Vuv laser-sustained plasma light source with long-pass filtering

Patent metadata

Field	Value
Publication number	US-2024276625-A1
Application number	US-202418438165-A
Country	US
Kind code	A1
Filing date	Feb 9, 2024
Priority date	Feb 14, 2023
Publication date	Aug 15, 2024
Grant date	—

Abstract

A laser-sustained broadband light source is disclosed. The light source may include a gas containment structure containing a mixture of a first noble gas and a second noble gas. The light source may include a laser pump source to generate an optical pump to sustain a plasma within the gas containment structure. The first noble gas absorbs broadband light within a first wavelength band and a second wavelength band. The light source may include a filter positioned within the gas containment structure and configured to absorb the broadband light emitted by the plasma having a wavelength below a selected wavelength threshold. The absorption of broadband light by the first noble gas and the filter provide long-pass filtering of broadband light below the selected wavelength to protect one or more downstream optical elements from damage.

First claim

1 . A laser-sustained broadband light source comprising:
a gas containment structure containing a mixture of a first noble gas and a second noble gas, a laser pump source configured to generate an optical pump to sustain a plasma within the gas containment structure, wherein the plasma generates broadband light, wherein the first noble gas absorbs a portion of the broadband light within a first wavelength band and a second wavelength band; and a filter positioned within the gas containment structure and configured to absorb a portion of the broadband light emitted by the plasma having a wavelength below a selected wavelength threshold, wherein absorption of broadband light by the first noble gas and the filter provide long-pass filtering of broadband light below the selected wavelength threshold to protect one or more downstream optical elements from damage.

2 . The broadband light source of claim 1 , wherein the absorption of broadband light at the first wavelength by the first noble gas protects the filter from degradation.

3 . The broadband light source of claim 1 , wherein a transmission edge of the long-pass filtering is tunable via adjustment of a partial pressure of the first noble gas within the gas containment structure.

4 . The broadband light source of claim 3 , wherein the transmission edge shifts to larger wavelength as the partial pressure of the first noble gas is increased.

5 . The broadband light source of claim 1 , wherein the first noble gas comprises at least one of krypton or xenon.

6 . The broadband light source of claim 1 , wherein the second noble gas comprises argon.

7 . The broadband light source of claim 1 , wherein the filter is formed from at least one of CaF 2 or sapphire.

8 . The broadband light source of claim 1 , wherein the first noble gas comprises krypton, the second noble gas comprises argon, and the filter is formed from CaF 2 .

9 . The broadband light source of claim 1 , wherein the first noble gas comprises xenon, the second noble gas comprises argon, and the filter is formed from sapphire.

10 . The broadband light source of claim 1 , wherein filter comprises at least one of a sheet or tube.

11 . The broadband light source of claim 1 , further comprising:
a collection optical element configured to collect at least a portion of the broadband light emitted from the plasma and direct the portion of the broadband light to the one or more downstream optical elements.

12 . The broadband light source of claim 11 , wherein the collection optical element comprises at least one of a mirror or lens.

13 . The broadband light source of claim 12 , wherein the collection optical element comprises a reflector assembly.

14 . The broadband light source of claim 13 , wherein the collection optical element comprises an elliptical reflector assembly.

15 . The broadband light source of claim 13 , wherein the collection optical element comprises a composite reflector assembly comprising an elliptical reflector assembly and a hemispherical retroreflector.

16 . The broadband light source of claim 1 , wherein the one or more downstream optical elements are formed from MgF 2 .

17 . The broadband light source of claim 1 , wherein the one or more downstream optical elements comprise at one of one or more transmissive optical elements or one or more reflective optical elements.

18 . The broadband light source of claim 17 , wherein the one or more downstream optical elements comprise at least one of a window, a lens, or a mirror.

19 . A characterization system comprising:
a broadband light source comprising:
a gas containment structure containing a mixture of a first noble gas and a second noble gas,
a laser pump source configured to generate an optical pump to sustain a plasma within the gas containment structure, wherein the plasma generates broadband light;
wherein the first noble gas absorbs a portion of the broadband light within a first wavelength band and a second wavelength band;
a filter positioned within the gas containment structure and configured to absorb a portion of the broadband light emitted by the plasma having a wavelength below a selected wavelength threshold, wherein absorption of broadband light by the first noble gas and the filter provide long-pass filtering of broadband light below the selected wavelength threshold to protect one or more downstream optical elements from damage; and
a collection optical element configured to collect broadband light emitted from the plasma and direct the broadband light to the one or more downstream optical elements;
a set of illumination optics configured to direct broadband light from the broadband light source to one or more samples; a set of collection optics configured to collect light emanating from the one or more samples; and a detector assembly.

20 . The characterization system of claim 19 , wherein the absorption of broadband light at the first wavelength by the first noble gas protects the filter from degradation.

21 . The characterization system of claim 19 , wherein a transmission edge of the long-pass filtering is tunable via adjustment of a partial pressure of the first noble gas within the gas containment structure.

22 . The characterization system of claim 21 , wherein the transmission edge shifts to larger wavelength as the partial pressure of the first noble gas is increased.

23 . The characterization system of claim 19 , wherein the first noble gas comprises at least one of krypton or xenon.

24 . The characterization system of claim 19 , wherein the second noble gas comprises argon.

25 . The characterization system of claim 19 , wherein the filter is formed from at least one of a CaF 2 or sapphire filter.

26 . The characterization system of claim 19 , wherein the first noble gas comprises krypton, the second noble gas comprises argon, and the filter is formed from CaF 2 .

27 . The characterization system of claim 19 , wherein the first noble gas comprises xenon, the second noble gas comprises argon, and the filter is formed from sapphire.

28 . The characterization system of claim 19 , wherein filter comprises at least one of a sheet or tube.

29 . The characterization system of claim 19 , wherein the collection optical element comprises at least one of a mirror or lens.

30 . The characterization system of claim 29 , wherein the collection optical element comprises a reflector assembly.

31 . The characterization system of claim 30 , wherein the collection optical element comprises an elliptical reflector assembly.

32 . The characterization system of claim 30 , wherein the collection optical element comprises a composite reflector assembly comprising an elliptical reflector assembly and a hemispherical retroreflector.

33 . The characterization system of claim 19 , wherein the one or more downstream optical elements are formed from MgF 2 .

34 . The characterization system of claim 19 , wherein the one or more downstream optical elements comprise at one of one or more transmissive optical elements or one or more reflective optical elements.

35 . The characterization system of claim 19 , wherein the one or more downstream optical elements comprise at least one of a windo

Assignees

• Kla Corp

Inventors

• Bezel Ilya
• Casey Patrick

Classifications

• H01J61/40

  by light filters; by coloured coatings in or on the envelope · CPC title

• H01J65/04 Primary

  Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating {plasma display panels} · CPC title

• H05G2/008 Primary

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

• H01J61/16 Primary

  having helium, argon, neon, krypton, or xenon as the principle constituent · CPC title

• H01J61/26

  Means for absorbing or adsorbing gas, e.g. by gettering; Means for preventing blackening of the envelope · CPC title