Method of and apparatus for extending electrode life in a laser chamber

Patent metadata

Field	Value
Publication number	US-11777271-B2
Application number	US-201816757553-A
Country	US
Kind code	B2
Filing date	Oct 9, 2018
Priority date	Oct 24, 2017
Publication date	Oct 3, 2023
Grant date	Oct 3, 2023

Abstract

Disclosed are methods of and apparatus for extending a useful lifetime of a laser discharge chamber in which a polarity of an electrode positioned at a fixed position within the chamber is caused to be positive with respect to the polarity of a second electrode defining a discharge gap with the first electrode and the first electrode is made of a material that forms an erosion resistant surface when the first electrode is used and an anode. Also disclosed is an arrangement in which a first electrode is positionable with respect a second electrode defining a discharge gap with the second electrode and the position of the first electrode controlled to maintain the width of the gap within a predetermined range.

First claim

What is claimed is:

1. A laser comprising:
a discharge chamber;
a first electrode positioned at least partially within the discharge chamber;
a second electrode positioned at least partially within the discharge chamber, the first electrode having a first discharge surface and the second electrode having a second discharge surface, the first discharge surface and the second discharge surface being arranged to confront one another across a gap;
a motor mechanically coupled to the second electrode to position the second discharge surface to control a width of the gap; and
a controller in signal communication with the motor and adapted to control the motor to make the width of the gap substantially equal to an original gap width,
wherein a polarity of the first electrode is positive with respect to a polarity of the second electrode so that the first electrode functions as an anode during a discharge in the discharge chamber.

2. A laser as claimed in claim 1 wherein a position of the first electrode is fixed with respect to the discharge chamber.

3. A laser as claimed in claim 1 wherein the first electrode comprises a material that forms an erosion resistant coating when the first electrode functions as an anode during a discharge in the discharge chamber.

4. A laser as claimed in claim 1 further comprising an erosion resistant coating applied to the first electrode.

5. A laser as claimed in claim 1 wherein the controller develops the control signal based at least in part on a magnitude of a voltage differential between the first electrode and the second electrode during discharge required to maintain substantially constant output power.

6. A laser as claimed in claim 1 further comprising a detector connected to the controller for measuring a width of the gap and providing a signal indicative of the width wherein the controller develops the control signal based at least in part on the width as measured by the detector.

7. A laser as claimed in claim 2 further comprising a power supply electrically connected to the first electrode and the second electrode for supplying a plurality of pulses to at least one of the first electrode and the second electrode, the power supply including a commutator module and a compression head module, wherein the commutator module and a compression head module are modified such that the polarity of the first electrode is positive with respect to a polarity of the second electrode so that the first electrode functions as an anode during the pulses.

8. A laser as claimed in claim 1 wherein the controller develops the control signal based at least in part on a number of discharges that have occurred in the discharge chamber.

9. A laser comprising:
a discharge chamber;
a first electrode positioned at least partially within the discharge chamber and fixed with respect to the discharge chamber;
a second electrode positioned at least partially within the discharge chamber, the first electrode having a first discharge surface and the second electrode having a second discharge surface, the first discharge surface and the second discharge surface being arranged to confront one another across a gap, a polarity of the first electrode being positive with respect to a polarity of the second electrode so that the first electrode functions as an anode during a discharge in the discharge chamber, the first electrode comprising a material that forms a corrosion resistant coating when the first electrode functions as an anode during a discharge in the discharge chamber;
a motor mechanically coupled to the second electrode to position the second discharge surface to control a width of the gap; and
a controller connected to the motor wherein the controller supplies a control signal to the motor to make the width of the gap substantially equal to an original gap width.

10. A laser as claimed in claim 9 wherein the controller develops the control signal based at least in part on a number of discharges that have occurred in the discharge chamber.

11. A laser comprising:
a discharge chamber;
a first electrode positioned at least partially within the discharge chamber and fixed with respect to the discharge chamber;
a second electrode positioned at least partially within the discharge chamber, the first electrode having a first discharge surface and the second electrode having a second discharge surface, the first discharge surface and the second discharge surface being arranged to confront one another across a gap;
a motor mechanically coupled to the second electrode to position the second discharge surface to control a width of the gap; and
a controller connected to the motor wherein the controller supplies a control signal to make the width of the gap substantially equal to an original gap width,
a polarity of the first electrode being positive with respect to a polarity of the second electrode so that the first electrode functions as an anode during a discharge in the discharge chamber, the first electrode comprising a material that forms an erosion resistant coating when the first electrode functions as an anode during a discharge in the discharge chamber.

12. A laser as claimed in claim 11 wherein the controller develops the control signal based at least in part on a magnitude of a voltage differential between the first electrode and the second electrode during discharge.

13. A laser as claimed in claim 11 further comprising a detector connected to the controller for measuring a width of the gap and providing a signal indicative of the width wherein the controller develops the control signal based at least in part on the width as measured by the detector.

14. A laser as claimed in claim 11 wherein the controller develops the control signal based at least in part on a number of discharges that have occurred in the discharge chamber.

15. A method of controlling operation of a laser, the laser including a discharge chamber and a first electrode and a second electrode spaced apart by a gap, the second electrode being positionable to establish a width of the gap, the method comprising the steps of:
operating the laser by causing a discharge to occur in the discharge chamber between the first electrode and the second electrode with a polarity of the first electrode being positive with respect to a polarity of the second electrode so that the first electrode functions as an anode during a discharge in the discharge chamber;
measuring a width of the gap; and
automatically controlling a position of the second electrode to make the width of the gap substantially equal to an original gap width.

16. A method of operating a laser including a first electrode and a second electrode, the first electrode and the second electrode spaced apart by a gap, the method comprising:
causing a first discharge to occur in the discharge chamber between the first electrode and the second electrode with a polarity of the first electrode being positive with respect to the second electrode so that the first electrode functions as an anode during the first discharge; and
causing a second discharge to occur in the discharge chamber between the first electrode and the second electrode with the polarity of the second electrode being positive with respect to the first electrode so that the second electrode functions as an anode during the second discharge.

17. The method as in claim 16 , wherein causing a first discharge to occur in the discharge chamber causes a first erosion resistant layer to form on the first electrode functioning as the anode.

18. The metho

Assignees

• Cymer LLC

Inventors

• Duffey Thomas Patrick
• Melcher Paul Christopher
• Gillespie Walter Dale

Classifications

• H01S3/0388 Primary

  Compositions, materials or coatings · CPC title

• H01S3/0971 Primary

  transversely excited (H01S3/0975 takes precedence) · CPC title

• H01S3/09705 Primary

  with particular means for stabilising the discharge · CPC title

• H01S3/225

  comprising an excimer or exciplex · CPC title

• H01S3/0381

  Anodes or particular adaptations thereof · CPC title