Extreme ultraviolet light generation system

Patent metadata

Field	Value
Publication number	US-9402297-B2
Application number	US-201514724737-A
Country	US
Kind code	B2
Filing date	May 28, 2015
Priority date	Mar 29, 2010
Publication date	Jul 26, 2016
Grant date	Jul 26, 2016

Abstract

An apparatus used with a laser apparatus may include a chamber, a target supply for supplying a target material to a region inside the chamber, a laser beam focusing optical system for focusing a laser beam from the laser apparatus in the region, and an optical system for controlling a beam intensity distribution of the laser beam.

First claim

What is claimed is:

1. An apparatus used with a laser apparatus, the apparatus comprising:
a chamber;
a target supply configured to supply a target to a first region inside the chamber;
a laser beam focusing optical system configured to focus laser beams on the first region,
the laser beams including a pre-pulse laser beam with which the target is irradiated and a main pulse laser beam with which the target is irradiated subsequent to the pre-pulse laser beam;
a laser apparatus configured to generate the pre-pulse laser beam having a pulse duration of less than 1 ns and to generate the main pulse laser beam; and
an intensity distribution control optical system configured to control intensity distribution along a first cross section of the pre-pulse laser beam,
the first cross section being located in the first region, the intensity distribution along the first cross section has a second region in which a variation value C={(Imax−Imin)/(Imax+Imin)}×100(%) is equal to or less than 20%, where Imax is the highest beam intensity in the second region and Imin is the lowest beam intensity in the second region, an area of the second region being larger than an area of a second cross-section of the target, the second cross-section being a maximum cross-section perpendicular to the traveling path of the pre-pulse laser beam.

2. The apparatus according to claim 1 , wherein the diameter of the second region is equal to or larger than the sum of the diameter of the second cross-section and a variation of a position of the target in the first region.

3. The apparatus according to claim 1 , wherein the target is supplied in the form of a droplet.

4. The apparatus according to claim 1 , wherein an area of a third cross-section of the main pulse laser beam in the first region is larger than an area of a fourth cross-section of the target having been irradiated with the pre-pulse laser beam, the fourth cross-section being a maximum cross-section perpendicular to a traveling path of the main pulse laser beam.

5. The apparatus according to claim 4 , wherein the diameter of the third cross-section is equal to or larger than the sum of the diameter of the fourth cross-section and a variation of a position of the target material having been irradiated with the pre-pulse laser beam.

6. The apparatus according to claim 1 , wherein
the pre-pulse laser beam and the main pulse laser beam travel along substantially the same traveling path to enter the chamber.

7. The apparatus according to claim 1 , wherein the intensity distribution control optical system does not control the intensity distribution of the main pulse laser beam.

8. The apparatus according to claim 1 , wherein
the intensity distribution control optical system is included in the laser apparatus configured to generate the pre-pulse laser beam having the second region.

9. The apparatus according to claim 8 , wherein the laser apparatus comprises:
an oscillator comprising an optical resonator and a laser medium, the optical resonator including the intensity distribution control optical system; and
at least one amplifier for amplifying a seed laser light, wherein
the intensity distribution control optical system is one of mirrors of the optical resonator, the one mirror having an aperture for outputting the seed laser light having the second region.

10. The apparatus according to claim 1 , wherein the second region has the highest beam intensity Imax at the periphery of the second region.

11. The apparatus according to claim 1 , wherein the intensity distribution control optical system controls the intensity distribution of the pre-pulse laser beam so that there are multiple peaks within the second region and that a gap between two adjacent peaks is equal to or smaller than a half of diameter of the second cross section.

12. The system according to claim 1 , wherein the laser apparatus is configured to generate the pre-pulse laser beam so that the target having been irradiated with the pre-pulse laser beam is to be diffused in a dome shape.

13. The system according to claim 12 , wherein the target diffused in the dome shape has a first portion where target material is diffused in an annular shape and a second portion which is adjacent to the first portion and in which the target material is diffused in a dome shape, and a density of the target material is higher in the first portion than in the second portion.

14. The system according to claim 13 , wherein the second portion of the target is diffused in the dome shape opposite to a direction in which the pre-pulse laser beam travels.

15. The system according to claim 14 , wherein the first portion of the target is diffused in the annular shape to a direction in which the pre-pulse laser beam travels.

16. The system according to claim 15 , wherein the target diffused in a dome shape further has a third portion surrounded by the first portion, and a density of the target material is higher in the first portion than in the third portion.

17. The system according to claim 16 , wherein the third portion is also surrounded by the second portion, and a density of the target material is higher in the second portion than in the third portion.

18. The system according to claim 17 , wherein the laser apparatus is configured to generate the pre-pulse laser beam having a fluence equal to or higher than 30 J/cm 2 .

Assignees

• Gigaphoton Inc

Inventors

• Wakabayashi Osamu
• Yanagida Tatsuya
• Mizoguchi Hakaru

Classifications

• H05G2/0086 Primary

  Optical arrangements for conveying the laser beam to the plasma generation location · CPC title

• H05G2/003

  the plasma being generated from a material in a liquid or gas state · CPC title

• H05G2/008 Primary

  involving an energy-carrying beam in the process of plasma generation · CPC title