Semiconductor device image inspection utilizing image subtraction and threshold imaging
First Claim
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1. A machine vision method for inspecting a semiconductor device, including either a semiconductor die surface or a semiconductor lead frame, the method comprising the steps of:
- illuminating the semiconductor device with an illumination source selected from a group of illumination sources including a direct on-axis light source and a diffuse off-axis light source;
generating a first on-axis image of the semiconductor device while it is so illuminated;
illuminating the semiconductor device with another illumination source selected from the aforesaid group;
generating a second on-axis image of the semiconductor device while it is so illuminated;
subtracting the second image from the first image to form a third image that emphasizes any defect on the semiconductor device;
isolating the defect in the third image;
the isolating step including(i) thresholding the third image to distinguish at least one of a defect and its edges from the semiconductor device, wherein the thresholding step includes the step of generating a threshold image from at least one of the first and second images, the threshold image having pixels representing local threshold intensity values; and
wherein the step of generating the threshold image includes the step of mapping image intensity values in at least one of the first and second images to generate the threshold image,(ii) using the threshold image to distinguish, in the third image, at least one of the defect and its edges from the semiconductor device.
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Abstract
Machine vision methods for inspection of semiconductor die surfaces include the steps of generating a first image of the die surface, generating a second image of the die surface and any defect thereon, and subtracting the second image from the first image. The methods are characterized in that the second image is generated such that subtraction of it from the first image emphasizes the defect with respect to the die surface.
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14 Claims
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1. A machine vision method for inspecting a semiconductor device, including either a semiconductor die surface or a semiconductor lead frame, the method comprising the steps of:
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illuminating the semiconductor device with an illumination source selected from a group of illumination sources including a direct on-axis light source and a diffuse off-axis light source; generating a first on-axis image of the semiconductor device while it is so illuminated; illuminating the semiconductor device with another illumination source selected from the aforesaid group; generating a second on-axis image of the semiconductor device while it is so illuminated; subtracting the second image from the first image to form a third image that emphasizes any defect on the semiconductor device; isolating the defect in the third image; the isolating step including (i) thresholding the third image to distinguish at least one of a defect and its edges from the semiconductor device, wherein the thresholding step includes the step of generating a threshold image from at least one of the first and second images, the threshold image having pixels representing local threshold intensity values; and
wherein the step of generating the threshold image includes the step of mapping image intensity values in at least one of the first and second images to generate the threshold image,(ii) using the threshold image to distinguish, in the third image, at least one of the defect and its edges from the semiconductor device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A machine vision method for inspecting a semiconductor device, including either a semiconductor die surface or a semiconductor lead frame, the method comprising the steps of:
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generating a first image of the semiconductor device; generating a second image of the semiconductor device and any defect thereon such that subtraction of the second image from the first image emphasizes the defect with respect to the semiconductor device; subtracting the second image from the first image to form a third image; generating a threshold image from the second image, the threshold image having pixels representing local threshold intensity values; subtracting the threshold image from the third image to generate a fourth image; and isolating the defect in the fourth image by any of segmentation, edge detection and tracking, connectivity analysis, and thresholding.
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14. A machine vision method for inspecting a semiconductor device, including either a semiconductor die surface or a semiconductor lead frame, comprising the steps of:
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generating a first image of the semiconductor device; generating a second image of the semiconductor device and any defect thereon such that subtraction of the second image from the first image emphasizes the defect with respect to the semiconductor device; at least one of registering and normalizing the first and second images with respect to one another; subtracting the second image from the first image to form a third image; generating a threshold image from the second image, the threshold image having pixels representing local threshold intensity values; subtracting the threshold image from the third image to generate a fourth image; and isolating the defect in the fourth image by any of segmentation, edge detection and tracking, connectivity analysis, and thresholding.
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Specification