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Proceedings Paper

Effective exposure-dose measurement in optical microlithography
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Paper Abstract

An accurate measurement technique for effective exposure dose in optical microlithography has been developed. The effective exposure dose can be obtained by a dose monitor mark in a photomask named effective dose-meter, consisting of plural segments including grating patterns with a pitch below the resolution limit and different duty ratios gradually. Since the effective dose-meter does not resolve on a wafer but it makes flood exposure with the dose as a function of the duty ratio, residual thickness of the photoresist after development changes according to the duty ratio. Therefore, the effective exposure dose can be obtained by grasping the duty ratio of the grating patterns in the effective dose-meter corresponding to the position that the photoresist had cleared completely. A calibration technique utilizing an aerial image measurement system also has been proposed to avoid the influence of intra- wafer process variation. The advantages of this method are (1) completely focus-free, (2) the effective dose-meter is small enough to ignore the influence of the intra-wafer process variation on the accuracy, and (3) highly dose resolution of less than 0.5%. It was found that this technique function effectively. The variation of the effective exposure dose in a wafer in the current krypton-fluoride-excimer-laser lithography process was measured as a demonstration of this technology.

Paper Details

Date Published: 2 June 2000
PDF: 9 pages
Proc. SPIE 3998, Metrology, Inspection, and Process Control for Microlithography XIV, (2 June 2000); doi: 10.1117/12.386445
Show Author Affiliations
Soichi Inoue, Toshiba Corp. (Japan)
Tadahito Fujisawa, Toshiba Corp. (Japan)
Kyoko Izuha, Toshiba Corp. (Japan)

Published in SPIE Proceedings Vol. 3998:
Metrology, Inspection, and Process Control for Microlithography XIV
Neal T. Sullivan, Editor(s)

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