Stabilizing EUV light power in an extreme ultraviolet light source

Patent metadata

Field	Value
Publication number	US-9713240-B2
Application number	US-201514824147-A
Country	US
Kind code	B2
Filing date	Aug 12, 2015
Priority date	Aug 12, 2015
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

A method includes providing a target material that includes a component that emits extreme ultraviolet (EUV) light when converted to plasma; directing a first beam of radiation toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target; directing a second beam of radiation toward the modified target, the second beam of radiation converting at least part of the modified target to plasma that emits EUV light; controlling a radiant exposure delivered to the target material from the first beam of radiation to within a predetermined range of radiant exposures; and stabilizing a power of the EUV light emitted from the plasma by controlling the radiant exposure delivered to the target material from the first beam of radiation to within the predetermined range of radiant exposures.

First claim

What is claimed is:

1. A method comprising:
providing a target material that comprises a component that emits extreme ultraviolet (EUV) light when converted to plasma;
directing a first beam of radiation toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target;
directing a second beam of radiation toward the modified target, the second beam of radiation converting at least part of the modified target to plasma that emits EUV light;
controlling a radiant exposure delivered to the target material from the first beam of radiation to within a predetermined range of radiant exposures by estimating an expansion rate of the modified target; and
stabilizing a power of the EUV light emitted from the plasma by controlling the radiant exposure delivered to the target material from the first beam of radiation to within the predetermined range of radiant exposures.

2. The method of claim 1 , wherein:
directing the first beam of radiation comprises directing the first beam of radiation through a first set of optical components including one or more first optical amplifiers; and
directing the second beam of radiation comprises directing the second beam of radiation through a second set of optical components including one or more second optical amplifiers;
wherein the first set of optical components are distinct from and separated from the second set of optical components.

3. The method of claim 1 , wherein:
directing the first beam of radiation comprises directing the first beam of radiation through a first set of one or more optical amplifiers; and
directing the second beam of radiation comprises directing the second beam of radiation through a second set of one or more optical amplifiers;
wherein at least one of the optical amplifiers in the first set is in the second set.

4. The method of claim 1 , wherein:
providing the target material comprises providing a droplet of target material; and
modifying the geometric distribution of the target material comprises transforming the droplet of target material into a disk shaped volume of molten metal having a substantially planar surface.

5. The method of claim 1 , wherein:
providing the target material comprises providing a droplet of target material; and
modifying the geometric distribution of the target material comprises transforming the droplet of target material into a mist shaped volume of molten metal particles.

6. The method of claim 1 , wherein the target material is transformed into the modified target in accordance with an expansion rate.

7. The method of claim 1 , wherein controlling the radiant exposure delivered to the target material from the first beam of radiation to within the predetermined range of radiant exposures comprises:
measuring one or more characteristics associated with one or more of the target material and the modified target relative to the first beam of radiation; and
maintaining an amount of radiant exposure delivered to the target material from the first beam of radiation based on the one or more measured characteristics to within a predetermined range of radiant exposures.

8. The method of claim 1 , wherein stabilizing the power of the EUV light emitted from the plasma by controlling the radiant exposure delivered to the target material from the first beam of radiation to within the predetermined range of radiant exposures comprises stabilizing the power of the EUV light while at least a portion of the EUV light emitted from the plasma is exposing a wafer.

9. The method of claim 1 , further comprising:
collecting at least a portion of the emitted EUV light; and
directing the collected EUV light toward a wafer to expose the wafer to the EUV light.

10. The method of claim 1 , wherein modifying the geometric distribution of the target material comprises transforming a shape of the target material into the modified target including expanding the modified target along at least one axis according to an expansion rate.

11. The method of claim 1 , wherein controlling the radiant exposure delivered to the target material from the first beam of radiation to within the predetermined range of radiant exposures comprises adjusting a property of the first beam of radiation.

12. The method of claim 11 , wherein adjusting the property of the first beam of radiation comprises adjusting an energy of the first beam of radiation.

13. A method comprising:
providing a target material that comprises a component that emits extreme ultraviolet (EUV) light when converted to plasma;
directing a first beam of radiation toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target;
directing a second beam of radiation toward the modified target, the second beam of radiation converting at least part of the modified target to plasma that emits EUV light;
controlling a radiant exposure delivered to the target material from the first beam of radiation to within a predetermined range of radiant exposures by maintaining an expansion rate of the modified target; and
stabilizing a power of the EUV light emitted from the plasma by controlling the radiant exposure delivered to the target material from the first beam of radiation to within the predetermined range of radiant exposures.

14. The method of claim 13 , wherein controlling the radiant exposure delivered to the target material from the first beam of radiation to within the predetermined range of radiant exposures comprises adjusting an energy of the first beam of radiation.

15. A method comprising:
providing a target material that comprises a component that emits extreme ultraviolet (EUV) light when converted to plasma;
directing a first beam of radiation toward the target material to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target;
directing a second beam of radiation toward the modified target, the second beam of radiation converting at least part of the modified target to plasma that emits EUV light;
controlling a radiant exposure delivered to the target material from the first beam of radiation to within a predetermined range of radiant exposures by determining whether a feature of the first beam of radiation should be adjusted; and
stabilizing a power of the EUV light emitted from the plasma by controlling the radiant exposure delivered to the target material from the first beam of radiation to within the predetermined range of radiant exposures.

16. The method of claim 15 , wherein controlling the radiant exposure delivered to the target material from the first beam of radiation to within the predetermined range of radiant exposures comprises adjusting the feature of the first beam of radiation by adjusting one or more of an energy content of each pulse of the first beam of radiation and an area of the first beam of radiation that interacts with the target material.

17. The method of claim 16 , wherein adjusting the energy content of each pulse of the first beam of radiation comprises adjusting one or more of: a width of each pulse of the first beam of radiation, a duration of each pulse of the first beam of radiation, and a power of each pulse of the first beam of radiation.

18. An apparatus comprising:
a chamber that defines an initial target location that receives a first beam of radiation and a target location that receives a second beam of radiation;
a target material

Assignees

• Asml Netherlands Bv

Inventors

• Riggs Daniel Jason
• Rafac Robert Jay

Classifications

• H05G2/0035

  the material containing metals as principal radiation-generating components · CPC title

• H05G2/0086

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

• H05G2/0084

  Control of the laser beam · CPC title

• H05G2/0088 Primary

  for preconditioning the plasma generating material · CPC title

• H05G2/008 Primary

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