RADIOACTIVE METAL TRACER INVESTIGATION OF PD2SI FORMATION

A radioactive metal tracer technique has been developed with a view to identify the dominant diffusing species and the diffusion mechanism during silicide growth. The position of a thin band of radioactive metal, originally at the silicon/metal interface, is determined after silicide formation by alternate use of Rutherford backscattering spectrometry, γ spectrometry, and Ar ion sputter etching. Application of this procedure to the formation of Pd2Si yields a 109Pd activity profile, the position and shape of which indicates that mainly silicon moves during this reaction, while the observed spreading of the profile points to some palladium vacancy diffusion. The data obtained with this approach demonstrate that the technique is well suited for the determination of the predominantly diffusing species, and confirm results of other inert marker and 31Si tracer diffusion experiments.