Pulsed light beam spectral feature control

Patent metadata

Field	Value
Publication number	US-9785050-B2
Application number	US-201514794508-A
Country	US
Kind code	B2
Filing date	Jul 8, 2015
Priority date	Jun 26, 2015
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

A system includes a first actuation module coupled to a first actuatable apparatus of an optical source, the first actuatable apparatus being altered by the first actuation module to adjust the spectral feature of the pulsed light beam; a second actuation module coupled to a second actuatable apparatus of the optical source, the second actuatable apparatus being altered by the second actuation module to adjust the spectral feature of the pulsed light beam; and a control system configured to receive an indication regarding the operating state of the first actuatable apparatus; and send a signal to the second actuation module to adjust the spectral feature of the pulsed light beam to either: prevent the first actuatable apparatus from saturating based on the operating state of the first actuatable apparatus, or desaturate the first actuatable apparatus if the first actuatable apparatus is saturated.

First claim

What is claimed is:

1. A system for controlling a spectral feature of a pulsed light beam produced by an optical source, the system comprising:
a first actuation module coupled to a first actuatable apparatus of the optical source, the first actuatable apparatus being altered within a range of values by the first actuation module to thereby adjust the spectral feature of the pulsed light beam;
a second actuation module coupled to a second actuatable apparatus of the optical source, the second actuatable apparatus being altered by the second actuation module to thereby adjust the spectral feature of the pulsed light beam; and
a control system connected to the first actuation module and the second actuation module, and configured to:
receive an indication regarding the operating state of the first actuatable apparatus; and
send a signal to the second actuation module to adjust the spectral feature of the pulsed light beam to either:
prevent the first actuatable apparatus from saturating based on the received indication of the operating state of the first actuatable apparatus, or
desaturate the first actuatable apparatus if the received indication of the operating state of the first actuatable apparatus indicates that it is saturated.

2. The system of claim 1 , wherein the control system is configured to:
receive a measurement of the spectral feature of the pulsed light beam output from the optical source; and
send a signal to one or more of the first actuation module and the second actuation module to adjust the spectral feature of the pulsed light beam to a new value based on the received measurement of the spectral feature of the pulsed light beam.

3. The system of claim 1 , wherein the optical source is a multi-stage gas discharge system, with the first stage being an oscillator apparatus that outputs a pulsed seed light beam and the second stage being an optical amplification apparatus that receives the pulsed seed light beam and outputs the pulsed light beam, and both stages include a gas discharge sub-system.

4. The system of claim 3 , wherein:
the first actuation module is a timing module that is connected to the first stage and the second stage to control a relative timing between a first trigger signal sent to the first stage and a second trigger signal sent to the second stage; and
the second actuation module includes a spectral selection module that is coupled to the first stage.

5. The system of claim 1 , wherein:
the second actuation module is a spectral selection module interacting with the pulsed light beam; and
the spectral selection module includes an optical system that is configured to adjust an optical magnification of the pulsed light beam.

6. The system of claim 1 , further comprising a third actuation module coupled to a third actuatable apparatus of the optical source, the third actuatable apparatus being altered by the third actuation module to thereby alter another spectral feature of the pulsed light beam.

7. The system of claim 1 , further comprising a metrology system including an observation system connected to the first actuation module and configured to: receive a characteristic of the pulsed light beam and output the indication regarding the operating state of the first actuatable apparatus.

8. The system of claim 7 , wherein the metrology system includes a spectral feature unit configured to measure a spectral feature of the pulsed light beam output from the optical source, and the control system is configured to receive the measurement of the spectral feature of the pulsed light beam.

9. The system of claim 7 , wherein the metrology system is separate from the first actuation module and the control system.

10. A method for controlling an optical source, the method comprising:
receiving an indication of an operating point of a first actuatable apparatus of the optical source, the operating point of the first actuatable apparatus being alterable between a lower limit and an upper limit to thereby adjust a spectral feature of a pulsed light beam produced by the optical source, and the first actuatable apparatus being in a saturated state when the operating point is at the lower limit or the upper limit and being in an unsaturated state when the operating point is between the upper limit and the lower limit;
determining a location of the operating point of the first actuatable apparatus between the upper limit and the lower limit based on the indication of the operating point of the first actuatable apparatus of the optical source;
determining whether the first actuatable apparatus is in the saturated state based on the determined location; and
if the first actuatable apparatus is determined to be in the saturated state, altering a second, distinct actuatable apparatus of the optical source to change the first actuatable apparatus to the unsaturated state and to adjust the spectral feature of the pulsed light beam.

11. The method of claim 10 , wherein
determining a location of the operating point of the first actuatable apparatus between the lower limit and the upper limit comprises determining the location of the operating point relative to one or more of an upper activation limit and a lower activation limit, the upper activation limit and the lower activation limit being between the upper limit and the lower limit,
determining whether the first actuatable apparatus is in the saturated state based on the determined location comprises determining whether the operating point is between the upper activation limit and the upper limit or between the lower activation limit and the lower limit, and
the unsaturated state of the first actuatable apparatus is between the upper activation limit and the lower activation limit.

12. The method of claim 11 , wherein, if the first actuatable apparatus is in the saturated state, further comprising continuing to alter the second, distinct apparatus until the operating point of the first actuatable apparatus is between an upper deactivation limit and a lower deactivation limit, the upper and lower deactivation limits being between the upper and lower activation limits.

13. The method of claim 12 , wherein the first actuatable apparatus is associated with a target operating point that is between the upper and lower deactivation limits.

14. The method of claim 10 , wherein the second, distinct actuatable apparatus comprises an optical element configured to interact with the pulsed light beam emitted from the optical source.

15. The method of claim 14 , wherein the second, distinct actuatable apparatus is altered only when the optical element is not interacting with the pulsed light beam.

16. The method of claim 14 , wherein altering the second, distinct actuatable apparatus comprises moving the optical element relative to a path of the pulsed light beam.

17. The method of claim 10 , wherein the first actuatable apparatus is associated with a target operating point that is between the upper limit and the lower limit, and determining a location of the operating point of the first actuatable apparatus between the upper limit and the lower limit comprises comparing the indication of the operating point to the target operating point.

18. The method of claim 17 , wherein altering the second, distinct actuatable apparatus to change the first actuatable apparatus to the unsaturated state comprises adjusting the operating point of the first actuatable apparatus to be:
closer to the target operating point; or
between a deactivation limit and the target operating point, the deactivation

Assignees

• Cymer LLC

Inventors

• O'Brien Kevin M
• Ahlawat Rahul

Classifications

• H01S3/134

  in gas lasers · CPC title

• H01S3/125

  using rotating prisms · CPC title

• H01S3/104

  in gas lasers · CPC title

• H01S3/1003 Primary

  tunable optical elements, e.g. acousto-optic filters, tunable gratings · CPC title

• G03F7/70141 Primary

  Illumination system adjustment, e.g. adjustments during exposure or alignment during assembly of illumination system · CPC title