Laser apparatus and method for measuring stress in a thin film using multiple wavelengths
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United States of America Patent
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Jul 28, 1992
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N/A
app pub date -
Aug 14, 1990
filing date -
Aug 14, 1990
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Expired
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Abstract
In accordance with the present invention, an apparatus and a method for measuring the radius of curvature of a surface using laser beams of multiple wavelengths are provided. The present invention avoids poor measurement due to destructive interference of the beams reflected at a thin film's upper and lower surfaces. The present invention is applicable to laser reflection stress measurement apparatuses of both scanning and beam-splitting types.
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