Radiation system and optical device

Patent metadata

Field	Value
Publication number	US-10359710-B2
Application number	US-201615766225-A
Country	US
Kind code	B2
Filing date	Oct 25, 2016
Priority date	Nov 11, 2015
Publication date	Jul 23, 2019
Grant date	Jul 23, 2019

Abstract

A radiation system comprises a fuel emitter configured to provide fuel to a plasma formation region, a laser arranged to provide a laser beam at the plasma formation region incident on the fuel to generate a radiation emitting plasma, and a reflective or transmissive device (30) arranged to receive radiation emitted by the plasma and to reflect or transmit at least some of the received radiation along a desired path, wherein the reflective or transmissive device comprises a body configured to reflect and/or transmit said at least some of the radiation, and selected secondary electron emission (SEE) material (34) arranged relative to the body such as to emit secondary electrons in response to the received radiation, thereby to clean material from a surface of the device.

First claim

The invention claimed is:

1. A radiation system comprising:
a fuel emitter configured to provide fuel to a plasma formation region;
a laser configured to provide a laser beam at the plasma formation region incident on the fuel to generate a radiation emitting plasma; and
a reflective or transmissive device configured to receive radiation emitted by the radiation emitting plasma and to reflect or transmit at least some of the received radiation along a desired path, wherein the reflective or transmissive device comprises:
a body configured to reflect or transmit the at least some of the received radiation; and
secondary electron emission (SEE) material arranged relative to the body such as to emit secondary electrons in response to the at least some of the received radiation, thereby to clean material from a surface of the reflective or transmissive device.

2. The radiation system of claim 1 , wherein:
the SEE material comprises an SEE layer that at least partly covers a surface of the body;
the body comprises a layered structure that is configured such that reflection of the at least some of the received radiation by the layered structure causes a standing wave to be formed in the reflective or transmissive device; and
the layered structure and the SEE layer are arranged such that in operation a maximum of the standing wave is formed in the SEE layer.

3. The radiation system of claim 2 , wherein the layered structure comprises a multi-layer mirror.

4. The radiation system of claim 1 , wherein the SEE material comprises a cap layer that at least partly covers a surface of the body.

5. The radiation system of claim 1 , wherein the SEE material is located at or near an edge of the reflective or transmissive device.

6. The radiation system of claim 5 , wherein:
the body comprises a layered structure configured to reflect the at least some of the received radiation, and
at least some of the SEE material located at or near the edge of the reflective or transmissive device is beyond a boundary of the layered structure.

7. The radiation system of claim 1 , further comprising a component comprising SEE material positioned adjacent to the reflective or transmissive device.

8. The radiation system of claim 1 , wherein:
the reflective or transmissive device is a collector, and
the SEE material comprises a coating on a rim of the collector.

9. The radiation system of claim 1 , wherein, for received radiation having a wavelength in a range of 10 nm to 100 nm, the SEE material has a secondary electron yield (SEY) of greater than 0.01 electron per photon, greater than 0.05 electrons per photon, or greater than 0.1 electrons per photon.

10. The radiation system of claim 1 , wherein the SEE material has a band gap energy of greater than 1 eV, greater than 3 eV, or greater than 5 eV.

11. The radiation system of claim 1 , wherein the SEE material has an electron affinity less than 4 eV, less than 1 eV, or less than 0 eV.

12. The radiation system of claim 1 , wherein the SEE material comprises an insulator or semiconductor.

13. The radiation system of claim 1 , wherein the SEE material comprises at least one of diamond, H-terminated diamond, ZrO, ZrN, TiO2, Al2O3, or quartz.

14. The radiation system of claim 1 , wherein the radiation comprises EUV radiation.

15. The radiation system of claim 1 , wherein the reflective or transmissive device is configured to collect EUV radiation.

16. The radiation system of claim 1 , wherein the material to be cleaned from material from the surface of the reflective or transmissive device comprises tin.

17. The radiation system of claim 1 , further comprising a source of hydrogen for providing hydrogen gas to a surface of the reflective or transmissive device.

18. A reflective and/or transmissive optical device for receiving radiation and reflecting and/or transmitting at least some of the received radiation, the reflective and/or transmissive optical device comprising:
a body configured to reflect and/or transmit the at least some of the received radiation; and
secondary electron emission (SEE) material arranged relative to the body such as to emit secondary electrons in response to the at least some of the received radiation, thereby to clean material from a surface of the reflective and/or transmissive optical device.

19. A radiation source comprising:
a fuel emitter configured to provide fuel to a plasma formation region, wherein plasma is formed in operation when the fuel is subject to laser radiation; and
a reflective and/or transmissive device configured to receive radiation emitted by the plasma and to reflect and/or transmit at least some of the received radiation along a desired path, wherein the reflective and/or transmissive device comprises:
a body configured to reflect and/or transmit the at least some of the received radiation; and
secondary electron emission (SEE) material arranged relative to the body such as to emit secondary electrons in response to the at least some of the received radiation, thereby to clean material from a surface of the reflective and/or transmissive device.

20. A lithographic system comprising:
a lithographic apparatus configured to project a pattern from a patterning device onto a substrate, and
a radiation system configured to provide radiation to the lithographic apparatus, the radiation system comprising:
a fuel emitter configured to provide fuel to a plasma formation region;
a laser configured to provide a laser beam at the plasma formation region incident on the fuel to generate a radiation emitting plasma that produces the radiation; and
a reflective or transmissive device configured to receive the radiation and to reflect or transmit at least some of the received radiation along a desired path, wherein the reflective or transmissive device comprises:
a body configured to reflect or transmit the at least some of the received radiation; and
secondary electron emission (SEE) material arranged relative to the body such as to emit secondary electrons in response to the at least some of the received radiation, thereby to clean material from a surface of the reflective or transmissive device.

21. A method comprising:
providing fuel to a plasma formation region;
providing a laser beam at the plasma formation region incident on the fuel to generate a radiation emitting plasma;
receiving, by a reflective and/or transmissive device, radiation emitted by the plasma;
reflecting or transmitting along a desired path, by a body of the reflective and/or transmissive device, at least some of the received radiation; and
emitting secondary electrons from secondary electron emission (SEE) material in response to the at least some of the received radiation thereby to clean material from a surface of the reflective and/or transmissive device.

Assignees

• Asml Netherlands Bv

Inventors

• Schimmel Hendrikus Gijsbertus
• Huijbregtse Jeroen Marcel
• Van Kampen Maarten
• Van Zwol Pieter-Jan

Classifications

• G03F7/70033

  by plasma extreme ultraviolet [EUV] sources · CPC title

• H05G2/00

  Apparatus or processes specially adapted for producing X-rays, not involving X-ray tubes, e.g. involving generation of a plasma (X-ray lasers H01S4/00) · CPC title

• H05G2/001

  Production of X-ray radiation generated from plasma · CPC title

• G03F7/70925

  Cleaning, i.e. actively freeing apparatus from pollutants, e.g. using plasma cleaning · CPC title

• H05G2/005

  Electricity · mapped topic