Sub-Pixel and Sub-Resolution Localization of Defects on Patterned Wafers

Patent metadata

Field	Value
Publication number	US-2016292840-A1
Application number	US-201615084340-A
Country	US
Kind code	A1
Filing date	Mar 29, 2016
Priority date	Mar 31, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

Methods and systems for determining if a defect detected on a specimen is a DOI (Defect of Interest) or a nuisance are provided. One system includes computer subsystem(s) configured for aligning output of an inspection subsystem for an area on a specimen to simulated output of the inspection subsystem for the area on the specimen and detecting a defect in the output for the area on the specimen. The computer subsystem(s) are also configured for determining a location of the defect in the output with respect to patterned features in the simulated output based on results of the detecting and aligning, determining a distance between the determined location of the defect and a known location of interest on the specimen, and determining if the defect is a DOI or a nuisance based on the determined distance.

First claim

What is claimed is:

1 . A system configured to determine if a defect detected on a specimen is a defect of interest or a nuisance, comprising:
an inspection subsystem comprising at least an energy source and a detector, wherein the energy source is configured to generate energy that is directed to a specimen, and wherein the detector is configured to detect energy from the specimen and to generate output responsive to the detected energy; and one or more computer subsystems configured for:
aligning the output of the inspection subsystem for an area on the specimen to simulated output of the inspection subsystem for the area on the specimen;
detecting a defect in the output for the area on the specimen;
determining a location of the defect in the output with respect to patterned features in the simulated output based on results of said detecting and said aligning;
determining a distance between the determined location of feet and a known location of interest on the specimen; and
determining if the defect is a defect of interest or a nuisance based on the determined distance.

2 . The system of claim 1 , wherein the known location f interest comprises a known location of a defect of interest.

3 . The system of claim 1 , wherein the one or more computer subsystems are further configured for generating different models of the specimen for different areas on the specimen and generating the simulated output for the area by selecting one of the different models corresponding to the area and simulating how the area would appear in the output generated by the inspection subsystem for the area based on the selected one of the different models.

4 . The system of claim 1 , wherein said aligning comprises performing multiple alignment steps in which the output for the area is separately aligned to multiple simulated outputs for the area, determining which of the multiple alignment steps produced the best alignment, and selecting results of the multiple alignment step determined to produce the best alignment as the results of the aligning used for determining the location of the defect.

5 . The system of claim 1 , wherein said aligning comprises maximizing a cross-correlation between the output and the simulated output.

6 . The system of claim 1 , wherein said aligning aligns the output to the simulated output with sub-pixel accuracy.

7 . The system of claim 1 , wherein said aligning aligns the output to the simulated output with sub-resolution accuracy.

8 . The system of claim 1 , wherein the output used for said aligning comprises a reference image for the area, wherein the output for the area further comprises a target image, and wherein the one or more computer subsystems are further configured for aligning the target image for the area to the reference image thereby aligning the target image to the simulated output.

9 . The system of claim 1 , wherein the output for the area comprises reference output and target output for the area, wherein detecting the defect comprises generating a difference image for the area by subtracting the reference output for the area from the target output for the area and detecting the defect in the difference image by applying a threshold to the difference image, and Wherein the threshold is a hot threshold.

10 . The system of claim 1 , wherein the output for the area comprises reference output and target output for the area, wherein detecting the defect comprises generating a difference image for the area by subtracting the reference output for the area from the target output for the area and applying a defect detection method to the difference image, and wherein determining the location of the defect is performed by fitting a portion of the difference image corresponding to the defect to a Gaussian function.

11 . The system of claim 1 , wherein the output for the area comprises reference output and target output for the area, wherein detecting the defect comprises generating a difference image for the area by subtracting the reference output for the area from the target output for the area and applying a defect detection method to the difference image, and wherein determining the location of the defect is performed by fitting a portion of the difference image corresponding to the defect to a function.

12 . The system of claim 1 , wherein the output for the area comprises reference output and target output for the area, wherein detecting the defect comprises generating a difference image for the area by subtracting the reference output for the area from the target output for the area and applying a defect detection method to the difference image, and wherein determining the location of the defect is performed by fitting a portion of the difference image corresponding to the defect to an Airy disc function.

13 . The system of claim 1 , wherein the output for the area comprises reference output and target output for the area, wherein detecting the defect comprises generating a difference image for the area by subtracting the reference output for the area from the target output for the area and applying a defect detection method to the difference image, and wherein determining the location of the defect is performed by determining a centroid of the defect in the difference image.

14 . The system of claim 1 , wherein the output for the area comprises reference output and target output for the area, wherein detecting the defect comprises generating a difference image for the area by subtracting the reference output for the area from the target output for the area and applying a defect detection method to the difference image, and wherein determining the location of the defect comprises shifting a simulated image of a profile of the defect relative to the difference image until a cross-correlation between the simulated image of the profile of the defect and the difference image is maximized.

15 . The system of claim 1 , wherein the output for the area comprises reference output and target output for the area, wherein detecting the defect comprises generating a difference image for the area by subtracting the reference output for the area from the target output for the area and applying a defect detection method to the difference image, and wherein determining the location of the defect comprises shifting a simulated image of a profile of the defect relative to the difference image until a sum-squared difference between the simulated image of the profile of the defect and the difference image is minimized.

16 . The system of claim 1 , wherein the output for the area comprises reference output and target output for the area, wherein detecting the defect comprises generating a difference image for the area by subtracting the reference output for the area from the target output for the area and applying a defect detection method to the difference image, and wherein determining the location of the defect comprises performing interpolation to upsample the difference image onto a grid of pixels that is finer than a grid of pixels in the output and using a location of a center of a pixel in the finer grid of pixels with the strongest signal as the location of the defect.

17 . The system of claim 1 , wherein the location of the defect with respect to the patterned features is determined with sub-pixel accuracy.

18 . The system of claim 1 , wherein the location of the defect with respect to the patterned features is determined with sub-resolution accuracy.

19 . The system of claim 1 , wherein determining i

Assignees

• Kla Tencor Corp

Inventors

• Konecky Soren

Classifications

• G06T2207/30148

  Semiconductor; IC; Wafer · CPC title

• G06T7/001 Primary

  using an image reference approach · CPC title

• G06T2207/10061

  from scanning electron microscope · CPC title

• G06T7/0044

  Physics · mapped topic

• G06T7/0024

  Physics · mapped topic