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Proceedings Paper

Inverse scattering approach to SEM linewidth measurements
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Paper Abstract

The inverse scattering approach presented here enables the calculation of estimates of top and bottom line width values, sidewall angle, corner rounding, the heights from top-down SEM images or line scans. It also represents a significant step in solving the accuracy problem that plagues CD SEM measurements today. A comprehensive software package has been developed for performing these measurements by comparing a SEM's line scan with a library of pre- calculated Monte Carlo simulations. The Monte Carlo model used was Metrolgia, which has undergone considerable improvement in the past year due to work done at the National Institute of Standards and Technology. A detailed beam shape model is included, which represents the electron density in the cross section of the primary electron beam as a product of a polynomial and a Gaussian function. Automatic alignment of the line scan data is also done. The Monte Carlo model does not include effects due to charging. The inverse scattering software attempts to partially correct for mild charging by applying a multiplicative operation to the Monte Carlo data which results in the average of both the Monte Carlo data and the real data being the same over a programmable range. Thus any signal production differences between the model and the data due to charging, extraction fields, or shadowing will tend to be eliminated. So long as the effects are mild, an inferred measurements will still be possible. This paper presents the first description of this model and the first experimental results using it. The same inverse scattering software can be used with libraries of real, measured data instead of Monte Carlo simulations if a more empirical approach is preferable.

Paper Details

Date Published: 14 June 1999
PDF: 10 pages
Proc. SPIE 3677, Metrology, Inspection, and Process Control for Microlithography XIII, (14 June 1999); doi: 10.1117/12.350850
Show Author Affiliations
Mark P. Davidson, Spectel Co. (United States)
Andras E. Vladar, Hewlett-Packard Co. (United States)


Published in SPIE Proceedings Vol. 3677:
Metrology, Inspection, and Process Control for Microlithography XIII
Bhanwar Singh, Editor(s)

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