Optical critical dimension measurement and illumination analysis using the through-focus focus metric

Ravikiran Attota; Richard M. Silver; Michael R. Bishop; Ronald G. Dixson

doi:10.1117/12.656421

24 March 2006 Optical critical dimension measurement and illumination analysis using the through-focus focus metric

Ravikiran Attota, Richard M. Silver, Michael R. Bishop, Ronald G. Dixson

Proceedings Volume 6152, Metrology, Inspection, and Process Control for Microlithography XX; 61520K (2006) https://doi.org/10.1117/12.656421
Event: SPIE 31st International Symposium on Advanced Lithography, 2006, San Jose, California, United States

Abstract

In this paper we present a unique method of evaluating the angular illumination homogeneity in an optical microscope using the through-focus focus metric. A plot of the sum of the mean square slope throughout an optical image as the target moves through the focus is defined as the through-focus focus metric. Using optical simulations we show that the angular illumination inhomogeneity causes the through-focus focus metric value to proportionately increase at specific focus positions. Based on this observation, we present an experimental method to measure angular illumination homogeneity by evaluating the through-focus focus metric values on a grid across the field of view. Using the same through-focus focus metric, we present a detailed study to measure critical dimensions with nanometer sensitivity with the aid of simulations.

Citation Download Citation

Ravikiran Attota, Richard M. Silver, Michael R. Bishop, and Ronald G. Dixson "Optical critical dimension measurement and illumination analysis using the through-focus focus metric", Proc. SPIE 6152, Metrology, Inspection, and Process Control for Microlithography XX, 61520K (24 March 2006); https://doi.org/10.1117/12.656421

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