Epitaxial Silicides

The formation and structures of epitaxial CoSi2, NiSi2, Pd2 Si and PtSi films on silicon are reviewed. Polycrystalline films of reasonable epitaxial quality can be grown with sharp interfaces on Si(111) by conventional deposition and heating techniques. The interfaces on (100) substrates, however, are faceted. Perfect singlecrystal CoSi2 films can be grown on Si(111) substrates by ultrahigh vacuum techniques using conventional deposition and annealing at about 900°C and molecular beam epitaxy codeposition at about 600°C. The single-crystal films are rotated 180° with respect to the substrate. Novel defect arrays are observed at the interface. Resistivities in epitaxial films are lower than those reported in polycrystalline layers. High quality silicon films can be grown on the silicides to form semiconductor/metal/semiconductor heterostructures.