Prolonging optical element lifetime in an euv lithography system

Patent metadata

Field	Value
Publication number	US-2022291591-A1
Application number	US-202217715641-A
Country	US
Kind code	A1
Filing date	Apr 7, 2022
Priority date	Mar 5, 2018
Publication date	Sep 15, 2022
Grant date	—

Abstract

Degradation of the reflectivity of one or more reflective optical elements in a system for generating EUV radiation is reduced by the controlled introduction of a gas into a vacuum chamber containing the optical element. The gas may be added to the flow of another gas such as hydrogen or alternated with the introduction of hydrogen radicals.

First claim

What is claimed is:

1 . Apparatus comprising:
a vacuum chamber; a reflective optical element arranged in the vacuum chamber; a gas distribution system for adding gas to the vacuum chamber, the gas distribution system including an interface for interfacing with a source of oxygen-containing gas; and a gas control system configured to control the gas distribution system to supply the oxygen-containing gas to the vacuum chamber until a partial pressure of the oxygen-containing gas reaches a first value, ceasing supply of the oxygen-containing gas to the vacuum chamber until the partial pressure of the oxygen-containing gas reaches a second value less than the first value, and resuming supply of the oxygen-containing gas to the vacuum chamber until the partial pressure of the oxygen-containing gas reaches a third value greater than the second value.

2 . Apparatus as claimed in claim 1 wherein the reflective optical element comprises a multilayer mirror comprising a capping layer and a plurality of underlying layers, with the capping layer being composed and arranged to protect the underlying layers from damage, the capping layer comprising an oxide.

3 . Apparatus as claimed in claim 2 wherein the oxide comprises a metal oxide.

4 . Apparatus as claimed in claim 1 wherein the oxygen-containing gas comprises H2O2.

5 . Apparatus as claimed in claim 1 wherein the oxygen-containing gas comprises O3.

6 . Apparatus as claimed in claim 1 wherein the oxygen-containing gas is mixed with argon or helium.

7 . Apparatus as claimed in claim 1 further comprising a gas pressure sensor arranged to sense a partial pressure of the oxygen-containing gas in the vacuum chamber and to generate a first signal indicative of the partial pressure to the gas control system, and wherein the gas control system controls supply of the oxygen-containing gas based at least in part on the first signal.

8 . Apparatus as claimed in claim 7 wherein the gas pressure sensor indirectly senses the partial pressure of the oxygen-containing gas by sensing a partial pressure of at least one gas other than the oxygen-containing gas.

9 . Apparatus as claimed in claim 7 wherein the gas pressure sensor is arranged to sense the partial pressure of the oxygen-containing gas proximate to the reflective optical element.

10 . A method of prolonging an operational lifetime of a reflective surface in a vacuum chamber of an EUV source, the method comprising the steps of:
providing a gas supply system operative to supply at least a first gas and a second gas to the vacuum chamber, the second gas comprising oxygen; sensing a partial pressure in the vacuum chamber of at least one of the first gas and the second gas; controlling the gas supply system to supply the second gas based at least in part on the sensed partial pressure.

11 . The method as claimed in claim 10 wherein the sensing step comprises sensing a partial pressure of the first gas.

12 . A method of prolonging an operational lifetime of a reflective surface in a vacuum chamber of an EUV source, the method comprising the steps of:
(a) supplying an oxygen-containing gas to the vacuum chamber; (b) ceasing supplying the oxygen-containing gas to the vacuum chamber when a partial pressure of the oxygen-containing gas reaches a first value; (c) supplying more oxygen-containing gas to the vacuum chamber when the partial pressure of the oxygen-containing gas reaches a second value less than the first value; (d) ceasing supplying the oxygen-containing gas to the vacuum chamber when the partial pressure of the oxygen-containing gas reaches a third value greater than the second value; and (e) repeating steps (c) and (d) to maintain the partial pressure of the oxygen-containing gas between the first value and the second value.

13 . The method as claimed in claim 12 wherein the third value is substantially equal to the first value.

14 . The method as claimed in claim 12 wherein the oxygen-containing gas comprises H2O.

15 . The method as claimed in claim 12 wherein the oxygen-containing gas comprises H2O2.

16 . The method as claimed in claim 12 wherein the oxygen-containing gas comprises O3.

17 . The method as claimed in claim 12 wherein the oxygen-containing gas is mixed with an inert gas.

18 . The method as claimed in claim 12 wherein each of steps (b), (c), and (d) comprises directly sensing a partial pressure of the oxygen-containing gas in the vacuum chamber.

19 . The method as claimed in claim 12 wherein each of steps (b), (c), and (d) comprises sensing a partial pressure of the oxygen-containing gas in the vacuum chamber proximate to the reflective surface.

20 . Apparatus for producing extreme ultraviolet (EUV) radiation, the apparatus comprising:
a vacuum chamber; a collector mirror arranged in the vacuum chamber to have a primary focus at an irradiation region in the vacuum chamber; a gas distribution system for adding gas to the vacuum chamber, the gas distribution system having an interface for interfacing with a source of a mitigation gas that mitigates, by chemical reaction, contamination of the collector mirror, the mitigation gas comprising H2O2; and a gas control system for controlling the gas distribution system, the gas control system having a state in which the mitigation gas from the source of gas is introduced into the interior of the vacuum chamber in a regulated manner by the gas distribution system.

21 . Apparatus as claimed in claim 20 wherein the collector mirror comprises a multilayer mirror comprising a capping layer and a plurality of underlying layers, the capping layer being arranged to protect the underlying layers from damage.

22 . Apparatus as claimed in claim 21 wherein the capping layer comprises an oxide.

23 . Apparatus as claimed in claim 21 wherein the capping layer comprises a nitride or a carbide.

24 . Apparatus as claimed in claim 20 wherein the gas distribution system is configured to add mitigation gas from the source of gas into the vacuum chamber by adding a quantity of mitigation gas to a flow of hydrogen-containing gas.

25 . Apparatus as claimed in claim 20 wherein the gas distribution system is configured to mix the mitigation gas with an inert gas.

Assignees

• Asml Netherlands Bv

Inventors

• Ma Yue
• Kempen Antonius Theodorus Wilhelmus
• Hummler Klaus Martin
• Moors Johannes Hubertus Josephina
• Rommers Jeroen Hubert
• Van De Wiel Hubertus Johannes
• LaForge Andrew David
• Brizuela Fernando
• Wieggers Rob Carlo
• Gomes Umesh Prasad
• Nedanovska Elena
• Korkmaz Celal
• Kim Alexander Downn
• Duarte Rodrigues Nunes Rui Miguel
• Van Dijck Hendrikus Alphonsus Ludovicus
• Van Drent William Peter
• Jonkers Peter Gerardus
• Zhu Qiushi
• Yaghoobi Parham
• Westerlaken Jan Steven Christiaan
• Leenders Martinus Hendrikus Antonius
• Ershov Alexander Igorevich
• Fomenkov Igor Vladimirovich
• Liu Fei
• Jacobs Johannes Henricus Wilhelmus
• Kuznetsov Alexey Sergeevich

Classifications

• H05G2/0094

  Reduction, prevention or protection from contamination; Cleaning · CPC title

• G03F7/70916

  Pollution mitigation, i.e. mitigating effect of contamination or debris, e.g. foil traps · CPC title

• G03F7/70925 Primary

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

• G03F7/70175

  Lamphouse reflector arrangements or collector mirrors, i.e. collecting light from solid angle upstream of the light source · CPC title

• G03F7/70166 Primary

  Capillary or channel elements, e.g. nested extreme ultraviolet [EUV] mirrors or shells, optical fibers or light guides · CPC title