Electrostatically-Driven Resonator on Soi with Improved Temperature Stability

This paper deals with a single-crystal-silicon (SCS) MEMS resonator with improved temperature stability. While simulations have shown that the temperature coefficient of resonant frequency can be down to 1 ppm/degrees C, preliminary measurements on non-optimised structures gave evidence of a temperature coefficient of 29 ppm/degrees C. Design, optimisation, experimental results with post process simulation and prospective work are presented.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Oblique angle deposition of Au/Ti porous getter films

International audienc

Les collectivités territoriales et leurs musées dans le cadre de la loi relative aux musées de France

La loi du 4 janvier 2002 relative aux musées de France a consacré la vocation de service public des musées, issus d’une tradition historique qui implique que ceux-ci sont à majorité gérés par des personnes publiques. Or, si l’État s’est toujours imposé comme l’autorité référente en matière de musée, il existe aujourd’hui plus de 1 200 musées gérés par les collectivités territoriales. Ces dernières se sont investies très tôt dans ce domaine, dans le cadre de relations parfois conflictuelles avec l’État. La loi de 2002 se pose alors comme l’aboutissement de la volonté de l’État d’imposer son contrôle sur les musées territoriaux. Cependant, ce contrôle doit être appréhendé dans le cadre du principe constitutionnel de libre administration des collectivités territoriales. Cet article est un extrait de la thèse relative aux collectivités territoriales et à leurs musées, parues aux PUAM en 2015. Il met en lumière les interrogations qui découlent de la nécessité de concilier les principes de la décentralisation avec les impératifs légaux de gestion des collections.The law of 4 January 2002 on the museums of France established the public service mission of museums, which emerged from a historical tradition that means that they are predominantly managed by public legal entities. However, although the State has always established itself as the reference authority in museum matters, more than 1,200 museums are currently managed by local authorities. They became involved in this area at a very early stage and have sometimes had conflictual relationships with the State. The law of 2002 is, therefore, the fulfilment of the State’s desire to exert its control over local museums. However, this control must be understood within the scope of the constitutional principle of the free administration of local authorities. This article is an excerpt from the thesis on local authorities and their museums, which was published by the PUAM in 2015. It highlights the issues arising from the need to balance the principles of decentralisation with the legal requirements of collections management

Neuropilin-1 Controls Endothelial Homeostasis by Regulating Mitochondrial Function and Iron-Dependent Oxidative Stress.

The transmembrane protein neuropilin-1 (NRP1) promotes vascular endothelial growth factor (VEGF) and extracellular matrix signaling in endothelial cells (ECs). Although it is established that NRP1 is essential for angiogenesis, little is known about its role in EC homeostasis. Here, we report that NRP1 promotes mitochondrial function in ECs by preventing iron accumulation and iron-induced oxidative stress through a VEGF-independent mechanism in non-angiogenic ECs. Furthermore, NRP1-deficient ECs have reduced growth and show the hallmarks of cellular senescence. We show that a subcellular pool of NRP1 localizes in mitochondria and interacts with the mitochondrial transporter ATP-binding cassette B8 (ABCB8). NRP1 loss reduces ABCB8 levels, resulting in iron accumulation, iron-induced mitochondrial superoxide production, and iron-dependent EC senescence. Treatment of NRP1-deficient ECs with the mitochondria-targeted antioxidant compound mitoTEMPO or with the iron chelator deferoxamine restores mitochondrial activity, inhibits superoxide production, and protects from cellular senescence. This finding identifies an unexpected role of NRP1 in EC homeostasis

Etude des propriétés électro-thermo-mécaniques de nanofils en silicium pour leur intégration dans les microsystèmes

Les propriétés électro-thermo-mécaniques remarquables qui peuvent apparaître dans les nanofils de silicium font l'objet d'un nombre croissant de travaux de recherche. Ces travaux de thèse de nature fortement expérimentale, visent à donner une meilleure connaissance de ces propriétés dans le cas de nanofils, en silicium monocristallin, fabriqués par approche descendante. Pour caractériser la piézorésistivité, deux méthodes de chargement mécaniques ont été développées : la flexion 4 points de puce et la traction/compression in situ avec un actionneur MEMS. La méthode 3 a été choisie pour des mesures de conductivité thermiques. Ces propriétés ont été étudiées en fonction de la température et la contrainte dans une station sous pointes cryogénique.Les résultats montrent que les nanofils fabriqués à partir de substrats SOI amincis peuvent, de manière inattendue, être fortement contraints en compression après fabrication. Les nanofils de type p présentent, même en régime de mesure dynamique, des coefficients piézorésistifs élevés qui décroissent fortement avec la température et permettent une détection intégrée de mouvement de MEMS avec une limite de détection inférieure à l'Angström. Les mesures thermiques confirment l effet d échelle attendu de la conductivité thermique, la décroissance avec la température est compatible avec les résultats théoriques et expérimentaux précédemment publiés.Remarkable nanoscale electro-thermo-mechanical properties of silicon nanowires are increasingly studies. This experimental thesis investigates such properties for top-down fabricated monocrystal silicon nanowires.A four points bending set-up and a MEMS actuator are developed to apply ex situ and in situ mechanical stress on nanowires. Those devices are characterised in a cryogenic environment within a microprobe station. Electrical properties and piezoresistivity are studied using those systems. Moreover, the 3 method measures the thermal conductivity of these nanowires.From buckling of silicon nanowires, unexpected high compressive stress (>100 MPa) was identified in top silicon layers of SOI substrates. Drift-compensated measurements show that p type silicon nanowires present large piezoresistive coefficients which decrease with temperature. Additionally, the MEMS device demonstrates the possibility to detect ample MEMS movements with sub-ångström resolution using the nanowires as piezoresistive nanogauges. The thermal conductivity was found consistent with previously reported values for silicon nanowires, and expectedly decreases with temperature.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Etude de matrices de filtres Fabry Pérot accordables en technologie MOEMS intégré 3D (Application à l'imagerie multispectrale)

L imagerie multispectrale permet d améliorer la détection et la reconnaissance de cibles dans les applications de surveillance. Elle consiste à analyser des images de la même scène acquises simultanément dans plusieurs bandes spectrales grâce à un filtrage. Cette thèse étudie la possibilité de réaliser une matrice de 4 filtres Fabry Pérot (FP) intégrés 3D et ajustables par actionnement électrostatique dans le domaine visible-proche infrarouge. Les miroirs fixes des filtres FP sont des multicouches ZnS/YF déposés sur un wafer de borosilicate, et les miroirs mobiles sont des membranes multicouches PECVD SiNH/SiOH encastrées sur une structure mobile très compacte micro-usinée dans un wafer en silicium. Les performances optiques des filtres FP ont été optimisées en prenant en compte la dissymétrie et le déphasage à la réflexion des miroirs. La structure mobile a été modélisée par éléments finis pour minimiser ses déformations lors de l actionnement. Les étapes critiques des procédés de fabrication des miroirs mobiles en technologie Si ou SOI ont été mises au point : i) la fabrication et la libération par gravures profondes DRIE et XeF des membranes multicouches avec une contrainte résiduelle ajustée par recuit et une réflectance voisine de 50% dans une large gamme spectrale, ii) le contrôle des vitesse de la gravure DRIE avec des motifs temporaires permettant la gravure simultanée de motifs de largeur et de profondeur variables, et iii) la délimitation de motifs sur surfaces fortement structurées à l aide de pochoirs alignés mécaniquement ou de films secs photosensibles. Ces travaux ouvrent la voie vers une réalisation complète d une matrice de filtres FP intégrés 3D.Multispectral imaging is used to improve target detection and identification in monitoring applications. It consists in analyzing images of the same scene simultaneously recorded in several spectral bands owing to a filtering. This thesis investigates the possibility to realize, an array of four 3D integrated Fabry-Perot (FP) filters that are tunable in the visible-near infrared range by electrostatic actuation. The fixed mirrors of the FP filters are ZnS/YF multilayers deposited on a borosilicate wafer, and the movable mirrors are PECVD SiNH/SiOH multilayer membranes clamped in a very compact movable structure micromachined in a Si wafer. A 3rd glass wafer is used for filters packaging. Optical performances of the FP filters have been optimized by taking into account the asymmetry and the reflection phase shift of the mirrors and the mobile structure has been modeled by finite elements analysis notably to minimize its deformation during actuation. The critical steps of the movable mirrors fabrication process in Si or SOI technology have been developed : i) the fabrication and the release by DRIE and XeF etching of 8 or 12 layers membranes with a residual stress tunable by annealing and a reflectance close to 50% in broad wavelength range (570-900nm), ii) the control with temporary patterns of the simultaneous deep etching of patterns with different widths and depths, and iv) various patterning techniques on highly structured surfaces based on shadow masks (with mechanical alignment) or laminated photosensitive dry films. These results open the way towards the full realization of an array of 3D integrated FP filters.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

In situ electrical characterization of YxTiy getter thin films during thermal activation

International audienceTransition metals alloys are the most studied getter films for wafer-level vacuum packaging of MEMS. In this work we investigated yttrium and Y x Ti y alloys films that could possibly overcome the limitations of usual getter materials, i.e. reversible sorption of hydrogen and low sorption ability for hydrocarbon gases. As a preliminary step towards this objective, properties of (co-)evaporated yttrium and Y x Ti y films were analyzed by SEM, EDS, XPS and in-situ sheet resistance measurements before, after and/or during annealing in vacuum. As deposited and annealed films have a small grain size and a columnar structure. It is shown that yttrium and Y x Ti y films can be activated after 1 hour of annealing in vacuum at 250 °C if the Y-content is larger than ~9 %. These results are promising for the use of Y-based films as low temperature getters for vacuum packaging

Characterization of the activation of yttrium-based getter films by electrical measurements and ion-beam analyses

International audienceGettering properties of thin films of pure yttrium and yttrium-based alloys have been studied for application to MEMS vacuum packaging at the wafer level. Thin films of Y, Zr-Y, Ti-Y and V-Y were co-evaporated under ultra-high vacuum. It is demonstrated that the sheet resistance measured by 4-probes technique before and after activation at 250°C gives a good estimation of the oxygen sorption ability determined by NRA. Pure yttrium has been found to be highly reactive after deposition (sheet resistance increases by 40% after 1 month in air) but poorly efficient in oxygen trapping after activation. Conversely, the sorption ability of Y-V, Y-Zr and Y-Ti alloys is extremely high and increases with the yttrium content in the film. The bests results for sorption are obtained with Y-V (2.7 10 22 atom/cm 3 for Y44V56)

A Comparison of TSV Etch Metrology Techniques

International audienceWe use three metrology techniques, vertical scanning interferometry (VSI), confocal chromatic microscopy (CCM), and time domain optical coherence tomography (TD-OCT), for depth measurement of through-silicon vias (TSVs) of various cross sections and depths. The merits of these techniques are discussed and compared. Introduction While sales of semiconductor equipment broke a new record this year, many metrology needs should be addressed to support the development and production of electronic chips based on "More than Moore" scaling. Among these scaling approaches, 3D integration based on TSVs offers superior integration density and reduces interconnect length/latency. Measurements are needed to evaluate the depth uniformity of etched TSVs. Indeed, upon metal filling, geometrical variations of TSVs can affect Cu nails coplanarity and can warp the wafer, resulting in a low stacking yield. Measuring the depth of TSVs is an increasingly challenging task as the diameter of many TSVs has now shrunk to only a few microns