FORMATION AND HIGH-TEMPERATURE STABILITY OF COSIX FILMS ON AN SIO2 SUBSTRATE

A thin α-Co layer with an amorphous Si underlayer has been sputter deposited onto a thermal SiO2 substrate, rapid thermal annealed in N2 at 700-1050°C, and the phases formed examined using Auger electron spectroscopy, transmission electron microscopy, electron diffraction, and sheet resistance measurements. A CoSix film results where x is constant with depth and determined by the relative amounts of Co and Si deposited. With increasing x, phases identified are α- and β-Co containing dissolved Si, Co2Si, CoSi, and CoSi2. At high temperatures, the CoSi2 film agglomerates and thins the underlying oxide probably on account of excess Si in the silicide film. Furthermore, in an N2 atmosphere, the CoSi2 globules are converted into CoSi in accordance with the phase diagram.