Xe+-irradiation effects on multilayer thin-film optical surfaces in EUV lithography

Abstract: In extreme ultraviolet lithography (EUVL) environments, transient plasma dynamics dictate conditions for particle/surface interactions. A critical challenge facing EUVL development is optical component lifetime in both gas-discharge-produced plasmas (DPP) and laser-produced plasma (LPP) devices. Optical components are exposed to impinging fast ions and neutrals, impurities (H, C, O, N) and debris, leading to component degradation and consequently limiting 13.5-nm light reflection intensity. This paper studies Xe+ irradiation-induced mechanisms that affect the performance of EUVL multilayer collector mirror surfaces. Irradiation conditions include: incident particle energies of 1keV and 5keV, Xe+ fluences ranging from about 3×1014–5×1016 Xe+/cm2 and surface temperatures of 273K and 473K. Measurements include in situ quartz crystal microbalance for sputtering rate measurements, ion scattering spectroscopy, X-ray reflectivity and atomic force microscopy. Three distinct erosion regimes for bombardment of MLM with Xe+ are: a low Xe+ fluence regime below ∼5×1014 Xe+/cm2, a moderate regime at fluences between 5×1014 and 5×1016 Xe+/cm2 and a high fluence regime >1017 Xe+/cm2. [Copyright &y& Elsevier]