The kinetics of silicide growth are classified into three different categories: (a) diffusion controlled, (b) nucleation controlled, (c) others (reaction rate controlled). These are analyzed with the aim of understanding both the phenomenology of growth and the specific atomic mechanisms of phase formation. Diffusion-controlled growth is discussed with respect to the Nernst-Einstein equation. Stress relaxation is considered as a possible cause of reaction-rate control. The relative merits of two different types of marker experiments are compared. A few silicides are discussed in terms of what can be inferred about diffusion mechanisms. The competition between reaction-rate and diffusion control phenomena is shown to have specific effects on the sequence of phase formation; it is also related to the formation of some amorphous compounds. Reactions between silicon and alloyed metal films are used to illustrate the respective influences of mobility and driving force factors on the kinetics of silicide growth; they can also be used to underline the dominance of nucleation over diffusion in some silicide formation processes.

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The Ni2Si lattice and grain boundary self-diffusion parameters have been studied using radiotracers 63Ni for Ni diffusion, 68Ge for Si diffusion, conventional sectioning techniques, and bulk specimens. The results obtained show that Ni diffuses faster than Ge(Si) in the lattice (and in the grain boundaries) of Ni2Si, in agreement with the structure of this silicide. The activation energies for Ni lattice and grain boundary diffusion are respectively 2.48 eV (measured between 650 and 910 °C) and 1.71 eV (530–710 °C). These values are comparable to those obtained in pure metals of similar melting temperature. They suggest that Ni diffuses on its own sublattice by a vacancy mechanism. Grain boundary diffusion in this intermetallic compound appears as a very efficient process for mass transport at low temperature. A quantitative comparison with the kinetic of formation of Ni2Si (by solid state reaction between a Ni film and a Si substrate) indicates that the growth of thin films is controlled by the diffusion of Ni along the silicide grain boundaries. This mechanism explains the rapidity of the formation and its low activation energy (≊1.6 eV).

The reaction between nanometric Ni films and Ge is analyzed using isothermal x-ray diffraction measurements and transmission electron microscopy. It is found that NiGe is formed during deposition at room temperature. The metal rich phase that grows during heat treatment has been clearly identified to be Ni5Ge3. The simultaneous growths of Ni5Ge3 and NiGe have been observed on amorphous and polycrystalline germanium. This is in contrast with the usual sequential growth reported in thin films.

The solid state reaction between Co and Si has been studied in bulk diffusion couples between 850 and 1100 °C. At the scale of the observations made, the three phases Co2Si, CoSi, and CoSi2 are found to grow simultaneously, according to diffusion controlled kinetics. The results are analyzed in term of the Nernst-Einstein equation that directly relates diffusion fluxes to the free energy changes driving the formation. The growth rates obtained for CoSi2 at high temperatures, in the present bulk samples, are compared with those determined by others in thin films, at much lower temperatures. The comparison requires that attention should be paid to two factors. The first one is that the laws of growth are slightly different for a phase growing simultaneously with two other ones (bulk) and one phase growing alone (thin films). The second factor is the grain size of the various samples, which varies with the temperature of reaction. Once this is done, excellent agreement is obtained between the two sets of measurements. Moreover it is shown that knowing the grain size, it is possible to calculate quite accurately the growth rate from the respective isotope diffusion coefficients both for lattice and grain boundaries of Co and Si in CoSi2.