Reduction Of Instrument Signature In Near Angle Scatter Measurements

John C. Stover; Kyle A. Klicker; Daniel R. Cheever; Fredrick M. Cady

doi:10.1117/12.939840

20 April 1987 Reduction Of Instrument Signature In Near Angle Scatter Measurements

John C. Stover, Kyle A. Klicker, Daniel R. Cheever, Fredrick M. Cady

Author Affiliations +

Proceedings Volume 0749, Metrology: Figure and Finish; (1987) https://doi.org/10.1117/12.939840
Event: OE LASE'87 and EO Imaging Symposium, 1987, Los Angeles, CA, United States

Abstract

The light scattered by optical components is a sensitive indication of component surface and bulk quality. Angular scatter measurement as an indication of component quality has been reported by a number of investigators since the early 1970's [1-4]. Most of these measurements are limited to angles outside a near angle cone centered about the reflected (or transmitted) specular beam. Measurements are more difficult at near angles because the instrument (scatterometer) source optics create scatter near the specular input beam that is superimposed on the sample scatter. This source scatter is often referred to as instrument signature and its presence must be considered when near angle scatter measurements are taken. The minimum measurable angle depends on the difference between instrument signature and sample scatter. Usually these two are of comparable size somewhere in the region of 0.50 to 50 from the specular beam. Inside this limit, sample scatter is referred to as near, small or low angle scatter. Outside this limit, sample scatter is referred to as far, large or high angle scatter. Because the scattered light density increases rapidly as the specular beam is approached, reduction of near angle scatter is a design concern for many modern optical systems. At least four investigators have reported scatter measurements in the near angle region [5-8], using various techniques to reduce or account for instrument signature.

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John C. Stover, Kyle A. Klicker, Daniel R. Cheever, and Fredrick M. Cady "Reduction Of Instrument Signature In Near Angle Scatter Measurements", Proc. SPIE 0749, Metrology: Figure and Finish, (20 April 1987); https://doi.org/10.1117/12.939840

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