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Method for Detection and Location of Defects in Integrated Circuits

IP.com Disclosure Number: IPCOM000043743D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Krakow, W: AUTHOR [+2]

Abstract

It is important to be able to rapidly inspect and observe the location of defects, particle contaminants, or other imperfections in integrated circuits. When inspections of these circuits are performed under a microscope or through an optical system, there are often many features present which make it difficult to observe defects or imperfections in structures. For example, it is difficult to sense small variations produced by defects when they are masked by the contrast of the perfect circuit structure. In order to avoid this masking problem, low-pass filtering is used in the optical imaging system. (Image Omitted) The images of periodic or repeating circuit elements are eliminated by placing a small aperture in the backfocal plane of the image-forming lens.

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Method for Detection and Location of Defects in Integrated Circuits

It is important to be able to rapidly inspect and observe the location of defects, particle contaminants, or other imperfections in integrated circuits. When inspections of these circuits are performed under a microscope or through an optical system, there are often many features present which make it difficult to observe defects or imperfections in structures. For example, it is difficult to sense small variations produced by defects when they are masked by the contrast of the perfect circuit structure. In order to avoid this masking problem, low-pass filtering is used in the optical imaging system.

(Image Omitted)

The images of periodic or repeating circuit elements are eliminated by placing a small aperture in the backfocal plane of the image-forming lens. The image would then be formed only from the non-periodic components in the original image. Schematically, the optical system is shown above. Only diffuse scattering is transmitted to the image plane, as opposed to strong scattering, with well- defined spatial frequencies of the periodic object. If a detector is placed in the image plane, it can sense when defects are present by a variation in image intensity due to the defects. The low-pass image will show defects as black dots against the white background. In practice, the low-pass filtering can be performed by a computer process of a digitized image of a photomicrograph of an actual integ...