Detecting defects on a wafer using defect-specific and multi-channel information

• US 9,092,846 B2
• Filed: 01/31/2014
• Issued: 07/28/2015
• Est. Priority Date: 02/01/2013
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation (KLA Corporation)
• Original Assignee: KLA-Tencor Corporation (KLA Corporation)
• Inventors: Wu, Kenong, Gao, Lisheng, Chen, Grace Hsiu-Ling, Shortt, David W.
• Primary Examiner(s): Alavi, Amir
• Application Number:
  US14/169,161
• Publication Number:
  US 20140219544A1
• Time in Patent Office: 543 Days
• US Class Current: 1/1
• CPC Class Codes: G01N 2021/8822 Dark field detection
• CPC Class Codes: G01N 2021/8848 Polarisation of light
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/8851 Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges G01N21/8806 and G01N21/93 - G01N21/95692 take precedence; optical measurement of dimensions G01B11/00; optical scanning G02B26/10; image transformation G06T3/00; computerised image enhancement G06T5/00; image processing per se for flaw detection G06T7/0002
• 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 21/956 Inspecting patterns on the surface of objects contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/0008 checking presence/absence
• CPC Class Codes: G06T 7/001 using an image reference approach
• CPC Class Codes: H01L 22/12 for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions electrical measurement of diffusions H01L22/14
• CPC Class Codes: H01L 22/34 Circuits for electrically characterising or monitoring manufacturing processes, e. g. whole test die, wafers filled with test structures, on-board-devices incorporated on each die, process control monitors or pad structures thereof, devices in scribe line switching, multiplexing, gating devices G01R19/25; process control with lithography, e.g. dose control, G03F7/20; structures for alignment control by optical means G03F7/70633

Abstract

Methods and systems for detecting defects on a wafer using defect-specific and multi-channel information are provided. One method includes acquiring information for a target on a wafer. The target includes a pattern of interest (POI) formed on the wafer and a known defect of interest (DOI) occurring proximate to or in the POI. The method also includes detecting the known DOI in target candidates by identifying potential DOI locations based on images of the target candidates acquired by a first channel of an inspection system and applying one or more detection parameters to images of the potential DOI locations acquired by a second channel of the inspection system. Therefore, the image(s) used for locating potential DOI locations and the image(s) used for detecting defects can be different.

Claims

1. A computer-implemented method for detecting defects on a wafer, comprising:

acquiring information for a target on a wafer, wherein the target comprises a pattern of interest formed on the wafer and a known defect of interest occurring proximate to or in the pattern of interest, and wherein the information comprises a first image of the pattern of interest on the wafer acquired by imaging the pattern of interest on the wafer with a first channel of an inspection system, a second image of the known defect of interest on the wafer acquired by imaging the known defect of interest with a second channel of the inspection system, a location of the pattern of interest on the wafer, a location of the known defect of interest relative to the pattern of interest, and one or more characteristics computed from the pattern of interest and the known defect of interest;

searching for target candidates within one die on the wafer, or on another wafer, wherein the target candidates comprise the pattern of interest; and

detecting the known defect of interest in the target candidates by identifying potential defect of interest locations based on images of the target candidates acquired by the first channel and applying one or more detection parameters to images acquired by the second channel of the potential defect of interest locations, wherein said detecting is performed using a computer system.

2. The method of claim 1, wherein design data for the wafer or the other wafer is not required for any step of the method.

3. The method of claim 1, wherein the location of the known defect of interest is obtained based on design data for the wafer.

4. The method of claim 1, wherein the location of the known defect of interest is obtained based on optical images or scanning electron microscope images of the wafer.

5. The method of claim 1, further comprising determining the location of the known defect of interest in an optical image of the wafer by correlating a scanning electron microscope image of the known defect of interest to the optical image of the wafer.

6. The method of claim 1, wherein acquiring the information for the target comprises grabbing images of the target on the wafer with multiple channels of the inspection system, and wherein the multiple channels comprise at least the first channel and the second channel.

7. The method of claim 1, wherein acquiring the information for the target comprises grabbing images of the pattern of interest with multiple channels of the inspection system, determining which of the grabbed images is best for pattern searching, and designating one of the multiple channels with which the best of the grabbed images for the pattern searching was grabbed as the first channel.

8. The method of claim 1, wherein acquiring the information for the target comprises generating additional images of the wafer at and proximate to the known defect of interest with multiple channels of the inspection system, determining which of the additional images is best for pattern searching, and selecting the pattern of interest from the additional image that is determined to be the best for the pattern searching.

9. The method of claim 1, wherein acquiring the information for the target comprises grabbing images of the known defect of interest with multiple channels of the inspection system, determining which of the grabbed images is best for said detecting, and designating one of the multiple channels with which the best of the grabbed images was grabbed as the second channel.

10. The method of claim 1, wherein acquiring the information for the target comprises specifying size, shape and location of care areas, size, shape and location of templates, and area where the one or more characteristics are determined in the images to which the one or more detection parameters are applied.

11. The method of claim 1, wherein acquiring the information for the target comprises grabbing templates for all known defects of interest in one die, on the wafer or the other wafer, in which said searching is performed with at least the first channel of the inspection system.

12. The method of claim 1, wherein acquiring the information for the target comprises determining a similarity between a template for the pattern of interest and an image of the target acquired by imaging the target on the wafer with the first channel and determining a uniqueness of the pattern of interest relative to other patterns proximate to the pattern of interest.

13. The method of claim 1, wherein the pattern of interest has a width and a height that are shorter than a width and a height, respectively, of dies formed on the wafer and the other wafer.

14. The method of claim 1, wherein the one or more characteristics comprise size, shape, intensity, contrast, or polarity of the known defect of interest.

15. The method of claim 1, wherein the one or more characteristics comprise one or more characteristics of the known defect of interest determined from the second image acquired with the second channel.

16. The method of claim 1, wherein the location of the known defect of interest is unique relative to the location of the pattern of interest.

17. The method of claim 1, wherein micro care areas are generated to cover one or more of the potential defect of interest locations.

18. The method of claim 1, wherein said acquiring and said searching are performed with the inspection system in a setup step before defect detection.

19. The method of claim 1, wherein said acquiring and said searching are performed with a different inspection system of the same type as the inspection system.

20. The method of claim 1, wherein said acquiring and said searching are performed in different dies on the wafer or the other wafer, and wherein said searching is performed in one die on the wafer or the other wafer using one or more templates for the target candidates.

21. The method of claim 1, further comprising determining one or more parameters of a care area based on results of said searching.

22. The method of claim 1, further comprising determining a care area location by correlating a template image for the pattern of interest and the images for the target candidates acquired by the first channel and applying the care area location to the images acquired by the second channel of the potential defect of interest locations.

23. The method of claim 1, further comprising selecting one or more characteristics of the target, selecting the one or more detection parameters, and determining one or more parameters of a care area such that defects other than the known defect of interest are not detected in the target candidates.

24. The method of claim 1, further comprising creating a template for the pattern of interest and modifying the template by changing the size of the template or flipping, rotating, or processing the template.

25. The method of claim 1, wherein the first channel, at least in part, defines the best optics mode for image matching of the images of the target candidates to the first image or a template for the pattern of interest.

26. The method of claim 1, further comprising determining the one or more detection parameters based on the information for the target.

27. The method of claim 1, wherein the inspection system uses different optics modes in the first and second channels, and wherein the different optics modes are defined by spectrum, aperture, polarization, or some combination thereof.

28. The method of claim 1, wherein the images acquired by the first and second channels are spatially registered to each other by image sensor calibration and alignment algorithms applied on the images.

29. A non-transitory computer-readable medium, storing program instructions executable on a computer system for performing a computer-implemented method for detecting defects on a wafer, wherein the computer-implemented method comprises:

acquiring information for a target on a wafer, wherein the target comprises a pattern of interest formed on the wafer and a known defect of interest occurring proximate to or in the pattern of interest, and wherein the information comprises a first image of the pattern of interest on the wafer acquired by imaging the pattern of interest on the wafer with a first channel of an inspection system, a second image of the known defect of interest on the wafer acquired by imaging the known defect of interest with a second channel of the inspection system, a location of the pattern of interest on the wafer, a location of the known defect of interest relative to the pattern of interest, and one or more characteristics computed from the pattern of interest and the known defect of interest;

searching for target candidates in one die on the wafer or on another wafer, wherein the target candidates comprise the pattern or interest; and

detecting the known defect of interest in the target candidates by identifying potential defect of interest locations based on images of the target candidates acquired by the first channel and applying one or more detection parameters to images acquired by the second channel of the potential defect of interest locations.

30. A system configured to detect defects on a wafer, comprising:

an inspection subsystem configured to acquire information for a target on a wafer, wherein the target comprises a pattern of interest formed on the wafer and a known defect of interest occurring proximate to or in the pattern of interest, and wherein the information comprises a first image of the pattern of interest on the wafer acquired by imaging the pattern of interest on the wafer with a first channel of the inspection subsystem and a second image of the known defect of interest on the wafer acquired by imaging the known defect of interest with a second channel of the inspection subsystem;

wherein the inspection subsystem is further configured to search for target candidates in one die on the wafer or on another wafer, wherein the target candidates comprise the pattern of interest; and

a computer system configured to detect the known defect of interest in the target candidates by identifying potential defect of interest locations based on images of the target candidates acquired by the first channel and applying one or more detection parameters to images acquired by the second channel of the potential defect of interest locations.

31. The system of claim 30, wherein design data for the wafer or the other wafer is not required for any step performed by the inspection subsystem or the computer system.

32. The system of claim 30, wherein a location of the known defect of interest is obtained based on design data for the wafer.

33. The system of claim 30, wherein a location of the known defect of interest is obtained based on optical images or scanning electron microscope images of the wafer.

34. The system of claim 30, wherein the computer system is further configured for determining a location of the known defect of interest in an optical image of the wafer by correlating a scanning electron microscope image of the known defect of interest to the optical image of the wafer.

35. The system of claim 30, wherein the inspection subsystem is further configured to acquire the information for the target by grabbing images of the target on the wafer with multiple channels of the inspection subsystem, and wherein the multiple channels comprise at least the first channel and the second channel.

36. The system of claim 30, wherein the inspection subsystem is further configured to acquire the information for the target by grabbing images of the pattern of interest with multiple channels of the inspection subsystem, and wherein the computer system is further configured for determining which of the grabbed images is best for pattern searching and designating one of the multiple channels with which the best of the grabbed images for the pattern searching was grabbed as the first channel.

37. The system of claim 30, wherein the inspection subsystem is further configured to acquire the information for the target by generating additional images of the wafer at and proximate to the known defect of interest with multiple channels of the inspection subsystem, and wherein the computer system is further configured for determining which of the additional images is best for pattern searching and selecting the pattern of interest from the additional image that is determined to be the best for the pattern searching.

38. The system of claim 30, wherein the inspection subsystem is further configured to acquire the information for the target by grabbing images of the known defect of interest with multiple channels of the inspection subsystem, and wherein the computer system is further configured for determining which of the grabbed images is best for detecting the known defect of interest and designating one of the multiple channels with which the best of the grabbed images was grabbed as the second channel.

39. The system of claim 30, wherein the computer system is further configured to acquire the information for the target by specifying size, shape and location of care areas, size, shape and location of templates, and area where one or more characteristics are determined in the images to which the one or more detection parameters are applied.

40. The system of claim 30, wherein the inspection subsystem is further configured to acquire the information for the target by grabbing templates for all known defects of interest in one die, on the wafer or the other wafer, in which the inspection subsystem searches for the target candidates with at least the first channel of the inspection subsystem.

41. The system of claim 30, wherein the computer system is further configured for acquiring the information for the target by determining a similarity between a template for the pattern of interest and an image of the target acquired by imaging the target on the wafer with the first channel and determining a uniqueness of the pattern of interest relative to other patterns proximate to the pattern of interest.

42. The system of claim 30, wherein the pattern of interest has a width and a height that are shorter than a width and a height, respectively, of dies formed on the wafer and the other wafer.

43. The system of claim 30, wherein the information for the target further comprises one or more characteristics computed from the pattern of interest and the known defect of interest, and wherein the one or more characteristics comprise size, shape, intensity, contrast, or polarity of the known defect of interest.

44. The system of claim 30, wherein the information for the target further comprises one or more characteristics computed from the pattern of interest and the known defect of interest, and wherein the one or more characteristics comprise one or more characteristics of the known defect of interest determined from the second image acquired with the second channel.

45. The system of claim 30, wherein a location of the known defect of interest is unique relative to a location of the pattern of interest.

46. The system of claim 30, wherein micro care areas are generated to cover one or more of the potential defect of interest locations.

47. The system of claim 30, wherein the inspection subsystem is further configured to acquire the information and search for the target candidates in a setup step before defect detection.

48. The system of claim 30, wherein the inspection subsystem is further configured to acquire the information and search for the target candidates in different dies on the wafer or the other wafer, and wherein the inspection subsystem is further configured to search for the target candidates in one die on the wafer or the other wafer using one or more templates for the target candidates,

49. The system of claim 30, wherein the computer system is further configured for determining one or more parameters of a care area based on results of searching for the target candidates.

50. The system of claim 30, wherein the computer system is further configured for determining a care area location by correlating a template image for the pattern of interest and the images for the target candidates acquired by the first channel and applying the care area location to the images acquired by the second channel of the potential defect of interest locations.

51. The system of claim 30, wherein the computer system is further configured for selecting one or more characteristics of the target, selecting the one or more detection parameters, and determining one or more parameters of a care area such that defects other than the known defect of interest are not detected in the target candidates.

52. The system of claim 30, wherein the computer system is further configured for creating a template for the pattern of interest and modifying the template by changing the size of the template or flipping, rotating, or processing the template.

53. The system of claim 30, wherein the first channel, at least in part, defines the best optics mode for image matching of the images of the target candidates to the first image or a template for the pattern of interest.

54. The system of claim 30, wherein the computer system is further configured for determining the one or more detection parameters based on the information for the target.

55. The system of claim 30, wherein the inspection subsystem uses different optics modes in the first and second channels, and wherein the different optics modes are defined by spectrum, aperture, polarization, or some combination thereof.

56. The system of claim 30, wherein the images acquired by the first and second channels are spatially registered to each other by image sensor calibration and alignment algorithms applied on the images.