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Abstract: Recently, promising results for epitaxial cobalt and nickel silicide formation have been obtained using a thin titanium interlayer and as a mechanism for such an interlayer promoting effect the removal of a native oxide from a silicon substrate due to the gettering effect of titanium was suggested. However, detailed information about transformations in the Ti layer during its growth and annealing process still lacks. In this paper, phase and structure transformations in the Ti interlayer during growth and consequent silicidation annealing are studied on the system Ni/Ti/Si(100). The Ni (4nm)/Ti (1.4nm) bilayers were deposited onto unheated (100) Si substrate with a native oxide layer by rf sputtering inside the AES – microscope and analyzed by in situ Auger electron spectroscopy, X-ray photoelectron spectroscopy and ex situ transmission electron microscopy. During the Ti interlayer deposition process a following sequence of the growth mechanism and phases were revealed. Initially, small 3D TiO2 islands are formed due to reduction of a native silicon oxide followed by the formation of the TiO and TiO x phase between TiO2 islands as well as on their top. During the silicidation annealing at 300°C the continuous Ti-related interlayer, composed mainly (∼85%) of Ti oxides (TiO and TiO2) transforms into less compact island-like TiO2 layer what promotes Ni diffusion into silicon resulting in the nickel silicide, NiSi2 formation. [Copyright &y& Elsevier]

Abstract: The initial growth stages of materials non-active to a substrate has been extensively studied for decades, whereas there had been fewer studies on the initial growth of active metals on silicon substrate, despite its technological importance. In this paper the very early growth stages of transition metal (Ti, V and Nb) films deposited by rf sputtering on unheated (100) Si substrate were studied by in situ X-ray photoelectron spectroscopy. The following sequence of the phase composition and the growth mechanism changes during deposition process was revealed. Initially in a submonolayer regime, small 3D TiO2 islands are formed via reduction of a native silicon oxide layer on a substrate followed by formation of a TiO phase between TiO2 islands and on their top. After deposition of ca. 2 monolayers a metallic Ti phase appears and later only the metal Ti film grows. The same growth behavior takes place at Nb and V deposition with a difference that in the case of Nb the above changes occur at earlier stages what can be explained by the highest niobium activity to the reduction of silicon oxide in the row V, Nb, Ti. [Copyright &y& Elsevier]

Abstract: A model for crystallization kinetics of thin amorphous film is developed by extension the Kolmogorov–Johnson–Mehl–Avrami (KJMA) model to take into account a finite film thickness. Two model versions, volume induced crystallization (VIC) and surface induced one (SIC), are explored. Finite film thickness effects lead to important consequences in the VIC: the crystallization profile reaches maximum in film middle, the crystallites population in a film is always higher than in a bulk material, the thinner film the slower it crystallizes and a spatially inhomogeneous structure with a fine-grained subsurface layer is formed. A VIC-kinetics follows a generalized KJMA equation with parameters depending on a film thickness and a range of the KJMA model validity is found. A SIC-kinetics obeys 2D KJMA equation in sufficiently thin film and is almost linear in a thick film. The model is extended to the case of non-constant growth rate and crystallization of subsurface film layer, and is shown to be consistent with experimental data. [Copyright &y& Elsevier]

A quantitative description of the surface morphology evolution in thin film growing via 3D island mechanism is presented. The treatment is based on the calculation of the survival probability for any point on (or above) a substrate during growth process. The paraboloid growth model is considered. In this model, the lateral growth of an island occurs in a circle form via capture of migrating adatoms, while its vertical growth proceeds at constant velocity owing to direct impingement of deposited atoms, so that a steady (in time) and random (in space) surface relief consisting of paraboloid growth hillocks is developed eventually. For this surface relief, forming at paraboloid growth, the height–height autocorrelation function is derived for different hillock shape and different nucleation mode generating different hillock space distribution. It is found that the hillock shape strongly affects on the overall surface roughness and the hillock space distribution influences on both the autocorrelation function form and the rms roughness. The surface height distribution is asymmetric, non-Gaussian with negative skewness. The random rough surface of thin film with surely non-Gaussian height distribution is characterized by close-to-Gaussian height–height correlation function. [Copyright &y& Elsevier]