Registration of CAD data with SEM images

Patent metadata

Field	Value
Publication number	US-9715724-B2
Application number	US-201414446295-A
Country	US
Kind code	B2
Filing date	Jul 29, 2014
Priority date	Jul 29, 2014
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

A method for image processing includes providing a microscopic image of a structure fabricated on a substrate and computer-aided design (CAD) data used in fabricating the structure. The microscopic image is processed by a computer so as to generate a first directionality map, which includes, for a matrix of points in the microscopic image, respective directionality vectors corresponding to magnitudes and directions of edges at the points irrespective of a sign of the magnitudes. The CAD data are processed by the computer so as to produce a simulated image based on the CAD data and to generate a second directionality map based on the simulated image. The first and second directionality maps are compared by the computer so as to register the microscopic image with the CAD data.

First claim

The invention claimed is:

1. A method for image processing, comprising:
providing a microscopic image of a structure fabricated on a substrate and computer-aided design (CAD) data used in fabricating the structure;
generating, by a computer, a first directionality map for the microscopic image, the first directionality map comprising, for a matrix of points in the microscopic image, respective directionality vectors corresponding to magnitudes and directions of edges at the points irrespective of a sign of the magnitudes;
producing a simulated image based on the CAD data;
generating, by the computer, a second directionality map based on the simulated image;
generating, based on the microscopic image, a first height map indicative of a three-dimensional (3D) shape of the structure;
generating a second height map of the structure based on the CAD data; and
registering the microscopic image with the CAD data based on a combination of a first comparison of the first and second directionality maps with a second comparison of the first and second height maps.

2. The method according to claim 1 , wherein the substrate is a semiconductor wafer, and the structure is a part of a microelectronic device formed on the wafer, and wherein providing the microscopic image comprises capturing the image using a scanning electron microscope (SEM).

3. The method according to claim 1 , wherein each of the first and second directionality maps is generated by applying a gradient operator to an image, thereby computing a respective gradient vector at each point, and doubling an angular component of the gradient vector at each point to find the directionality vectors.

4. The method according to claim 1 , wherein generating the first directionality map and producing the simulated image comprises post-processing the directionality vectors in at least one of the first and second directionality maps to modify the magnitudes of at least one of the directionality vectors responsively to the directions thereof.

5. The method according to claim 4 , wherein post-processing the directionality vectors comprises applying an operation to the directionality vectors selected from a group of operations consisting of whitening, X-Y balancing, and corner balancing.

6. The method according to claim 1 , wherein registering comprises:
computing a correlation map between the first and second directionality maps; and
identifying a peak in the correlation map in order to define a transformation between the CAD data and the microscopic image.

7. Apparatus for image processing, comprising:
a memory, which is configured to store a microscopic image of a structure fabricated on a substrate and computer-aided design (CAD) data used in fabricating the structure; and
a processor, which is configured to generate a first directionality map for the microscopic image, the first directionality map comprising a matrix of points in the microscopic image, respective directionality vectors corresponding to magnitudes and directions of edges at the points irrespective of a sign of the magnitudes;
produce a simulated image based on the CAD data;
generate a second directionality map based on the simulated image;
generate, based on the microscopic image, a first height map indicative of a three-dimensional (3D) shape of the structure;
generate a second height map of the structure based on the CAD data; and
register the microscopic image with the CAD data based on a combination of a first comparison of the first and second directionality maps with a second comparison of the first and second height maps.

8. The apparatus according to claim 7 , wherein the substrate is a semiconductor wafer, and the structure is a part of a microelectronic device formed on the wafer, and wherein the microscopic image is a scanning electron microscope (SEM) image.

9. The apparatus according to claim 7 , wherein the processor is to generate the first and second directionality maps by applying a gradient operator to an image, thereby computing a respective gradient vector at each point, and doubling an angular components of the gradient vector at each point to find the directionality vectors.

10. The apparatus according to claim 7 , wherein to generate the first directionality map and produce the simulate image, the processor is to:
post-process the directionality vectors in at least one of the first and second directionality maps to modify the magnitudes of at least one of the directionality vectors responsively to the directions thereof.

11. The apparatus according to claim 10 , wherein the processor is to post-process the directionality vectors by applying an operation to the directionality vectors selected from a group of operations consisting of whitening, X-Y balancing, and corner balancing.

12. The apparatus according to claim 7 , wherein to register, the processor is to:
compute a correlation map between the first and second directionality maps; and
identify a peak in the correlation map in order to define a transformation between the CAD data and the microscopic image.

13. A computer software product, comprising a non-transitory computer-readable medium in which program instructions are stored, which instructions, when read by a computer, cause the computer to:
receive a microscopic image of a structure fabricated on a substrate and computer-aided design (CAD) data used in fabricating the structure;
generate a first directionality map for the microscopic image, the first directionality map comprising, for a matrix of points in the microscopic image, respective directionality vectors corresponding to magnitudes and directions of edges at the points irrespective of a sign of the magnitudes;
produce a simulated image based on the CAD data;
generate a second directionality map based on the simulated image;
generate, based on the microscopic image, a first height map indicative of a three-dimensional (3D) shape of the structure;
generate a second height map of the structure based on the CAD data; and
register the microscopic image with the CAD data based on a combination of a first comparison of the first and second directionality maps with a second comparison of the first and second height maps.

14. The product according to claim 13 , wherein the instructions cause the computer to generate the first and second directionality maps by applying a gradient operator to an image, thereby computing a respective gradient vector at each point, and doubling an angular component of the gradient vector at each point to find the directionality vectors.

15. The product according to claim 13 , wherein to generate the first directionality map and produce the simulated image, the computer is to post-process the directionality vectors in at least one of the first and second directionality maps to modify the magnitudes of at least one of the directionality vectors responsively to the directions thereof.

16. The product according to claim 13 , wherein the instructions cause the computer to post-process the directionality vectors by applying an operation to the directionality vectors selected from a group of operations consisting of whitening, X-Y balancing, and corner balancing.

17. The product according to claim 13 , wherein to register, the computer is to:
compute a correlation map between the first and second directionality maps; and
identify a peak in the correlation map in order to define a transformation between the CAD data and the microscopic image.

18. A method for image processing, comprising:
receiving, by a computer fr

Assignees

• Applied Materials Israel Ltd

Inventors

• Schwarzband Ishai
• Ivanchenko Yan
• Ravid Daniel
• Zvitia Orly
• Kaizerman Idan

Classifications

• G06V10/44

  Local feature extraction by analysis of parts of the pattern, e.g. by detecting edges, contours, loops, corners, strokes or intersections; Connectivity analysis, e.g. of connected components · CPC title

• G06T2207/30148

  Semiconductor; IC; Wafer · CPC title

• G06T7/001 Primary

  using an image reference approach · CPC title

• G06T2207/10028

  Range image; Depth image; 3D point clouds · CPC title

• G06T2207/10061

  from scanning electron microscope · CPC title