METHOD AND APPARATUS FOR VISUAL INSPECTION

• US 20100194876A1
• Filed: 04/07/2010
• Published: 08/05/2010
• Est. Priority Date: 07/22/2005
• Status: Active Grant

• Current Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Original Assignee: Hitachi High-Technologies Corporation (Hitachi, Ltd.)
• Inventors: SHIMURA, Kei
• Granted Patent: US 8,126,259 B2
• Time in Patent Office: Days
• US Class Current: 348/86
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

In the case of die-to-die comparison, threshold processing units process the differential image between the image of a sample chip and the images of left and right adjacent chips using a second threshold value lower than a first threshold value thereby to determine a defect candidate for the sample chip. Further, threshold processing units process the differential image using the first threshold value. The defect candidates which develops a signal not smaller than the first threshold is detected as a defect. Also in the cell-to-cell comparison, the differential image is first processed by the second threshold value to determine a defect candidate, and the differential image is further processed by the first threshold value. The defect candidates which develops a signal not smaller than the first threshold value is detected as a defect.

Claims

1-3. -3. (canceled)

4. An inspection apparatus comprising:

an image data acquisition unit for acquiring a first image data of an object to be inspected;

an image generating unit for generating a second image displaced from the first image of the object acquired by the image data acquisition unit, by an amount equal to an integer multiple of the period of the periodical structure of the object to be inspected;

a processing unit for processing the differential image between the first and second images using a second threshold value;

a defect candidate determining unit for determining a defect candidate in the case where the differential image develops a peak exceeding the second threshold value at two points at the same interval as the distance of the displacement; and

a defect detection unit for detecting the pixel of the first image corresponding to the defect candidate as a defect, when at least one of the two peaks associated with the defect candidate exceeds the first threshold value higher than the second threshold value.

5. A defect inspection method comprising steps of:

acquiring, at an image data acquisition unit, a first image of an object to be inspected at an image input unit;

generating a second image displaced from the first image by an amount equal to an integer multiple of a period of the periodical structure of the object to be inspected;

obtaining a differential image, at an image comparator, by subtracting the second image from the first image;

in a first processing step, at a first threshold processing unit, processing the differential image with a first threshold value;

in a second processing step, at a second threshold processing unit, processing the differential image with a second threshold value;

determining, at a defect candidate determining unit, a defect candidate in a case where the differential image develops a peak exceeding the second threshold value at two points at the same interval as the distance of the displacement; and

determining, at a defect detection unit, as a defect a pixel of the first image corresponding to the defect candidate, when at least one of the two peaks associated with the defect candidate exceeds the first threshold value higher than the second threshold value.