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 4He+ 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 Pd2Si. Annealing at higher temperatures (∼600 °C) leads to a uniform layer of VSi2 formed on top of the Pd2Si. 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 Pd2Si at the interface and a mixed (nonuniform) structure of Pd2Si and VSi2 in the outer surface region. For a Pd-rich alloy (Pd80V20), a reaction started at about 300 °C and produced Pd2Si by depleting Pd from the alloy. This resulted in a mixed structure of Pd2Si and VSi2 in the outer region, similar to the final stage of the Si/V/Pd system. For a V-rich alloy (Pd90V10), the formation temperature of Pd 2Si is raised to ∼500 °C and again leads to a mixed structure. The amount of accumulation of Pd2Si at the substrate-silicide interface increases with the Pd content in the alloy.