The Formation of Silicides

The formation of silicides in reaction couples, for example, of the MesAl-SiC type, where Me is a transition metal, is more complicated. In this case, in addition to the Me2Si layer, the MeAl layer (or some other aluminide layer) also grows, i.e. the Me3Al-MeAl-(Me2Si+C)-SiC system is formed. The mechanism of its occurrence is probably as follows. The Me3Al phase is decomposed at the Me3Al-MeAl interface by the reaction... 

G. Ottaviani. Metallurgical aspects of the formation of silicides // Thin Solid Films.-1986.-V.140, No.l.-P.3-21. 

Since the reactive gas in the RE process is in a molecular state and thus less likely to react with the vapor species, the formation of a well crystallized stoichiometric film requires high thermal activation at the substrate. This problem becomes acute in situations where the reactive gas consists of more than one element. The typical examples are S1H and CH CgHg for the formation of silicides and carbides respectively. The concept of electron impact ionization and excitation of the reactive gas in the substrate-source space, as introduced by Bunshah and Raghuram solved this problem. The ionization and excitation of the gas activates the compound forming reactions and the compound films can be synthesl2 d at a much lower substrate temperature. This process is known as Activated Reactive Evaporation (ARE). 

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