Target expansion rate control in an extreme ultraviolet light source

Patent metadata

Field	Value
Publication number	US-10674591-B2
Application number	US-201916391890-A
Country	US
Kind code	B2
Filing date	Apr 23, 2019
Priority date	Aug 12, 2015
Publication date	Jun 2, 2020
Grant date	Jun 2, 2020

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;
interacting a first beam of radiation with the target material to deliver energy to the target material including modifying a geometric distribution of the target material to form a modified target;
interacting a second beam of radiation with the modified target, the second beam of radiation converting at least part of the modified target to plasma that emits EUV light;
measuring a spatial aspect of the modified target with a first measurement system and measuring a spatial aspect of the modified target with a second measurement system; and
controlling a beam of radiation based on the measurements from the first and second measurement systems.

2. The method of claim 1 , wherein measuring the spatial aspect of the modified target comprises measuring one or more of a size, a position, and an orientation of the modified target.

3. The method of claim 2 , wherein measuring one or more of a size, a position, and an orientation of the modified target includes measuring the orientation of the modified target and measuring the orientation of the modified target comprises measuring an angle of the modified target relative to a direction that lies in an XY plane, the XY plane being perpendicular to the direction of the second beam of radiation.

4. The method of claim 2 , further comprising determining a distance between the target material and an axis of the first beam of radiation along a direction that is transverse to the direction of the first beam of radiation and based on the measured orientation of the modified target.

5. The method of claim 2 , further comprising determining a distance between the target material and a beam waist of the first beam of radiation along a longitudinal direction of the first beam of radiation and based on the measured size of the modified target.

6. The method of claim 5 , wherein controlling the beam of radiation comprises controlling an energy of the first beam of radiation to compensate for an error in the longitudinal placement of a position of the target material relative to the beam waist of the first beam of radiation.

7. The method of claim 2 , wherein measuring one or more of a size, a position, and an orientation of the modified target includes measuring the size of the modified target and measuring the size of the modified target comprises measuring an expanse of the modified target.

8. The method of claim 1 , wherein controlling the beam of radiation comprises adjusting one or more properties of the first beam of radiation.

9. The method of claim 1 , wherein controlling the beam of radiation comprises controlling an amount of radiant exposure delivered to the target material from the first beam of radiation.

10. The method of claim 1 , wherein controlling the beam of radiation comprises controlling a unit area of surface of target material exposed to or intercepted by the first beam of radiation.

11. The method of claim 1 , wherein measuring the spatial aspect of the modified target comprises using a shadowgraph technique that includes a pulsed backlighting illumination and a camera.

12. The method of claim 1 , wherein interacting the first beam of radiation with the target material comprises overlapping the target material with an area of the first beam of radiation.

13. The method of claim 1 , wherein measuring the spatial aspect of the modified target comprises measuring the spatial aspect of the modified target before the second beam of radiation interacts with the modified target.

14. The method of claim 1 , wherein controlling the beam of radiation comprises adjusting an energy content of a pulse of the first beam of radiation including one or more of adjusting a width of the pulse, adjusting a duration of the pulse, and adjusting an average power within the pulse.

15. 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 a target axis according to an expansion rate, the target axis not parallel with an optical axis of the second beam of radiation.

16. The method of claim 1 , wherein the modified target has a disk shape, and an angular orientation of the disk shape depends on a position of the first beam of radiation as it interacts with the target material.

17. The method of claim 1 , wherein controlling the beam of radiation comprises controlling an interaction between the first beam of radiation and the target material.

18. The method of claim 17 , wherein controlling the interaction between the first beam of radiation and the target material comprises one or more of:
steering the first beam of radiation to intercept the target material; and
adjusting the timing of the first beam of radiation to intercept the target material.

19. An apparatus comprising:
a chamber that defines an initial target location configured to receive a first beam of radiation and a target location configured to receive 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 arrangement configured to:
interact the first beam of radiation with the target material in the initial target location to deliver energy to the target material and modify a geometric distribution of the target material to form a modified target; and
interact the second beam of radiation with the modified target in the target location to convert at least part of the modified target to plasma that emits EUV light;

two measurement systems, each measurement system configured to measure a spatial aspect of the modified target; and
a control system connected to the target material delivery system, the optical arrangement, and the measurement systems, the control system configured to receive measurement data from the two measurement systems and to send one or more signals to the optical arrangement to control a beam of radiation based on the received measurement data.

20. The apparatus of claim 19 , wherein each measurement system is configured to measure the spatial aspect of the modified target by measuring one or more of a size, a position, and an orientation of the modified target.

21. The apparatus of claim 19 , wherein each measurement system includes a backlighting illuminator and a camera.

22. The apparatus of claim 21 , wherein the camera is a charged-coupled device camera.

23. The apparatus of claim 19 , wherein the optical arrangement comprises an optical source configured to produce the first beam of radiation and the second beam of radiation, and an optical steering system configured to steer the first beam of radiation toward the initial target location and to steer the second beam of radiation toward the target location.

24. The apparatus of claim 22 , wherein the optical steering system comprises a focusing apparatus configured to focus the first beam of radiation at or near the initial target location and to focus the second beam of radiation at or near the target location.

25. The apparatus of claim 19 , further comprising a beam adjustment system in communication with the optical arrange

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