Substrate thickness measurement using oblique incidence multispectral interferometry
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United States of America Patent
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Mar 26, 1996
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app pub date -
Sep 13, 1994
filing date -
Sep 13, 1994
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Abstract
An oblique incidence multispectral interferometric apparatus and the process of using it for measuring gross surface height errors of for measuring the total thickness of a substrate such as a semiconductor wafer or a photo mask. The instrumentation can be configured to either measure the air film between a reference flat and the substrate, or it can measure the air film on both sides of a substrate placed between reference flats. If the substrate is a flexible silicon wafer then it can be held against a known reference flat using a vacuum or other suitable means or the wafer surface can be measured from both sides in a free standing mode. In all cases the thickness map of the air space or spaces between the substrate surface or surfaces and a corresponding calibrated reference surface is measured using multispectral pattern matching.
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