Formation and structure of epitaxial NiSi₂ and CoSi₂

Transmission electron microscopy has been applied to study the formation and structure of epitaxial NiSi₂ and CoSi₂ thin films on silicon. Bright field and dark field imaging reveal the interface planes of faceted silicides through the strain contrast, analogous to the contrast of the precipitate-matrix interface of coherent or semicoherent precipitates. Superlattice dark field imaging depicts the distribution of twin-related and epitaxial silicides in these systems. {111} interfaces were found to be more prominent than {001} interfaces. Twin-related silicides were observed to cover more area on the substrate silicon than epitaxial silicides did. In situ annealing of nickel and cobalt thin films on silicon provides a unique means of investigation of the transformation from polycrystalline to epitaxial silicides. The NiSi₂ transformation was found to be very rapid at 820°C, whereas the CoSi₂ transformation appeared to be very sluggish. Furnace annealing confirmed that only a small fraction of CoSi₂ transforms to epitaxial CoSi₂ after annealing at 850°C for 4 h. Diffraction contrast analysis has been applied to interfacial dislocations of epitaxial NiSi₂/Si and CoSi₂/Si systems. The dislocations were found to be of edge type with 1 6〈112〉 and 1 2〈110〉 Burgers' vectors. The average spacings are close to their respective theoretically predicted values. © 1982.