Hybrid approach to reconstruct nanoscale grating dimensions using scattering and fluorescence with soft X-rays

Abstract

Scatterometry is a tested method for measuring periodic semiconductor structures. As modern semiconductor structures have reached the nanoscale, determining their shape with sub-nanometer accuracy has become challenging. To increase scatterometry's resolution, short wavelength radiation like soft X-rays can be used. However, scatterometry reconstructs the geometry of periodic nanostructures that can lead to ambiguous solutions and needs increased sensitivity to determine the shape of even more complex periodic nanostructures made up of different materials. To achieve unique solutions with smaller uncertainties, soft X-ray scattering can leverage exciting materials that consist of elements with low atomic numbers. Additional information from stimulated emission via soft X-ray fluorescence analysis in a hybrid measurement approach can help resolve ambiguous scatterometry results and reduce uncertainty. In this work, the hybrid approach is used to compare solutions from the dimensional reconstruction and determine the actual solution over ambiguous ones.