Automatic rejection of diffraction effects in thin film metrology
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United States of America Patent
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Sep 10, 1996
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N/A
app pub date -
Dec 21, 1994
filing date -
Dec 21, 1994
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Abstract
A layer thickness determination system (10) is employed for detecting a thickness of at least one layer (12a) disposed over a surface of a wafer (13) having one or more first regions characterized by circuit and other features, and one or more second regions characterized by an absence of circuit and other features. The system includes an optical system (14) having an optical axis (14a) for collecting light reflecting from the at least one layer and the surface of the wafer. The system further includes a camera (16) coupled to the optical system for obtaining an image from the collected light; a first light source (22) for illuminating the layer with light that is directed along the optical axis and within the cone of acceptance angles; and at least one second light source (18) for illuminating the layer with light that is directed off the optical axis and outside of the cone of acceptance angles. A data processor operates to generate an image mask that differentiates planar film regions from non-planar film regions, and, in one embodiment, further operates to detect a thickness of the at least one layer only within the planar film regions.
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