Image preprocessing for probe mark inspection
View Patent ↗Digital image processing methods are applied to an image of a semiconductor interconnection pad to preprocess the image prior to an inspection or registration. An image of a semiconductor pads exhibiting spatial patterns from structure, texture or features are filtered without affecting features in the image not associated with structure or texture. The filtered image is inspected in a probe mark inspection operation.
1. A method of analyzing an object, comprising the steps of:
acquiring an image of the object, the object having an oriented structured pattern and at least one probe mark;
transforming the image into a frequency domain to provide a transformed image of the object;
using a processor to filter the transformed image by employing an image processing filter to filter out the oriented structured pattern of the object so as to provide a filtered image of the object that includes the at least one probe mark; and
wherein the image processing filter is selected based upon parameters associated with the transformed image of the object.
2. The method of claim 1 wherein the image processing filter is a spatial band reject filter having a frequency parameter corresponding to a frequency having a peak magnitude in the transformed image of the object.
3. The method of claim 2 wherein the spatial band reject filter is a Gabor band reject filter.
4. The method of claim 1 wherein the image processing filter is a spatial band pass filter having a frequency parameter corresponding to the transformed image of the object.
5. The method of claim 1 further comprising the step of:
transforming the filtered image of the object into a spatial domain.
6. The method of claim 1 further comprising the step of:
convolving the transformed image with a spatial filter.
7. The method of claim 6 wherein the spatial filter is a 3×3 kernel.
8. The method of claim 1 wherein the image processing filter is selected by:
filtering the transformed image with a spatial band-reject filter using a frequency parameter corresponding to a frequency having a peak magnitude in the transformed image, to provide a first score;
providing at least one comparison frequency;
filtering the transformed image with a spatial band pass filter using a frequency parameter corresponding to the at least one comparison frequency to provide a second score; and
selecting a frequency by comparing the first score and the second score to provide a selected frequency.
9. The method of claim 8 , wherein the comparison frequency is computed from the frequency parameter corresponding to the frequency having a peak magnitude in the transformed image and a step size parameter.
10. An apparatus for inspecting an object having an oriented structured pattern, the apparatus comprising:
a camera configured to acquire image data corresponding to the object;
a machine vision system operatively connected to the camera and configured to transform the image data acquired by the camera into a frequency domain by applying an image processing filter to filter out the oriented structured pattern so as to provide a transformed image, and thereafter perform an inspection on the transformed image; and
wherein the image processing filter is selected based upon parameters corresponding to the transformed image.
11. The apparatus of claim 10 wherein the transformed image is filtered with an oriented spatial band pass filter to convert the transformed image into a spatial domain to provide a filtered image.
12. The apparatus of claim 10 wherein the machine vision system includes a processor operatively connected to a controller that controls operation of the machine vision system, and the controller is in communication with the processor to fetch instructions from memory and decode the instructions so that the machine vision system is configured to acquire image data corresponding to the pad, applying the image processing filter on the acquired image data, and perform the probe mark inspection.
13. The apparatus of claim 10 , wherein the machine vision system registers the pad in the transformed image of the pad.
14. A method of analyzing an object, comprising the steps of:
providing an image of the object, the object having an oriented structured pattern and at least one probe mark;
filtering the image of the object, using a processor, by employing an image processing filter to filter out the oriented structured pattern of the image so as to provide a filtered image of the object;
wherein the image processing filter is selected based upon parameters associated with the image of the object; and
wherein the filtered image of the object includes the at least one probe mark.
15. The method of claim 14 wherein the filtering is performed on a transformed image of the object, acquired by transforming the image into a frequency domain, and the image processing filter is selected based upon a frequency parameter corresponding to a frequency having a peak magnitude in the transformed image of the object.
16. The method of claim 15 wherein the image processing filter is a spatial band reject filter having a frequency parameter corresponding to the frequency having a peak magnitude in the transformed image of the object.
17. The method of claim 15 wherein the image processing filter is a spatial band pass filter having a frequency parameter corresponding to a frequency parameter corresponding to the transformed image of the object.
18. The method of claim 14 further comprising:
transforming the filtered image into a spatial domain.
19. The method of claim 14 wherein the step of providing comprises acquiring the image of the object using a camera.
20. The method of claim 14 wherein the image processing filter is selected based upon parameters associated with the oriented structured pattern of the object.