Dynamically Adjustable Semiconductor Metrology System

• US 20130114085A1
• Filed: 10/26/2012
• Published: 05/09/2013
• Est. Priority Date: 10/27/2011
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation
• Original Assignee: KLA-Tencor Corporation
• Inventors: Wang, David Y., Zhuang, Guorong Vera, de Veer, Johannes D., Krishnan, Shankar, Peterlinz, Kevin
• Granted Patent: US 9,228,943 B2
• Time in Patent Office: Days
• US Class Current: 356/445
• CPC Class Codes: G01N 2021/213 Spectrometric ellipsometry
• CPC Class Codes: G01N 2021/556 Measuring separately scattering and specular
• CPC Class Codes: G01N 21/211 Ellipsometry optical thickness measurement G01B11/06
• CPC Class Codes: G01N 21/55 Specular reflectivity

Abstract

The present invention may include an illumination source, a detector, a selectably adjustable optical system including a dynamically adjustable illumination pupil of the illumination arm, a dynamically adjustable collection pupil of the collection arm, a dynamically adjustable illumination field stop of the illumination arm, a dynamically adjustable collection field stop of the collection arm, a sensor configured to measure one or more optical characteristics of one or more components of the optical system, and a control system configured to selectably dynamically adjust at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop, and a spectral radiance of the illumination source.

Claims

1. A dynamically adjustable metrology system, comprising:

an illumination source configured to illuminate one or more metrology targets disposed on a surface of a sample disposed on a sample stage;

a detector configured to detect at least a portion of light reflected from the one or more metrology targets;

a selectably adjustable optical system including an illumination arm and a collection arm, the illumination source and the detector being optically coupled by the optical system, the optical system further including at least one of the group including;

a dynamically adjustable illumination pupil positioned in the illumination arm;

a dynamically adjustable collection pupil positioned in the collection arm;

a dynamically adjustable illumination field stop positioned in the illumination arm; and

a dynamically adjustable collection field stop positioned in the collection arm;

a sensor configured to measure one or more optical characteristics of at least one of the dynamically adjustable illumination pupil, the dynamically adjustable collection pupil, the dynamically adjustable illumination field stop, the dynamically adjustable collection field stop and the one or more metrology targets of the sample;

a control system communicatively coupled to at least one of the dynamically adjustable illumination pupil, the dynamically adjustable collection pupil, the dynamically adjustable illumination field stop and the dynamically adjustable collection field stop, wherein the control system is configured to;

receive one or more optical characteristics of at least one of the dynamically adjustable illumination pupil, the dynamically adjustable collection pupil, the dynamically adjustable illumination field stop, the dynamically adjustable collection field stop and the one or more metrology targets of the sample from the sensor;

monitor one or more optical characteristics of one or more metrology targets of the sample;

responsive to the measured one or more optical characteristics, selectably dynamically adjust at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop, and a spectral radiance of the illumination source.

2. The apparatus of claim 1, wherein the control system is configured to selectably adjust at least one of the illumination pupil and the collection pupil in order to control at least one of a numerical aperture (NA), an angle of incidence (AOI), an azimuth angle (AZ) and pupil apodization of the metrology system.

3. The apparatus of claim 1, wherein the control system is configured to selectably adjust the illumination field stop and the collection field stop in order to control a field of view (FOV) of the metrology system.

4. The apparatus of claim 1, wherein the control system is configured to selectably adjust the spectral radiance of the illumination source in order to reduce signal contamination below a selected tolerance level.

5. The apparatus of claim 4, wherein the illumination source comprises:

a dynamically adjustable illumination source, wherein one or more spectral characteristics of the illumination source are adjustable in response to the control system.

6. The apparatus of claim 4, further comprising:

a dynamically adjustable filter configured to attenuate spectral radiance at a wavelength range having a contamination level above a selected tolerance level.

7. The apparatus of claim 4, wherein the control system is configured to selectably adjust a spectral radiance of illumination from the sample utilizing a spectral radiance weighting algorithm and spectral selecting algorithm.

8. The apparatus of claim 4, wherein the control system is further configured to:

selectably adjust at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop, and the spectral radiance in order to inhibit contamination associated with one or more metrology targets below a selected contamination level.

9. The apparatus of claim 4, wherein the control system is further configured to:

selectably adjust at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop, and the spectral radiance in order to adjust the PSF of illumination at a sample plane of the sample.

10. The apparatus of claim 9, wherein the control system is configured to selectably adjust at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop, and the spectral radiance in order to optimize the PSF of illumination at a sample plane of the sample.

11. The apparatus of claim 1, wherein the control system is further configured to:

selectably adjust a spectral radiance of the illumination source in order to optimize metrology measurement capabilities for each metrology target of the sample.

12. The apparatus of claim 1, wherein the dynamically adjustable illumination pupil of the illumination arm comprises:

at least one of a one-dimensional and two-dimensional reflective MEMS mirror situated at or near the illumination pupil configured to dynamically adjust at least one of an AOI, an AZ, a NA, and pupil apodization of the illumination from the illumination source.

13. The apparatus of claim 1, wherein the dynamically adjustable collection pupil of the collection arm comprises:

at least one of one-dimension and two-dimensional reflective MEMS mirror situated at or near the collection pupil configured to dynamically adjust at least one of an AOI, an AZ, a NA, and pupil apodization of the illumination from the one or more metrology targets.

14. The apparatus of claim 1, wherein the dynamically adjustable illumination pupil of the illumination arm comprises:

at least one of one-dimensional and two-dimensional liquid crystal cell spatial light modulator situated at or near the illumination pupil configured to dynamically adjust at least one of an AOI, an AZ, a NA, and pupil apodization of the illumination from the illumination source.

15. The apparatus of claim 1, wherein the dynamically adjustable collection pupil of the collection arm comprises:

a two-dimensional liquid crystal cell spatial light modulator situated at or near the collection pupil configured to dynamically adjust at least one of an AOI, an AZ, a NA, and pupil apodization of the illumination from the one or more metrology targets.

16. The apparatus of claim 1, wherein the dynamically adjustable collection field stop of the collection arm comprises:

a one dimensional or two-dimensional liquid crystal cell spatial light modulator configured to dynamically adjust a field of view (FOV) of the metrology system.

17. The apparatus of claim 1, wherein the dynamically adjustable illumination field stop of the illumination arm comprises:

a one dimensional or two-dimensional liquid crystal cell spatial light modulator configured to dynamically adjust a field of view (FOV) of the metrology system.

18. The apparatus of claim 1, wherein the dynamically adjustable collection field stop of the collection arm comprises:

a MEMS configured to dynamically adjust a field of view (FOV) of the metrology system.

19. The apparatus of claim 1, wherein the dynamically adjustable illumination field stop of the illumination arm comprises:

a MEMS configured to dynamically adjust a field of view (FOV) of the metrology system.

20. The apparatus of claim 1, wherein the sensor is configured to measure an illumination point spread function at a sample plane of the sample.

21. The apparatus of claim 1, wherein the sensor is configured to measure an illumination spot size at a sample plane of the sample.

22. The apparatus of claim 1, wherein the sensor is configured to measure one or more scattering characteristics at a sample plane of the sample.

23. The apparatus of claim 1, wherein the sensor is configured to measure one or more wavefront characteristics at a sample plane of the sample.

24. The apparatus of claim 1, wherein the sensor is configured to measure at least one of angle of incidence, azimuthal angle, field of view, and numerical aperture of illumination at the sample plane of the sample.

25. The apparatus of claim 1, wherein the optical characteristics monitored by the control system comprise:

at least one of a PSF of illumination at a sample plane of the sample, a spot size of illumination at a sample plane of the sample, and one or more scattering characteristics at a sample plane of the sample.

26. The apparatus of claim 1, wherein the illumination source comprises:

at least one broad band illumination source.

27. The apparatus of claim 1, wherein the illumination source comprises:

at least one narrow band light source.

28. The apparatus of claim 1, further comprising:

an layer of illumination absorbing material disposed about the one or more metrology targets, wherein the illumination absorbing material is suitable for absorbing at least 95% of illumination impinging on the illumination absorbing material.

29. A dynamically adjustable metrology system, comprising:

an illumination source configured to illuminate one or more metrology targets disposed on a surface of a sample disposed on a sample stage;

a spectrograph configured to measure spectral properties of at least a portion of light reflected from the one or more metrology targets;

a selectably adjustable optical system including an illumination arm and a collection arm, the illumination source and the detector being optically coupled by the optical system, the optical system further including at least one of the group including;

a dynamically adjustable illumination pupil positioned in the illumination arm;

a first polarizing element positioned in the illumination arm;

a dynamically adjustable illumination field stop positioned in the illumination arm;

a dynamically adjustable collection pupil positioned in the collection arm;

a second polarizing element disposed in the collection arm; and

a dynamically adjustable collection field stop positioned in the collection arm;

a sensor configured to measure one or more optical characteristics of at least one of the dynamically adjustable illumination pupil, the dynamically adjustable collection pupil, the dynamically adjustable illumination field stop the dynamically adjustable collection field stop and one or more metrology targets of the sample.

a control system communicatively coupled to the dynamically adjustable illumination pupil, the dynamically adjustable collection pupil, the dynamically adjustable illumination field stop and the dynamically adjustable collection field stop, wherein the control system is configured to;

receive one or more optical characteristics of at least one of the dynamically adjustable illumination pupil, the dynamically adjustable collection pupil, the dynamically adjustable illumination field stop and the dynamically adjustable collection field stop from the sensor;

monitor one or more optical characteristics at one or more metrology targets of the sample;

responsive to the measured one or more optical characteristics, selectably dynamically adjust at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop, and a spectral radiance of the illumination source.

30. The apparatus of claim 29, wherein the control system is configured to selectably adjust at least one of the illumination pupil and the collection pupil in order to control at least one of a numerical aperture (NA), an angle of incidence (AOI), an azimuth angle (AZ) and pupil apodization of the metrology system.

31. The apparatus of claim 29, wherein the control system is configured to selectably adjust the illumination field stop and the collection field stop in order to control a field of view (FOV) of the metrology system.

32. The apparatus of claim 29, wherein the control system is configured to selectably adjust the spectral radiance of the illumination source in order to reduce signal contamination below a selected tolerance level.

33. The apparatus of claim 32, wherein the illumination source comprises:

a dynamically adjustable illumination source, wherein one or more spectral characteristics of the illumination source are adjustable in response to the control system.

34. The apparatus of claim 32, further comprising:

a dynamically adjustable filter configured to attenuate spectral radiance at a wavelength range having a contamination level above a selected tolerance level.

35. The apparatus of claim 32, wherein the control system is configured to selectably adjust a spectral radiance of illumination from the sample utilizing a spectral radiance weighting algorithm.

36. The apparatus of claim 32, wherein the control system is further configured to:

selectably adjust at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop, and the spectral radiance in order to inhibit contamination associated with one or more metrology targets below a selected contamination level.

37. The apparatus of claim 32, wherein the control system is further configured to:

selectably adjust at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop, and the spectral radiance in order to adjust the PSF of illumination at a sample plane of the sample.

38. The apparatus of claim 37, wherein the control system is configured to selectably adjust at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop, and the spectral radiance in order to optimize the PSF of illumination at a sample plane of the sample.

39. The apparatus of claim 29, wherein the control system is further configured to:

selectably adjust a spectral radiance of the illumination source in order to optimize metrology measurement capabilities for each metrology target of the sample

40. The apparatus of claim 29, wherein the dynamically adjustable illumination pupil of the illumination arm comprises:

at least one of a one-dimensional and two-dimensional reflective MEMS mirror situated at or near the illumination pupil configured to dynamically adjust at least one of an AOI, an AZ, a NA, and pupil apodization of the illumination from the illumination source.

41. The apparatus of claim 29, wherein the dynamically adjustable collection pupil of the collection arm comprises:

at least one of one-dimension and two-dimensional reflective MEMS mirror situated at or near the collection pupil configured to dynamically adjust at least one of an AOI, an AZ, a NA, and pupil apodization of the illumination from the one or more metrology targets.

42. The apparatus of claim 29, wherein the dynamically adjustable illumination pupil of the illumination arm comprises:

at least one of one-dimensional and two-dimensional liquid crystal cell spatial light modulator situated at or near the illumination pupil configured to dynamically adjust at least one of an AOI, an AZ, a NA, and pupil apodization of the illumination from the illumination source.

43. The apparatus of claim 29, wherein the dynamically adjustable collection pupil of the collection arm comprises:

a two-dimensional liquid crystal cell spatial light modulator situated at or near the collection pupil configured to dynamically adjust at least one of an AOI, an AZ, a NA, and pupil apodization of the illumination from the one or more metrology targets.

44. The apparatus of claim 29, wherein the dynamically adjustable collection field stop of the collection arm comprises:

a one dimensional or two-dimensional liquid crystal cell spatial light modulator configured to dynamically adjust a field of view (FOV) of the metrology system.

45. The apparatus of claim 29, wherein the dynamically adjustable illumination field stop of the illumination arm comprises:

a one dimensional or two-dimensional liquid crystal cell spatial light modulator configured to dynamically adjust a field of view (FOV) of the metrology system.

46. The apparatus of claim 29, wherein the dynamically adjustable collection field stop of the collection arm comprises:

a MEMS configured to dynamically adjust a field of view (FOV) of the metrology system.

47. The apparatus of claim 29, wherein the dynamically adjustable illumination field stop of the illumination arm comprises:

a MEMS configured to dynamically adjust a field of view (FOV) of the metrology system.

48. The apparatus of claim 29, wherein the sensor is configured to measure an illumination point spread function at a sample plane of the sample.

49. The apparatus of claim 29, wherein the sensor is configured to measure an illumination spot size at a sample plane of the sample.

50. The apparatus of claim 29, wherein the sensor is configured to measure one or more scattering characteristics at a sample plane of the sample.

51. The apparatus of claim 29, wherein the sensor is configured to measure one or more wavefront characteristics at a sample plane of the sample.

52. The apparatus of claim 29, wherein the sensor is configured to measure at least one of angle of incidence, azimuthal angle, field of view, and numerical aperture of illumination at the sample plane of the sample.

53. The apparatus of claim 29, wherein the optical characteristics monitored by the control system comprise:

at least one of a PSF of illumination at a sample plane of the sample, a spot size of illumination at a sample plane of the sample, and one or more scattering characteristics at a sample plane of the sample.

54. The apparatus of claim 29, wherein the illumination source comprises:

at least one broad band illumination source.

55. The apparatus of claim 29, wherein the illumination source comprises:

at least one narrow band light source.

56. The apparatus of claim 29, wherein the control system is further configured to:

selectably adjust a spectral radiance of the illumination source in order to reduce signal contamination below a selected tolerance level.

57. The apparatus of claim 29, wherein the dynamically adjustable illumination pupil of the illumination arm comprises:

a two-dimensional reflective MEMS mirror situated at or near the illumination pupil configured to dynamically adjust illumination at least one of an AOI, an AZ, a NA, and apodization of the illumination from the illumination source.

58. The apparatus of claim 29, wherein the dynamically adjustable collection pupil of the collection arm comprises:

A two-dimensional reflective MEMS mirror situated at or near the collection pupil configured to dynamically adjust at least one of an AOI, an AZ, a NA, and apodization of the illumination from the one or more metrology targets.

59. The apparatus of claim 29, wherein the dynamically adjustable illumination pupil of the illumination arm comprises:

a two-dimensional liquid crystal cell spatial light modulator situated at or near the illumination pupil configured to dynamically adjust illumination at least one of an AOI, an AZ, a NA, and apodization of the illumination from the illumination source.

60. The apparatus of claim 29, wherein the dynamically adjustable collection pupil of the collection arm comprises:

a two-dimensional liquid crystal cell spatial light modulator situated at or near the collection pupil configured to dynamically adjust at least one of an AOI, an AZ, a NA, and apodization of the illumination from the one or more metrology targets.

61. The apparatus of claim 29, wherein the dynamically adjustable collection field stop of the collection arm comprises:

a two-dimensional liquid crystal cell spatial light modulator configured to dynamically adjust a field of view (FOV) of the metrology system.

62. The apparatus of claim 29, wherein the dynamically adjustable illumination field stop of the illumination arm comprises:

a two-dimensional liquid crystal cell spatial light modulator configured to dynamically adjust a field of view (FOV) of the metrology system.

63. The apparatus of claim 29, wherein the dynamically adjustable collection field stop of the collection arm comprises:

a MEMS configured to dynamically adjust a field of view (FOV) of the metrology system.

64. The apparatus of claim 29, wherein the dynamically adjustable illumination field stop of the illumination arm comprises:

a MEMS configured to dynamically adjust a field of view (FOV) of the metrology system.

65. The apparatus of claim 29, wherein the illumination source comprises:

at least one broad band illumination source.

66. The apparatus of claim 29, wherein the illumination source comprises:

at least one narrow band light source.

67. The apparatus of claim 29, wherein the first polarizing element comprises:

at least one of a polarizer and compensator.

68. The apparatus of claim 29, wherein the second polarizing element comprises:

at least one of a compensator and analyzer.

69. The apparatus of claim 29, further comprising:

an layer of illumination absorbing material disposed about the one or more metrology targets, wherein the illumination absorbing material is suitable for absorbing at least 95% of illumination impinging on the illumination absorbing material.

70. A dynamically adjustable metrology system, comprising:

an illumination source configured to illuminate one or more metrology targets disposed on a surface of a sample disposed on a sample stage;

a detector configured to detect at least a portion of light reflected from the one or more metrology targets;

a selectably adjustable optical system including an illumination arm and a collection arm, the illumination source and the detector being optically coupled by the optical system, the optical system further including at least one of the group including;

an illumination pupil positioned in the illumination arm;

a collection pupil positioned in the collection arm;

an illumination field stop positioned in the illumination arm; and

a collection field stop positioned in the collection arm, wherein at least one of the illumination pupil, the collection pupil, the illumination field stop and the collection field stop is dynamically adjustable, wherein at least one of the illumination pupil, the collection pupil, the illumination field stop and the collection field stop is static;

a sensor configured to measure one or more optical characteristics of at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop and the one or more metrology targets of the sample;

a control system communicatively coupled to at least one of the illumination pupil, the collection pupil, the illumination field stop and the collection field stop, wherein the control system is configured to;

receive one or more optical characteristics of at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop and the one or more metrology targets of the sample from the sensor;

monitor one or more optical characteristics of one or more metrology targets of the sample;

responsive to the measured one or more optical characteristics, selectably dynamically adjust at least one of the illumination pupil, the collection pupil, the illumination field stop, the collection field stop, and a spectral radiance of the illumination source.