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National audience; Electret microphones dedicated to consumer electronics and medical applications (hearing aids) have reached the miniaturization limits. Since the release of the first microphone based on silicon micromachining, electret microphones are constantly replaced by MEMS microphones. Regardless of the transduction principle (capacitive, piezoresistive, piezoelectric, optical), all of the MEMS microphones reported in the state of the art literature are based on a membrane deflecting out of the plane of the base wafer. On the contrary, the novel microphone architecture that is developed in the frame of the ANR MADNEMS project uses micro beams that deflect in the plane of the base wafer. The presented microphone profits of the well known technological platform developed at CEA LETI that integrates micro and nanofabrication to deliver high- performance MEMS sensors. Transduction is achieved by piezoresistive nano gauges integrated in the microsystem, arranged in a Wheatstone bridge and attached to micro beams. Acoustic pressure fluctuations lead to the deflection of the micro beams which produces a stress concentration in the nano gauges. Such architecture enables us to reduce the surface of the deflecting element and leads to a microphone with a smaller footprint that preserves at the same time high performance. Accurate simulations of the discussed transducer couple acoustic, mechanic and electric behavior of the system. Due to micrometric dimensions of acoustic vents, thermal and viscous boundary layers have to be taken into account. Additionally the influence of backspace volume on pressure response has to be examined. The paper will initially present general principle of operation and the technological process; then, the coupled microphone model will be briefly presented. Finally we will focus on the parametric tests (technological process properties) and electromechanical test (mechanical properties of MEMS) of the microphones.

The aim of this PhD thesis is to realize a bistable microswitch using integrated magnets. New designs of such micro-switches have been drawn in order to obtain both higher contact forces and lower commutation currents compared to such existing systems. Magnetic simulation softwares have been used to assess static and dynamic behaviour of the micro-switches. Then thick films (>1 µm) of high performance hard magnetic materials (NdFeB, SmCo) have been deposited with triode sputtering, which enables high deposition rates on large areas. Conditions of sputtering and heat treatments were studied to get high coercivities, high remanences and special textures. Basic technological steps have been developed to integrate these magnetic films into a micro-technological process in order to finally realize new magnetic micro-systems. This work was part of the project Nanomag2 whose final goal is to fabricate a RF-micro-switch for spatial applications., Le but de ce travail de thèse est de réaliser un microswitch magnétique bistable à base d'aimants permanents. De nouveaux designs de tels microswitch ont été dessinés afin d'obtenir à la fois des forces de contact plus élevés et des courants de commutation plus faibles que les systèmes semblables existants déjà. Des logiciels de simulations magnétiques ont été utilisés afin d'évaluer le comportement statique et dynamique de ces micro relais. Des couches épaisses (>1 µm) de matériaux magnétiques durs hautes performances (NdFeB, SmCo) ont été déposées par pulvérisation cathodique triode. Cette technique de pulvérisation permet d'avoir des vitesses de dépôt élevées sur de grandes surfaces. Les conditions de dépôt et de traitements thermiques de ces couches ont été étudiés afin d'obtenir de grandes coercivités, de grandes rémanences et des textures particulières. Enfin, des briques de base technologiques ont été développées afin d'intégrer ces films magnétiques dans un process de microtechnologie et de réaliser finalement de nouveaux microsystèmes magnétiques. Ce travail est inclus dans le projet ANR Nanomag2 dont le but final est de fabriquer des micro-relais RF pour des applications spatiales.