System and method for imaging a sample with an illumination source modified by a spatial selective wavelength filter

Patent metadata

Field	Value
Publication number	US-10616987-B2
Application number	US-201514839338-A
Country	US
Kind code	B2
Filing date	Aug 28, 2015
Priority date	Aug 28, 2015
Publication date	Apr 7, 2020
Grant date	Apr 7, 2020

Abstract

A system for illuminating a sample with a spectrally filtered illumination source includes an illumination source configured to generate a beam of illumination having a first set of wavelengths. In addition, the system includes a wavelength filtering sub-system, a sample stage, an illumination sub-system, a detector, and an objective to focus illumination from the surface of one or more samples and focus the collected illumination to the detector. Further, the wavelength filtering sub-system includes one or more first dispersive elements positioned to introduce spatial dispersion into the beam, a spatial filter element, and one or more dispersive elements positioned to remove spatial dispersion from the beam. The spatial filter element is further positioned to pass at least a portion of the beam including a second set of wavelengths, wherein the second set of wavelengths is a subset of the first set of wavelengths.

First claim

What is claimed is:

1. An ultraviolet illumination source with wavelength selection control, comprising:
an illumination source configured to generate a beam of illumination that includes a first set of wavelengths;
a first set of one or more optical elements, wherein the first set of one or more optical elements includes one or more first dispersive elements positioned to introduce spatial dispersion into the beam to form a set of sub-beams associated with each of the first set of wavelengths;
one or more focusing elements;
a spatial filter element, wherein the spatial filter element is positioned in a plane conjugate to the illumination source, wherein the one or more focusing elements are configured to focus each of the set of sub-beams of the beam onto the spatial filter element, wherein the spatial filter element is configured to pass at least a subset of the sub-beams, wherein the subset of the sub-beams directed from the spatial filter element are associated with a second set of wavelengths, wherein the second set of wavelengths is a subset of the first set of wavelengths, wherein the second set of wavelengths comprises wavelengths in at least one of the extreme ultraviolet spectrum, the deep ultraviolet spectrum, or the vacuum ultraviolet spectrum; and
a second set of one or more optical elements, wherein the second set of one or more optical elements is positioned to collect at least a portion of the beam, wherein the second set of one or more optical elements includes one or more second dispersive elements positioned to remove spatial dispersion from the beam containing the subset of the sub-beams.

2. The ultraviolet illumination source of claim 1 , wherein the spatial filter element comprises an aperture having one or more openings and is positioned such that the sub-beams associated with the second set of wavelengths passes through the one or more openings.

3. The ultraviolet illumination source of claim 1 , wherein the spatial filter element comprises a spatial light modulator.

4. The ultraviolet illumination source of claim 3 , wherein the spatial light modulator includes a deformable mirror.

5. The ultraviolet illumination source of claim 1 , wherein the illumination source comprises a laser-sustained plasma light source.

6. The ultraviolet illumination source of claim 1 , wherein the illumination source comprises a discharge source.

7. The ultraviolet illumination source of claim 1 , wherein at least one of the first set of optical elements or the second set of optical elements includes a cylindrical mirror.

8. The ultraviolet illumination source of claim 1 , wherein at least one of the one or more first dispersive elements or the one or more second dispersive elements includes one or more prisms.

9. The ultraviolet illumination source of claim 8 , wherein the one or more prisms includes one or more prism arrays.

10. The ultraviolet illumination source of claim 1 , wherein at least one of the one or more first dispersive elements or the one or more second dispersive elements includes one or more diffraction gratings.

11. The ultraviolet illumination source of claim 10 , wherein the one or more diffraction gratings includes at least one of a planar diffraction grating or a curved diffraction grating.

12. A system for illuminating a sample with a spectrally filtered illumination source, comprising:
an illumination source configured to generate a beam of illumination that includes a first set of wavelengths;
a wavelength filtering sub-system, comprising:
a first set of one or more optical elements, wherein the first set of one or more optical elements includes one or more first dispersive elements positioned to introduce spatial dispersion into the beam to form a set of sub-beams associated with each of the first set of wavelengths;
one or more focusing elements;
a spatial filter element, wherein the spatial filter element is positioned in a plane conjugate to the illumination source, wherein the one or more focusing elements are configured to focus each of the set of sub-beams of the beam onto the spatial filter element, wherein the spatial filter element is configured to pass at least a subset of the sub-beams, wherein the subset of the sub-beams directed from the spatial filter element are associated with a second set of wavelengths, wherein the second set of wavelengths is a subset of the first set of wavelengths, wherein the second set of wavelengths comprises wavelengths in at least one of the extreme ultraviolet spectrum, the deep ultraviolet spectrum, or the vacuum ultraviolet spectrum; and
a second set of one or more optical elements, wherein the second set of one or more optical elements is positioned to collect at least a portion of the beam, wherein the second set of one or more optical elements includes one or more second dispersive elements positioned to remove spatial dispersion from the beam containing the subset of the sub-beams;

a sample stage for securing one or more samples;
an illumination sub-system configured to illuminate at least a portion of the one or more samples with at least a portion of the second set of wavelengths via an illumination pathway;
a detector; and
an objective configured to focus illumination from a surface of the one or more samples and focus the collected illumination via a collection pathway to the detector to form an image of at least a portion of the surface of the one or more samples on the detector.

13. The system of claim 12 , wherein the spatial filter element comprises an aperture having one or more openings, wherein the spatial filter element is positioned such that the second set of wavelengths pass through the one or more openings.

14. The system of claim 12 , wherein the spatial filter element comprises a spatial light modulator.

15. The system of claim 14 , wherein the spatial light modulator includes a deformable mirror.

16. The system of claim 12 , wherein the illumination source comprises a laser-sustained plasma.

17. The system of claim 12 , wherein the illumination source comprises a discharge source.

18. The system of claim 12 , wherein at least one of the first set of optical elements or the second set of optical elements includes a cylindrical mirror.

19. The system of claim 12 , wherein at least one of the one or more first dispersive elements or the one or more second dispersive elements includes one or more prisms.

20. The system of claim 19 , wherein the one or more prisms includes one or more prism arrays.

21. The system of claim 12 , wherein at least one of the one or more first dispersive elements or the one or more second dispersive elements includes one or more diffraction gratings.

22. The system of claim 21 , wherein the one or more diffraction gratings includes at least one of a planar diffraction grating or a curved diffraction grating.

23. The system of claim 12 , wherein the detector comprises at least one of a CCD detector or a TDI detector.

24. A system for illuminating a sample with an illumination source, comprising:
an illumination source configured to generate a beam of illumination that includes a first set of wavelengths;
a wavelength filtering sub-system, comprising:
one or more optical elements, wherein the one or more optical elements includes one or more dispersive elements positioned to introduce spatial dispersion into the beam, wherein the one or more optical elements include one or more focusing elements; and
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Assignees

• Kla Tencor Corp

Inventors

• Zhao Wei
• Gross Kenneth P
• Bezel Ilya
• Panzer Matthew

Classifications

• G01J3/0208

  using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction · CPC title

• G01J2003/1286

  Polychromator in general · CPC title

• G01J3/14

  using refracting elements, e.g. prisms (G01J3/18, G01J3/26 take precedence {prisms per se G02B5/04}) · CPC title

• G01N21/956

  Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} · CPC title

• G01J3/18

  using diffraction elements, e.g. grating (gratings per se G02B) · CPC title