High throughput brightfield/darkfield wafer inspection system using advanced optical techiques

• US 20050062962A1
• Filed: 11/04/2004
• Published: 03/24/2005
• Est. Priority Date: 06/06/1995
• Status: Active Grant

• Current Assignee: Bin-Ming Benjamin Tsai, Christopher R. Fairley, Gershon Perelman, Tao Y.I. Fu
• Original Assignee: Bin-Ming Benjamin Tsai, Christopher R. Fairley, Gershon Perelman, Tao Y.I. Fu
• Inventors: Tsai, Bin-Ming Benjamin, Fairley, Christopher R., Perelman, Gershon, Fu, Tao Yi
• Granted Patent: US 7,164,475 B2
• Time in Patent Office: Days
• US Class Current: 356/237.200
• CPC Class Codes: G01N 2021/8825 Separate detection of dark field and bright field
• 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
• CPC Class Codes: G01N 21/95607 using a comparative method
• CPC Class Codes: G01N 21/95623 using a spatial filtering method per se G02B

Abstract

The broadband brightfield/darkfield wafer inspection system provided receives broadband brightfield illumination information via a defect detector, which signals for initiation of darkfield illumination. The defect detector forms a two dimensional histogram of the defect data and a dual mode defect decision algorithm and post processor assess defects. Darkfield radiation is provided by two adjustable height laser beams which illuminate the surface of the wafer from approximately 6 to 39 degrees. Each laser is oriented at an azimuth angle 45 degrees from the orientation of the Manhattan geometry on the wafer, and 90 degrees in azimuth from one another. Vertical angular adjustability is provided by modifying cylindrical lens position to compensate for angular mirror change by translating an adjustable mirror, positioning the illumination spot into the sensor field of view, rotating and subsequently moving the cylindrical lens. A brightfield beamsplitter in the system is removable, and preferably replaced with a blank when performing darkfield illumination. Light level control for the system is provided by a dual polarizer first stage. Light exiting from the second polarizer passes through a filter which absorbs a portion of the light and comprises the second stage of light control. The beam then passes through a polarizing beamsplitter. The second channel is further reflected and polarized and both beams thereafter illuminate the substrate.

Claims

1. (canceled)

2-16. -16. (canceled)

17. A system for inspecting a specimen, comprising:

a variable angle illuminator having the ability to generate an incident beam at a variable angle and direct said incident beam to a predetermined region of said specimen;

a light collection system for collecting light scattered from the predetermined region with a predetermined collection angle and utilizing a variable angle design to select from the collected light; and

a sensor for receiving the collected light and generating data representative thereof.

18. The system of claim 17, further comprising a brightfield illuminator, and wherein a dual mode representation of the specimen is possible using combined data collected from the brightfield illuminator and the darkfield illuminator.

19. The system of claim 18, further comprising a defect detector, said defect detector comprising:

a comparator for comparing darkfield illuminations of said specimen with ideal darkfield images; and

a combined scan generator which produces a dual mode representation of said specimen using combined data from the broadband brightfield illuminator and the darkfield illuminator.

20. The system of claim 18, wherein the sensor senses energy transmitted from both said brightfield illuminator and said darkfield illuminator.

21. The system of claim 20, further comprising:

an input buffer configured to receive information from said sensor; and

a post processor configured to receive information from said defect detector.

22. The system of claim 21, further comprising a delay between said input buffer and said defect detector.

23. The system of claim 22, further comprising a feedback connection from said defect detector to at least one of said brightfield illuminator and said darkfield illuminator;

wherein said feedback connection provides an indication of completion of broadband brightfield or darkfield image defect detection.

24. The system of claim 18, wherein said dual mode representation comprises a two dimensional histogram having both brightfield data and darkfield data.

25. The system of claim 20, wherein said defect detector further comprises a defect detection algorithm.

26. The system of claim 25, wherein said defect detection algorithm detects defects from both broadband brightfield anomalies and darkfield anomalies.

27. An apparatus for inspecting a specimen, comprising:

a light source providing light energy toward said specimen;

a movable light energy redirector for advantageously redirecting light energy toward said specimen at a first angle; and

a diversion element for receiving light from the light energy redirector and diverting said light energy at a second angle toward a predetermined position on the specimen.

28. The apparatus of claim 27, further comprising a sensor for sensing light energy reflected from said specimen.

29. The apparatus of claim 28, wherein the sensor comprises a TDI sensor.

30. The apparatus of claim 29, wherein the TDI sensor comprises an anti-blooming TDI sensor.

31. The apparatus of claim 27, wherein said apparatus employs darkfield illumination.

32. The apparatus of claim 31, further comprising a brightfield illumination source.

33. The apparatus of claim 32, further comprising a combined scan generator which produces a dual mode representation of said specimen using combined data from the brightfield illumination source and the darkfield illumination source.

34. The apparatus of claim 33, wherein said dual mode representation comprises a two dimensional histogram having both brightfield data and darkfield data.

35. A variable illumination angle inspection system, comprising:

a light source providing a light beam;

a movable optical element for imparting scanning deflection to the light beam to provide a beam approaching a specimen at a first angle; and

a variable angle deflection device for deflecting the beam so as to approach the specimen at a second angle.

36. The system of claim 35, further comprising a sensor for sensing light energy reflected from said specimen.

37. The system of claim 36, wherein the sensor comprises a TDI sensor.

38. The system of claim 37, wherein the TDI sensor comprises an anti-blooming TDI sensor.

39. The system of claim 35, wherein said system employs darkfield illumination.

40. The system of claim 39, further comprising a brightfield illumination source.

41. The system of claim 40, further comprising a combined scan generator which produces a dual mode representation of said specimen using combined data from the brightfield illumination source and the darkfield illumination source.

42. The system of claim 41, wherein said dual mode representation comprises a two dimensional histogram having both brightfield data and darkfield data.

47. The system of claim 42, wherein said system employs darkfield illumination.

48. The system of claim 47, further comprising a brightfield illumination source.

49. The system of claim 48, further comprising a combined scan generator which produces a dual mode representation of said specimen using combined data from the brightfield illumination source and the darkfield illumination source.

50. The system of claim 49, wherein said dual mode representation comprises a two dimensional histogram having both brightfield data and darkfield data.

43. A variable illumination angle inspection system for inspecting a specimen, comprising:

a light source providing a light beam;

adjustable means for outputting the light beam along a first optical path toward the specimen, the first optical path including a portion incident to the specimen and forming a first angle relative to the specimen; and

redirecting means for diverting the light beam received from the adjustable means at the first angle along a second optical path including a portion incident to the specimen and forming a second angle relative to the specimen;

wherein the first angle is different from the second angle.

44. The system of claim 43, further comprising a sensor for sensing light energy reflected from said specimen.

45. The system of claim 44, wherein the sensor comprises a TDI sensor.

46. The system of claim 45, wherein the TDI sensor comprises an anti-blooming TDI sensor.

51. A variable illumination angle inspection system for inspecting a specimen, comprising:

an alterable light source arrangement having the ability to provide a light beam toward the specimen at a variable angle, said alterable light source arrangement comprising a light source;

a deflection arrangement for redirecting light energy received from said alterable light source arrangement at an angle differing from said variable angle, wherein said differing angle redirects light energy toward the specimen; and

a sensor for receiving light energy reflected from the specimen.

52. The system of claim 51, wherein the sensor comprises a TDI sensor.

53. The system of claim 52, wherein the TDI sensor comprises an anti-blooming TDI sensor.

54. The system of claim 51, wherein said system employs darkfield illumination.

55. The system of claim 54, further comprising a brightfield illumination source.

56. The system of claim 55, further comprising a combined scan generator which produces a dual mode representation of said specimen using combined data from the brightfield illumination source and the darkfield illumination source.

57. The system of claim 56, wherein said dual mode representation comprises a two dimensional histogram having both brightfield data and darkfield data.