Silicide formation with Pd-V alloys and bilayers

Solid phase reactions in the temperature range between 250 and 600 °C between Si and V-Pd bilayers as well as alloy layers have been studied by MeV ⁴ He ⁺ backscattering and x-ray diffraction techniques. When a Pd layer is interposed between Si and V, the bilayer system starts to react at <300 °C with the formation of Pd ₂ Si. Annealing at higher temperatures (∼600 °C) leads to a uniform layer of VSi ₂ formed on top of the Pd ₂ Si. Reversing the bilayer sequence (Si/V/Pd) raises the reaction temperature of the system to ∼500 °C with V mixing into the Pd layer. Annealing at higher temperature leads to the formation and accumulation of Pd ₂ Si at the interface and a mixed (nonuniform) structure of Pd ₂ Si and VSi ₂ in the outer surface region. For a Pd-rich alloy (Pd ₈₀ V ₂₀ ), a reaction started at about 300 °C and produced Pd ₂ Si by depleting Pd from the alloy. This resulted in a mixed structure of Pd ₂ Si and VSi ₂ in the outer region, similar to the final stage of the Si/V/Pd system. For a V-rich alloy (Pd ₉₀ V ₁₀ ), the formation temperature of Pd ₂ Si is raised to ∼500 °C and again leads to a mixed structure. The amount of accumulation of Pd ₂ Si at the substrate-silicide interface increases with the Pd content in the alloy.