Advancing x-ray scattering metrology using inverse genetic algorithms

Adam F. Hannon; Daniel F. Sunday; Donald Windover; R. Joseph Kline

doi:10.1117/1.JMM.15.3.034001

7 July 2016 Advancing x-ray scattering metrology using inverse genetic algorithms

Adam F. Hannon, Daniel F. Sunday, Donald Windover, R. Joseph Kline

Journal of Micro/Nanolithography, MEMS, and MOEMS, Vol. 15, Issue 3, 034001 (July 2016). https://doi.org/10.1117/1.JMM.15.3.034001

Abstract

We compare the speed and effectiveness of two genetic optimization algorithms to the results of statistical sampling via a Markov chain Monte Carlo algorithm to find which is the most robust method for determining real-space structure in periodic gratings measured using critical dimension small-angle x-ray scattering. Both a covariance matrix adaptation evolutionary strategy and differential evolution algorithm are implemented and compared using various objective functions. The algorithms and objective functions are used to minimize differences between diffraction simulations and measured diffraction data. These simulations are parameterized with an electron density model known to roughly correspond to the real-space structure of our nanogratings. The study shows that for x-ray scattering data, the covariance matrix adaptation coupled with a mean-absolute error log objective function is the most efficient combination of algorithm and goodness of fit criterion for finding structures with little foreknowledge about the underlying fine scale structure features of the nanograting.

Citation Download Citation

Adam F. Hannon, Daniel F. Sunday, Donald Windover, and R. Joseph Kline "Advancing x-ray scattering metrology using inverse genetic algorithms," Journal of Micro/Nanolithography, MEMS, and MOEMS 15(3), 034001 (7 July 2016). https://doi.org/10.1117/1.JMM.15.3.034001

Published: 7 July 2016

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