Grenzflächen‐optimierte Mo/Si Multischichten als Reflektoren für den EUV Spektralbereich. Interface‐optimized Mo/Si multilayers as reflectors for the EUV spectral range

EUV lithography is the most promising technique for the fabrication of semiconductor structures below 50 nm. This requires the use of reflecting multilayers as optical elements. These multilayers must have reflectances as high as possible since it determines the efficiency of the technique and therefore the throughput of a future chip fab. In this work we present investigations on the interface quality of Mo/Si multilayers which are prepared by magnetron sputter deposition. Starting from the two‐component Mo/Si system, that has mainly been optimized with respect to interface roughness, we show that interface interdiffusion can also be reduced by the introduction of tiny barrier layers. In pure Mo/Si multilayers particularly a low Ar sputter gas pressure is important to get smooth layers, whereas the interdiffusion can be reduced by the deposition of C and B₄C barrier layers on the individual interfaces. As result of our work, we have prepared Mo/Si multilayers with outstanding high reflectances: R_EUV = 70.1 % (λ = 13.3 nm, α = 1.5°), R_EUV = 71.4 % (λ = 12.5 nm, α = 22.5°).