A theoretical study of aluminium chemical vapour deposition using dimethylaluminium hydride: a surface reaction mechanism on Al(111)

The theoretical reaction mechanism for the epitaxial growth of aluminium in the aluminium chemical vapour deposition (Al-CVD) method using dimethylaluminium hydride (DMAH) as a material gas is studied. Density-functional theory (DFT) and the cluster model approach are employed to obtain the potential energies and structures of adsorbed molecules on the Al(111) surface. The model clusters representing the Al(111) surface are assessed by comparing the averaged bond strength with the experimental value. The adsorption of DMAH on the aluminium surface, the movements of admolecules formed by the dissociation of DMAH on the aluminium surface, the surface reactions between admolecules and the desorption of products from the surface are also considered. It is concluded that no activation energy is required for the direct adsorption of DMAH on to the aluminium surface, but considerable activation energy is required for indirect adsorption (the reaction between DMAH and the adsorbent hydrogen atom to produce methane by the Eley–Rideal mechanism). We also consider that the rate-determining step could be the dissociation of methylaluminium to form an aluminium atom and a methyl group.