Improved secondary electron extraction efficiency model for accurate measurement of narrow-space patterns using model-based library matching

Shishido, Chie; Tanaka, Maki; Hamamatsu, Akira; Nagao, Tomoharu

doi:doi:10.1117/1.3664410

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Journal of Micro/Nanolithography, MEMS, and MOEMS / Volume 10 / Issue 4 / Articles

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Improved secondary electron extraction efficiency model for accurate measurement of narrow-space patterns using model-based library matching

J. Micro/Nanolith. MEMS MOEMS 10, 043017 (Dec 22, 2011); http://dx.doi.org/10.1117/1.3664410

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Abstract

References (18)

Chie Shishido, Maki Tanaka, and Akira Hamamatsu

Hitachi Ltd., Yokohama Research Laboratory, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa 244-0817, Japan E-mail: chie.shishido.gd@hitachi.com

Tomoharu Nagao

Yokohama National University, 79-1 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 244-8501, Japan

In order to accurately measure narrow-space patterns, we propose an improved secondary-electron extraction efficiency model for the model-based library method. In the conventional model, the same extraction efficiency is applied to all electrons, regardless of from where the electrons are emitted. This is a simplified model that assumes a uniform extraction electric-field strength. In the improved model, the extraction efficiency is calculated as a function of the pattern shape and the emission position of the electrons. The function is based on simulation results for the electric-field strength of critical-dimension scanning electron microscopy (SEM) optics. We verify the effectiveness of the improved extraction model by applying this model to measurements of actual patterns with space widths in the (20 to 30) nm range. The measurement bias of the sidewall angle (SWA) is evaluated through comparison to cross-sectional SEM measurements. We demonstrate that the average SWA bias is improved from 0.8 deg for the conventional model to 0.04 deg for the improved model.

History

Received Jun 18, 2011
Accepted Nov 08, 2011
Revised Oct 31, 2011
Published online Dec 22, 2011

Digital Object Identifier

http://dx.doi.org/10.1117/1.3664410

Citation

Chie Shishido, Maki Tanaka, Akira Hamamatsu and Tomoharu Nagao, "Improved secondary electron extraction efficiency model for accurate measurement of narrow-space patterns using model-based library matching", J. Micro/Nanolith. MEMS MOEMS 10, 043017 (Dec 22, 2011); http://dx.doi.org/10.1117/1.3664410