Stability of amorphous Fe-W alloys in multilayer metallizations on silicon

Co-sputtered amorphous Fe 0.37 W 0.63 alloys were investigated for applications as diffusion barriers in multilayer metallizations on silicon. Interface reactions and recrystallization during thermal annealing at 400–800°C were studied by back-scattering spectrometry and X-ray diffraction. On SiO 2 substrates the recrystallization of these films occurs at approximately 700°C. On silicon the recrystallization is accompanied by the formation of a silicide layer containing FeSi 2 and WSi 2 phases. No detectable reaction is observed when the alloy film is amorphous. In contact with an overlay metal such as aluminum, copper, nickel or platinum the amorphous Fe 0.37 W 0.63 layer prevents direct interaction between the silicon substrate and an overlay metal film 1000 Å thick during thermal annealing for 30 min at 650°C. The lifetime of the barrier is limited by dissolution and compound formation at the interface and at grain boundaries of the overlay metal.