Variable Radius Mirror Dichroic Beam Splitter Module for Extreme Ultraviolet Source

Patent metadata

Field	Value
Publication number	US-2016174351-A1
Application number	US-201514804976-A
Country	US
Kind code	A1
Filing date	Jul 21, 2015
Priority date	Dec 16, 2014
Publication date	Jun 16, 2016
Grant date	—

Abstract

A laser produced plasma extreme ultraviolet laser source comprising at least one variable radius mirror. The at least one variable radius mirror to adjust a beam diameter of a main pulse at a specified distance from a pre-pulse focal plane, where the pre-pulse radiates droplets into target droplets and the main pulse radiates the target droplets into a plasma state to generate the extreme ultraviolet radiation.

First claim

1 . An extreme ultraviolet radiation source comprising;
a droplet generator to provide a droplet; at least one laser source to provide a pre-pulse to irradiate the droplet so as to create a target droplet, the pre-pulse associated a pre-pulse focal plane, and to provide a main pulse to irradiate the target droplet into a plasma state, the main pulse associated with a main pulse focal plane; a dichroic splitter module to focus the pre-pulse and the main pulse, the dichroic splitter module comprising at least one variable radius mirror; and a controller coupled to the at least one variable radius mirror to adjust a radius of curvature of the at least one variable radius mirror to adjust a distance between the pre-pulse focal plane and the main pulse focal plane of the main pulse.

2 . The extreme ultraviolet radiation source of claim 1 , the controller further setting the radius of curvature of the at least one variable radius mirror to an initial value based upon a desired value for a beam diameter of the main pulse at a specified distance from the pre-pulse focal plane.

3 . The extreme ultraviolet radiation source of in claim 2 , the controller further to
operate the at least one laser source to provide the main pulse based with the radius of curvature set to the initial value; measure the main pulse with a wavefront sensor to provide a measured value corresponding to the beam diameter of the main pulse at the specified distance from the pre-pulse focal plane; and adjust the radius of curvature of the at least one variable radius mirror based upon the initial value and the measured value.

4 . The extreme ultraviolet radiation source of in claim 2 , wherein to set the radius of curvature of the at least one variable radius mirror includes to set a pressure of a fluid applied to the at least one variable radius mirror.

5 . The extreme ultraviolet radiation source of in claim 1 , the at least one laser source comprising:
a first laser source to provide the pre-pulse; and a second laser source to provide the main pulse.

6 . The extreme ultraviolet radiation source of in claim 1 , the dichroic splitter module further comprising:
a first dichroic splitter to reflect the main pulse to the at least one variable radius mirror; and a second dichroic splitter to reflect the main pulse toward the target droplet after the main pulse has been reflected by the at least one variable radius mirror.

7 . A method for providing a laser beam to a chamber configured for generating EUV light, comprising:
propagating a pre-pulse through a dichroic splitter module toward the chamber, the pre-pulse having a pre-pulse focal plane within the chamber, the dichroic splitter module comprising a first dichroic splitter, a second dichroic splitter, and a variable radius mirror having a radius of curvature; propagating a main pulse through the dichroic splitter module toward the chamber, the propagating the main pulse through the dichroic splitter module comprising reflecting the main pulse with the variable radius mirror and reflecting the main pulse with the second dichroic splitter toward the chamber, the main pulse having a beam diameter at a specified distance from the pre-pulse focal plane; measuring the main pulse to provide a set of values indicative of the beam diameter at the specified distance for a set of values indicative of the radius of curvature of the variable radius mirror; and storing in a memory a data structure indicative of the set of values indicative of the beam diameter and the set of values indicative of the radius of curvature of the variable radius mirror, the data structure providing a one-to-one mapping of the set of values indicative of the beam diameter to the set of values indicative of the radius of curvature of the variable radius mirror.

8 . The method of in claim 7 , further comprising:
setting the radius of curvature of the variable radius mirror to an initial value based on the data structure.

9 . The method of in claim 8 , further comprising:
setting the radius of curvature of the variable radius mirror to the initial value based on a desired value for the beam diameter.

10 . The method of in claim 8 , further comprising:
setting the radius of curvature of the variable radius mirror to the initial value based on a desired power node when converting target droplets in the chamber to a plasma state to provide extreme ultraviolet radiation.

11 . The method of in claim 10 , further comprising:
providing the main pulse at various time instances to a plurality of target droplets in the chamber, the various time instances occurring after the setting the radius of curvature of the variable radius mirror.

12 . The method of in claim 8 , further comprising:
measuring the main pulse with a wavefront sensor to provide a measured value corresponding to the beam diameter of the main pulse at the specified distance from the pre-pulse focal plane; and adjusting the radius of curvature of the at least one variable radius mirror based upon the initial value of the radius of curvature and the measured value.

13 . The method of in claim 12 , further comprising:
providing the main pulse at various time instances to a plurality of target droplets in the chamber, the various time instances occurring after the adjusting the radius of curvature of the at least one variable radius mirror.

14 . A method for providing a laser beam to a chamber configured for generating EUV light, comprising:
propagating a pre-pulse through a dichroic splitter module toward the chamber, the pre-pulse having a pre-pulse focal plane within the chamber, the dichroic splitter module comprising a first dichroic splitter, a second dichroic splitter, a first variable radius mirror having a first radius of curvature, and a second variable radius mirror having a second radius of curvature; propagating a main pulse through the dichroic splitter module toward the chamber, the propagating the main pulse through the dichroic splitter module comprising reflecting the main pulse with the first dichroic splitter, reflecting the main pulse with the first variable radius mirror and the second variable radius mirror, and reflecting the main pulse with the second dichroic splitter toward the chamber, the main pulse having a beam diameter at a specified distance from the pre-pulse focal plane; measuring the main pulse to provide a family of sets of values indicative of the beam diameter at the specified distance for a family of sets of values indicative of the first radius of curvature of the first variable radius mirror, each set of values indicative of the beam diameter and each set of values indicative of the first radius of curvature indexed by a set of values indicative of the second radius of curvature of the second variable radius mirror; and storing in a memory a data structure indicative of the family of sets of values indicative of the beam diameter and the family of sets of values indicative of the first radius of curvature of the first variable radius mirror.

15 . The method of in claim 14 , wherein the family of sets of values indicative of the first radius of curvature of the first variable radius mirror consists of one set of values indicative of the first radius of curvature of the first variable radius mirror.

16 . The method of in claim 14 , wherein the data structure is indicative of a family of one-to-one mappings, each one-to-one mapping in the family of one-to-one mappings between a set of values in the family of sets of values indicative of the beam diameter and a set of values in the fa

Assignees

• Asml Netherlands Bv

Inventors

• Zhang Kevin W
• Purvis Michael
• Rafac Robert J
• Schafgans Alexander

Classifications

• G02B26/0825

  the reflecting element being a flexible sheet or membrane, e.g. for varying the focus (flexible mirrors for cosmetic use A45D42/24) · CPC title

• G02B27/141

  using dichroic mirrors · CPC title

• G01J11/00

  Measuring the characteristics of individual optical pulses or of optical pulse trains · CPC title

• H05G2/0088

  for preconditioning the plasma generating material · CPC title

• H05G2/0086 Primary

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