Image-based nanoscale dimensional metrology

An-Shun Liu; Yi-Sha Ku; Nigel Smith

doi:10.1117/12.655932

24 March 2006 Image-based nanoscale dimensional metrology

An-Shun Liu, Yi-Sha Ku, Nigel Smith

Proceedings Volume 6152, Metrology, Inspection, and Process Control for Microlithography XX; 61522G (2006) https://doi.org/10.1117/12.655932
Event: SPIE 31st International Symposium on Advanced Lithography, 2006, San Jose, California, United States

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.

Citation Download Citation

An-Shun Liu, Yi-Sha Ku, and Nigel Smith "Image-based nanoscale dimensional metrology", Proc. SPIE 6152, Metrology, Inspection, and Process Control for Microlithography XX, 61522G (24 March 2006); https://doi.org/10.1117/12.655932

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