Target expansion rate control in an extreme ultraviolet light source

Patent metadata

Field	Value
Publication number	US-10314153-B2
Application number	US-201715724104-A
Country	US
Kind code	B2
Filing date	Oct 3, 2017
Priority date	Aug 12, 2015
Publication date	Jun 4, 2019
Grant date	Jun 4, 2019

Abstract

A method includes 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; 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 controlling 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 energies.

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;
measuring a size of the modified target;
analyzing the measured size of the modified target; and
controlling an amount of radiant exposure delivered to the target material from the first beam of radiation based on the analysis of the measured size of the modified target to within a predetermined range of radiant exposures.

2. The method of claim 1 , wherein measuring the size of the modified target comprises using a shadowgraph technique.

3. The method of claim 1 , wherein measuring the size of the modified target comprises measuring the size of the modified target before the second beam of radiation converts at least part of the modified target to plasma.

4. The method of claim 1 , further comprising estimating an expansion rate of the modified target,
wherein controlling the amount of radiant exposure delivered to the target material from the first beam of radiation is based on the analysis of both the measured size of the modified target and the estimated expansion rate of the modified target.

5. The method of claim 1 , further comprising measuring the position of the target material.

6. The method of claim 5 , wherein measuring the position of the target material comprises measuring the position of the target material relative to a beam waist of the first beam of radiation.

7. The method of claim 6 , wherein measuring the position of the target material comprises measuring the position of the target material along a direction that is parallel with a beam axis of the first beam of radiation.

8. The method of claim 5 , wherein controlling the amount of radiant exposure delivered to the target material from the first beam of radiation is based on the analysis of both the measured size of the modified target and the measured position of the target.

9. The method of claim 5 , wherein the modified target has a disk shape, and an angular orientation of the disk shape of the modified target depends on the position of the first beam of radiation as it strikes the target material.

10. The method of claim 5 , wherein measuring the position of the target material comprises measuring the position along two or more non-parallel directions.

11. The method of claim 1 , wherein measuring the size of the modified target comprises measuring an expanse of the modified target along a direction perpendicular to a direction of the second beam of radiation.

12. The method of claim 11 , further comprising measuring an orientation of the modified target.

13. The method of claim 1 , further comprising measuring an orientation of the modified target.

14. 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 delivery system configured to provide target material to the initial target location, the target material comprising a material that emits extreme ultraviolet (EUV) light when converted to plasma;
an optical steering system configured to:
direct a first beam of radiation from an optical source toward the initial target location to deliver energy to the target material to modify a geometric distribution of the target material to form a modified target, and
direct a second beam of radiation from the optical source toward the target location to convert at least part of the modified target to plasma that emits EUV light;

a measurement system configured to measure a size of the modified target; and
a control system connected to the target material delivery system, the optical source, the optical steering system, and the measurement system, wherein the control system is configured to:
receive the measured size from the measurement system;
analyze the received measured size; and
send one or more signals to the optical source to control an amount of radiant exposure delivered to the target material from the first beam of radiation based on the analysis of the measured size.

15. The apparatus of claim 14 , wherein the measurement system includes a pulsed backlighting illuminator and a camera.

16. The apparatus of claim 15 , wherein the measurement system employs a shadowgraph technique.

17. The apparatus of claim 14 , further comprising another measurement system configured to measure a position of the target material relative to a target position.

18. The apparatus of claim 17 , wherein the control system is configured to receive the measured position from the other measurement system; analyze the received measured position; and send one or more signals to the optical source to control the amount of radiant exposure delivered to the target material from the first beam of radiation based on the analysis of the measured size and the analysis of the measured position.

19. The apparatus of claim 17 , wherein the other measurement system is configured to measure the position of the target material along two or more non-parallel directions.

20. The apparatus of claim 17 , wherein the other measurement system is configured to measure the position of the target material relative to a beam waist of the first beam of radiation.

21. The apparatus of claim 17 , wherein the other measurement system is configured to measure the position, along a direction that is parallel with a beam axis of the first beam of radiation, of the target material.

22. The apparatus of claim 14 , wherein the optical source comprises:
a first dedicated sub-system that produces the first beam of radiation; and
a second dedicated sub-system that produces the second beam of radiation, the second dedicated sub-system being separate from the first dedicated sub-system within the optical source.

23. The apparatus of claim 22 , further comprising a beam delivery system having respective subsystems through which each of the first and second beams of radiation travel so that the first and second beams of radiation follow two separate paths on the way to the respective first and second target locations.

24. 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;
measuring a set of distinct characteristics associated with one or more of the target material and the modified target relative to the first beam of radiation;
analyzing each of the measured characteristics in the set and determining how the first beam of radiation interacts with the target material to form the modified target based on the combined analysis of each of the measured characteristics; and
controlling an amoun

Assignees

• Asml Netherlands Bv

Inventors

• Riggs Daniel Jason
• Rafac Robert Jay

Classifications

• H05G2/008 Primary

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

• H05G2/0027

  Arrangements for controlling the supply; Arrangements for measurements · CPC title

• H05G2/0088 Primary

  for preconditioning the plasma generating material · CPC title