Modélisation et simulation du dépôt des oxydes à forte permittivité par la technique du Monte-Carlo cinétique

Miniaturiser les composants impose des changements radicaux pour l'élaboration des dispositifs micro électroniques du futur. Dans ce cadre, les oxydes de grille MOS atteignent des épaisseurs limites qui les rendent perméables aux courants de fuite. Une solution est de remplacer le SiO2 par un matériau de permittivité plus élevée permettant l'utilisation de couches plus épaisses pour des performances comparables. Dans ce travail nous présentons une modélisation multi-échelle de la croissance par couche atomique (ALD) d'HfO2 sur Si permettant de relier la nano-structuration d'une interface au procédé d'élaboration. Nous montrons que la connaissance de processus chimiques élémentaires, via des calculs DFT, permet d'envisager une simulation procédé qui repose sur le développement d'un logiciel de type Monte Carlo Cinétique nommé "HIKAD". Au delà des mécanismes les plus évidents, adsorption, désorption, décomposition et hydrolyse des précurseurs sur la surface, nous introduirons la notion de mécanismes de densification des couches d'oxyde déposées. Ces mécanismes sont l'élément clé permettant de comprendre comment s'effectue la croissance de la couche en termes de couverture. Mais au delà de cet aspect ils nous permettent d'appréhender comment, à partir de réactions de type moléculaire le système évolue vers un matériau massif. Nous discuterons ces divers éléments à la lumière de résultats de caractérisations obtenus récemment sur le plan expérimental du dépôt d'oxydes d'hafnium.Miniaturizing components requires radical changes in the development of future micro electronic devices. In this perspective, the gate dielectric of MOS devices can become so thin as to be made permeable to leakage currents. One solution is to replace SiO2 by a material with a higher permittivity which would allow the use of thicker layers with similar results. My work presents a multi-scale modelling of the growth of HfO2 on Si by atomic layer (ALD), which allows me to link the nano-structuration of an interface with the process of development. I demonstrate that knowing how basic chemical processes work, thanks to DFT calculations, allows considering a process simulation based on the development of a Kinetic Monte Carlo software named "HIKAD." Going beyond rather obvious mechanisms, I introduce the notion of densification mechanisms of deposited oxide layers. These mechanisms are the key element to understand how the growth of the layer in terms of coverage works. But even beyond that aspect, they allow to study the system's evolution towards a massive material, starting from molecular reactions. I shall discuss all those points in the light of recent experimental characterisation results concerning the deposition of hafnium oxides

Nanocolumnar TiN thin film growth by oblique angle sputter-deposition: Experiments vs. simulations

Nanostructured columnar titanium nitride (TiN) thin films were produced by oblique angle deposition using reactive magnetron sputtering. The influence of the angular distribution of the incoming particle flux on the resulting filmmorphology (columntilt angle, porosity, surface roughness) was studied by varying the inclination angle α of the substrate at two different working pressures, 0.3 and 0.5 Pa. The microstructural features and columns tilt angles βexp determined experimentally were compared to those simulated from two kinetic Monte Carlo (KMC) models. With increasing pressure, the TiN columns were found to be less defined but no significant changes in βexp were revealed. Both KMC models satisfactorily reproduced the experimental findings, the agreement being closer at 0.5 Pa. The evolution of β angle is also discussed with respect to the resulting incidence angle θres of the incoming flux, this latter quantity accounting for the local incidence angle of individual particles,which may greatly differ fromthe geometrical angle α, especially at highworking pressure due to the incoming particle – gas collisions. Crossover phenomena between the 0.3 and 0.5 Pa series were revealed from the evolution of the film resistivity, as well as simulated layer density and surface roughness versus α angle.This work has been performed within the M.ERA-NET project MC2 “Multi-scale Computational-driven design of novel hard nanostructured Coatings” and funded by the French ANR program (Project No. ANR-13-MERA-0002-02). BB acknowledges the financial support from the Algerian Ministry of Higher Education and Scientific Research through the grant n°173 of the PNE 2016-17 program

Modélisation et simulation du dépôt des oxydes à forte permittivité par la technique du Monte-Carlo cinétique

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Texture and Stress Evolution in HfN Films Sputter-Deposited at Oblique Angles

International audienceIn this study, polycrystalline hafnium nitride (HfN) thin films were grown by oblique angle deposition (OAD) technique to investigate the relationship between column tilt angle, texture development and residual stress evolution with varying inclination angle α of the substrate. The films (~1 μm thickness) were grown at various angles (α = 5°, 25°, 35°, 65°, 75°, and 85°) with respect to the substrate normal by reactive magnetron sputtering at 0.3 Pa and 300 °C. The film morphology, crystal structure and residual stress state were characterized by scanning electron microscopy and X-ray diffraction (XRD), including pole figure and sin2ψ measurements. All HfN films had a cubic, NaCl-type crystal structure with an [111] out-of-plane orientation and exhibited a biaxial texture for α ≥ 35°. XRD pole figures reveal that the crystal habit of the grains consists of {100} facets constituting triangular-base pyramids, with a side and a corner facing the projection of the incoming particle flux (indicative of a double in-plane alignment). A columnar microstructure was formed for α ≥ 35°, with typical column widths of 100 nm. It is observed that the column tilt angle β increases monotonously for α ≥ 35°, reaching β = 34° at α = 85°. This variation at microscopic scale is correlated with the tilt angle of the (111) crystallographic planes, changing from −24.8 to 11.3° with respect to the substrate surface. The residual stress changes from strongly compressive (~−5 GPa at α = 5°) to negligible or slightly tensile for α ≥ 35°. The observed trends are compared to previous works of the literature and discussed based on existing crystal growth and stress models, as well as in light of energy and angular distribution of the incident particle flux calculated by Monte Carlo. Importantly, a decrease of the average kinetic energy of Hf particles from 22.4 to 17.7 eV is found with increasing α due to an increase number of collisions

Defect generation during silicon oxidation: A Kinetic Monte Carlo study

International audienceWe present a synthetic review of elementary chemical mechanisms source of the oxidation of pure silicon (100) surfaces. These mechanisms are then discussed from their ability to build a mesoscale model of the Kinetic Monte Carlo type dedicated to the process simulation of silicon thermal oxidation. We show that oxidation is driven by two main processes: (i) charge transfer arising from the formation of SiO bonds in contact to pure silicon at the interface, (ii) destructive oxidation in which SiO building blocks rearrange at the interface to form a hexagonal-based oxide network directly in contact to cubic Si layers. Based on these considerations, simulations at the process scale exhibit epitaxial behavior within the interfacial domain. The resulting oxide layers are analyzed in terms of local to more extended defects. We observe two types of defects: (i) “intra-domain defects” which are related to local distortion of the elementary hexagonal oxide pattern Si6O6 (ii) “inter-domain defects”, which are related to global oxide structural transitions from one orientation to another