Systems for Providing Illumination in Optical Metrology

• US 20140240951A1
• Filed: 02/22/2013
• Published: 08/28/2014
• Est. Priority Date: 02/22/2013
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation (KLA Corporation)
• Original Assignee: KLA-Tencor Corporation (KLA Corporation)
• Inventors: Shchegrov, Andrei V., Rotter, Lawrence D., Shaughnessy, Derrick, Shchemelinin, Anatoly, Bezel, Ilya, Hill, Andrew V., Bachar, Ohad, Markowitz, Moshe, Sela, Ilan, Manassen, Amnon, Svizher, Alexander, Abramov, Avi, Kandel, Daniel, Ghinovker, Mark, Brady, Gregory R., Arain, Muzammil A., Vasiliev, Anatoly A., Allen, James Andrew, Shulepov, Oleg, Ish-Shalom, Yaron, Khokhlov, Maxim, Tsibulevsky, Oleg
• Granted Patent: US 9,512,985 B2
• Time in Patent Office: Days
• US Class Current: 362/19
• CPC Class Codes: F21V 13/00 Producing particular characteristics or distribution of the light emitted by means of a combination of elements specified in two or more of main groups F21V1/00 - F21V11/00 controlling the distribution of the light emitted by adjustment of elements F21V14/00
• CPC Class Codes: F21V 13/08 the elements being filters or photoluminescent elements and reflectors
• CPC Class Codes: F21V 13/14 the elements being filters or photoluminescent elements, reflectors and refractors
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/12 Generating the spectrum; Monochromators
• CPC Class Codes: G02B 6/29332 Wavelength selective couplers, i.e. based on evanescent coupling between light guides, e.g. fused fibre couplers with transverse coupling between fibres having different propagation constant wavelength dependency non wavelength-selective light guide couplers G02B6/28
• CPC Class Codes: G02B 6/29362 Serial cascade of filters or filtering operations, e.g. for a large number of channels
• CPC Class Codes: G02B 6/29388 for lighting or use with non-coherent light
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02B 6/3508 Lateral or transverse displacement of the whole waveguides, e.g. by varying the distance between opposed waveguide ends, or by mutual lateral displacement of opposed waveguide ends
• CPC Class Codes: G02B 6/353 the optical element being a shutter, baffle, beam dump or opaque element absorbers on light guide termination G02B6/243
• CPC Class Codes: H01J 65/04 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

Abstract

The disclosure is directed to systems for providing illumination to a measurement head for optical metrology. In some embodiments of the disclosure, illumination beams from a plurality of illumination sources are combined to deliver illumination at one or more selected wavelengths to the measurement head. In some embodiments of the disclosure, intensity and/or spatial coherence of illumination delivered to the measurement head is controlled. In some embodiments of the disclosure, illumination at one or more selected wavelengths is delivered from a broadband illumination source configured for providing illumination at a continuous range of wavelengths.

Claims

1. A system for providing illumination to a measurement head, comprising:

a plurality of illumination sources including a first illumination source, a second illumination source, a third illumination source, a fourth illumination source, a fifth illumination source, and a sixth illumination source;

a first fold mirror configured to reflect illumination from the first illumination source along a guidance path;

a second fold mirror configured to reflect illumination from the second illumination source along the guidance path;

a first dichroic combiner configured to transmit illumination from the first illumination source along the guidance path, the first dichroic combiner further configured to reflect illumination from the third illumination source along the guidance path;

a second dichroic combiner configured to transmit illumination from the second illumination source along the guidance path, the second dichroic combiner further configured to reflect illumination from the fourth illumination source along the guidance path;

a third dichroic combiner configured to transmit illumination from the first illumination source and illumination from the third illumination source along the guidance path, the third dichroic combiner further configured to reflect illumination from the fifth illumination source along the guidance path;

a fourth dichroic combiner configured to transmit illumination from the sixth illumination source along the guidance path;

the fourth dichroic combiner further configured to reflect illumination from the second illumination source and illumination from the fourth illumination source along the guidance path; and

a fifth dichroic combiner configured to transmit illumination from the second illumination source, illumination from the fourth illumination source, and illumination from the sixth illumination source along an illumination path to a measurement head, the fifth dichroic combiner further configured to reflect illumination from the first illumination source, illumination from the third illumination source, and illumination from the fifth illumination source along the illumination path to the measurement head.

2. The system of claim 1, wherein the system further includes:

a plurality of shutters, each shutter configured to receive illumination from an illumination source of the plurality of illumination sources, the plurality of shutters configured to allow illumination at a selected wavelength to be delivered along the illumination path.

3. The system of claim 1, wherein each illumination source of the plurality of illumination sources is configured to provide illumination at a selected wavelength.

4. The system of claim 1, wherein each illumination source of the plurality of illumination sources is configured to provide illumination at a selected intensity.

5. The system of claim 4, wherein the selected intensity of each illumination source is controlled by pulse width modulation.

6. The system of claim 4, wherein the selected intensity of each illumination source is controlled utilizing an acousto-optic filter.

7. The system of claim 1, wherein the illumination path includes one or more optical elements configured to separate illumination into orthogonal polarization components.

8. The system of claim 1, wherein the system further includes:

a wavelength monitor configured to receive a portion of illumination from the illumination path.

9. The system of claim 1, wherein the illumination path includes one or more single-mode optical fibers configured to deliver illumination to the measurement head.

10. The system of claim 1, wherein the illumination path includes one or more multi-mode optical fibers configured to deliver illumination to the measurement head.

11. The system of claim 10, wherein the illumination path further includes:

a coupling lens configured to focus illumination;

a fold mirror configured to receive focused illumination from the coupling lens; and

an actuator coupled to the fold mirror, the actuator configured for actuating the fold mirror to scan focused illumination across at least one core of the one or more multi-mode fibers.

12. The system of claim 10, wherein the illumination path further includes:

a coupling lens configured to focus illumination delivered to the one or more multi-mode fibers;

an actuator coupled to a tip of the one or more multi-mode fibers, the actuator configured for actuating the tip of the one or more multi-mode fibers so that focused illumination is scanned across at least one core of the one or more multi-mode fibers.

13. The system of claim 10, wherein the illumination path further includes:

an actuator configured to vibrate the one or more multi-mode fibers.

14. A system for providing illumination to a measurement head, comprising:

a plurality of illumination sources including a first illumination source, a second illumination source, a third illumination source, a fourth illumination source, a fifth illumination source, and a sixth illumination source;

a first dichroic combiner configured to transmit illumination from the first illumination source along a guidance path, the first dichroic combiner further configured to reflect illumination from the second illumination source along the guidance path;

a second dichroic combiner configured to transmit illumination from the third illumination source along the guidance path, the second dichroic combiner further configured to reflect illumination from the first illumination source and illumination from the second illumination source along the guidance path;

a third dichroic combiner configured to transmit illumination from the fourth illumination source along the guidance path, the third dichroic combiner further configured to reflect illumination from the fifth illumination source along the guidance path;

a fourth dichroic combiner configured to transmit illumination from the fourth illumination source and illumination from the fifth illumination source along an illumination path to a measurement head, the fourth dichroic combiner further configured to reflect illumination from the first illumination source, illumination from the second illumination source, and illumination from the third illumination source along the illumination path to the measurement head; and

a beam splitter configured to direct illumination from the sixth illumination source along the illumination path to the measurement head.

15. The system of claim 14, wherein the system further includes:

a plurality of shutters, each shutter configured to receive illumination from an illumination source of the plurality of illumination sources, the plurality of shutters configured to allow illumination at a selected wavelength to be delivered along the illumination path.

16. The system of claim 14, wherein each illumination source of the plurality of illumination sources is configured to provide illumination at a selected wavelength.

17. The system of claim 14, wherein each illumination source of the plurality of illumination sources is configured to provide illumination at a selected intensity.

18. The system of claim 17, wherein the selected intensity of each illumination source is controlled by pulse width modulation.

19. The system of claim 17, wherein the selected intensity of each illumination source is controlled utilizing an acousto-optic filter.

20. The system of claim 14, wherein the illumination path includes one or more optical elements configured to separate illumination into orthogonal polarization components.

21. The system of claim 14, wherein the system further includes:

a wavelength monitor configured to receive a portion of illumination from the illumination path.

22. The system of claim 14, wherein the illumination path includes one or more single-mode optical fibers configured to deliver illumination to the measurement head.

23. The system of claim 14, wherein the illumination path includes one or more multi-mode optical fibers configured to deliver illumination to the measurement head.

24. The system of claim 23, wherein the illumination path further includes:

a coupling lens configured to focus illumination;

a fold mirror configured to receive focused illumination from the coupling lens; and

an actuator coupled to the fold mirror, the actuator configured for actuating the fold mirror to scan focused illumination across at least one core of the one or more multi-mode fibers.

25. The system of claim 23, wherein the illumination path further includes:

a coupling lens configured to focus illumination delivered to the one or more multi-mode fibers;

an actuator coupled to a tip of the one or more multi-mode fibers, the actuator configured for actuating the tip of the one or more multi-mode fibers so that focused illumination is scanned across at least one core of the one or more multi-mode fibers.

26. The system of claim 23, wherein the illumination path further includes:

an actuator configured to vibrate the one or more multi-mode fibers.

27. A system for providing illumination to a measurement head, comprising:

a plurality of illumination sources configured to provide illumination at a plurality of wavelengths along a plurality of optical fibers, each optical fiber configured to receive illumination at a different wavelength;

a coupling lens configured to receive illumination at a selected wavelength from a selected optical fiber of the plurality of optical fibers, the coupling lens further configured to direct illumination at the selected wavelength along a delivery optical fiber;

a ferrule configured to hold the plurality of optical fibers;

an actuator mechanically coupled to at least one of the ferrule, the coupling lens, and the delivery optical fiber, the actuator configured to align the selected optical fiber with at least one of the coupling lens and the delivery optical fiber; and

a collimation lens configured receive illumination at the selected wavelength from the delivery optical fiber, the collimation lens further configured to direct illumination at the selected wavelength along an illumination path to a measurement head.

28. The system of claim 27, wherein each illumination source of the plurality of illumination sources is configured to provide illumination at a selected intensity.

29. The system of claim 28, wherein the selected intensity of each illumination source is controlled by pulse width modulation.

30. The system of claim 28, wherein the selected intensity of each illumination source is controlled utilizing an acousto-optic filter.

31. The system of claim 27, wherein the illumination path includes one or more optical elements configured to separate illumination into orthogonal polarization components.

32. The system of claim 27, wherein the system further includes:

a wavelength monitor configured to receive a portion of illumination from the illumination path.

33. The system of claim 27, wherein the illumination path includes one or more single-mode optical fibers configured to deliver illumination to the measurement head.

34. The system of claim 27, wherein the illumination path includes one or more multi-mode optical fibers configured to deliver illumination to the measurement head.

35. The system of claim 34, wherein the illumination path further includes:

a coupling lens configured to focus illumination;

a fold mirror configured to receive focused illumination from the coupling lens; and

an actuator coupled to the fold mirror, the actuator configured for actuating the fold mirror to scan focused illumination across at least one core of the one or more multi-mode fibers.

36. The system of claim 34, wherein the illumination path further includes:

a coupling lens configured to focus illumination delivered to the one or more multi-mode fibers;

an actuator coupled to a tip of the one or more multi-mode fibers, the actuator configured for actuating the tip of the one or more multi-mode fibers so that focused illumination is scanned across at least one core of the one or more multi-mode fibers.

37. The system of claim 34, wherein the illumination path further includes:

an actuator configured to vibrate the one or more multi-mode fibers.

38. A system for providing illumination to a measurement head, comprising:

a plurality of illumination sources configured to provide illumination at a plurality of wavelengths along a plurality of optical fibers, each optical fiber configured to receive illumination at a different wavelength;

a waveguide structure configured to direct illumination from the plurality of optical fibers along an illumination path to a measurement head; and

a plurality of shutters disposed between the plurality of illumination sources and the waveguide structure, the plurality of shutters configured to allow illumination at a selected wavelength to be delivered along the illumination path.

39. The system of claim 38, wherein the waveguide structure includes a plurality of cascaded single-mode optical fiber splitters.

40. The system of claim 39, wherein the illumination path includes a bifurcated optical fiber configured to direct a portion of illumination to each polarization channel of the measurement head.

41. The system of claim 38, wherein the waveguide structure includes a planar lightwave circuit.

42. The system of claim 41, wherein the planar lightwave circuit includes a plurality of intensity modulators configured to control intensity of illumination received from each illumination source.

43. The system of claim 41, wherein the system further includes single-mode fibers configured to deliver illumination to polarization channels of the measurement head, wherein the planar lightwave circuit includes a splitter configured to direct a portion of illumination along each of the single-mode optical fibers to each of the polarization channels of the measurement head.

44. A system for providing illumination to a measurement head, comprising:

a broadband illumination source;

one or more multi-mode optical fibers configured deliver illumination from the broadband illumination source along an illumination path to a measurement head; and

a filter mechanism disposed between the broadband illumination source and the one or more multi-mode optical fibers, the filter mechanism configured to allow illumination at a selected wavelength to be delivered along the illumination path.

45. The system of claim 44, wherein the filter mechanism includes an plurality of narrowband dielectric thin film filters.

46. The system of claim 44, wherein the filter mechanism includes a tunable dielectric filter.

47. The system of claim 44, wherein the filter mechanism is further configured to allow unfiltered illumination to be delivered along the illumination path.

48. The system of claim 44, wherein the filter mechanism includes a monochromator with a rotating dispersive element.

49. The system of claim 44, wherein the filter mechanism includes a dispersive element configured to direct portions of illumination at selected wavelengths along a plurality of optical fibers.

50. The system of claim 44, wherein the one or more multi-mode optical fibers have selected numerical aperture and selected core size based upon etendue of at least one of the broadband illumination source and the measurement head.

51. The system of claim 44, wherein the broadband illumination source comprises a laser sustained plasma source.

52. The system of claim 51, wherein the laser sustained plasma source is configured to provide illumination along the axis of plasma emissions of the laser sustained plasma source.

53. The system of claim 51, wherein the laser sustained plasma source includes:

a pump source configured to provide illumination at at least one selected wavelength and at least one selected power level for generating plasma; and

a gas cell containing pressurized gas, the gas cell configured to receive illumination from the pump source to generate plasma, the gas cell further configured to provide broadband illumination emitted from the generated plasma.

54. The system of claim 53, wherein the laser sustained plasma source further includes:

an ellipsoidal mirror configured to focus illumination delivered to the gas cell, the ellipsoidal mirror further configured to collect and collimate broadband illumination emitted from the generated plasma.

55. The system of claim 53, wherein the laser sustained plasma source further includes:

a collimation lens configured to collimate illumination delivered to the gas cell; and

a paraboloidal mirror configured to focus illumination delivered to the gas cell, the paraboloidal mirror further configured to collect and collimate broadband illumination emitted from the generated plasma.

56. The system of claim 53, wherein the laser sustained plasma source further includes:

a cold mirror configured to separate illumination from the pump source from broadband illumination emitted from the generated plasma, the cold mirror further configured to direct broadband illumination emitted from the generated plasma along an emission path.

57. The system of claim 44, wherein the filter mechanism includes:

a plurality of dichroic splitters, each dichroic splitter configured to direct a respective range of wavelengths along a respective delivery path; and

a plurality of shutters, each shutter configured to receive illumination from the respective delivery path of a respective one of the plurality of dichroic splitters, the plurality of shutters configured to allow illumination at a selected wavelength to be delivered along the illumination path.

58. A system for providing illumination to a measurement head, comprising:

one or more illumination sources including at least one of a broadband illumination source and a plurality of laser sources;

a wavelength selection mechanism including at least one of a tunable filter, a plurality of shutters, a ferrule, and a plurality of waveguide modulators, the wavelength selection mechanism configured receive illumination from the one or more illumination sources, the wavelength selection mechanism further configured to direct at least a portion of received illumination having a selected wavelength along an illumination path;

an intensity controller including at least one of a pulse width modulator, an acousto-optic filter, and a waveguide intensity modulator, the intensity controller configured to control intensity of the portion of illumination delivered along the illumination path; and

a coherence controller including at least one of an optical fiber actuator, a fold mirror actuator, and an incoherent illumination source, the coherence controller configured to decrease speckle in the portion of illumination delivered along the illumination path.

59. The system of claim 58, wherein the one or more illumination sources include a broadband source and a plurality of laser sources.