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Proceedings Paper

A Fluorescent Linewidth Measurement System For Vlsi Fabrication
Author(s): Stephen J. Erasmus; Michael L. Reed; Ulrich Kaempf
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Paper Abstract

The fabrication of small VLSI circuits (1.25 μ m minimum feature size) requires accurate, routine linewidth measurements of resist structures after exposure and development. The evaluation of several commercial instruments, all of which used a brightfield measurement technique, revealed that they suffered from the same limitations and that none of them were sufficiently accurate. This paper describes experiments demonstrating that thickness variations of films beneath the photoresist are a major source of inaccuracy with these systems. After exploring several potential solutions, UV excitation of a fluorescent dye in the photoresist and measurement of the resulting fluorescence image was selected and enhanced. This technique is insensitive to the optical properties of the subsurface layers and offers improved accuracy. Extensive measurements of 1 to 1.5 ym photoresist structures were made with a commercial measurement system and fluorescent illumination. The desired long term precision of 0.015 μ m (lσ) and accuracy (when compared to SEM measurements) of 0.03 μ m (l σ ) ^were achieved. Fluorescent linewidth measurement systems are now in routine use at Hewlett-Packard's VLSI production facilities.

Paper Details

Date Published: 15 October 1984
PDF: 8 pages
Proc. SPIE 0480, Integrated Circuit Metrology II, (15 October 1984); doi: 10.1117/12.943048
Show Author Affiliations
Stephen J. Erasmus, Hewlett-Packard Company (United States)
Michael L. Reed, Hewlett-Packard Company and Stanford Electronics Laboratory (United States)
Ulrich Kaempf, Hewlett-Packard Company (United States)

Published in SPIE Proceedings Vol. 0480:
Integrated Circuit Metrology II
Diana Nyyssonen, Editor(s)

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