Optics: measuring and testing – Inspection of flaws or impurities – Having predetermined light transmission regions
Patent
1995-11-29
1998-01-20
Font, Frank G.
Optics: measuring and testing
Inspection of flaws or impurities
Having predetermined light transmission regions
250548, G01N 2188
Patent
active
057106240
ABSTRACT:
An aligner for exposing a pattern image of an original plate by projecting the image onto an exposure surface of a substrate, which is held on a table, in a focused state through a projection optical system includes a defocusing detection device for detecting a deviation from a focusing position at each of a plurality of points within an exposure region on the surface of the substrate, which is arranged at an exposure position, a device for determining an approximate plane of the exposure surface of the substrate within the exposure region on the basis of deviation detection values detected at the plurality of points by the defocusing detection device and a decision device for determining a deviation of the approximate plane of the exposure surface of the substrate, on the basis of the deviation detection values detected at each of the plurality of points, to decide whether contamination is present between the table and the back side of the substrate. Also disclosed is a contamination detecting method applied to such an aligner.
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Canon Kabushiki Kaisha
Font Frank G.
Smith Zandra V.
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