Composants Passifs Intégrés en Technologie CMOS pour la Miniaturisation des Circuits RF

Une démarche originale pour le développement de composants passifs dans une filière industrielle consiste à effectuer un report des contraintes en performances sur les caractéristiques électriques des matériaux utilisés en couches minces. Nous présentons dans cet article la démarche adoptée à travers trois phases clés du développement d’une technologie faibles coûts de composants passifs intégrés en filière CMOS. Le développement et la caractérisation de films minces d’oxyde de titane et de tantale. L’intégration de films résistifs d’oxynitrure de titane en filière industrielle et la modélisation électrique d’inductances spirales intégrées en CMOS

Etude de l'accordabilité des matériaux ferroélectriques

National audienceDans le cadre de nos travaux, des couches minces de PbZr0,57Ti0,43O3 ont été réalisés par un procédé sol-gel modifié basé sur des précurseurs alkoxydes. L’accordabilité et les pertes (tan d) à des fréquences allant jusqu’à 100 kHz sous une tension V(t) = Va sin (wt) + Vbias ont été étudiées en fonction de la valeur de la tension alternative, de la tension de bias et de la fréquence. La comparaison du cycle d’hystérésis en polarisation avec celui en capacité permet de décomposer la partie linéaire et non linéaire du cycle d’hystérésis en s’appuyant sur le modèle de Rayleigh. Finalement, le film dans une géométrie condensateur plan est intégré dans un circuit RLC constituant ainsi un filtre passe bande accordable en fréquence

Thermal conductivity of aluminium nitride thin films prepared by reactive magnetron sputtering

International audienceThe relationship between thermal conductivity and microstructures of aluminium nitride films is reported. Films were deposited on silicon substrates by magnetron sputtering of a pure Al target in nitrogen argon plasma at low temperatures (<300 °C) with thickness ranging from 150 to 3500 nm. Balanced and unbalanced magnetron configurations were used for different nitrogen contents in the gas phase. Various microstructures were thus created and their thermal conductivity was measured with the transient hot strip technique. Depending on the crystalline structure of the films, the bulk thermal conductivity of the AlN films at room temperature varied between 2 and 170 W m−1 K−1. Unbalanced magnetron allowed achieving highly dense (0 0 2) oriented AlN films with a grain size in the 100 nm range, a low oxygen content close to 0.5 at% and a resulting bulk thermal conductivity as high as 170 W m−1 K−1. Such a crystalline quality resulted from the ion energy involved in the growth process. In contrast, balanced magnetron led to weakly textured AlN films containing 5 at% oxygen with a grain size in the 30 nm range and a resulting thermal conductivity ranging from 2 to 100 W m−1 K−1 depending on the microstructure. Otherwise, the thermal boundary resistance between AlN films deposited by unbalanced magnetron and the silicon substrate was found to be as low as 1.0 × 10−8 K m2 W−1. Such a value was in good agreement with the thickness of the interfacial amorphous layer determined in the 2 nm range by high resolution transmission electron microscopy

Influences of Bioavailability, Trophic Position, and Growth on Methylmercury in Hakes (Merluccius merluccius) from Northwestern Mediterranean and Northeastern Atlantic

Methylmercury (MeHg) determinations in hake, its food-chain, and the surrounding waters and sediments allowed us to show that the higher length or age normalized mercury concentrations of Northwestern Mediterranean (Gulf of Lions: GoL) muscle hakes compared to its Northeastern Atlantic (Bay of Biscay: BoB) counterpart are due to both biotic and abiotic differences between their ecosystems. Bioenergetic modeling reveals that the slower growth rate of Mediterranean hake favors the MeHg bioaccumulation in the fish muscle and explains most of the difference between GOL and BoB hake populations. In addition, the waters of the Mediterranean hake habitat favor a higher MeHg exposition, due to the upper position of the thermohalocline, where MeHg is formed. Furthermore, we show that, within the Mediterranean hake population, a major increase in the biomagnification power (the slope of the relationships between logMeHg and δ15N), from 0.36 up to 1.12, occurs when individuals enter adulthood, resulting from the combined effects of lowering growth rate and change in feeding habits. Finally, δ15N normalized Hg concentrations indicate that the highest Hg concentrations are for hake from the shelf edge and the lowest are for hake from the Rhône prodelta area, suggesting a lower Hg bioavailability in inshore environments, consistent with MeHg distributions in water, sediment, and preys. © 2012 American Chemical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Investigation of BST thin films deposited by RF magnetron sputtering in pure Argon

International audienceBa0.5Sr0.5TiO3 (BST) thin films were deposited by rf magnetron sputtering using a Ba0.5Sr0.5TiO3 target in pure Argon on two electrodes (Pt and RuO2) at room temperature. The interface formation between BST and bottom electrode (Pt or RuO2) was investigated by XPS for thicknesses in the 1 to 50 nm range. The chemical composition of the BST layers can be modified by the electrode nature over the first five nanometers. A 1 h ex-situ annealing, under flowing oxygen at 600 degrees C, was necessary to obtain crystallized 150 nm thick BST films, as evidenced by XRD and TEM analysis