Chemisorption of H radical generated volatile Si hydrides on Ru films

• Volatile SiH x (x=0-4), generated by H* exposure of Si, chemisorb on Ru • SiH 4 dissociates on Ru without native oxide with a sticking probability ∼ 5·10 -7 • SiH x radicals are the main adsorption agents in an environment containing H* • Full coverage of the Ru surface with a complete Si outermost layer is observed • Si adsorption is self-limiting when the dominating gas phase specie is H* In this work, we investigate how Ru thin film surfaces adsorb Si by exposure to H radicals (H*) in a vacuum system containing solid Si. H* effectively reduce the native oxide of Ru and etch Si, forming volatile SiH x . We demonstrate that Ru without native oxide catalyzes dissociation of SiH 4 near room temperature (in the absence of H*) with a SiH 4 sticking probability of ∼ 5·10 -7 and an adsorption limit of ∼ 1 monolayer (ML), due to saturation of reactive Ru sites. In the presence of H*, gas phase reactions are supposed to convert SiH 4 to SiH x * radicals. SiH x * , formed in this way, has a sticking probability of ≥ 0.5 and an adsorption limit of ∼ 2.6 ML on Ru. This adsorption limit exceeds the adsorption limit of 1 ML for catalytic SiH4 dissociation. Interaction of SiH x * and Ru leads to a thermodynamically favorable Si and Ru intermixing and formation of RuxSiy with a Si surface layer. Observations suggest that SiH x * species only chemisorb to Ru surface sites, making the adsorption self-limiting.