Unbiased wafer defect samples

• US 8,948,494 B2
• Filed: 03/11/2013
• Issued: 02/03/2015
• Est. Priority Date: 11/12/2012
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation (KLA Corporation)
• Original Assignee: KLA-Tencor Corporation (KLA Corporation)
• Inventors: Plihal, Martin, Anantha, Vidyasagar, Paramasivam, Saravanan, Lee, Chris W.
• Primary Examiner(s): CONWAY, THOMAS A
• Application Number:
  US13/793,709
• Publication Number:
  US 20140133737A1
• Time in Patent Office: 694 Days
• Field of Search: None
• US Class Current: 382/145
• CPC Class Codes: F04C 2270/0421 Controlled or regulated
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 7/0004 Industrial image inspection
• CPC Class Codes: G06T 7/0008 checking presence/absence

Abstract

Methods and systems for generating unbiased wafer defect samples are provided. One method includes selecting the defects detected by each of multiple scans performed on a wafer that have the most diversity in one or more defect attributes such that a diverse set of defects are selected across each scan. In addition, the method may include selecting the defects such that any defect that is selected and is common to two or more of the scans is not selected twice and any defects that are selected are diverse with respect to the common, selected defect. Furthermore, no sampling, binning, or classifying of the defects may be performed prior to selection of the defects such that the sampled defects are unbiased by any sampling, binning, or classifying method.

Claims

1. A computer-implemented method for generating a defect sample for a wafer, comprising:

identifying individual defects common to two or more of sets of defects, wherein each of the sets of defects is produced by a different one of multiple scans of a wafer;

acquiring two or more sampling parameter sets, one for each of the multiple scans such that each of the two or more sampling parameter sets corresponds to one of the sets of defects, wherein the two or more sampling parameter sets are selected independent of each other by a user, and wherein each of the two or more sampling parameter sets comprises one or more defect attributes;

selecting defects from each of the sets of defects based on the two or more sampling parameter sets, wherein said selecting comprises;

selecting, from each of the sets of defects, defects having the most diversity in the one or more defect attributes in the sampling parameter set corresponding to each of the sets of defects; and

if the defects selected from a first of the sets of defects comprise one of the individual defects that is common to the first set of defects and at least a second of the sets of defects;

selecting defects from the second set of defects that are diverse with respect to the one or more defect attributes, in the sampling parameter set corresponding to the second set of defects, of the one of the individual defects; and

not selecting a defect in the second set of defects that is common with the one of the individual defects; and

creating a defect sample for the wafer comprising the defects selected from each of the sets of defects, wherein said identifying, said acquiring, said selecting, and said creating are performed by a computer system.

2. The method of claim 1, further comprising setting up an inspection recipe based on the defect sample.

3. The method of claim 1, wherein the defect sample comprises real defects and nuisance defects.

4. The method of claim 1, wherein the wafer has unknown defectivity.

5. The method of claim 1, wherein sampling, binning, or classifying the defects in the sets of defects is not performed prior to said selecting.

6. The method of claim 1, wherein at least one of the one or more defect attributes included in at least one of the two or more sampling parameter sets is different than at least one of the one or more defect attributes included in at least one other of the two or more sampling parameter sets.

7. The method of claim 1, wherein the two or more sampling parameter sets further comprise a defect sample size for each of the multiple scans.

8. The method of claim 1, wherein at least one of the defects in at least one of the sets of defects is a known defect, and wherein said selecting, from each of the sets of defects, the defects having the most diversity comprises selecting, from at least the one of the sets of defects, defects having the most diversity, in the one or more defect attributes in the sampling parameter set corresponding to the at least one of the sets of defects, with respect to the known defect.

9. The method of claim 1, wherein at least one of the multiple scans is a hot scan.

10. The method of claim 1, wherein at least two of the multiple scans are performed with different values for one or more parameters of an inspection system that performs the multiple scans.

11. The method of claim 1, further comprising separating the defects in at least one of the sets into segments of defects and acquiring two or more additional sampling parameter sets, one corresponding to each of the segments of defects, wherein the two or more additional sampling parameter sets are selected independent of each other by the user, wherein each of the two or more additional sampling parameter sets comprises one or more additional defect attributes, and wherein said selecting the defects from each of the sets of defects further comprises selecting defects from each of the segments of defects based on the two or more additional sampling parameter sets.

12. The method of claim 11, wherein said selecting the defects from each of the sets of defects further comprises selecting, from each of the segments of defects, defects having the most diversity in the one or more additional defect attributes in the additional sampling parameter set corresponding to each of the segments of defects.

13. The method of claim 11, wherein if the defects selected from a first of the segments of defects in the first set of defects comprise one of the individual defects that is common to the first set of defects and at least the second set of defects, said selecting further comprises:

selecting defects from a second of the segments of defects in the second set of defects that are diverse with respect to the one or more additional defect attributes, in the additional sampling parameter set corresponding to the second of the segments, of the one of the individual defects; and

not selecting a defect in the second of the segments that is common with the one of the individual defects.

14. The method of claim 11, wherein each of the two or more additional sampling parameter sets further comprises a defect sample size for each of the segments.

15. The method of claim 11, wherein at least two of the segments correspond to two or more areas on the wafer spaced at different distances from an edge of the wafer.

16. The method of claim 11, wherein at least two of the segments correspond to different regions of interest on the wafer.

17. The method of claim 1, wherein at least one of the two or more sampling parameter sets further comprises one or more biasing parameters for at least one of the one or more defect attributes in the at least one sampling parameter set.

18. The method of claim 17, wherein said selecting, from each of the sets of defects, defects having the most diversity comprises selecting, in a diversification space defined by the one or more defect attributes in the sampling parameter set corresponding to at least one of the sets of defects, regions having the most diversity from each other and selecting one or more of the defects in each of the regions based on the one or more biasing parameters.

19. A non-transitory computer-readable medium, storing program instructions executable on a computer system for performing a computer-implemented method for generating a defect sample for a wafer, wherein the computer-implemented method comprises:

identifying individual defects common to two or more of sets of defects, wherein each of the sets of defects is produced by a different one of multiple scans of a wafer;

acquiring two or more sampling parameter sets, one for each of the multiple scans such that each of the two or more sampling parameter sets corresponds to one of the sets of defects, wherein the two or more sampling parameter sets are selected independent of each other by a user, and wherein each of the two or more sampling parameter sets comprises one or more defect attributes;

selecting defects from each of the sets of defects based on the two or more sampling parameter sets, wherein said selecting comprises;

selecting, from each of the sets of defects, defects having the most diversity in the one or more defect attributes in the sampling parameter set corresponding to each of the sets of defects; and

if the defects selected from a first of the sets of defects comprise one of the individual defects that is common to the first set of defects and at least a second of the sets of defects;

selecting defects from the second set of defects that are diverse with respect to the one or more defect attributes, in the sampling parameter set corresponding to the second set of defects, of the one of the individual defects; and

not selecting a defect in the second set of defects that is common with the one of the individual defects; and

creating a defect sample for the wafer comprising the defects selected from each of the sets of defects.

20. A system configured to generate a defect sample for a wafer, comprising:

an inspection subsystem configured to perform multiple scans of a wafer to produce sets of defects, each produced by a different one of the multiple scans; and

a computer subsystem configured for;

identifying individual defects common to two or more of the sets of defects;

acquiring two or more sampling parameter sets, one for each of the multiple scans such that each of the two or more sampling parameter sets corresponds to one of the sets of defects, wherein the two or more sampling parameter sets are selected independent of each other by a user, and wherein each of the two or more sampling parameter sets comprises one or more defect attributes;

selecting defects from each of the sets of defects based on the two or more sampling parameter sets, wherein said selecting comprises;

selecting, from each of the sets of defects, defects having the most diversity in the one or more defect attributes in the sampling parameter set corresponding to each of the sets of defects; and

if the defects selected from a first of the sets of defects comprise one of the individual defects that is common to the first set of defects and at least a second of the sets of defects;

selecting defects from the second set of defects that are diverse with respect to the one or more defect attributes, in the sampling parameter set corresponding to the second set of defects, of the one of the individual defects; and

not selecting a defect in the second set of defects that is common with the one of the individual defects; and

creating a defect sample for the wafer comprising the defects selected from each of the sets of defects.