Wavelength selection for multilayer coatings for lithography generation beyond extreme ultraviolet

Abstract

Abstract. The spectral properties of LaN/B and LaN∕B 4 C multilayer mirrors have been investigated in the 6.5 to 6.9 nm wavelength range, based on measured B and B 4 C optical constants. We show that the wavelength of optimal reflectance for boron-based optics is between 6.63 and 6.65 nm, depending on the boron chemical state. The wavelength of the maximum reflectance of the LaN∕B 4 C multilayer system is confirmed experimentally. Calculations of the wavelength-integrated reflectance for perfect ten-multilayer-mirror stacks show that a B-based optical column can be optimized for a wavelength larger than 6.65 nm.

Optical and structural characterization of CeO2/B4C multilayers near boron K-edge energy

“…The potentiality of using near edge EUV reflectivity measurements in combination with X-ray reflectivity (XRR) to improve analysis and characterization of buried interfaces of ML structures has been discussed in recent papers [19][20][21]. There, the measurements were designed in such a way that structural and optical properties of MLs can be derived with precision, simplicity, reliability and consistency.…”

Depth-resolved compositional analysis of W/B4C multilayers using resonant soft X-ray reflectivity

“…To further reduce the feature sizes, researchers are working on next-generation EUV lithography using radiation of shorter wavelength. The wavelength range around = 6.7 nm was preferred for next-generation EUV lithography (Makhotkin et al, 2012a). In this region B-based multilayers give the highest reflectivity because this region is within the anomalous dispersion of the optical constants of boron (Medvedev et al, 2013;Chkhalo et al, 2013;Tsarfati et al, 2009;Kuznetsov et al, 2015;Platonov et al, 2011).…”

6.7-nm Emission from Gd and Tb Plasmas over a Broad Range of Irradiation Parameters Using a Single Laser

“…Highly ionized Gd and Tb plasmas emitting at wavelengths near λ = 6.7 nm [4,5] in the form of an unresolved transition array (UTA) are primary light source candidates for BEUVL [6]. They can produce intense emission within the reflection region of La/B based multilayer mirrors, whose near normal incidence reflectivity can theoretically reach values up to 80% [7]. A reflectivity of 64.1% at λ = 6.65nm with 0.06nm FWHM bandwidth has been already realized experimentally [ 8 ].…”