Caracterisation des proprietes physico-chimiques des siliciures de nickel sous forme de couches minces

In this project, six phases of the Ni-Si system, stable at room temperature, were studied: Ni3Si, Ni31Si12, Ni2Si, Ni3Si2, NiSi and NiSi2. The main objective was to study their physicochemical properties as thin films. Properties studied were: resistivity and its dependence on temperature; acoustic velocity; optical constants n and k; Raman spectra; and etch rate in Piranha, Aqua Regia, RCA2 diluted HF solutions. Standard samples used to measure these properties were formed by a Ni/Si/Ni thin film stack deposited by magnetron sputtering, where the layers thicknesses were chosen in order to produce a 200 nm thin film after annealing at a rate of 3°C/s and quenched at a specific temperature, determined by in situ X-ray diffraction (XRD) studies. Thin films are mechanically supported by a thermally oxidized Si substrate.; Standards microstructure was determined by means of XRD, transmission electrons microscopy (TEM), Rutherford backscattering spectrometry (RBS) and optical microscopy. Thin films grains have an average height of 100nm in every standard and a layer of Si-saturated Ni was observed by TEM and RBS in the Ni3Si standard.; Metallic behavior of the nickel silicides was demonstrated using temperature dependent resistivity curves, where a linear dependence between resistivity and temperature was observed, with a small quadratic coefficient for Ni 3Si, Ni31Si12, Ni2Si and Ni3Si 2.; Optical constant spectra were measured over an energy range between 0,71 and 4,41 eV and have also confirmed the metallic behavior of the nickel silicides. 'k' constant spectral values show that the penetration length is always less than the thin film thickness over the whole spectrum. Measurements using a second incidence angle were used to validate the optical constant spectra and to confirm that the standards contained only one phase and did not have any contamination layer at the surface.; Acoustic velocities were measured by picosecond ultrasonics and ranged between 6,08 and 7,70 km/s. Principal characteristic Raman nickel silicide peak values do not overlap and allow non-ambiguous identification of the phase, providing useful ex situ complementary information for XRD measurements. The Ni3Si standard was found not to be Raman active as was the central Ni layer within.; Finally, wet etch experiments have confirmed that Piranha and Aqua Regia solutions are good candidates to provide a selective etch of Ni with respect to NiSi. For diluted HF and RCA2 solutions, etch rate is proportional to the Ni fraction of the nickel silicide phase.