Unbiased wafer defect samples

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.

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.