Grazing incidence interaction of Sn particles with EUV Lithography ruthenium mirrors - Condensed Matter > Materials ScienceReport as inadecuate




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Abstract: The new EUV Lithography tools for IC High Volume Manufacture at 22nm make useof EUV radiation at \lambda = 13.5nm. High power Laser LPP and DischargeDPPEUV light sources are based on Sn plasmas for the optimum conversion ofelectrical power to in-band radiation. Sn-fueled sources emit debris such as Snparticles in a rather wide energy spectrum: from thermalized Sn to several tenskeV fast ions. Tin interaction with the collector mirrors surfaces facing thehigh power EUV light source leads to the degradation of the optical performanceand productivity of the litho tool, therefore debris must be suppressed and thesurface modification of the mirror materials during the particle irradiationmust be carefully investigated both theoretically and experimentally. For DPPSn-fueled sources the collector is a grazing incidence mirror that reflects theEUV light in the grazing angle range from about 1\degree to 20\degree. The mostused material for these collector mirrors is Ru. The knowledge of theinteraction process of Sn particles at different energies and angles with Rumirrors is crucial to understand mirror degradation and to tune the parametersof the source and of the debris suppression devices to reach optimal mirrorlifetime. We carried out a study of the modification of the ruthenium surfaceexposed to the simultaneous flux of thermalized and energetic Sn at grazingincidence, for energies varying from 300eV to 30keV. The computational study isperformed with the Monte Carlo codes TRIDYN and TRIM.SP based on binarycollision approximation assumptions. These tools allow to follow dynamicallyand at steady state the evolution of the surface composition and to modelsurface binding energy and density for predicting sputtering, reflection,ion-assisted deposition and depth profiles in the nm surface region.



Author: Valentino Rigato

Source: https://arxiv.org/







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