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Proceedings Paper

Image-based nanoscale dimensional metrology
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Paper Abstract

Optical interference leads to errors in the determination of the location of lines and in feature dimension measurements. Multi-peaked focus plots were observed from the metrology tools when the target includes sub-resolution lines. In this paper we present a new algorithm for determining nano-scale feature dimensions of grating structures with a bright-field metrology tool. The algorithm is based on the intensity of images obtained with varying amounts of defocus. By evaluating the variations of the different captured images through analysis of the optical images intensity obtained at various off-focus positions, the through-focus curves experimentally demonstrate nanometer sensitivity with grating structure. An empirical quadratic model was developed to fit the experimental results of image intensity deviation versus critical dimension. Our model and experimental data both shows that the grating structure with critical dimension at half pitch has maximum focus measure. A quadratic symmetry distribution data were shown when the critical dimension increase or decrease with the same dimensional intervals. The results demonstrate that the sub-wavelength feature dimensions can be evaluated using regular optical microscopes with exceptional resolution by implementing this algorithm.

Paper Details

Date Published: 24 March 2006
PDF: 10 pages
Proc. SPIE 6152, Metrology, Inspection, and Process Control for Microlithography XX, 61522G (24 March 2006); doi: 10.1117/12.655932
Show Author Affiliations
An-Shun Liu, Industrial Technology Research Institute (Taiwan)
Yi-Sha Ku, Industrial Technology Research Institute (Taiwan)
Nigel Smith, Accent Optical Technologies (Taiwan)


Published in SPIE Proceedings Vol. 6152:
Metrology, Inspection, and Process Control for Microlithography XX
Chas N. Archie, Editor(s)

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