Le diamant est souvent défini comme le matériau ultime pour la réalisation de composants à semi-conducteurs pour des applications d'électronique de puissance. Bien que plusieurs interrupteurs de puissance en diamant soient parus à l'échelle mondiale, ils sont à l'heure actuelle à l'état de prototype et de preuve de concept. Il est donc nécessaire de comprendre leurs mécanismes de fonctionnement afin de pouvoir utiliser tout leur potentiel dans des convertisseurs de puissance. Dans cette thèse, l'analyse se focalise sur des diodes Schottky en diamant de structure pseudo-verticale. Des caractérisations statiques et en commutation des diodes Schottky ont tout d'abord été réalisées. Elles ont permis d'extraire les caractéristiques des composants et de les intégrer dans des convertisseurs de puissance afin d'analyser leur comportement en commutation. L'utilisation et la gestion des diodes dans des convertisseurs ont ensuite été étudiées. Ces études ont permis de proposer des modifications de la structure des diodes afin d'améliorer la performance de leur intégration dans des convertisseurs de puissance. Finalement l'analyse théorique des performances d'une diode Schottky en diamant dans un convertisseur est réalisée. La comparaison entre ces performances et celles d'une diode Schottky en SiC a permis de mettre en évidence les particularités des composants en diamant ainsi que les bénéfices qu'ils peuvent apporter à l'électronique de puissance. / Diamond is considered as the ultimate semiconductor for power electronics applications. Even if diamond semiconductor devices have been realized worldwide, it is still prototype or proof of concept devices. It is then necessary to understand how do they operate to use their entire benefits in power converters. In this thesis, we focused the analysis on pseudo-vertical diamond Schottky diodes. Firstly, static and switching characterizations have been realized. They allow us to extract devices characteristics in the way to integrate them in power converters to analyze their switching abilities. Management of diodes in power converters is then studied. These studies allow us to propose device structure modifications in the way to improve diodes performances and their integration in power converters. Finally, a theoretical analysis on a diamond Schottky diode performances in a power converter is realized. It has been compared to the performances of a SiC Schottky diode. It highlights the particularities of diamond devices and the benefits they might bring to power electronics applications.

L’évolution des performances des dispositifs microélectroniques se heurte aux limites de la miniaturisation. Les contraintes mécaniques constituent un levier potentiel pour dépasser ces limitations. Il est cependant indispensable de bien maitriser leur génération et de connaitre leur influence sur le transport dans le canal. L’objectif de cette thèse vise à étudier l’évolution de la contrainte mécanique en technologie CMOS et son influence sur le transport électronique dans des technologies sub-20nm réalistes. Ce travail s’appuie sur des simulations mécaniques bidimensionnelles. Différentes architectures TriGate et FDSOI sont alors étudiées. Les contraintes obtenues sont comparées à des mesures issues de la diffraction électronique. Plusieurs méthodes de caractérisation électrique et d’extraction de paramètres de transistor MOS sont utilisées. Parmi elles figurent notamment la technique de l’extraction de la mobilité par magnétorésistance. Nous analysons les variations de mobilité en fonction des dimensions et de leur impact sur la contrainte mécanique. Enfin nous utilisons la simulation TCAD pour explorer le potentiel de nouvelles briques technologiques innovantes en voie de développement pour des générations ultérieures. Parmi elles, citons l’intégration des zones fortement contraintes par des source-drains en SiGe à fort pourcentage en germanium ou l’impact des relaxations introduites par l’utilisation des grilles sacrificielles au cours de la fabrication. Dans cette perspective, des simulations électriques basées sur une approche piézo-résistive deviennent indispensables. / In microelectronic, the device's performance evolution is limited by the down-scaling. The mechanical stresses are a potential mobility booster to overcome these limitations. However it is essential to properly control their process integration and to understand their influence on channel transport. The aim of this thesis is to study the mechanical stress evolution in CMOS technology and its impact on electronic transport in sub-20nm realistic technologies. This work is based on bidimensional mechanical simulations. Different architectures FDSOI and TriGate are then studied. The simulated stress maps are compared to experimental characterization from electron diffraction. Several methods of electrical characterization and extraction of MOS transistor are used, especially the magnetoresistance technique. We analyze the mechanical stress impact on the mobility variations according to geometrical dimensions. Finally, we use the TCAD simulation in order to explore the potential of new innovative devices under development for future generations. Among them, the integration of high germanium concentration in source-drain regions or the impact of relaxations induced by dummy gates in process flow. In this perspective, electrical simulations based on piezoresistive approach become essential.

Les mémoires non-volatiles sont devenues récemment un moteur clé de la croissance du secteur des semiconducteurs, et constituent un pivot pour les nouvelles applications et les nouveaux concepts dans le domaine des technologies de l'information et de la communication (TIC). Afin de surmonter les limites en termes de miniaturisation, de consommation électrique et de complexité de fabrication des mémoires non-volatiles à grille flottante (FLASH), l'industrie des semiconducteurs évalue actuellement des solutions alternatives. Parmi celles-ci, les mémoires résistives à pont conducteur ou CBRAM (Conductive Bridge Random Access Memory), qui reposent sur la commutation de résistance d'un électrolyte par migration et oxydo/réduction d'ions métalliques, semblent être des plus prometteuses. L'attractivité de cette technologie innovante vient d'une part de la simplicité de sa structure à deux terminaux et d'autre part de ses performances électriques très prometteuses en termes de consommation électrique et vitesse d'écriture/effacement. De surcroît la CBRAM is une technology mémoire qui s'intègre facilement dans le back end of line (BEOL) du procédé CMOS standard. Dans cette thèse, nous étudions les performances électriques et la fiabilité de deux technologies CBRAM, utilisant des chalcogénures (GeS2) ou un oxyde métallique pour l'électrolyte. Tout d'abord nous nous concentrons sur les CBRAM à base de GeS2, ou l'effet du dopage de l'électrolyte avec de l'argent (Ag) ou de l'antimoine (Sb) est étudié à la lumière d'une analyse des caractérisations électriques. Les mécanismes physiques gouvernant la cinétique de commutation et la stabilité thermique sont aussi discutés sur la base de mesures électrique, d'un modèle empirique et des résultats de calculs ab initio. L'influence des différentes conditions de set/reset est étudiée sur une CBRAM à base d'oxyde métallique. Grâce à cette analyse, les conditions permettant de maximiser la fenêtre mémoire, améliorer l'endurance et minimiser la variabilité sont déterminées. / Non-volatile memory technology has recently become the key driver for growth in the semiconductor business, and an enabler for new applications and concepts in the field of information and communication technologies (ICT). In order to overcome the limitations in terms of scalability, power consumption and fabrication complexity of Flash memory, semiconductor industry is currently assessing alternative solutions. Among them, Conductive Bridge Memories (CBRAM) rely on the resistance switching of a solid electrolyte induced by the migration and redox reactions of metallic ions. This technology is appealing due to its simple two-terminal structure, and its promising performances in terms of low power consumption, program/erase speed. Furthermore, the CBRAM is a memory technology that can be easily integrated with standard CMOS technology in the back end of line (BEOL). In this work we study the electrical performances and reliability of two different CBRAM technologies, specifically using chalcogenides (GeS2) and metal oxide as electrolyte. We first focus on GeS2-based CBRAM, where the effect of doping with Ag and Sb of GeS2 electrolyte is extensively investigated through electrical characterization analysis. The physical mechanisms governing the switching kinetics and the thermal stability are also addressed by means of electrical measurements, empirical model and 1st principle calculations. The influence of the different set/reset programming conditions is studied on a metal oxide based CBRAM technology. Based on this analysis, the programming conditions able to maximize the memory window, improve the endurance and minimize the variability are determined.

L’industrie des transports aéronautique et terrestre voit une augmentation constante de l’électrification de ses fonctions. Les actionneurs mécaniques ou hydrauliques sont au fil des évolutions technologiques remplacés par des actionneurs électriques.Les composants qui dominent le marché actuellement ne semblent plus capables de suivre la tendance. En effet, les composants de puissance à base de silicium règnent toujours sur le marché actuel, grâce à leur faible coût. Ce matériau commence par contre à atteindre ses limites théoriques en termes de performances. Dans ce contexte, différentes structures en semi-conducteurs à large bande interdite sont en train d’émerger afin de succéder au silicium.Cette étude a pour objectif d’évaluer la fiabilité des transistors de puissance à base de Nitrure de Gallium. Ces composants semblent être très prometteurs pour des applications moyennes puissances. Cependant, les mécanismes de défaillance dont peuvent souffrir ces composants ne sont pas encore suffisamment étudiés. L’étude consiste en l’application de vieillissements alliant contraintes thermiques et électriques. Ces vieillissements sont effectués à différentes conditions de tension et de température. L’objectif de cette méthode est, dans un premier temps, d’isoler l’effet de chaque facteur de stress sur l’état des composants, et dans un second temps, d’identifier les mécanismes de défaillances activés en fonction des conditions de vieillissement.Ce travail a permis d’identifier l’existence de différents mécanismes de défaillance pouvant être activés selon les conditions de vieillissement. En effet, il est apparu que la gamme de température de vieillissement utilisée influe grandement sur la prédominance des mécanismes de défaillance activés. Les résultats obtenus remettent en question les normes de qualification actuellement appliquées aux composants en Nitrure de Gallium. Ces normes devraient revoir à la hausse les températures de vieillissement utilisées afin de couvrir des gammes plus proches des températures d’utilisation pour ce type de composants. / The aeronautical and terrestrial transport industries know a steady increase in the electrification of their functions. In fact, the mechanical or hydraulic actuators are gradually replaced by electric ones.The components dominating the market today seem unable to follow the trend anymore. In fact, silicon-based power components still prevail in the current market, thanks to their low cost. However, this material begins to reach its theoretical limits in terms of performance. In this context, different wide bandgap semiconductor structures are emerging to take on from silicon.The aim of this study is to assess the reliability of power transistors based on Gallium Nitride. These components are very promising for medium power applications. However, the failure mechanisms of these components are not yet sufficiently studied. The study consists in the application of aging tests combining thermal and electrical stresses. These agings are carried out under different conditions of tension and temperature. The objective of this method is, firstly, to isolate the effect of each stressor on the state of the components, and secondly, to identify the failure mechanisms activated according to the aging conditions.This work made it possible to identify the existence of different failure mechanisms that can be activated according to the aging conditions. Indeed, it has emerged that the aging temperature range used influences the predominance of activated failure mechanisms. The results challenge the adequacy of current qualification standards for Gallium Nitride components. These standards should revise upwards the aging temperatures used to cover ranges closer to the operating temperatures of this kind of components.

Les développements récents en électronique de puissance visent à augmenter la densité de puissance totale dans les systèmes de conversion d'énergie. Cela contraint alors de plus en plus les matériaux isolants, tels que l'encapsulation dans les modules de puissance. Si les renforcements de champ électrique au sein des polymères isolants atteignent des valeurs critiques, cela peut entraîner une activité de décharges partielles, des arborescences voire la rupture totale de l'isolation. L'objectif de cette thèse est d'étudier l'adaptation des propriétés diélectriques d'un polymère composite isolant afin de réduire les contraintes autour des zones de renforcements de champ électrique. Nous proposons une nouvelle approche de gradation de potentiel pour minimiser les renforcements de champ à travers une structuration locale du matériau composite sous forme d'un gradient de permittivité auto-adaptatif localisé là où les contraintes sont les plus intenses. Cette structuration est réalisée via l'application d'un champ électrique DC lors du procédé d'élaboration du matériau composite, permettant le déplacement par électrophorèse des particules. Le composite à gradient de permittivité est composé d'une matrice époxy chargée en particules à forte permittivité (titanate de strontium SrTiO3 ou titanate de baryum BaTiO3). L'action d'un champ électrique DC sur la résine liquide chargée en particules engendre leur accumulation vers l'électrode de plus fort potentiel, formant ainsi une couche fortement chargée, qui confère à cette région une permittivité plus élevée. Chaque région du composite structuré (zone de la couche accumulée et zone faiblement chargée en particules) a été caractérisée en termes de propriétés diélectriques (permittivité et pertes). Alors que la région des composites faiblement chargée en particules conserve une permittivité voisine de celle des composites homogènes, la couche accumulée présente une augmentation importante liée à l'augmentation de la densité de particules. Les concentrations en particules de chaque région du matériau structuré ont été déterminées précisément, et les valeurs de permittivités associées se corrèlent bien avec les valeurs de permittivité des matériaux composites homogènes de taux de chargement équivalent. Cela montre que la couche accumulée ne s'est pas organisée d'une façon particulière. Concernant la rigidité diélectrique de la couche accumulée, elle présente des valeurs suffisantes pour tenir les contraintes rencontrées et ses valeurs suivent la loi de puissance classique en fonction de l'épaisseur. Des simulations par éléments finis confirment l'intérêt de ces matériaux pour la minimisation des renforcements de champ électrique au niveau du point triple dans les modules de puissance. Ces résultats montrent tout le potentiel applicatif de ces nouveaux matériaux à gradient de champ. Ils pourraient permettre l'amélioration de la fiabilité et de la robustesse des modules de puissance et autres systèmes électriques travaillant sous fort champ. / New developments in power electronics allow increasing the power density of the conversion systems. This means that the insulating materials, such as the encapsulation in power modules, are more are more stressed. If the electric field reinforcements in insulating polymers reach critical values, this can lead to a partial discharge activity, electrical treeing and eventually a complete breakdown of the insulation. The objective of this thesis is to study the appropriate matching of the dielectric properties of insulating polymer composites in order to reduce the electrical stress in the regions of field reinforcement. A new approach to minimize the reinforcements is proposed through a local structuration of the composite material allowing an auto-adaptive permittivity gradient where the largest stresses are present. This structuration is achieved thanks to the application of a DC electric field during the elaboration process of the composite material, leading to the displacement of the particles by electrophoresis. The field grading material is an epoxy matrix filled with high permittivity particles (strontium titanate SrTiO3 or barium titanate BaTiO3). Applying a DC electric field on the liquid resin containing the particles induces their accumulation on the high voltage electrode, building an accumulated layer highly concentrated in particles, conferring to this region a higher permittivity. Each region of the structured composite (accumulated layer and low concentrated region) was characterized in terms of dielectric properties (permittivity and losses). While the low concentrated region of particles keeps a permittivity close to that of homogeneous composites one, the accumulated layer exhibits a significant increase due to the increase in the local particle content. The particle concentration in each region of the structured material were precisely determined, and the related permittivity values are in good agreement with the permittivity values of the homogeneous composite materials of the same filler content. This shows that the accumulated layer was not organized in a particular way. Regarding the dielectric strength of the accumulated layer, its values are large enough for the applications and these values follow the typical power law versus thickness. Finite element methods prove that these materials are appropriate for minimizing the electric field reinforcements at the triple point, between the metal, the ceramic and the encapsulation. These results highlight the interests of these new kind of field grading materials. They could allow improving the reliability and the robustness of power modules or other electrical systems working at high field.

L’architecture FDSOI (silicium sur isolant totalement déserté) permet une amélioration significative du comportement électrostatique des transistors MOSFETs pour les technologies avancées et est employée industriellement à partir du noeud 28 nm.L’implémentation de protections contre les décharges électrostatiques (ESD pour« Electro Static Discharge ») dans ces technologies reste un défi. Alors que l’approche standard repose sur l’hybridation du substrat SOI (gravure de l’oxyde enterré : BOX)permettant de fabriquer des dispositifs de puissance verticaux, nous nous intéressons ici à des structures dans lesquelles la conduction s’effectue latéralement, dans le film de silicium. Dans ces travaux, des approches alternatives utilisant des dispositifs innovants(Z²-FET et BBC-T) sont proposées. Leurs caractéristiques statiques, quasi-statiques et transitoires sont étudiées, par le biais de simulations TCAD et de caractérisations électriques. / FDSOI architecture (Fully Depleted Silicon On Insulator) allows a significantimprovement of the electrostatic behavior of the MOSFETs transistors for the advancedtechnologies. It is industrially employed from the 28 nm node. However, theimplementation of ESD (Electrostatic Discharges) protections in these technologies isstill a challenge. While the standard approach relies on SOI substrate hybridization (byetching the BOX (buried oxide)), allowing to fabricate vertical power devices, we focushere on structures where the current flows laterally, in the silicon film. In this work,alternative approaches using innovative devices (Z²-FET and BBC-T) are proposed. Theirstatic, quasi-static and transient characteristics are studied in detail, with TCADsimulations and electrical characterizations.

Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2016-10-14T14:07:00Z No. of bitstreams: 1 TeseRCG.pdf: 9443950 bytes, checksum: c796772c281fb76668fa0cfcaa9debe4 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-21T13:11:34Z (GMT) No. of bitstreams: 1 TeseRCG.pdf: 9443950 bytes, checksum: c796772c281fb76668fa0cfcaa9debe4 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-21T13:11:44Z (GMT) No. of bitstreams: 1 TeseRCG.pdf: 9443950 bytes, checksum: c796772c281fb76668fa0cfcaa9debe4 (MD5) / Made available in DSpace on 2016-10-21T13:11:56Z (GMT). No. of bitstreams: 1 TeseRCG.pdf: 9443950 bytes, checksum: c796772c281fb76668fa0cfcaa9debe4 (MD5) Previous issue date: 2016-08-09 / Não recebi financiamento / The element germanium is part of the history of electronic equipment based on semiconductor from its early days with the invention of the transistor, until today with current research related to growth of germanium nanowires and their application in devices such as transistors, sensors, solar cells, etc. Different experimental methods can be used for obtaining germanium nanowires. Among these, one of the most widely used and efficient is the vapor-liquid-solid mechanism, in which vapor phase germanium is adsorbed onto a liquid seed metal catalyst, usually gold, and then precipitated at the liquid-solid interface, resulting in the nanowire. Although the metal has only the catalyst function, some atoms may diffuse along the nanowires and affect their properties. Then, one of the aims of this work was to synthesize germanium nanowires by the vapor-liquid-solid method with the use of five different catalysts – gold, silver, copper, indium and nickel – and verify the influence of the metal on structural properties of the nanowires. As result of this stage it was found that is possible to obtain nanowires basically composed of single crystalline germanium with diamond structure, without apparent defects, having long-range order and with length/ diameter ratio of 103, using all the tested metals. Also in this stage it was observed that the metal catalyst had an influence on: the settings of synthesis process, such as the temperature of the heat treatment and the synthesis temperature, and consequently in the germanium oxide around the nanowires; the diameters and diameter distributions of the nanowires, that lead to phonon confinement effect in nanowires with small diameters grown using nickel. Regarding applications, the current interest in germanium is justified by some of its properties such as high carrier mobility (electrons and holes), small values of indirect (0,66eV) and direct (0,8eV) energy gaps associated with high absorption coefficient of electromagnetic radiation in visible an infrared wavelength, and a large excitonic Bohr radius which highlights quantization effects. Thus, another objective of this research was to investigate electrical and optoelectronic characteristics of the produced germanium nanowires, constructing single nanowire devices and nanowire networks devices. The results of this part showed that: all the devices presented the semiconductor behavior expected for single crystalline germanium; the metal-semiconductor contact behavior – ohmic or Schottky – depended on the synthesis temperature and for the Schottky contacts, an insulating layer on the metal-nanowire interface, probably composed by germanium oxide, caused an increasing linear dependence of the barrier height with temperature; both thermal activation mechanism as well as variable range hopping were observed in germanium nanowire network devices, since small differences in diameter or on the surface of the nanowires can change the dominant transport mechanism, due to the large surface/ volume ratio of these nanostructures; the photoconductor and the photodiode constructed with germanium nanowire network presented photo-response in a wide range of illumination power in visible and infrared light wavelengths. Finally, complementing this PhD program, the activities of science dissemination developed at the IFSP campus Sertãozinho prepared this institution for scientific research in physics and showed the first results both in physics as in the physics teaching; motivating high school and college students to continue their studies. / O elemento químico germânio faz parte da história dos equipamentos eletrônicos baseados em semicondutores desde seus anos iniciais, com a fabricação do primeiro transistor, até os dias de hoje, com pesquisas como as que estão sendo realizadas nos últimos anos sobre o crescimento de nanofios de germânio e sua aplicação em dispositivos como transistores, sensores, células solares, etc. Os nanofios de germânio podem ser sintetizados por vários métodos, sendo um dos mais comuns e eficientes o mecanismo vapor-líquido-sólido, em que vapor de germânio é adsorvido por um metal catalisador em estado líquido, geralmente ouro, e precipita-se na interface líquido-sólido compondo o nanofio cristalino. Ainda que o metal tenha somente a função de catalisador, alguns átomos podem se difundir no nanofio afetando suas propriedades. Assim, um dos objetivos deste trabalho foi sintetizar nanofios de germânio pelo método vapor-líquido-sólido com o uso de cinco diferentes catalisadores – ouro, prata, cobre, índio e níquel – e verificar a influência do catalisador em propriedades estruturais desses nanofios. Como resultados desta etapa, verificou-se que é possível sintetizar nanofios constituídos basicamente por germânio monocristalino em estrutura diamante, sem defeitos aparentes, com ordem de longo alcance e relação comprimento diâmetro da ordem de 103 para todos os metais de teste. Observou-se, ainda nesta etapa, que o metal catalisador exerceu influência: em configurações do processo de síntese, como temperatura de tratamento térmico e temperatura de síntese, e como consequência desta última, na camada de óxido de germânio ao redor dos nanofios; nos diâmetros e distribuição de diâmetros dos nanofios, com consequente efeito de confinamento de fônons nos nanofios de menor diametro crescidos com o níquel. Em relação às aplicações, o interesse atual pelo germânio se justifica por algumas de suas características, como a alta mobilidade de portadores (elétrons e buracos), os pequenos valores de gap de energia direto (0,8eV) e indireto (0,66eV) associados a um alto coeficiente de absorção de radiação eletromagnética em comprimentos de onda da luz visível e infravermelha, além de um grande raio excitônico de Bohr que destaca os efeitos de quantização. Desta forma, outro objetivo desta pesquisa foi investigar características elétricas e optoeletrônicas dos nanofios de germânio produzidos, através da construção de dispositivos de um único nanofio e de rede de nanofios. Os resultados desta parte do trabalho mostraram que: todos os dispositivos apresentaram o comportamento semicondutor esperado para o germânio monocristalino; o comportamento do contato metal-semicondutor – ôhmico ou Schottky – dependeu da temperatura de síntese dos nanofios e que, para os contatos Schottky, uma camada isolante na interface metal-nanofio, provavelmente de óxido de germânio, gerou uma dependência linear crescente da altura de barreira com a temperatura e contribuiu com a condução de corrente através de processos de tunelamento; tanto o mecanismo de ativação térmica quanto o hopping de alcance variável participaram do transporte de portadores nos dispositivos de rede de nanofios de germânio, já que pequenas diferenças no diâmetro ou na superfície dos nanofios podem alterar o mecanismo de transporte dominante, devido à grande razão superfície/ volume nessas nanoestruturas; que o fotocondutor e o fotodiodo construídos com a rede de nanofios de germânio apresentaram foto-resposta em uma larga faixa de potências de iluminação em comprimentos de onda da luz visível e infravermelha. Por fim, complementando o doutorado, as atividades de difusão da ciência realizadas no IFSP campus Sertãozinho prepararam esta instituição para a pesquisa científica na área de física, mostraram os primeiros resultados tanto na área de física quanto de ensino de física e motivaram a continuidade de estudos em estudantes de ensino médio e superior.

Orientador: Marco Antonio Robert Alves / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e Computação / Made available in DSpace on 2018-08-05T19:44:58Z (GMT). No. of bitstreams: 1 Porto_LesnirFerreira_M.pdf: 4190794 bytes, checksum: 1dec9fdc0b3dd1bffb34d78bccf2648b (MD5) Previous issue date: 2005 / Resumo: Este trabalho de mestrado teve como objetivos a fabricação e o estudo do comportamento elétrico das ponteiras de silício de emissão de campo a vácuo (PECV) recobertas com filme fino de carbono tipo diamante (DLC). Apresentamos o processo de fabricação das ponteiras de silício que é realizado através das etapas de fotolitografia, corrosão por íon reativo no plasma de SF6 (hexafluoreto de enxofre), oxidação térmica seca para afinamento, e deposição do filme DLC por PECVD (Plasma Enhanced Chemical Vapor Deposition). Mostramos os resultados obtidos da caracterização elétrica das ponteiras sem o filme e com o filme DLC, através do levantamento das curvas características I x V (corrente x tensão) e I x t (corrente x tempo). Verificamos que as curvas I x V obedeceram ao modelo de emissão de elétrons de Fowler-Nordheim. Comparamos estes resultados a fim de avaliarmos as mudanças na tensão de limiar, corrente emitida, e estabilidade de emissão. Neste estudo fabricamos PECV recobertas por filme DLC com espessura de aproximadamente 170 Å / Abstract: The objectives of this dissertation were the fabrication of silicon field emitter tips coated with diamond like carbon (DLC) thin films, and the study of its electrical behavior. We present the fabrication process of silicon tips that consists on four stages: photolithography, reactive ion etching SF6 plasma, thermal oxidation for sharpening, and the DLC deposition by PECVD (Plasma Enhanced Chemical Vapor Deposition). We show results obtained from the electrical characterization of tips without film and tips with DLC, by the characteristics curves I x V (current x voltage) and I x t (current x time). Current-voltage measurements followed a Fowler-Nordheim electron emission behavior. We compare these results to evaluate the change of the threshold voltage, emitted current, and emission stability, as a function of the coating with the film. In this study we fabricated silicon tips coated with DLC film with thickness of approximately 170 Å / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

.Aujourd’hui, la course à la miniaturisation a engendré de nouveaux défis dans l’industrie microélectronique. En plus de la forte concurrence que subissent les fabricants de composants, de nouvelles contraintes liées à la fiabilité des dispositifs se sont imposées. En effet, le passage d’une technologie « tout silicium » relativement simple à une technologie high-k/grille métal plus complexe, a entrainé une forte réduction des marges de fiabilité des oxydes de grille. A ce titre, Il est devenu nécessaire d’investiguer de nouvelles approches pouvant offrir davantage de gain en durée de vie pour les transistors MOS. C’est dans ce contexte que s’inscrit ce travail de thèse. Dans un premier temps, une présentation des différentes méthodes de caractérisations adaptées à l’étude du vieillissement des dispositifs high-k à grille métallique est faite. Dans ce cadre, des techniques de mesures rapides (type FAST BTI) sont mises en place et adaptée à l’étude du claquage d’oxyde. Ensuite, afin de démontrer que les durées de vie estimées aujourd’hui sont pessimistes, une étude de fiabilité portant sur la compréhension et la modélisation du mécanisme de TDDB (Time Dependent Dielectric Breakdown) sur les technologies avancées à base d’oxyde IL/high-k est présentée. Enfin, le manuscrit se focalise sur un certain nombre d’axes de travail qui pourraient permettre de dégager une marge significative sur la durée de vie TDDB. / .Today, in the race for miniaturization, the microelectronics industry faces new challenges. In addition to the strong competition of other component manufacturers, new constraints related to the reliability of devices have emerged. Indeed, the transition from the "all silicon" technology relatively simple to the high-k/metal gate technology has generated a reduction in reliability margins of gate oxides. As such, it becomes necessary to investigate new approaches that can provide more gain in lifetime for the MOS transistors. In this respect, this work gives firstly an overview of different methods of characterization used for the study of aging high-k metal gate devices. In this context, the need to develop and implement new fast techniques essential to the study of the oxide breakdown is exposed. Afterwards, in order to show that the estimated lifetimes today are pessimistic, we presented a reliability study based on understanding and modeling the mechanism of TDDB (Time Dependent Dielectric Breakdown) on advanced high-k/metal gate stacks based technology. Finally, the manuscript focuses on a number of investigation areas that could provide a significant margin for the TDDB lifetime.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Barium Titanate (BaTiO3 BT) based Ceramic materials have a wide industrial application as Multilayer Ceramic Capacitors (MLCCs) mainly due to its high dielectric constant and good capacitance stability with the temperature change, however this material also presents some limitations, for example, oxidation of low cost electrodes. Several ways of BT modifications have been proposed in Literature, as example, the use of different synthesis methods and the doping with different ions. Therefore, the present work had as objectives the synthesis, sintering and electrical characterization of the BaTiO3 and Ba0.77Ca0.23TiO3 (Barium Calcium Titanate) ceramics. The Sol Gel Proteic method was used to powder synthesis, in this method, coconut water is employed as polymeric agent instead of the conventional alcoxide precursors. The characterization was done using the differential thermal analysis, thermogravimetry, x-ray powder diffraction, scanning electron microscopy and impedance spectroscopy techniques. Both, the calcined powders at 1100 °C and the sintered ceramics at 1350 °C presented single crystalline phase, with good microstructural homogeneity and relative density higher than 90%. The sintered ceramics presented a dielectric constant value at room temperature of 1200 (BT) and 680 (BCT), and dielectric loss of 4,8% (BT) and 1,8% (BCT). Besides, the BCT ceramics presented a Curie temperature on average 14 °C above that observed in Literature. Finally, the activation energies of the conductive process of the grain an grain boundary regions were evaluated following two distinct methods using: i) the Brick-layer model; and ii) the average relaxation frequency of each ceramic region, grain and grain boundary. The obtained values by the two methods are in accordance with them and suggest that the dominant conduction mechanism occurs by oxygen vacancy diffusion created still during the sintering process. / Materiais cerâmicos a base de titanato de bário (BaTiO3 BT Barium Titanate ) possuem uma larga aplicação industrial como Capacitores Cerâmicos Multicamadas (MLCCs Multi layers ceramic capacitors ) devido, principalmente, a sua alta constante dielétrica e boa estabilidade da capacitância com a variação da temperatura, porém esse material apresenta também algumas limitações, como por exemplo, a oxidação de eletrodos de baixo custo. Diversas modificações no BT têm sido sugeridas na literatura, como a utilização de diferentes métodos de síntese e a dopagem com diferentes íons. Dessa forma, o presente trabalho objetivou a síntese, a sinterização e a caracterização elétrica de cerâmicas de BaTiO3 e Ba0.77Ca0.23TiO3 (Titanato de Bário e Cálcio BCT Barium Calcium Titanate ). Para a síntese dos pós foi utilizado o método sol-gel proteico, neste método, a água de coco é utilizada como agente polimérico, ao invés dos alcóxidos convencionais. Para a caracterização das amostras foram utilizadas as técnicas de análise térmica diferencial, termogravimetria, difração de raios X, microscopia eletrônica de varredura e espectroscopia de impedância. Os pós calcinados a 1100°C bem como as cerâmicas sinterizadas a 1350°C e apresentaram fase cristalina única, com boa homogeneidade microestrutural e densidade relativa superior a 90%. O valor da constante dielétrica à temperatura ambiente foi de 1200 para o BT e 680 para o BCT com perda dielétrica de 4,8% e 1,8%, respectivamente. Além disso, as cerâmicas de BCT apresentaram uma temperatura de Curie em média 14 °C acima dos valores observados na Literatura. Por ultimo, as energias de ativação dos processos condutivos nas regiões de grão e de contorno de grão foram obtidas seguindo dois procedimentos distintos: i) utilizando o modelo de brick-layer; e ii) utilizando a frequência de relaxação média de cada região da cerâmica, grão e contorno de grão. Os valores obtidos pelos dois métodos concordaram entre si e sugerem que o mecanismo de condução dominante ocorre por vacâncias de O2- formadas ainda durante o processo de sinterização.