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Browse Prior Art Database

Eyepiece Mask for Dark-Field Microscope

IP.com Disclosure Number: IPCOM000043679D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Lessmann, B: AUTHOR

Abstract

To avoid retina irritations during the visual inspection of integrated circuits (ICs) and the like, a blocking mask is inserted into the focal plane of the eyepiece to suppress light scattered at error-free structures of the sample being tested. Visual detection of minor defects (< 2 m) in IC patterns requires dark-field observation with very high illumination levels, so that the regular structures of the pattern, e.g., edges, appear as very bright areas in an almost totally dark environment. The retinal receptors are thus exposed to high local illuminations and extreme changes of brightness when the pattern is shifted; this causes irritations of the retina and headaches. These irritations are avoided if a blocking mask, patterned according to the error-free scattering structure of the sample, e.g.

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Eyepiece Mask for Dark-Field Microscope

To avoid retina irritations during the visual inspection of integrated circuits (ICs) and the like, a blocking mask is inserted into the focal plane of the eyepiece to suppress light scattered at error-free structures of the sample being tested. Visual detection of minor defects (< 2 m) in IC patterns requires dark-field observation with very high illumination levels, so that the regular structures of the pattern, e.g., edges, appear as very bright areas in an almost totally dark environment. The retinal receptors are thus exposed to high local illuminations and extreme changes of brightness when the pattern is shifted; this causes irritations of the retina and headaches. These irritations are avoided if a blocking mask, patterned according to the error-free scattering structure of the sample, e.g., the edge pattern in an IC, is inserted into the focal plane of the eyepiece. For adjusting the eyepiece mask to the sample, a low illumination level is used until all or most of the bright areas are blocked out; then the illumination is increased, so that small defects in the otherwise dark areas are readily visible. An example of a blocking mask consists of parallel dark stripes covering the light scattered at parallel edges of an IC. A microscope with a zoom lens is useful to adapt different pattern structures to a single blocking mask.

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