The accurate determination of critical dimensions and roughness is necessary to ensure the quality of photoresist masks that are crucial for the operational reliability of electronic components. Scatterometry provides a fast indirect optical nondestructive method for the determination of profile parameters that are obtained from scattered light intensities using inverse methods. We illustrate the effect of line roughness on the reconstruction of grating parameters employing a maximum likelihood scheme. Neglecting line roughness introduces a strong bias in the parameter estimations. Therefore, such roughness has to be included in the mathematical model of the measurement in order to obtain accurate reconstruction results. In addition, the method allows to determine line roughness from scatterometry. The approach is demonstrated for simulated scattering intensities as well as for experimental data of extreme ultraviolet light scatterometry measurements. The results obtained from the experimental data are in agreement with independent atomic force microscopy measurements.
© 2012 Optical Society of America
Diffraction and Gratings
Original Manuscript: October 29, 2012
Manuscript Accepted: November 16, 2012
Published: December 13, 2012
Mark-Alexander Henn, Sebastian Heidenreich, Hermann Gross, Andreas Rathsfeld, Frank Scholze, and Markus Bär, "Improved grating reconstruction by determination of line roughness in extreme ultraviolet scatterometry," Opt. Lett. 37, 5229-5231 (2012)