Online calibration for repetition rate dependent performance variables

Patent metadata

Field	Value
Publication number	US-9762023-B2
Application number	US-201514976829-A
Country	US
Kind code	B2
Filing date	Dec 21, 2015
Priority date	Dec 21, 2015
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

Online calibration of laser performance as a function of the repetition rate at which the laser is operated is disclosed. The calibration can be periodic and carried out during a scheduled during a non-exposure period. Various criteria can be used to automatically select the repetition rates that result in reliable in-spec performance. The reliable values of repetition rates are then made available to the scanner as allowed values and the laser/scanner system is then permitted to use those allowed repetition rates.

First claim

What is claimed is:

1. A system comprising:
a laser capable of running at multiple repetition rates;
a laser control unit operatively connected to the laser for controlling a repetition rate at which the laser operates;
a measurement unit arranged to measure an output from the laser for measuring at least one operating parameter of the laser at a repetition rate;
a comparison unit operatively connected to the measurement unit for providing an indication of whether a measured value for the operating parameter is within a predetermined range of values for the operating parameter; and
a storage unit operatively connected to the comparison unit for storing a value based on the indication and associated with the repetition rate;
the laser control unit being operatively connected to the storage unit and configured to permit operation of the laser at the repetition rate only if the value stored in association with the repetition rate indicates that the operating parameter was measured to be within the predetermined range.

2. A system as claimed in claim 1 wherein the at least one operating parameter is energy stability.

3. A system as claimed in claim 1 wherein the at least one operating parameter is bandwidth stability.

4. A system as claimed in claim 1 wherein the at least one operating parameter is wavelength stability.

5. A system as claimed in claim 1 wherein the at least one operating parameter is beam shape stability.

6. A system as claimed in claim 1 wherein the at least one operating parameter is an actuator output.

7. A system comprising:
a laser capable of running at multiple repetition rates;
a laser control unit operatively connected to the laser for driving the laser to operate sequentially at a plurality of repetition rates;
a measurement unit arranged to measure an output from the laser for measuring at least one operating parameter of the laser for each of the plurality of repetition rates;
a comparison unit operatively connected to the measurement unit for providing an indication of whether a measured value for the operating parameter is within a predetermined range of values for each of the plurality of repetition rates; and
a storage unit operatively connected to the comparison unit for storing a first value based on the indication and a second value indicative of the repetition rate at which the value was obtained for each of the plurality of repetition rates; and
the laser control unit being operatively connected to the storage unit and configured to permit operation of the laser at a selected repetition rate only if the selected repetition rate is one of the plurality of repetition rates for which the value stored in association with the repetition rate indicates that the operating parameter was measured to be within the predetermined range.

8. A system as claimed in claim 7 wherein the at least one operating parameter is energy stability.

9. A system as claimed in claim 7 wherein the at least one operating parameter is bandwidth stability.

10. A system as claimed in claim 7 wherein the at least one operating parameter is wavelength stability.

11. A system as claimed in claim 7 wherein the at least one operating parameter is beam shape stability.

12. A system as claimed in claim 7 wherein the at least one operating parameter is an actuator output.

13. A system as claimed in claim 7 wherein the laser control unit operatively connected to the laser for driving the laser to operate sequentially at a plurality of repetition rates is configured to step the laser through a series of repetition rates.

14. A system as claimed in claim 13 wherein the laser control unit operatively connected to the laser for driving the laser to operate sequentially at a plurality of repetition rates is configured to step the laser through a series of repetition rates where the difference in repetition rate between steps is maintained substantially constant.

15. A system as claimed in claim 13 wherein the laser control unit operatively connected to the laser for driving the laser to operate sequentially at a plurality of repetition rates is configured to step the laser through a series of repetition rates where the difference in repetition rate between steps is increased with repetition rate.

16. A system as claimed in claim 13 wherein the laser control unit operatively connected to the laser for driving the laser to operate sequentially at a plurality of repetition rates is configured to step the laser through a series of repetition rates where the difference in repetition rate between steps is decreased with repetition rate.

17. A system comprising:
a measurement module configured to record a dependence of at least one performance characteristic with respect to a pulse repetition rate of a pulsed laser;
a comparison module operatively connected to the measurement module and configured to identify an allowed set of pulse repetition rates of the pulsed laser, based at least in part on the recorded dependence and a specification criterion; and
an output operatively connected to the comparison module and configured to communicate the allowed set of pulse repetition rates to a scanner of a photolithography tool.

18. A system as claimed in claim 17 wherein the at least one performance characteristic is energy stability.

19. A system as claimed in claim 17 wherein the at least one performance characteristic is bandwidth stability.

20. A system as claimed in claim 17 wherein the at least one performance characteristic is wavelength stability.

21. A system as claimed in claim 17 wherein the at least one operating parameter is beam shape stability.

22. A system as claimed in claim 17 wherein the at least one operating parameter is an actuator output.

23. A system comprising:
a laser capable of running at multiple repetition rates;
a laser control unit operatively connected to the laser for driving the laser to operate sequentially at a plurality of repetition rates;
a measurement unit arranged to measure an output from the laser for measuring at least one operating parameter of the laser for each of the plurality of repetition rates;
a scoring unit operatively connected to the measurement unit for determining a score for each of the plurality of repetition rates based at least in part on the measured operating parameter; and
a storage unit operatively connected to the scoring unit for storing first values based on the scores and respective second values indicative of the repetition rate for which the score was determined for each of the plurality of repetition rates,
the laser control unit being operatively connected to the storage unit and configured to determine a repetition rate at which to operate the laser based on the score of the repetition rate.

24. A method comprising the steps of:
a series of steps performed during a nonexposure period for a laser, the series including the steps of
serially running the laser at a plurality of repetition rates;
measuring at least one operating parameter of the laser for each of the plurality of repetition rates;
providing an indication of whether a measured value for the operating parameter is within a predetermined range of values for each of the plurality of repetition rates; and
storing a first value based on the indication and a second value indicative of the repetition rate at which the value was obtained for each of the plurality of repetition rates;
and a step

Assignees

• Cymer LLC
• Asml Netherlands Bv

Inventors

• Thornes Joshua Jon
• Aggarwal Tanuj
• O'Brien Kevin Michael
• Everts Frank
• Godfried Herman Philip
• BURDT Russell Allen

Classifications

• G01J11/00 Primary

  Measuring the characteristics of individual optical pulses or of optical pulse trains · CPC title

• H01S3/10069

  Memorized or pre-programmed characteristics, e.g. look-up table [LUT] · CPC title

• H01S3/10046

  Pulse repetition rate control (H01S3/11 takes precedence) · CPC title

• H01S3/0014

  Monitoring arrangements not otherwise provided for (photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003) · CPC title

• G03F7/70558

  Dose control, i.e. achievement of a desired dose · CPC title