System and method for selection of a reference die
First Claim
Patent Images
1. A system for selection of a reference die image comprising:
- a die image comparator operable to create a difference image based upon a first die image and a second die image; and
a difference image analysis system coupled to the die image comparator, the difference image analysis system generating histogram data from the difference image and analyzing the slope of the histogram data to determine the length of a region over which the slope of the histogram data increases and then decreases, wherein the length of the anomalous region is then used to determine whether the first die image and the second die image may each be used as the reference die image for subsequent comparison with other dies on a wafer.
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Abstract
A system for selecting reference die images, such as for use with a visual die inspection system, is provided. The system includes a die image comparator, which compares a first die image to a second die image in order to create a difference image that contains only the differences between the two die images. The system also includes a difference image analysis system that receives data from the die image comparator. The difference image analysis system analyzes the difference image and determines whether there are any features of the difference image that indicate that either the first die image or the second die image should not be used as a reference die image.
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Citations
26 Claims
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1. A system for selection of a reference die image comprising:
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a die image comparator operable to create a difference image based upon a first die image and a second die image; and
a difference image analysis system coupled to the die image comparator, the difference image analysis system generating histogram data from the difference image and analyzing the slope of the histogram data to determine the length of a region over which the slope of the histogram data increases and then decreases, wherein the length of the anomalous region is then used to determine whether the first die image and the second die image may each be used as the reference die image for subsequent comparison with other dies on a wafer. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A system for inspecting dies comprising:
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a camera configured to obtain an image of two or more dies; and
a reference die detection system coupled to the camera, the reference die detection system operable to analyze slope changes in histogram data a difference between a first die image and a second die image to determine the length of a region over which the slope of the histogram data increases and then decreases, wherein the length of the anomalous region is then used to determine whether the first die image and the second die image can be used as reference images for subsequent comparison with other dies on a wafer. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for selecting a reference die image comprising:
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subtracting a first die image from a second die image to create a difference image;
generating histogram data from the difference image;
determining the length of a region over which a slope of the histogram data increases and then decreases;
determining whether the difference image contains unacceptable data based on whether the length of the region exceeds predetermined allowable criteria; and
determining whether the first die image and the second die image can be used as reference images for subsequent comparison with other dies on the wafer.- View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26)
forming a histogram from difference image data; and
determining whether a slope of the histogram changes from negative to positive.
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22. The method of claim 18 wherein determining whether the difference image contains unacceptable data comprises determining whether a size of an area having a brightness deviation exceeds a predetermined allowable size.
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23. The method of claim 18 wherein determining whether the difference image contains unacceptable data comprises determining whether a size of an area having an image data deviation for image data other than brightness data that exceeds a predetermined allowable size.
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24. The method of claim 18 wherein determining whether the difference image contains unacceptable data comprises determining whether a number of areas having brightness deviations exceeds a predetermined allowable number of areas having brightness deviations per unit area.
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25. The method of claim 18 wherein determining whether the difference image contains unacceptable data comprises determining whether a number of areas having other image data deviations exceeds a predetermined allowable number of areas having image data deviations per unit area for image data other than brightness data.
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26. The method of claim 18 further comprising:
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selecting two or more difference images that do not contain unacceptable data, where each difference image is selected from a different predetermined region of the silicon wafer; and
combining the die images used to create the two or more difference images to form a reference image for use in comparing with each die of the silicon wafer.
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Specification