Methods and systems for inspection of a specimen using different inspection parameters

• US 8,384,887 B2
• Filed: 06/08/2010
• Issued: 02/26/2013
• Est. Priority Date: 09/04/2003
• Status: Active Grant

• Current Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Original Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Inventors: Lange, Steve R., Marella, Paul Frank, Ceglio, Nat, Hwang, Shiow-Hwei, Fu, Tao-Yi
• Primary Examiner(s): Chowdhury, Tarifur
• Assistant Examiner(s): AKANBI, ISIAKA O
• Application Number:
  US12/796,047
• Publication Number:
  US 20100238433A1
• Time in Patent Office: 994 Days
• Field of Search: 3562371-2375
• US Class Current: 356/237.1
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10

Abstract

Methods and systems for inspection of a specimen using different parameters are provided. One computer-implemented method includes determining optimal parameters for inspection based on selected defects. This method also includes setting parameters of an inspection system at the optimal parameters prior to inspection. Another method for inspecting a specimen includes illuminating the specimen with light having a wavelength below about 350 nm and with light having a wavelength above about 350 nm. The method also includes processing signals representative of light collected from the specimen to detect defects or process variations on the specimen. One system configured to inspect a specimen includes a first optical subsystem coupled to a broadband light source and a second optical subsystem coupled to a laser. The system also includes a third optical subsystem configured to couple light from the first and second optical subsystems to an objective, which focuses the light onto the specimen.

Claims

1. A method for inspecting a specimen, comprising:

illuminating the specimen with light having at least one wavelength below about 350 nm using a first subsystem and with light having at least one wavelength above about 350 nm using a second subsystem;

collecting light from the specimen;

detecting the collected light to produce optical phase signals representative of a first portion of the collected light and brightfield optical signals representative of a second portion of the collected light; and

processing the signals to detect defects or process variations on the specimen.

2. The method of claim 1, wherein the collected light comprises a bright field image of at least a portion of the specimen.

3. The method of claim 1, wherein at least a portion of a surface of the specimen comprises polysilicon, single crystal silicon, silicon dioxide, silicon nitride, or any combination thereof.

4. The method of claim 1, wherein the first and second subsystems are optimized for the at least one wavelength below and above about 350 nm, respectively.

5. The method of claim 1, wherein the at least one wavelength of the second subsystem is selected to increase contrast in the signals for a material of the specimen, and wherein the at least one wavelength of the first subsystem is selected to increase sensitivity to the defects.

6. The method of claim 1, wherein the first subsystem comprises a laser.

7. The method of claim 1, wherein the second subsystem comprises a polychromatic light source.

8. The method of claim 1, wherein the second subsystem comprises an arc lamp.

9. The method of claim 1, wherein the second subsystem comprises a laser.

10. The method of claim 1, wherein the first and second subsystems comprise a common laser.

11. The method of claim 1, wherein the first subsystem comprises a first laser, and wherein the second subsystem comprises a second laser.

12. The method of claim 1, wherein the first and second subsystems comprise a common polychromatic light source.

13. The method of claim 1, wherein the first subsystem comprises a first polychromatic light source, and wherein the second subsystem comprises a second polychromatic light source.

14. The method of claim 1, wherein the first subsystem comprises a dark field illumination source, and wherein said processing comprises Fourier filtering the signals corresponding to the collected light resulting from said illuminating using the first subsystem.

15. The method of claim 1, wherein said illuminating comprises illuminating the specimen using the first and second subsystems substantially simultaneously.

16. The method of claim 1, wherein said illuminating comprises illuminating the specimen using the first and second subsystems at different times.

17. A method for inspecting a specimen, comprising:

illuminating the specimen;

collecting light from the specimen;

detecting the collected light to produce optical phase signals representative of a first portion of the collected light and brightfield optical signals representative of a second portion of the collected light; and

processing the optical phase signals and the brightfield optical signals separately to detect defects or process variations on the specimen.

18. The method of claim 17, wherein said illuminating comprises illuminating the specimen with light having at least one wavelength below about 350 nm and illuminating the specimen with light having at least one wavelength above about 350 nm.

19. A system configured to inspect a specimen, comprising:

a first optical subsystem coupled to a broadband light source, wherein the first optical subsystem comprises an ellipsoidal mirror;

a second optical subsystem coupled to a laser, wherein the laser is configured to generate light having a wavelength less than about 350 nm;

a third optical subsystem configured to couple light from the first and second optical subsystems to an objective, wherein the objective is configured to focus the light onto the specimen;

a detection subsystem configured to detect light from the specimen and to produce signals representative of the detected light; and

a processor configured to process the signals to detect defects or process variations on the specimen.

20. The system of claim 19, wherein the ellipsoidal mirror is configured to produce a substantially aberration-free image of the broadband light source.

21. The system of claim 19, wherein the ellipsoidal mirror is configured to provide substantially efficient coupling of light from the broadband light source to the third optical subsystem.

22. The system of claim 19, wherein the first optical subsystem further comprises a beam shaping element configured to direct edge radiance of the broadband light source to a central portion of a pupil of the first optical subsystem for brightfield illumination.

23. The system of claim 19, wherein the first optical subsystem further comprises a beam shaping element configured to alter a beam profile of the broadband light source such that the beam profile is substantially uniform.

24. The system of claim 19, wherein the first optical subsystem further comprises a double zooming element configured to alter an optical invariant of the broadband light source.

25. The system of claim 24, wherein the first optical subsystem further comprises a light pipe disposed between individual zooming elements of the double zooming element.

26. The system of claim 19, wherein the third optical subsystem is further configured to allow substantially efficient coupling of the light from the second optical subsystem to the objective.

27. The system of claim 19, wherein the objective is further configured to illuminate the specimen with the light from the first and second optical subsystems substantially simultaneously.

28. The system of claim 19, wherein the laser is further configured to generate light having a wavelength of about 266 nm.

29. The system of claim 19, wherein the broadband light source is configured to generate visible light, ultraviolet light, deep ultraviolet light, or a combination thereof.

30. The system of claim 19, wherein the third optical subsystem comprises a polarization beamsplitter configured to direct the light from the second optical subsystem to a dichroic beamsplitter, and wherein the dichroic beamsplitter is configured to direct the light from the second optical subsystem to the objective.

31. The system of claim 30, wherein the dichroic beamsplitter is further configured to direct at least a portion of the light from the first optical subsystem to the objective.

32. The system of claim 31, wherein the light from the specimen passes through the objective to the dichroic beamsplitter which directs the light from the specimen to the polarization beamsplitter, and wherein the polarization beamsplitter is further configured to direct the light from the specimen to the detection subsystem.

33. A system configured to inspect a specimen, comprising:

a first illumination subsystem configured to illuminate the specimen with light having a wavelength less than about 350 nm;

a second illumination subsystem configured to illuminate the specimen with light having a wavelength greater than about 350 nm, wherein the first and second illumination subsystems are further configured to illuminate the specimen in a narrow-band mode;

a first detection subsystem configured to detect a first portion of light from the specimen to produce optical phase signals representative of the first portion of the light;

a second detection subsystem configured to detect a second portion of light from the specimen to produce brightfield optical signals representative of the second portion of the light, wherein the first portion of light and the second portion of light have at least one different characteristic; and

a processor configured to process the signals produced by the first and second detection subsystems to detect defects or process variations on the specimen.

34. The system of claim 33, wherein the at least one different characteristic comprises different wavelengths.

35. The system of claim 33, wherein the at least one different characteristic comprises different polarizations.

36. The system of claim 33, wherein the first and second illumination subsystems have different illumination apertures.

37. The system of claim 33, wherein the first and second detection subsystems have different magnification settings.

38. The system of claim 33, wherein the first portion of light is produced from illumination of the specimen using the first illumination subsystem, and wherein the first detection subsystem has a magnification setting that is higher than a magnification setting of the second detection subsystem.

39. The system of claim 33, further comprising an auto-focus subsystem configured to operate at wavelengths within about 80 nm of the wavelength greater than about 350 nm.

40. The system of claim 33, wherein the first and second illumination subsystems are further configured to illuminate the specimen substantially simultaneously.

41. The system of claim 33, wherein the first and second detection subsystems are further configured to detect the first and second portions of light substantially simultaneously.