Pattern matching method and apparatus

Patent metadata

Field	Value
Publication number	US-10318805-B2
Application number	US-201313783333-A
Country	US
Kind code	B2
Filing date	Mar 3, 2013
Priority date	Apr 24, 2012
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

When the degree of matching between patterns decreases due to a pattern fluctuation or an appearance fluctuation that has occurred during manufacturing steps, a heavy work burden would be placed on an operator. A data processing unit of a pattern matching apparatus calculates a threshold for determination of matching between a first template image and a partial region of a search target image obtained by capturing an image of the surface of a sample, on the basis of a result of evaluation of a similarity between the search target image and a second template image, the second template image having been captured in a wider range than the first template image.

First claim

What is claimed is:

1. A pattern matching method for matching a search target image comprising:
capturing a search target image formed based on an output of a particle detector configured to detect a secondary particle emitted from an irradiation region of a charged particle beam;
selecting a first template image and a second template image, the second template image having a field of view wider than a field of view of the first template image;
overlaying the search target image and the second template image one on top of the other;
determining, using an image processor, a similarity degree comprising a correlation value, of a common region of the overlaid search target image and the second template image;
adjusting, using the image processor, a similarity threshold on the basis of a result of the evaluation of the similarity degree using the first template image, wherein the similarity threshold determines a matching position or a candidate of the matching position from the search target image, and wherein the adjusting of the similarity threshold is performed in accordance with the correlation value such that the similarity threshold decreases as the correlation value decreases;
searching, using the image processor, for the matching position and the candidate of the matching position in the search target image, using the first template image and the adjusted similarity threshold, within the search target image whose similarity degree has been evaluated; and
extracting a region of the search target image having a pattern similarity which exceeds the adjusted similarity threshold.

2. The pattern matching method according to claim 1 , further comprising, when the result of the matching between the first template image and the search target image is below the similarity threshold:
registering, using the image processor, a first template image newly set in or around the search target image, and a new second template image including the newly set first template image or a pattern around the newly set first template image.

3. The pattern matching method according to claim 2 , further comprising:
registering, using the image processor, position information on alignment reference position coordinates corresponding to the first template image, and position information on the first and second template images, together with the first and second template images.

4. The pattern matching method according to claim 1 , further comprising, when a plurality of regions whose similarities are evaluated to be above the similarity threshold are detected in the search target image:
setting, with the image processor, a region with a highest reliability among the plurality of regions as a matched region on the basis of position information on the second template image and the first template image.

5. A pattern matching apparatus for matching a search target image, the apparatus comprising:
a charged particle beam source configured to irradiate a surface of a sample with a charged particle beam;
a particle detector configured to detect a secondary particle emitted from an irradiation region of the charged particle beam; and
an image processor configured to perform image processing based on an output of the particle detector,
wherein a storage device accessible by the image processor comprises a non-transitory memory storing a first template image for local matching, a second template image for global matching having a field of view wider than the first template image, and a sequence of programmed instructions which, when executed by the image processor, cause the image processor to
capture a search target image formed based on an output of the particle detector;
overlay the search target image and the second template image one on top of the other;
determine a similarity degree comprising a correlation value of a common region of the overlaid search target image and the second template image;
adjust a threshold value used for determining a matching candidate in accordance with the correlation value such that the similarity threshold decreases as the correlation value decreases; and
perform template matching using the first template image and the adjusted threshold value within the search target image whose similarity degree has been evaluated; and
extract a region of the search target image having a pattern similarity which exceeds the adjusted similarity threshold.

6. The pattern matching apparatus according to claim 5 , wherein
the image processor is further configured to, when the result of matching between the first template image and the search target image is below the similarity threshold, register a first template image newly set in or around the search target image and a new second template image including the newly set first template image or a pattern around the newly set first template image.

7. The pattern matching apparatus according to claim 6 , wherein the image processor is further configured to register position information on alignment reference position coordinates corresponding to the first template image, and position information on the first and second template images, together with the first and second template images.

8. The pattern matching apparatus according to claim 5 , wherein the image processor is further configured to, when a plurality of regions whose similarities are evaluated to be above the similarity threshold are detected from the search target image, set, as a matched region, a region with a highest reliability among the plurality of regions on the basis of position information on the second template image and the first template image.

9. A non-transitory computer-readable medium, storing program instructions executed on a computer system for performing a computer-implemented method for performing template matching using a template image, which, when executed by the computer system, cause the computer system to perform the computer-implemented method comprising:
capturing a search target image formed based on an output of a particle detector configured to detect a secondary particle emitted from an irradiation region of a charged particle beam;
selecting a first template image and a second template image, the second template image having a field of view wider than a field of view of the first template image;
overlaying the search target image and the second template image one on top of the other;
determining a similarity degree comprising a correlation value of a common region of the overlaid search target image and the second template image;
adjusting a similarity threshold used for determining matching, as the threshold to determine a matching candidate, wherein when performing a search using the first template image, wherein the adjusting of the similarity threshold is performed in accordance with the correlation value such that the similarity threshold decreases as the correlation value decreases;
performing template matching using the first template image and the adjusted threshold within the search target image whose similarity degree has been evaluated; and
extracting a region of the search target image having a pattern similarity which exceeds the adjusted similarity threshold.

Assignees

• Hitachi High Tech Corp

Inventors

• Nakayama Hideki
• Sakamoto Masashi

Classifications

• G06F2218/12

  Classification; Matching · CPC title

• G06T7/33 Primary

  using feature-based methods · CPC title

• G06K9/00536 Primary

  Physics · mapped topic

• G06T7/001 Primary

  using an image reference approach · CPC title

• G06T2207/30148

  Semiconductor; IC; Wafer · CPC title