Kinetic and chemistry effects during the early stages of growth of metallic thin films : multi-scale understanding by an experimental approach and numerical modeling

Description

PhD Thesis Clarisse Furgeaud
This thesis deals with the growth dynamics of thin metal films by magnetron sputtering and their correlation with film properties, such as residual stress, microstructure and surface morphology. Various in situ and real-time diagnostic tools (substrate curvature-MOSS, Optical surface reflectivity spectroscopy-SDRS, X-ray diffraction (XRD), X-ray reflectivity (XRR) and electrical resistivity) were implemented. Coupling these investigations with ex situ characterization (HRTEM, STEM, DRX, XRR, EBSD) allows to understand the influence of kinetic and chemical effects (interfacial reactivity, alloying effect) on the early stages of growth (percolation and continuity) but also on the structural and morphological evolutions of high (Cu, Ag) and low (W) mobility metal films. A modeling approach was used for the case of Cu growth, where kinetic Monte Carlo atomistic simulations (kMC) give access to elementary growth mechanisms. This code, developed in-house to model the growth of thin films by magnetron sputtering, takes into account the specificities of this technique: angular and energetic distribution of the incident flux, energy deposition in (sub-)surface and evolution of the stress at grain boundaries. This coupling of experiments and modelling has demonstrated a complex interdependence of the deposition rate and energy deposition on the growth morphology and the intrinsic stress of Cu and Ag films. The stress level in these systems results from the competition of different atomic mechanisms. The kMC code shows that, in the absence of energetic particles, the compressive stress due to the diffusion of adatoms in the grain boundaries decreases with the deposition rate.In addition, the chemical effects studied comparatively in the Cu/Ge and Ag/Ge systems revealed a competition between interface energy, chemical reactivity and Ge segregation during growth. The growth mechanisms are different for both metals however, the presence of Ge (co-deposited or sublayer) leads to the same microstructural consequences, namely an improvement of the texture (111) and a decrease of grain size and surface roughness.Finally, this methodology applied to the growth of W-Si alloys showed that the critical thickness of the amorphous / crystal transition and the nucleation of either the or the phase strongly depends on the Si content.

Période	22 nov. 2019
Candidat	Clarisse Furgeaud
L'examen a eu lieu à	Université de Poitiers
Degré de reconnaissance	International