Abstract:Hydrogen interaction with ruthenium is of particular importance for the ruthenium-capped multilayer reflectors used in extreme ultraviolet (EUV) lithography. Hydrogen causes blistering, which leads to a loss of reflectivity. This problem is aggravated by tin. This study aims to uncover the mechanism via which tin affects the hydrogen uptake, with a view to mitigation. We report here the results of a study of hydrogen interaction with the ruthenium surface in the presence of tin using Density Functional Theory … Show more
“…In previous publications, we examined the effect of tin on hydrogen penetration into ruthenium, and the mechanism via which hydrogen becomes trapped under the normally near-impermeable ruthenium. 8,9 We found that the proximity of tin to a hydrogen atom on the surface resulted in a lowering of the energy barrier to its penetration into the subsurface; furthermore, we showed a that the saturation of the surface with hydrogen and tin inhibited diffusion of hydrogen out of the ruthenium layer from the top surface. These computational studies of the effect of tin have so far been limited to the interactions of ruthenium and hydrogen with dispersed tin atoms and tin hydrides on the exposed ruthenium surface.…”
“…In previous publications, we examined the effect of tin on hydrogen penetration into ruthenium, and the mechanism via which hydrogen becomes trapped under the normally near-impermeable ruthenium. 8,9 We found that the proximity of tin to a hydrogen atom on the surface resulted in a lowering of the energy barrier to its penetration into the subsurface; furthermore, we showed a that the saturation of the surface with hydrogen and tin inhibited diffusion of hydrogen out of the ruthenium layer from the top surface. These computational studies of the effect of tin have so far been limited to the interactions of ruthenium and hydrogen with dispersed tin atoms and tin hydrides on the exposed ruthenium surface.…”
“…The ''injection'' of hydrogen into the subsurface is caused by the presence of tin, which lowers the penetration barrier. 13 The diffusion coefficients we have calculated indicate that hydrogen diffusion within the ruthenium proceeds at a rate similar to that of hydrogen in other metals, and poses no great obstacle. Tin on the surface also affects surface diffusion of hydrogen, i.e.…”
Section: Discussionmentioning
confidence: 68%
“…11 Although H 2 dissociates and asdsorbs on the surface, 12 the resulting atoms do not penetrate the Ru lattice easily. In a previous publication, 13 we reported that the energy of formation of interstitial hydrogen in ruthenium was found to be positive for both interstitial sites. Our calculations showed that the DFT-calculated energy barrier to subsurface penetration is large for hydrogen, but the presence of tin on the surface leads to a significant lowering of the barrier.…”
Section: Introductionmentioning
confidence: 66%
“…it may reduce the rate at which sites are freed. 13 Thus the likelihood of diffusion to the interface and subsequent blistering is greatly increased when the concentration of hydrogen in the subsurface is significantly raised. In this way, the surface site blocking effect of hydrogen and tin plays a key role in the blistering of the ruthenium film.…”
“…A study towards the mitigation of hydrogen uptake in ruthenium aided by tin is presented by Onwudinanti et al [8] as to avoid blistering of ruthenium-capped multilayer reflectors. DFT calculations and charge density analyses showed a significant drop in the energy barrier for hydrogen to penetrate the ruthenium surface when a tin atom was present.…”
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