EUV refractive index measurements with improved accuracy and their impact in component modeling

Franck Delmotte; Regina Soufli; Catherine Burcklen; Eirini Papagiannouli; Farhad Salmassi; Eric Gullikson

doi:10.1117/12.2660664

28 April 2023 EUV refractive index measurements with improved accuracy and their impact in component modeling

Franck Delmotte, Regina Soufli, Catherine Burcklen, Eirini Papagiannouli, Farhad Salmassi, Eric Gullikson

Proceedings Volume 12494, Optical and EUV Nanolithography XXXVI; 1249409 (2023) https://doi.org/10.1117/12.2660664
Event: SPIE Advanced Lithography + Patterning, 2023, San Jose, California, United States

Abstract

Precise knowledge of the wavelength-dependent refractive index of materials is required to accurately design, build and calibrate the in-band and out-of-band performance of EUV/x-ray instruments. Such instruments include exposure and patterning tools, imagers, microscopes and spectrometers for photolithography, plasma physics, synchrotron and laser science, solar physics and astrophysics. Yet, the available refractive index values in the EUV/x-ray are often unreliable. This is due to the extreme sensitivity of materials to contamination and oxidation, to the difficulty in fabricating appropriate thin film samples, to the presence of near-edge absorption fine structure, and to multiple reflections present at the longer EUV wavelengths, which are complicating the measurements. We are presenting a new methodology to measure the EUV refractive index and new sets of measurements for several important EUV materials. We use combinations of transmittance and reflectance data in the spectral range 826.5 eV (1.5 nm) to 15 eV (82.5 nm) and reveal for the first time highly resolved fine structure in the regions of L, M, N and O absorption edges, in both the absorptive and dispersive portions of the refractive index, resulting in improvements of up to a factor of 3 compared to earlier values. The improved refractive index accuracy is validated by sum rule tests and by simulating experimental data of multilayer coatings containing these materials.

Conference Presentation

Citation Download Citation

Franck Delmotte, Regina Soufli, Catherine Burcklen, Eirini Papagiannouli, Farhad Salmassi, and Eric Gullikson "EUV refractive index measurements with improved accuracy and their impact in component modeling", Proc. SPIE 12494, Optical and EUV Nanolithography XXXVI, 1249409 (28 April 2023); https://doi.org/10.1117/12.2660664

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