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

• US 20050052643A1
• Filed: 09/03/2004
• Published: 03/10/2005
• 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: Hwang, Shiow-Hwei, Fu, Tao-Yi, Marella, Paul Frank, Ceglio, Nat, Lange, Steve R.
• Granted Patent: US 7,738,089 B2
• Time in Patent Office: Days
• US Class Current: 356/237.100
• 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 computer-implemented method, comprising:

determining optimal parameters for inspection of a specimen based on defects selected for detection on the specimen; and

setting parameters of an inspection system at the optimal parameters prior to the inspection of the specimen.

2. The method of claim 1, wherein the optimal parameters result in more of the defects being detected during the inspection than that which would be detected during the inspection using other parameters.

3. The method of claim 1, wherein the optimal parameters result in fewer non-selected defects being detected during the inspection than that which would be detected during the inspection using other parameters.

4. The method of claim 1, wherein the optimal parameters result in a number of false defects detected during the inspection equal to or less than that which would be detected during the inspection using other parameters.

5. The method of claim 1, wherein the defects are selected by a user.

6. The method of claim 1, wherein said setting is performed by a computer.

7. The method of claim 1, wherein the defects comprise relatively low contrast defects.

8. The method of claim 1, wherein said determining comprises performing one or more test inspections of the specimen with different parameters and identifying which of the different parameters produces the largest capture rate of the defects.

9. The method of claim 8, wherein said identifyng comprises classifying defects detected during the one or more test inspections.

10. The method of claim 8, wherein said identifying comprises automatically classifying defects detected during the one or more test inspections.

11. The method of claim 8, wherein said determining further comprises determining which of the different parameters produces the largest capture rate of the defects without increasing a number of false defects that are detected.

12. The method of claim 1, wherein said determining comprises performing one or more test inspections of a test specimen, known to have one or more of the defects, with different parameters and identifying which of the different parameters produces the largest capture rate of the defects.

13. The method of claim 1, wherein the specimen is a wafer or a reticle.

14. 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 signals representative of the collected light; and

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

15. The method of claim 14, wherein the collected light comprises a bright field image of at least a portion of the specimen.

16. The method of claim 14, wherein at least a portion of a surface of the specimen comprises polysilicon, single crystal silicon, silicon dioxide, silicon nitride, or any combination thereof.

17. The method of claim 14, wherein the first and second subsystems are optimized for the at least one wavelength below and above about 350 nm, respectively.

18. The method of claim 14, 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.

19. The method of claim 14, wherein the first subsystem comprises a laser.

20. The method of claim 14, wherein the second subsystem comprises a polychromatic light source.

21. The method of claim 14, wherein the second subsystem comprises an arc lamp.

22. The method of claim 14, wherein the second subsystem comprises a laser.

23. The method of claim 14, wherein the first and second subsystems comprise a common laser.

24. The method of claim 14, wherein the first subsystem comprises a first laser, and wherein the second subsystem comprises a second laser.

25. The method of claim 14, wherein the first and second subsystems comprise a common polychromatic light source.

26. The method of claim 14, wherein the first subsystem comprises a first polychromatic light source, and wherein the second subsystem comprises a second polychromatic light source.

27. The method of claim 14, 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.

28. The method of claim 14, wherein said illuminating comprises illuminating the specimen using the first and second subsystems substantially simultaneously.

29. The method of claim 14, wherein said illuminating comprises illuminating the specimen using the first and second subsystems at different times.

30. 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.

31. The method of claim 30, 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.

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

a first optical subsystem coupled to a broadband light source;

a second optical subsystem coupled to a laser;

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.

33. The system of claim 32, wherein the first optical subsystem comprises an ellipsoidal mirror configured to produce a substantially aberration-free image of the broadband light source.

34. The system of claim 32, wherein the first optical subsystem comprises an ellipsoidal mirror configured to provide substantially efficient coupling of light from the broadband light source to the third optical subsystem.

35. The system of claim 32, wherein the first optical subsystem 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.

36. The system of claim 32, wherein the first optical subsystem comprises a beam shaping element configured to alter a beam profile of the broadband light source such that the beam profile is substantially uniform.

37. The system of claim 32, wherein the first optical subsystem comprises a double zooming element configured to alter an optical invariant of the broadband light source.

38. The system of claim 37, wherein the first optical subsystem further comprises a light pipe disposed between individual zooming elements of the double zooming element.

39. The system of claim 32, wherein the third optical subsystem is further configured to allow substantially efficient coupling of the light from the second optical subsystem to the objective.

40. The system of claim 32, wherein the objective is further configured to illuminate the specimen with the light from the first and second optical subsystems substantially simultaneously.

41. The system of claim 32, wherein the laser is configured to generate light having a wavelength less than about 350 nm.

42. The system of claim 32, wherein the laser is configured to generate light having a wavelength of about 266 nm.

43. The system of claim 32, wherein the broadband light source is configured to generate visible light, ultraviolet light, deep ultraviolet light, or a combination thereof.

44. The system of claim 32, 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.

45. The system of claim 44, wherein the dichroic beamsplitter is further configured to direct at least a portion of the light from the first optical subsystem to the objective.

46. The system of claim 45, 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.

47. 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;

a first detection subsystem configured to detect a first portion of light from the specimen;

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

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

48. The system of claim 47, wherein the at least one different characteristic comprises different wavelengths.

49. The system of claim 47,-wherein the at least one different characteristic comprises different polarizations.

50. The system of claim 47, wherein the first and second illumination subsystems have different illumination apertures.

51. The system of claim 47, wherein the first and second detection subsystems have different magnification settings.

52. The system of claim 47, 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.

53. The system of claim 47, further comprising an auto-focus subsystem configured to operate at wavelengths within about 80 nm of the wavelength greater than about 350 nm.

54. The system of claim 47, wherein the first and second illumination subsystems are further configured to illuminate the specimen in a narrow-band mode.

55. The system of claim 47, wherein the first illumination subsystem is further configured to illuminate the specimen in a narrow-band mode, and wherein the second illumination subsystem is further configured to illuminate the specimen in a broadband mode.

56. The system of claim 47, wherein the first and second illumination subsystems are further configured to illuminate the specimen substantially simultaneously.

57. The system of claim 47, wherein the first and second detection subsystems are further configured to detect the first and second portions of light substantially simultaneously.