No description available.

Transition metal nitrides (TMNs) refractory ceramic materials are  widely employed as wear-resistant protective coatings in industrial machining as well as diffusion barriers inhibiting migration of metal impurities from the interconnects to the semiconducting region of electronic devices. TiN is the prototype of this class of materials and the most studied among TMNs. However, also for this system, a complete picture of the migration processes occurring at the atomic scale is still lacking. In this work I investigate the stability of Ti vacancy configurations and corresponding migration rates in TiN by means of density functional theory (DFT) calculations and ab-initio molecular dynamics simulations (AIMD). DFT calculations show that Ti vacancies tend to stay isolated because of repulsive interaction which decreases as the inverse of the distance between the vacancies.The equilibrium jump rate of single Ti vacancies in TiN is extrapolated temperature as a function of temperature from the results of non-equilibrium AIMD simulations accelerated by a bias force field according to the color diffusion algorithm. For each force field and, the jump occurrence times are fitted with the two parameters Gamma distribution in order to obtain the non equilibrium jump rate with the corresponding uncertainty. Extrapolated equilibrium values show an Arrhenius-like behavior, with activation energy Ea= (3.78 ± 0.28)eV and attempt frequency A = 4.45 (x3.6±1) x 1014 s-1.

[pt] Os nitretos, especialmente os de metais de transição, têm recebido nos últimos anos, grande atenção, devido às suas propriedades físicas e químicas serem únicas. Dentre estes nitretos, temos o nitreto de titânio (TiN) que apresenta muitas propriedades interessantes, que fazem com que tenha grandes potencialidades para aplicações à nível industrial. A importância do nitreto de titânio (TiN) se deve às suas propriedades de alta condutividade térmica, dureza, resistência ao desgaste, alta condutividade elétrica e não é tóxico. Assim, a sua principal área de uso, está relacionada como um material que apresenta aplicações nos campos químicos e mecânicos. Na indústria aeroespacial, é utilizado em equipamentos, como turbinas e motores a jato, e, no ramo da medicina, sob a forma de revestimento em próteses ortopédicas, válvulas cardíacas e próteses dentárias. O objetivo desta dissertação é estudar a produção e a caracterização de nano partículas de nitreto de titânio (TiN), a partir de uma reação na fase gasosa entre o tetracloreto de titânio (TiCl4) e a amônia (NH3) em um reator tubular, e a influência dos parâmetros reacionais (temperatura e tempo espacial), sobre o tamanho médio das partículas. Os resultados experimentais mostraram que as variações destes parâmetros produziram pós de TiN com diferentes tamanhos de partículas. Além da produção de pó de nitreto de titânio (TiN), constatou-se a presença de cloreto de amônio (NH4Cl). Durante o manuseio do pó de TiN produzido, houve a formação de TiO2 (anatásio) através da reação do primeiro com o ar atmosférico. / [en] Nitrides, especially those of transition metals, have received increasing attention in recent years because of their unique chemical and physical properties. Among them, TiN presents many interesting properties, which make it interesting for some potential industrial applications. The importance of nitride titanium (TiN) is due to its properties of high thermal conductivity, chemical inertial, hardness, wear resistance, high electrical conductivity and nontoxicity. The objective of this master thesis is the production of TiN powder from gas phase reaction between titanium tetrachloride (TiCl4) and ammonia (NH3) in a tubular reactor and the study of the effects of the reaction parameters, temperature and space time, on particle size. The experimental results showed that the variation of these parameters produced nanoparticles of TiN with different sizes, heterogeneous. Besides the production of titanium nitride powder, there was also the presence of ammonium chloride (NH4Cl), co-product of the nitridation reaction. During the handling of the TiN powder occurred the formation of TiO2 due to its reaction with atmospheric air.

[pt] Os nitretos, carbetos, boretos e óxidos de metais de transição na forma de nanopartículas, têm recebido nos últimos anos uma grande atenção no mundo científico, por apresentar propriedades físicas e químicas bem específicas, com aplicações diretas na indústria de alta tecnologia. Esta tese de doutorado foi motivada pelo desenvolvimento e avaliação experimental de uma nova configuração de reator, tubular e de fluxo cruzado, que promove um melhor contato entre as fases gasosas reagentes, possibilitando a execução da síntese de nanopartículas em temperaturas mais baixas. O reator consiste em um tubo de quartzo e um sistema de alimentação de gás NH3(g), dotado de chicanas que o redireciona promovendo uma distribuição mais homogênea deste nos orifícios de alimentação no reator. O TiCl4, uma vez vaporizado, é arrastado pelo argônio na direção axial do reator e o NH3 é injetado na direção radial central do reator. No aparato experimental desenvolvido foram avaliados os efeitos das variáveis do processo, temperatura, tempo espacial e pressão parcial do TiCl4 sobre o tamanho médio de cristalitos das partículas sintetizadas. Os resultados experimentais obtidos mostraram que no reator proposto foi possível produzir, na temperatura ambiente, nitreto de titânio (TiN) com 100por cento de conversão e tamanhos de cristalitos abaixo de 20 nm. Além da produção do TiN, também observou-se a formação de um co-produto, também particulado, o cloreto de amônio (NH4Cl). Nas análises por difração de Raios-X observou-se a presença de dióxido de titânio (TiO2) na forma de anatásio e de oxinitreto de titânio. O aparecimento destas fases pode ser explicado pela alta reatividade do nitreto de titânio com o oxigênio e vapor de água presentes na atmosfera e a sua elevada superfície específica. / [en] Nitrides, carbides, borides and oxides of transition metals in the form of nanoparticles have received in recent years the attention in the scientific world, by their specific physical and chemical properties, with direct applications to the high technology industry. This thesis was motivated by the development and experimental evaluation of a new reactor concept, tubular and cross-flow, which promotes better contact between the gas-phase reactants, allowing the execution of nanoparticle synthesis at lower temperatures. The reactor consists of a quartz tube and a gas supply system (NH3), equipped with baffles that redirects the gas promoting a more homogeneous distribution of it in the holes that feed the reactor. The TiCl4 vaporized is carried by argon gas, in the axial direction, to the reactor and NH3 is injected in the radial direction in the central region of the reactor. In the experimental apparatus developed were evaluated the effects of process variables, temperature, space time and TiCl4 partial pressure, on average crystallite size of the synthesized particles. The experimental results obtained show that in the proposed reactor was possible to produce, at room temperature, titanium nitride with 100% conversion and crystallite size below 20nm. Besides the production of the titanium nitride was also observed the formation of a particulate co- product, the ammonium chloride (NH4Cl). In the X-ray diffraction analyzes was observed the presence of titanium dioxide (anatase) and titanium oxynitride. The occurrence of these phases can be explained by the high reactivity of titanium nitride with oxygen and water vapor present in the atmosphere and their high specific surface.

<p>The development and implementation of a metal gate technology (alloy, compound, or silicide) into metal-oxide-semiconductor field effect transistors (MOSFETs) is necessary to extend the life of planar CMOS devices and enable further downscaling. This thesis examines possible metal gate materials for improving the performance of the gate stack and discusses process integration as well as improved electrical and physical measurement methodologies, tested on capacitor structures and transistors. </p><p>By using reactive PVD and gradually increasing the N₂/Ar flow ratio, it was found that the work function (on SiO₂) of the TiN_x and ZrN_x metal systems could be modulated ~0.7 eV from low near nMOS work functions to high pMOS work functions. After high-temperature anneals corresponding to junction activation, both metals systems reached mid-gap work function values. The mechanisms behind the work function changes are explained with XPS data and discussed in terms of metal gradients and Fermi level pinning due to extrinsic interface states.</p><p>A modified scheme for improved Fowler-Nordheim tunnelling is also shown, using degenerately doped silicon substrates. In that case, the work functions of ALD/PVD TaN were accurately determined on both SiO₂ and HfO₂ and benchmarked against IPE (Internal Photoemission) results. KFM (Kelvin Force Microscopy) was also used to physically measure the work functions of PVD TiN and Mo deposited on SiO₂; the results agreed well with <i>C-V</i> and <i>I-V</i> data.</p><p>Finally, an appealing combination of novel materials is demonstrated with ALD TiN/Al₂O₃/HfAlO_x/Al₂O₃/strained-SiGe surface channel pMOS devices. The drive current and transconductance were measured to be 30% higher than the Si reference, clearly demonstrating increased mobility and the absence of polydepletion. Finally, using similarly processed transistors with Al₂O₃ dielectric instead, low-temperature water vapour annealing was shown to improve the device characteristics by reducing the negative charge within the ALD Al₂O₃.</p>

The development and implementation of a metal gate technology (alloy, compound, or silicide) into metal-oxide-semiconductor field effect transistors (MOSFETs) is necessary to extend the life of planar CMOS devices and enable further downscaling. This thesis examines possible metal gate materials for improving the performance of the gate stack and discusses process integration as well as improved electrical and physical measurement methodologies, tested on capacitor structures and transistors. By using reactive PVD and gradually increasing the N2/Ar flow ratio, it was found that the work function (on SiO2) of the TiNx and ZrNx metal systems could be modulated ~0.7 eV from low near nMOS work functions to high pMOS work functions. After high-temperature anneals corresponding to junction activation, both metals systems reached mid-gap work function values. The mechanisms behind the work function changes are explained with XPS data and discussed in terms of metal gradients and Fermi level pinning due to extrinsic interface states. A modified scheme for improved Fowler-Nordheim tunnelling is also shown, using degenerately doped silicon substrates. In that case, the work functions of ALD/PVD TaN were accurately determined on both SiO2 and HfO2 and benchmarked against IPE (Internal Photoemission) results. KFM (Kelvin Force Microscopy) was also used to physically measure the work functions of PVD TiN and Mo deposited on SiO2; the results agreed well with C-V and I-V data. Finally, an appealing combination of novel materials is demonstrated with ALD TiN/Al2O3/HfAlOx/Al2O3/strained-SiGe surface channel pMOS devices. The drive current and transconductance were measured to be 30% higher than the Si reference, clearly demonstrating increased mobility and the absence of polydepletion. Finally, using similarly processed transistors with Al2O3 dielectric instead, low-temperature water vapour annealing was shown to improve the device characteristics by reducing the negative charge within the ALD Al2O3.

The demands for faster, smaller, and less expensive electronic equipments are basically the driving forces for improving the speed and increasing the packing density of microelectronic components. Down-scaling of the devices is the principal method to realize these requests. For future CMOS devices, new materials are required in the transistor structure to enable further scaling and improve the transistor performance. This thesis focuses on novel metal gate and high-κ dielectric materials for future CMOS technologies. Specifically, TiN and ZrN gate electrode materials were studied with respect to work function and thermal stability. High work function, suitable for pMOS transistors, was extracted from both C-V and I-V measurements for PVD and ALD TiN in TiN/SiO2/Si MOS capacitor structures. ZrNx/SiO2/Si MOS capacitors exhibited n-type work function when the low-resistivity ZrNx was deposited at low nitrogen gas flow. Further, variable work function by 0.6 eV was achieved by reactive sputter depositing TiNx or ZrNx at various nitrogen gas flow. Both metal-nitride systems demonstrate a shift in work function after RTP annealing, which is discussed in terms of Fermi level pinning due to extrinsic interface states. Still, the materials are promising in a gate last process as well as show potential as complementary gate electrodes. The dielectric constant of as-deposited (Ta2O5)1-x(TiO2)x thin films is around 22, whereas that of AlN is about 10. The latter is not dependent on the degree of crystallinity or on the measurement frequency up to 10 GHz. Both dielectrics exhibit characteristics appropriate for integrated capacitors. Finally, utilization of novel materials were demonstrated in strained SiGe surface-channel pMOSFETs with an ALD TiN/Al2O3 gate stack. The transistors were characterized with standard I-V, charge pumping, and low-frequency noise measurements. Correlation between the mobility and the oxide charge was found. Improved transistor performance was achieved by conducting low-temperature water vapor annealing, which reduced the negative charge in the Al2O3.

L’avenir des nouvelles caméras embarquées pour l’astrophysique spatiale semble passer par unaccroissement du nombre de pixels et un fonctionnement à très basse température (en dessous de 0,1 K).Avec cette évolution, le nombre important de fils en sortie du détecteur refroidi représente souvent lacharge thermique prédominante sur la source froide (cryostat).Dans ce contexte, l’isolation thermique entre les différents circuits de détection est un point crucial pources caméras. Une brique technologique innovante a été développée pour apporter une solution présentantune excellente conduction électrique couplée à une grande isolation thermique. Cette innovation,protégée par un brevet, permet de résoudre cet apparent paradoxe. La solution proposée consiste enl’empilement d’un grand nombre de couches minces de matériaux supraconducteurs dans lesinterconnexions.La résistance thermique à chaque interface est dépendante des propriétés élastiques des matériaux,de la qualité des interfaces et de la température à laquelle le système fonctionne. A très basse température,le modèle AMM, couplé aux mesures des caractéristiques des matériaux composants la multicouche,permettent une estimation théorique de la résistance thermique pour une interface. Les mesures effectuéesavec les liaisons supraconductrices à forte résistivité thermique concordent avec les estimationsthéoriques. Nous avons ainsi pu mesurer des résistances thermiques de l’ordre de 3,3.105 K/W à 200 mKpour une multicouche composée d’une succession (62 interfaces) de couches minces de nitrure de titaneet de niobium sur une surface de 16 mm2. Dans les conditions d’utilisation prévues pour une camérarayons X de 4000 pixels microcalorimétriques, l’utilisation de cette brique technologique devrait assurerune charge thermique sur la source froide (à 50 mK) très inférieure au μW pour plus de 8000 pointsde contact. Ce dispositif pourra être utilisé à l’avenir dans nombre de projets cryogéniques, lorsqu’une excellenteisolation thermique associée à une excellente conduction électrique sera recherchée. / Future of the next camera onboard space observatories implies a major enhancement in number of pixelsand a very low operative temperature (below 0.1 K). In this evolution, the large number of output wiresfrom the cool detector is often responsible of the most important thermal load onto the cold bath(cryostat).In this context, the thermal insulation between the different detection circuits is the bottleneck for thesecameras. An innovative technological component, protected by a patent, has been developed to tackle thisproblem. This device has both an excellent electrical resistivity and a very high thermal resistivity.The proposed solution is a stack of thin superconducting layers at electrical interconnections.The thermal resistance at each interface relies on the elastic properties of the materials used, the quality ofthe interfaces and temperature. The AMM model used in conjunction with the measured materialcharacteristics allows a theorical estimation of the thermal resistance per interface. The measurementsundertaken with superconducting connections with very high thermal resistivity are very well describedby this AMM model. We have measured thermal resistances as high as 3.3 105 K/W @ 200 mKfor a multilayer of 62 interfaces built with titaniun nitride and niobium alternatively on a 16 mm2 array.In the conditions foreseen for a 4000 micro-calorimeters camera operating at 50 mK in X-rays,this multilayer technique should allow a thermal load onto the cold bath that is much lower that 1 mWfor more than 8000 contacts.

Submitted by Lucas Jorge Affonço (lucas_jorgeaffonco@yahoo.com.br) on 2018-09-25T18:16:47Z No. of bitstreams: 1 Dissertação_POSMAT_LucasJorgeAffonco.pdf: 1122070 bytes, checksum: 3aa8bf900f18ab0cc3c2d9fdbbc0ce2e (MD5) / Rejected by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br), reason: Solicitamos que realize uma nova submissão seguindo as orientações abaixo: 1 - Inserir no corpo do texto uma cópia da ata de defesa, pois é um item obrigatório. Agradecemos a compreensão on 2018-09-26T13:33:08Z (GMT) / Submitted by Lucas Jorge Affonço (lucas_jorgeaffonco@yahoo.com.br) on 2018-09-26T13:39:25Z No. of bitstreams: 1 Dissertação_POSMAT_LucasJorgeAffonco.pdf: 1731555 bytes, checksum: 7c7c9ba43b8b832af33307bef8e74d22 (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2018-09-26T17:02:25Z (GMT) No. of bitstreams: 1 affonço_lj_me_bauru.pdf: 1731555 bytes, checksum: 7c7c9ba43b8b832af33307bef8e74d22 (MD5) / Made available in DSpace on 2018-09-26T17:02:25Z (GMT). No. of bitstreams: 1 affonço_lj_me_bauru.pdf: 1731555 bytes, checksum: 7c7c9ba43b8b832af33307bef8e74d22 (MD5) Previous issue date: 2018-07-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O nitreto de titâno apresenta uma vasta gama de aplicações. Entre elas destacam-se as aplicações em recobrimento de superfícies que exploram características mecânicas tais como dureza e módulo de elasticidade do material para aplicações em biomateriais. Essas características e suas correlações com a microestrutura são investigadas, nesse trabalho, em função dos parâmetros de deposição de filmes de TiN. Os filmes foram depositados pela técnica de magnetron sputtering reativo em rádio frequência, sobre substratos de titânio, de sílica, de silício e de uma liga de titânio-nióbio. Nas deposições, foi utilizado um alvo de titânio puro e misturas gasosas de argônio e nitrogênio, com diferentes fluxos de nitrogênio. As potências empregadas foram de 240 W e 300 W, com diferentes tempos de deposição. Medidas de taxa de deposição e emissão óptica do plasma auxiliaram na escolha dos parâmetros de deposição. As análises das difrações de raios X mostraram que com o aumento do fluxo de nitrogênio os cristalitos tendem a apresentar uma orientação preferencial com os planos (200) do TiN paralelos à superfície do substrato, além de indicar a presença de strain nos filmes. Medidas de nanoindentação foram realizadas nas amostras, com o intuito de obter a dureza e o módulo de elasticidade dos filmes depositados com diferentes fluxos de nitrogênio. Buscando assim determinar a influência do fluxo sobre as propriedades mecânicas e a microestrutura dos filmes. Verificou-se que a dureza nas amostras depositadas a 10 sccm foi a maior, variando de 10 a 18 GPa de acordo com a profundidade de penetração, sendo essa amostra a que apresentou maior textura de orientação favorecendo os planos (200). O módulo de elasticidade foi maior para a amostra de 8 sccm, em torno de 140 GPa, sendo essa a amostra que apresentou maior strain compressivo. Verificou-se que a técnica de sputtering reativo é versátil para o crescimento dos filmes de nitreto de titânio, e que o fluxo de nitrogênio usado nas deposições é um parâmetro de grande impacto nas características mecânicas e estruturais dos filmes obtidos. / The titanium nitride (TiN) has mechanical properties that are useful in a wide range of applications. In special, it is being investigated to improve the surfaces of bone implants. The mechanical properties of TiN films deposited by reactive magnetron sputtering and their correlations with microstructure will be investigated in this dissertation as a function of the deposition parameters. The films were deposited in titanium, silica, silicon and titanium-niobium substrates. A pure titanium target and a mix of argon and nitrogen gases were used in the depositions. The influence of the variation of the reactive gas fluxes on the mechanical properties and in the microstructure of the films were investigated, for applied powers of 240 W and 300 W at 13.6 MHz. Deposition rate and plasma optical emission measurements helped to control the deposition parameters. X ray diffraction analysis show that all films present compressive strain and, at high nitrogen fluxes, a preferred crystallite orientation of planes (200) parallel to the substrate surface occurs. Nanoidentation measurements were performed, for different nitrogen fluxes, to obtain the hardness and elastic modulus of TiN films. The hardness of films deposited at 10 sccm, varied between 10 and 18 GPa, as a function of the penetration depth, and is higher than the observed in other samples. These films also showed the higher (200) plane texture. The elastic modulus is higher on films deposited at 8 sccm N2 flow (around 140 GPa). These films also showed the higher compressive strain. It was checked that the reactive sputtering is a resourceful technique for titanium nitride deposition, and nitrogen flux present a high impact in the structure and mechanical properties of the deposited films.

La pulvérisation cathodique magnétron pulsée à haute puissance (HiPIMS) est un procédé de dépôt de couches minces dans lequel le flux de dépôt est principalement composé d’ions du matériau pulvérisé. Ce type de décharge permet de contrôler l’énergie et la direction des espèces qui seront déposées, ce qui est favorable à la modification de la structure et des propriétés finales des couches. Malgré tous les travaux de recherches menés pour caractériser et comprendre les conditions de décharge HiPIMS, la nécessité de développer des couches minces utiles à la société reste toujours d’actualité. La finalité de ce travail est l’obtention de couches minces HiPIMS plus performantes que celles obtenues aujourd'hui en utilisant des techniques de dépôt classiques. Pour cela il est indispensable d'identifier et d'optimiser les paramètres de dépôt permettant de modifier à la fois la microstructure des couches, la contrainte résiduelle et les propriétés liées à l'énergie telles que la résistivité électrique et la bande interdite. Trois matériaux sont au cœur de ce travail : le cuivre, le dioxyde de titane et le nitrure de titane. Les études expérimentales ont montré que les paramètres les plus importants pour obtenir les propriétés souhaitées étaient la quantité et l’énergie cinétique des espèces ionisées irradiant la couche au cours de sa croissance. Par ailleurs, les paramètres de croissance optimale entre couches métalliques et couches composées diffèrent considérablement. / High power impulse magnetron sputtering (HiPIMS) is a thin film deposition technique where the deposition flux is predominantly composed of ionized sputtered material. This enables control of energy and direction of the film-forming species and is thereby beneficial for tailoring the film structure and final properties. Although researchers world-wide have spent significant time and efforts characterizing and understanding the plasma process conditions in HiPIMS, research in new and improved HiPIMS-based thin film materials that find applications in areas of importance for society is still required. The goal of this work has been to identify and optimize the deposition parameters that allow tailoring the film microstructure, intrinsic stress and energy-related properties, such as electrical resistivity and optical band gap, to ultimately achieve superior HiPIMS coatings compared to what is achieved today using conventional deposition techniques. Three material systems constitute the core of the work: copper, titanium dioxide, and titanium nitride. From the work carried out it is concluded that the most important parameters affecting the film structure and properties are the amount as well as the kinetic energy of the ionized sputtered species irradiating the film during growth. These parameters differ substantially for optimum growth conditions of metallic and compound films.