OMCVD OF TRANSITION-METALS AND THEIR SILICIDES USING METALLOCENES AND (DI) SILANE OR SILICON TETRA-BROMIDE

In this work we investigated the feasibility of OMCVD of metals and silicides with the metallocenes of Fe, Co and Ni and various Si-precursors. Layers of pure Fe and Co can be deposited with H2 as the carrier gas at atmospheric pressure. This deposition is found to be completely inhibited on bare silicon substrates. Nickelocene cannot be used because of preliminary reduction by H2 at transport temperature. The Si-precursors silane and disilane are found to react with the metallocenes, leading to the incorporation of approximately 30 at % carbon in the silicide, independent of deposition conditions. For cobalt silicide deposited on silicon substrates in H2, a thin layer of carbon-free epitaxial CoSi2 is found at the substrate interface, even on Si(100). The carbon incorporation can be reduced to approximately 15 at % by using silicon tetra-bromide with an increase in the relative thickness of the carbon-free layer. The deposition of silicon from the non-conventional precursor silicon tetra-bromide was briefly studied. Carbon incorporation can be completely avoided by introducing the metallocene and the silicon precursor alternately in the reactor. The stoichiometry of the layer can then be controlled by adjusting the partial pressures of the precursors and/or the pulse durations. The silicide growth by this method is also inhibited on silicon substrates.