minimum or maximum value;coarse actuator control applies corrective action in such a way as to move the fine actuator back towards a centered value.

21. The apparatus of claim 13 further comprising: the centered value comprises nominally 50% where control authority is balanced in both the positive and negative directions.

22. The apparatus of claim 14 further comprising: the centered value comprises nominally 50% where control authority is balanced in both the positive and negative directions.

23. The apparatus of claim 15 further comprising: the centered value comprises nominally 50% where control authority is balanced in both the positive and negative directions.

24. The apparatus of claim 16 further comprising: the centered value comprises nominally 50% where control authority is balanced in both the positive and negative directions.

25. The apparatus of claim 17 further comprising: the centered value comprises nominally 50% where control authority is balanced in both the positive and negative directions.

26. The apparatus of claim 18 further comprising: the centered value comprises nominally 50% where control authority is balanced in both the positive and negative directions.

27. The apparatus of claim 19 further comprising: the centered value comprises nominally 50% where control authority is balanced in both the positive and negative directions.

28. The apparatus of claim 20 further comprising: the centered value comprises nominally 50% where control authority is balanced in both the positive and negative directions.

29. A line narrowed high average power high pulse repetition laser micro-photolithography light source bandwidth control system comprising: a laser operating parameter metrology module measuring the laser operating parameter of a laser output light pulse beam pulse produced by the light source and providing a laser operating parameter measurement;a laser operating parameter error signal generator receiving the laser operating parameter measurement and a laser operating parameter setpoint and providing a laser operating parameter error signal;a laser operating parameter error signal modifier modifying the laser operating parameter error signal according to the sensitivity of the laser operating parameter to another laser operating parameter comprising a real time estimation filter.

30. The apparatus of claim 29 further comprising: the laser operating parameter error signal modifier modifies the laser operating parameter error signal according to the sensitivity of the laser operating system parameter to a each of a plurality of other laser operating parameters.

31. The apparatus of claim 39 further comprising: the laser operating parameter is selected from the group comprising bandwidth (Exx), bandwidth (FWXM), energy out of the seed laser (EMO), differential firing time between the seed laser and amplifier gain medium (dtMOPA), and voltage (V).

32. The apparatus of claim 30 further comprising: the laser operating parameter is selected from the group comprising bandwidth (Exx), bandwidth (FWXM), energy out of the seed laser (EMO), differential firing time between the seed laser and amplifier gain medium (dtMOPA), and voltage (V).

33. The apparatus of claim 29 further comprising: the other laser operating parameter is selected from the group comprising duty cycle (DC) and laser system output energy (Esht) and voltage (V).

34. The apparatus of claim 30 further comprising: the other laser operating parameter is selected from the group comprising duty cycle (DC) and laser system output energy (Esht) and voltage (V).

35. The apparatus of claim 31 further comprising: the other laser operating parameter is selected from the group comprising duty cycle (DC) and laser system output energy (Esht) and voltage (V).

36. The apparatus of claim 32 further comprising: the other laser operating parameter is selected from the group comprising duty cycle (DC) and laser system output energy (Esht) and voltage (V).

37. The apparatus of claim 33 further comprising: the error signal modifier comprises a recursive filter.

38. The apparatus of claim 34 further comprising: the error signal modifier comprises a recursive filter.

39. The apparatus of claim 35 further comprising: the error signal modifier comprises a recursive filter.

40. The apparatus of claim 36 further comprising: the error signal modifier comprises a recursive filter.

41. The apparatus of claim 29 further comprising: the error signal modifier comprises an RLS filter.

42. The apparatus of claim 30 further comprising: the error signal modifier comprises an RLS filter.

43. The apparatus of claim 31 further comprising: the error signal modifier comprises an RLS filter.

44. The apparatus of claim 32 further comprising: the error signal modifier comprises an RLS filter.

45. The apparatus of claim 29 further comprising: the error signal modifier implements the following:

46. The apparatus of claim 30 further comprising: the error signal modifier implements the following:

47. The apparatus of claim 31 further comprising: the error signal modifier implements the following:

48. The apparatus of claim 32 further comprising: the error signal modifier implements the following:

49. A line narrowed high average power high pulse repetition laser micro-photolithography light source fluorine injection control system comprising: a laser operating parameter measurement mechanism measuring a laser operating parameter of the light source;a laser operating parameter tracking mechanism providing a representation of the value of the laser operating parameter over time;a laser system gas refill prediction mechanism predicting the time for a gas fill based upon the trending of the value of the laser operating parameter between a first relatively constant steady state trend value and a limiting value.

50. The apparatus of claim 49 further comprising: the laser operating parameter is selected from the group comprising voltage (V) and differential firing time (dtMOPA), bandwidth at the energy percentage integral, i.e., Exx %, energy out of the master oscillator, EMO, energy out of the amplification gain medium, or energy output of the laser system at the shutter, Esht.