Multi-step image alignment method for large offset die-die inspection

• US 10,522,376 B2
• Filed: 10/15/2018
• Issued: 12/31/2019
• Est. Priority Date: 10/20/2017
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation
• Original Assignee: KLA-Tencor Corporation
• Inventors: Lauber, Jan, Vajaria, Himanshu, Zhang, Yong
• Primary Examiner(s): Pontius, James M
• Application Number:
  US16/160,515
• Publication Number:
  US 20190122913A1
• Time in Patent Office: 442 Days
• CPC Class Codes: G06T 2207/20016 Hierarchical, coarse-to-fine, multiscale or multiresolution image processing; Pyramid transform
• CPC Class Codes: G06T 2207/20021 Dividing image into blocks, subimages or windows
• CPC Class Codes: G06T 2207/20056 Discrete and fast Fourier transform, [DFT, FFT]
• CPC Class Codes: G06T 2207/20081 Training; Learning
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 3/14 Transformations for image registration, e.g. adjusting or mapping for alignment of images
• CPC Class Codes: G06T 3/20 Linear translation of whole images or parts thereof, e.g. panning
• CPC Class Codes: G06T 3/608 by skew deformation, e.g. two-pass or three-pass rotation
• CPC Class Codes: G06T 7/001 using an image reference approach
• CPC Class Codes: G06T 7/337 involving reference images or patches
• CPC Class Codes: G06T 7/74 involving reference images or patches
• CPC Class Codes: H01L 21/67288 Monitoring of warpage, curvature, damage, defects or the like

Abstract

A die-die inspection image can be aligned using a method or system configured to receive a reference image and a test image, determine a global offset and rotation angle from local sections on the reference image and test image, and perform a rough alignment de-skew of the test image prior to performing a fine alignment.

Claims

1. A method for obtaining an aligned die-die inspection image, comprising:

receiving a reference image at a processor, the reference image comprising rows and columns of pixels;

selecting a first local section from the reference image using the processor;

receiving a test image at the processor, the test image comprising rows and columns of pixels;

selecting a second local section from the test image using the processor;

determining, using the processor, an estimated rotation offset and an estimated translation offset from the first local section and the second local section;

performing a rough alignment comprising a test image de-skew using the processor, thereby making a partially-aligned test image; and

performing a fine alignment comprising partitioned translation on the partially-aligned test image to obtain an aligned die-die inspection image.

2. The method of claim 1, wherein the test image de-skew comprises:

determining a skew angle of the test image using the processor; and

de-skewing the test image using the processor.

3. The method of claim 2, wherein the skew angle of the test image is determined by performing a skew comparison of the first local section from the reference image and the second local section from the test image.

4. The method of claim 3, wherein the skew comparison comprises:

performing a fast Fourier transform on the first local section from the reference image using the processor to obtain a reference scene function;

performing a fast Fourier transform on the second local section from the test image using the processor to obtain a test scene function; and

comparing the test scene function to the reference scene function using the processor to determine the skew angle.

5. The method of claim 3, wherein the skew comparison comprises performing a pattern recognition of one or more prominent features in the test image to determine the skew angle.

6. The method of claim 3, wherein the skew comparison is performed using a machine learning module to determine the skew angle.

7. The method of claim 2, wherein de-skewing the test image comprises:

determining, based on the skew angle, for each of the pixels in the test image, a column shift vector and a row shift vector using the processor, wherein

the column shift vector comprises a quantity of pixels to shift collinear to the column containing the pixel and a direction; and

the row shift vector comprises a quantity of pixels to shift collinear to the row containing the pixel and a direction; and

shifting each of the pixels according to its column shift vector and row shift vector using the processor.

8. The method of claim 1, wherein the partitioned translation comprises:

partitioning, using the processor, the reference image into at least one reference image sub-section;

partitioning, using the processor, the test image into at least one test image sub-section; and

translating, using the processor, the test image sub-section to align with the reference image sub-section corresponding to the test image sub-section.

9. A non-transitory computer-readable storage medium, comprising one or more programs for executing the following steps on one or more computing devices:

receive a reference image, the reference image comprising rows and columns of pixels;

select a first local section from the reference image;

receive a test image, the test image comprising rows and columns of pixels;

select a second local section from the test image;

determine an estimated rotation offset and an estimated translation offset from the first local section and the second local section;

perform a rough alignment on the test image comprising a test image de-skew, thereby making a partially-aligned test image; and

perform a fine alignment comprising partitioned translation on the partially-aligned test image to obtain an aligned die-die inspection image.

10. The non-transitory computer-readable storage medium of claim 9, wherein the test image de-skew comprises:

determining a skew angle of the test image; and

de-skewing the test image, comprising;

determining, based on the skew angle, for each of the pixels in the test image, a column shift vector and a row shift vector, wherein

the column shift vector comprises a quantity of pixels to shift collinear to the column containing the pixel and a direction; and

the row shift vector comprises a quantity of pixels to shift collinear to the row containing the pixel and a direction; and

shifting each of the pixels according to its column shift vector and row shift vector.

11. The non-transitory computer-readable storage medium of claim 10, wherein the skew angle of the test image is determined by performing a skew comparison of the first local section from the reference image and the second local section from the test image.

12. The non-transitory computer-readable storage medium of claim 11, wherein the skew comparison comprises:

performing a fast Fourier transform on the first local section from the reference image to obtain a reference scene function;

performing a fast Fourier transform on the second local section from the test image to obtain a test scene function; and

comparing the test scene function to the reference scene function to determine the skew angle.

13. The non-transitory computer-readable storage medium of claim 9, wherein the partitioned translation comprises:

partitioning the reference image into at least one reference image sub-section;

partitioning the test image into at least one test image sub-section; and

translating the test image sub-section to align with the reference image sub-section corresponding to the test image sub-section.

14. A semiconductor die-die inspection system comprising a sensor to capture images of features of a die and a computing system comprising:

a beam source, wherein the beam source is a light source or an electron beam source;

a stage configured to hold a wafer in a path of a beam produced by the beam source, wherein the beam is a light beam from the light source or an electron beam from the electron beam source;

a detector configured to receive a portion of the beam reflected from the wafer; and

a processor in electronic communication with the detector configured to perform;

a rough alignment of a test image comprising a test image de-skew, thereby making a partially-aligned test image, and

a fine alignment comprising partitioned translation of the partially-aligned test image.

15. The semiconductor die-die inspection system of claim 14, wherein the processor is further configured to:

receive a reference image, the reference image comprising rows and columns of pixels;

select a first local section from the reference image;

receive a test image, the test image comprising rows and columns of pixels;

select a second local section from the test image; and

determine the estimated rotation offset and the estimated translation offset from the first local section and the second local section.

16. The semiconductor die-die inspection system of claim 14, wherein the test image de-skew comprises:

determining a skew angle of the test image; and

de-skewing the test image.

17. The semiconductor die-die inspection system of claim 16, wherein the skew angle of the test image is determined by performing a skew comparison of the first local section from the reference image and the second local section from the test image.

18. The semiconductor die-die inspection system of claim 17, wherein the skew comparison comprises:

performing a fast Fourier transform on the first local section from the reference image to obtain a reference scene function;

performing a fast Fourier transform on the second local section from the test image to obtain a test scene function; and

comparing the test scene function to the reference scene function to determine the skew angle.

19. The semiconductor die-die inspection system of claim 16, wherein de-skewing the test image comprises:

determining, based on the skew angle, for each of the pixels in the test image, a column shift vector and a row shift vector, wherein

the column shift vector comprises a quantity of pixels to shift collinear to the column containing the pixel and a direction; and

the row shift vector comprises a quantity of pixels to shift collinear to the row containing the pixel and a direction; and

shifting each of the pixels according to its column shift vector and row shift vector.

20. The semiconductor die-die inspection system of claim 15, wherein the partitioned translation comprises:

partitioning the reference image into at least one reference image sub-section;

partitioning the test image into at least one test image sub-section; and

translating the test image sub-section to align with the reference image sub-section corresponding to the test image sub-section.