While it is possible to grow epitaxial CoSi2 films of a high quality using UHV technology it is much more difficult to produce films of similar quality under high vacuum and non-“clean room” conditions. Tung et al.1 have however shown that films of a good quality can be produced under these poorer conditions with the aid of a laser anneal of an appropriate power followed by a short thermal anneal. In this paper the role of the laser anneal, and of the (post laser) thermal anneal, in the production of epitaxial films is examined. It appears that the principle role of the laser anneal is to induce the epitaxial CoSi2 formation at the silicon / silicide interface, and that this epitaxial layer then acts as a seed for epitaxial film growth during the subsequent thermal anneal.

Taking advantage of controllable interdiffusion and reaction processes by using a 50 nm thin Ti interlayer an annealing step in the temperature range from 450 to 475°C transforms the TiNiAg layer sequence on silicon into a stable final state, whereby a contamination free, homogeneous nanoscale NiSi contact layer arises with low values of the contact resistance. Intercalating a thin Ti layer the nickel silicide growth rate is lowered by 2 orders of magnitude. Low sheet resistance and a good bondability are preserved by the remaining Ni-Ag top layer sequence which does not interact during the contact formation process.

Many silicides, including TaSi2, CoSi2, TiSi2 and others, form eutectics with silicon. Directional solidification of melts with the eutectic composition and controlled doping of the silicon matrix results in two-phase electronic composites with oriented structures. Such composites have unusual microstructures and interesting properties resulting from the high density of Schottky junctions. In this paper, the growth, microstructure, transport properties and device applications of silicon-silicide composites are reviewed, concentrating mostly on the benchmark Si-TaSi2 system. The Si-TaSi2 interface, formed upon solidification, is characterized electrically as well as structurally by electron-beam induced current techniques, x-ray diffraction and high resolution TEM. It is shown that the interface is of remarkably good quality allowing the fabrication of very high quantum efficiency (80%) photodiodes and high voltage (up to 6kV) transistors.

Buried single crystalline CoSi2 layers in Si(100) have been grown using molecular beam allotaxy. In this paper, we investigated the diffusive interaction of two buried silicide precipitate layers, one with a small Co peak concentration of 10 at% and another one with 26 at%. Annealing causes first local coarsening in each layer, and then dissolution of the thinner precipitate layer. The accumulation of the Co atoms at the thicker layer is described by a simple model for the diffusional redistribution.

CrSi2 is of technological interest because it is a silicon-based semiconductor with a small band gap. Due to the lack of success with conventional molecular beam epitaxy of CrSi2 on Si, growth on mesotaxy-produced template layers and allotaxy have been attempted. After removal of the Si capping layer, epitaxy of additional CrSi2 on template layers formed by mesotaxy was found to be possible. However, single-crystal continuous films were not obtained, due at least in part to the presence of a network of cracks in the starting template. Allotaxy of CrSi2 was found to allow the formation of large grains of CrSi2 embedded in a single-crystal Si matrix, but coalescence of these grains into a continuous layer was not achieved.

Electrical transport properties of thin film and single crystal silicides will be reviewed and discussed. The presentation will be made by considering that most of the compounds behave as metals, with the resistivity which increases with the temperature, and few of them are semiconductors. Semiconductor silicides have band-gaps which span between 0.1 and 1.2 eV for ReSi2 and IrSil.75, respectively. Several metallic silicides show, expecially in the high-temperature limit, a resistivity-temperature dependence different from the classical linearity. The deviation, related to the intrinsic properties of the compound, can be affected by the presence of structural defects and impurities. The role played of such defects on the residual resistivity at low temperature will also be considered. Anisotropic effects will be discussed in relation with the shape of the Fermi surfaces.

Electrical transport properties of thin film and single crystal silicides will be reviewed and discussed. The presentation will be made by considering that most of the compounds behave as metals, with the resistivity which increases with the temperature, and few of them are semiconductors. Semiconductor silicides have band-gaps which span between 0.1 and 1.2 eV for ReSi2 and IrSil.75, respectively. Several metallic silicides show, expecially in the high-temperature limit, a resistivity-temperature dependence different from the classical linearity. The deviation, related to the intrinsic properties of the compound, can be affected by the presence of structural defects and impurities. The role played of such defects on the residual resistivity at low temperature will also be considered. Anisotropic effects will be discussed in relation with the shape of the Fermi surfaces.

The optical properties of polycrystalline layers of CrSi2, MnSi1.73, β-FeSi2, and Ir3Si5 prepared by single layer and codeposition methods on different substrates are measured over the spectral range from the infrared to 24 eV. The spectral features in the interband region are attributed to transitions between Si p-metal d bonding and antibonding states mediated by energy dependent matrix elements. The IR spectra of CrSi2 and β-FeSi2, exhibiting six phonon modes, are simulated by an oscillator model.

We present point-contact-spectroscopy measurements on VSi2, NbSi2 and TaSi2 high quality single crystals. These three compounds crystallise in the same hexagonal structure (structure C40, space group P6222) and they are isoelectronic. Phonon spectra deduced by this technique are in good agreement with phonon parameters previously obtained from resistivity and low temperature specific heat measured on the same samples.