Procédés plasmas pour l'optimisation des matériaux intervenant dans le management thermique et la passivation de composants de puissance hyperfréquences à base de GaN et AlGaN

This work is dedicated to the development and the optimization of a low temperature (<300°C) thin film deposition process. The targeted material is a nitride dielectric (AlN, BN) with a high thermal conductivity dedicated to the passivation of high power high frequency HEMT GaN devices. Nowadays, the GaN HEMT (High Electron Mobility Transistor) performances are directly limited by their thermal resistance. The integration of a dielectric material with a high thermal conductivity is expected to improve the thermal behavior of the device and to increase their performances. The magnetron sputtering has been chosen for its compatibility with microelectronic processes. This study addressed first an in depth study of magnetron sputtering deposition process for thin films (AlN and BN) and second a extended study of the physico chemical properties of the obtained thin films using XRD, FTIR, Raman spectroscopy, SAED and HRTEM. The magnetron sputtering process was study by Langmuir probe measurement and Optical Emission Spectroscopy. In the case of AlN films, we highlighted the first order effect of the magnetic field configuration on the film properties. Such a process control allowed obtaining an epitaxial growth of AlN films on AlGaN substrate at temperature below 250°C. The thermal properties of the thin films were investigated using an original electro-thermal measurement method well adapted to thin films. Such studies allowed underlining the relationship between thermal conductivity and thin film microstructure and to reach a further optimization of the thermal properties of AlN thin films up to 170 W.K-1.m-1.Ces travaux concernent la mise au point d'un procédé de synthèse de couches minces à basse température d'un matériau diélectrique à forte conductivité thermique pour la passivation de composants HEMT GaN hyperfréquence de puissance. A l'heure actuelle, les performances des composants HEMT (High Electron Mobility Transistor) GaN, bien que très supérieures aux performances des HEMT GaAs, sont directement limitées par la résistance thermique du dispositif. L'intégration d'un matériau de passivation à forte conductivité thermique devrait permettre de diminuer la résistance thermique des composants et d'accroître leurs performances. Le procédé magnétron a été choisi pour sa compatibilité avec les contraintes de température imposées par les technologies de la microélectronique. Notre étude s'est orientée sur l'optimisation de la croissance de films minces de nitrure (AlN et BN) et leur caractérisation structurale par DRX, FTIR, SAED et HRTEM. Le procédé de dépôt a été caractérisé par sonde de Langmuir et analyses OES. Dans le cas de l'AlN, nous avons mis en évidence l'effet prépondérant de la configuration du champ magnétique sur la qualité structurale des films. Un tel contrôle du procédé a permis d'obtenir une croissance épitaxiale de l'AlN sur AlGaN. Les propriétés thermiques des films ont été déterminées grâce au développement d'une méthode de mesure originale bien adaptée à la caractérisation des couches minces. Celle-ci nous a permis de mettre en évidence la corrélation entre les valeurs de conductivité thermique et les caractéristiques des films. In fine, une conductivité thermique de 170 W.K-1.m-1 a été obtenue pour les films d'AlN

Characterization of experimental complex fungal bioaerosols: Impact of analytical method on fungal composition measurements

The microbial composition of bioaerosols is an important issue to investigate to better understand occupational risks linked to exposure to airborne particles. Traditional methods are based on culture followed by colony identification by morphological, molecular biology or biochemical approaches.We have carried out a preliminary study which aims to generate reproducible complex bioaerosols and compares a high-throughput sequencing approach to the traditional culture-based approach. Mixed fungal bioaerosols containing four fungal strains (Aspergillus niger, Cladosporium cladosporioides, Penicillium brevicompactum and Wallemia melicolla) were generated in the laboratory using a bubbling aerosolizer. The fungal composition was assessed by culture and sequencing.Two genetic targets were sequenced and two assignment methods were compared. Wallemia was poorly detected by the culture-based approach, whereas Aspergillus was readily observed, in significant proportions, only by this method.The proportions in the liquid suspensions and in the bioaerosols generated were nearly identical. Sequencing of the ITS2 region provided results better reflecting the theoretical composition than 18S rDNA sequencing. The findings show that results of fungal composition investigations are strongly dependent on the analysis method used.Further studies will be required to assess the impact of these findings when considering biodiversity in complex and unknown environments

Procédés plasmas pour l'optimisation des matériaux intervenant dans le management thermique et la passivation de composants de puissance hyperfréquences à base de GaN et A1GaN

Ces travaux concernent la mise au point d un procédé de synthèse de couches minces à basse température d un matériau diélectriqueà forte conductivité thermique pour la passivation de composants HEMT GaN hyperfréquence de puissance. A l heure actuelle, les performances des composants HEMT (High Electron Mobility Transistor) GaN, bien que très supérieures aux performances des HEMT GaAs, sont directement limitées par la résistance thermique du dispositif. L intégration d un matériau de passivation à forte conductivité thermique devrait permettre de diminuer la résistance thermique des composants et d accroître leurs performances. Le procédé magnétron a été choisi pour sa compatibilité avec les contraintes de température imposées par les technologies de la microélectronique. Notre étude s est orientée sur l optimisation de la croissance de films minces de nitrure (AlN et BN) et leur caractérisation structurale par DRX, FTIR, SAED et HRTEM. Le procédé de dépôt a été caractérisé par sonde de Langmuir et analyses OES. Dans le cas de l AlN, nous avons mis en évidence l effet prépondérant de la configuration du champ magnétique sur la qualité structurale des films. Un tel contrôle du procédé a permis d obtenir une croissance épitaxiale de l AlN sur AlGaN. Les propriétés thermiques des films ont été déterminées grâce au développement d une méthode de mesure originale bien adaptée à la caractérisation des couches minces. Celle-ci nous a permis de mettre en évidence la corrélation entre les valeurs de conductivité thermique et les caractéristiques des films. In fine, une conductivité thermique de 170 W.K-1.m-1 a été obtenue pour les films d AlNThis work is dedicated to the development and the optimization of a low temperature (<300C) thin film deposition process. The targeted material is a nitride dielectric (AlN, BN) with a high thermal conductivity dedicated to the passivation of high power high frequency HEMT GaN devices. Nowadays, the GaN HEMT (High Electron Mobility Transistor) performances are directly limited by their thermal resistance. The integration of a dielectric material with a high thermal conductivity is expected to improve the thermal behavior of the device and to increase their performances. The magnetron sputtering has been chosen for its compatibility with microelectronic processes. This study addressed first an in depth study of magnetron sputtering deposition process for thin films (AlN and BN) and second a extended study of the physico chemical properties of the obtained thin films using XRD, FTIR, Raman spectroscopy, SAED and HRTEM. The magnetron sputtering process was study by Langmuir probe measurement and Optical Emission Spectroscopy. In the case of AlN films, we highlighted the first order effect of the magnetic field configuration on the film properties. Such a process control allowed obtaining an epitaxial growth of AlN films on AlGaN substrate at temperature below 250C. The thermal properties of the thin films were investigated using an original electro-thermal measurement method well adapted to thin films. Such studies allowed underlining the relationship between thermal conductivity and thin film microstructure and to reach a further optimization of the thermal properties of AlN thin films up to 170 W.K-1.m-1NANTES-BU Sciences (441092104) / SudocSudocFranceF

Association between antithrombotic treatment and outcomes at 1-year follow-up in patients with atrial fibrillation: the EORP-AF General Long-Term Registry

International audienceAims In recent years, stroke prevention in patients with atrial fibrillation (AF) has radically changed, with increasing use of non-vitamin K antagonist oral anticoagulants (NOACs). Contemporary European data on AF thromboprophylaxis are needed. Methods and results We report 1-year follow-up data from the EURObservational Research Programme in Atrial Fibrillation (EORP-AF) General Long-Term Registry. Outcomes were assessed according to antithrombotic therapy. At 1-year follow-up, 9663 (88.0%) patients had available data for analysis: 586 (6.1%) were not treated with any antithrombotic; 681 (7.0%) with antiplatelets only; 4066 (42.1%) with vitamin K antagonist (VKA) only; 3167 (32.8%) with NOACs only; and 1163 (12.0%) with antiplatelet and oral anticoagulant. At 1-year follow-up, there was a low rate of stroke (0.7%) and any thromboembolic event (TE) (1.2%), while haemorrhagic events occurred in 222 patients (2.3%). Cardiovascular (CV) death and all-cause death occurred in 3.9% and 5.2% of patients, respectively. Cumulative survival for all the three main outcomes considered was highest amongst patients treated only with NOACs (P &lt; 0.0001). Multivariable-adjusted Cox regression analysis found that VKA or NOACs use was independently associated with a lower risk for any TE/acute coronary syndrome/CV death, while all treatments were independently associated with a lower risk for CV death and all-cause death. Conclusion The 1-year follow-up of EORP-AF General Long-Term Registry reported a low occurrence of thromboembolic and haemorrhagic events, although mortality was high. Both VKA and NOACs were associated with a lower risk of all main adverse outcomes. All treatments were associated with a lower risk for CV death and all-cause death