Implementation of GdSi2as lowhyphen;barrier (0.4 eV) Schottky contacts in a Si device requires a diffusion barrier between the GdSi2and Al interconnects to prevent Al penetration. In this work, the effectiveness of vanadium films as such a diffusion barrier has been studied by using a set of complimentary experimental techniques: nuclear backscattering, xhyphen;ray diffraction, and currenthyphen;voltage measurement of Schottky barrier height on bothnhyphen;type andphyphen;type Si substrates. We found that the effectiveness depends strongly on how the thinhyphen;film structure of Al/V/GdSi2/Si was made, and especially on the formation process of GdSi2. The GdSi2, which was formed upon deposition onto a highhyphen;temperature substrate, is superior in stability by showing no Al penetration to other processing schemes investigated. These results are explained by structural and compositional changes occurring in the layered films of Al/V/Gd/Si as a function of heat treatment. In order to understand the complex interdiffusion and compound formation in the layered structure, the reactions between neighboring layers have been studied: Al interacts with V at sim;450thinsp;deg;C, forming Al3V and possibly Al10V; V does not react with Gd, even at 700thinsp;deg;C; and Gd is known to react with Si to form GdSi2atsim;350thinsp;deg;C. On the other hand, Al reacts readily with Gd at 250thinsp;deg;C to form a metastable compound of Al4Gd, which then transforms to Al3Gd at 400thinsp;deg;C, and the formation of these compounds has been found to retard the reaction between Gd and Si.
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