Thermal stability and diffusion processes in Mo x Si y /Si multilayers studied with high-resolution RBS

Abstract

Mo x Si y /Si multilayers with a period thickness of ∼7.5 nm and bilayers Mo x Si y /Si have been fabricated by e−-beam evaporation in UHV at a deposition temperature of 150°C [1]. The composition of the as-deposited layer systems and changes in the composition after baking the samples have been studied with high-resolution RBS. For a multilayer with a mixing ratioy/x≃2, no interdiffusion is observed up to a baking temperature of 830°C. For samples with a mixing ratioy/x≃1, diffusion is observed up to a baking temperature of 630°C, resulting in a mixing ratio close toy/x≃2. This mixing ratio remains almost stable up to ∼830°C, and considerable interdiffusion is only observed in those systems where regions with a mixing ratio smaller than 2 still exist. Possible reasons for the high thermal stability of the samples are the lack of a concentration gradient for Si in the system \(Si/Mo_{0.\bar 3} Si_{0.\bar 6}\) and/or the crystallization of MoSi2.