La présente étude porte sur la modélisation de la structure des joints de grains (JG) et sur les phénomènes de ségrégation. Dans les matériaux polycristallins, la ségrégation aux joints de grains a des conséquences importantes sur leurs propriétés structurelles et fonctionnelles : glissement intergranulaire, corrosion intergranulaire et modification des propriétés mécaniques. Ce phénomène devient particulièrement important pour les matériaux irradiés où la ségrégation intergranulaire induite par irradiation peut conduire à une modification locale de la composition des joints de grains et par conséquent, à une évolution parfois néfaste des propriétés macroscopiques de ces matériaux. Dans ce manuscrit, nous nous sommes focalisés sur le développement de la méthode des quasiparticules pour pouvoir modéliser ce phénomène dans des systèmes binaires. La méthode des quasi-particules est un modèle continu qui permet de modéliser les phénomènes physiques à l’échelle atomique. Un des avantages est lié à la possibilité de modéliser les déplacements des atomes dans l’espace continu, tout en permettant de modéliser des transitions diffusives s’étalant sur des temps longs. Dans ce travail la méthode des quasi-particules a été appliquée pour étudier la ségrégation du phosphore aux JG. Le lien entre les différentes structures des JG et la concentration du phosphore aux JG a été établi. Pour modéliser les phénomènes qui ont lieu aux JG dans les matériaux irradiés le modèle des quasi-particules a été développé pour pouvoir inclure des lacunes ou des auto-interstitiels puis décrire leurs cinétiques. Ensuite la diffusion et l’annihilation des lacunes (ou des auto-interstitiels) aux JG ont été modélisées. Il a été montré que lorsque la force de puits du JG est assez importante, les lacunes diffusent vers les JG et des cavités se forment aux JG en ayant une forme allongée, ce qui concorde avec les données expérimentales. Le modèle des quasi-particules a été également appliqué pour étudier la croissance des grains dans un polycristal. / This thesis focuses on the modeling of grain boundaries (GB) structure and segregation phenomena. Segregation at GB in polycrystalline materials can have profound consequences on structural and functional properties : intergranular slipping, intergranular corrosion and mechanical properties. Segregation becomes really important in irradiated materials where radiation-induced segregation can change th local composition of GB and sometimes impact the macroscopic properties of materials. In this work, the quasi-particles approach is developed to model these phenomena in binary systems. The quasi-particles approach is a continuous model able to model physical phenomena at atomic scale. One of the insight of this model is the capability to simulate atomic displacement in continuum space and diffusive transitions at mesoscale. In this work, the quasi-particles approach is used to study phosphorus segregation at GB. The link between GB structure and phosphorus concentration is highlighted. Next, vacancies or self-interstitial are introduced into the quasi-particles approach to model some specific phenomena which occur in irradiated materials. In particular, the diffusion and annihilation of vacancies (or self-interstitials) at GB could be modeled. When sink strength of GB is large enough, vacancies diffuse to GB and create voids with elongated shape, consistantly with experimental observation. Finally, the quasi-particles approach is used to study grain growth in polycrystalline materials.

Revealing the prior austenite grain boundaries from a martensitic structure is well known to be very difficult and dependent on the chemical composition and the thermomechanical processing of the steel. In the present study, four different chemical etching reagents and additional thermal etching have been conducted for thermomechanical simulated tool steels Orvar Supreme and Stavax ESR. The etching results have been characterized using light optical microscopy and electron backscattered diffraction. The obtained results show that saturated aqueous picric acid, oxalic and sodium bisulfite based acid reveals prior austenite grain boundaries well for Orvar Supreme. For Stavax ESR, only aqueous CrO3-NaOH-picric acid provides good results in revealing the prior austenite grain boundaries. Thermal etching shows good potential and if conducted properly, thermal etching is a good alternative to the chemical reagents from a health- and environmental perspective.

The research reported in this dissertation focuses on the response of grain boundaries in polycrystalline metallic nanostructures to applied strain using molecular dynamics simulations and empirical interatomic force laws. The specific goals of the work include establishing how local grain boundary structure affects deformation behavior through the quantitative estimation of various plasticity mechanisms, such as dislocation emission and grain boundary sliding. The effects of strain rate and temperature on the plastic deformation process were also investigated. To achieve this, molecular dynamics simulations were performed on both thin-film and quasi-2D virtual samples constructed using a Voronoi tessellation technique. The samples were subjected to virtual mechanical testing using uniaxial strain at strain rates ranging from 105s-1 to 109s-1. Seven different interatomic embedded atom method potentials were used in this work. The model potentials describe different metals with fcc or bcc crystal structures. The model was validated against experimental results from studying the tensile deformation of irradiated austenitic stainless steels performed by collaborators at the University of Michigan. The results from the model validation include a novel technique for detecting strain localization through adherence of gold nanoparticles to the surface of an experimental sample prior to deformation. Similar trends with respect to intergranular crack initiation were observed between the model and the experiments. Simulations of deformation in the virtual samples revealed for the first time that equilibrium grain boundary structures can be non-planar for model potentials representing fcc materials with low stacking fault energy. Non-planar grain boundary features promote dislocation as deformation mechanisms, and hinder grain boundary sliding. This dissertation also reports the effects of temperature and strain rate on deformation behavior and correlates specific deformation mechanisms that originate from grain boundaries with controlling material properties, deformation temperature and strain rate. / Ph. D.

Electron beam induced current (EBIC) and atom probe tomography (APT) were used in this study to determine electrical activities and impurity compositions at extended defects in multicrystalline silicon (mc-Si) samples. The results provide, for the first time, information regarding the chemical species present at defects whose electrical activity has previously been measured. A new APT specimen fabrication process was developed with the ability to select a specific defect for APT analysis. Development of the APT specimen fabrication process proceeded by first selecting and optimising the preferential etching for nano-scale defect delineation. Three etchants were evaluated, namely Secco, Sirtl and Dash, from which the Secco etch was selected. Three parameters were optimised to produce etch pits with geometries that meet the requirements imposed by APT specimen fabrication methods. The optimum parameters were 0.05M potassium dichromate concentration, 20°C etch temperature, and 30sec etch time. In the second stage, marking techniques were developed in order for the defects to be located throughout the APT specimen fabrication process. However, it became apparent that the conventional APT specimen fabrication method could not be used to fabricate APT specimens containing selected defects in a mc-Si sample. This led to the development of a novel APT specimen fabrication approach which allowed APT specimens to be fabricated, reproducibly, containing grain boundaries and isolated dislocations. In order to evaluate accurately iron contamination in mc-Si, four atom probe parameters were optimised to maximise detection sensitivity: the evaporation rate, the laser beam energy, the pulse repetition rate and the specimen temperature. The optimisation process can be divided in to two parts. In the first part, a matrix of pre-sharpened single-crystal silicon specimens was subjected to a variety of experimental parameters. The optimised parameters were determined to be 0.3% evaporation rate, 0.5nJ beam energy, 160kHz repetition rate and 55K specimen temperature. The second part was to determine the iron detection efficiency –the percentage of detected Fe ions that can be correctly identified as Fe– and sensitivity using these parameters to analyse a specially prepared iron calibration specimen. The values were determined to be a detection efficiency of about 35% and sensitivity of 54ppm or 2.70x10¹⁸ atom/cm³. The APT specimen fabrication process and the optimised APT analysis parameters were used to analyse four extended defects in mc-Si samples subjected to three different processing conditions, namely gold-contaminated, as-grown and phosphorus diffusion gettering (PDG). The important aspects of the analysis are listed below: • Gold was not detected at the grain boundary and its associated dislocations in the gold-contaminated specimen. The binding enthalpy of gold to such defects is thus less than 0.63eV. • Iron was not detected in any specimen. • Copper was observed at the grain boundary in the as-grown specimen in the form of individual atoms as well as clusters with diameters ranging between 4nm and 9nm. The electrical activity of the grain boundary was about 58%. • Nickel and carbon were detected at the grain boundary in the post-PDG specimen with the former having platelet structures with diameters and thicknesses ranging between 4nm-7nm and 2nm-4nm, respectively. The recombination strength of the defect was about 22%. • Two nickel clusters were found at the isolated dislocation in the post-PDG specimen. The clusters were spherical with an average diameter of 10nm. The distance between the two clusters was 35nm. The recombination strength of the defect was about 4%.

Foram efetuados experimentos de sinterização em cerâmica policristalina de ZrO2: 3 mol% Y2O3 (3YSZ) por três métodos: aquecimento seguindo o perfil temperatura ambiente 1400 °C temperatura ambiente (sinterização convencional), aquecimento a partir da temperatura ambiente até 1000-1100 °C sob aplicação de campo elétrico AC (sinterização dinâmica assistida por campo elétrico), e aquecimento até 1000-1100 °C para aplicação do campo elétrico AC (sinterização isotérmica assistida por campo elétrico). O último método foi aplicado em amostras sob diferentes condições (amostras a verde, amostras a verde compactadas isostaticamente com diferentes pressões, amostras pré-sinterizadas a 1400 °C) e diferentes condições experimentais (diferentes frequências do campo elétrico AC, campo elétrico DC, diferentes limites de densidade de corrente, aplicação de carga simultaneamente à aplicação do campo elétrico). Todas as amostras de 3YSZ sinterizadas, além de terem a densidade aparente determinada, tiveram a superfície observada em microscópio eletrônico de varredura para avaliação do tamanho médio de grão e distribuição do tamanho de grão (em alguns casos, ao longo da superfície, do centro para a borda). Além disso, análises de espectroscopia de impedância foram feitas para avaliar a contribuição intergranular (principalmente contorno de grão) e intragranular (grãos) para a resistividade elétrica. A ideia principal foi coletar dados sobre sinterização assistida por campo elétrico, procurando entender o mecanismo atuando no método de sinterização, conhecido por produzir peças cerâmicas densas em temperaturas menores do que as usadas em sinterização convencional, em tempos curtos, e com inibição do crescimento de grão. Os resultados principais mostram que: 1) o nível de retração depende da frequência do campo elétrico AC, 2) quanto maior a porosidade, maior o efeito do campo elétrico, 3) quanto maior o valor da densidade de corrente, maior a densificação, até um determinado limite a partir do qual a amostra é danificada, 4) o pulso de corrente elétrica flui preferencialmente pela região intergranular, e 5) amostras submetidas a sinterização assistida por campo elétrico mostraram aumento da condutividade do contorno de grão. Um mecanismo para a sinterização assistida por campo elétrico é proposto, baseado em que 1) aquecimento Joule é o efeito principal, 2) a corrente elétrica, que surge como resultado da aplicação do campo elétrico, flui pela região intergranular, 3) o aquecimento Joule difunde as espécies químicas depletadas nas interfaces de volta aos grãos, aumentando a concentração de defeitos, levando ao aumento da condutividade do grão, e 4) o aquecimento Joule é responsável por diminuir a barreira potencial na região de carga espacial, inibindo o bloqueio dos íons de oxigênio nos contornos de grão. / Experiments on sintering ZrO2: 3 mol% Y2O3 polycrystalline ceramics (Y-TZP, hereafter 3YSZ) were carried out by three methods: heating following the room temperature-1400°C-room temperature profile (conventional sintering), heating from room temperature to 1000-1100°C under an applied AC electric field (dynamic electric field-assisted sintering), and heating to 1000-1100°C for application of an AC electric field (isothermal electric field-assisted sintering). The last method was performed under different specimen conditions (green pellets, green pellets isostatically pressed with different loads, pellets pre-sintered at 1400°C) and different experimental conditions (different frequencies of the AC electric field, DC electric fields, different limitation of the electric current densities, applying loads simultaneously to application of the electric field). All 3YSZ sintered samples, besides having their apparent densities determined, had their surfaces observed in a scanning electron microscope to evaluate average grain size and distribution of grain sizes (some, along the surface from the center to the border). Moreover, impedance spectroscopy analyses were carried out to evaluate the intergranular (mainly grain boundary) and intragranular (bulk) contributions to the electrical resistivity. The primary idea was to collect data on electric field-assisted sintering looking for understanding the mechanisms behind that sintering method, known to produce dense ceramic pieces at temperatures lower than those used in conventional sintering, in short times and inhibiting grain growth. The main results show that 1) the shrinkage level depends on the AC frequency, 2) the larger the porosity the higher the electric field effect, 3) higher current densities promotes higher densification up to a limit that could damage the sample, 4) the electric current pulse follows preferentially the intergranular instead of the bulk pathway, and 5) electric field-assisted sintered specimens show enhanced grain boundary conductivity. A mechanism for the electric field-assisted sintering is proposed based on that 1) Joule heating is the primary event, 2) the electric current, as a result of the electric field, follows the intergranular pathway, 3) Joule heating diffuses chemical species depleted at the interfaces back to the bulk, increasing the defect concentration, leading to the enhancement of the bulk conductivity, and 4) that same Joule heating is responsible for the decrease of the potential barrier at the space charge region, inhibiting the blocking of oxide ions at the grain boundaries.

Foram efetuados experimentos de sinterização em cerâmica policristalina de ZrO2: 3 mol% Y2O3 (3YSZ) por três métodos: aquecimento seguindo o perfil temperatura ambiente 1400 °C temperatura ambiente (sinterização convencional), aquecimento a partir da temperatura ambiente até 1000-1100 °C sob aplicação de campo elétrico AC (sinterização dinâmica assistida por campo elétrico), e aquecimento até 1000-1100 °C para aplicação do campo elétrico AC (sinterização isotérmica assistida por campo elétrico). O último método foi aplicado em amostras sob diferentes condições (amostras a verde, amostras a verde compactadas isostaticamente com diferentes pressões, amostras pré-sinterizadas a 1400 °C) e diferentes condições experimentais (diferentes frequências do campo elétrico AC, campo elétrico DC, diferentes limites de densidade de corrente, aplicação de carga simultaneamente à aplicação do campo elétrico). Todas as amostras de 3YSZ sinterizadas, além de terem a densidade aparente determinada, tiveram a superfície observada em microscópio eletrônico de varredura para avaliação do tamanho médio de grão e distribuição do tamanho de grão (em alguns casos, ao longo da superfície, do centro para a borda). Além disso, análises de espectroscopia de impedância foram feitas para avaliar a contribuição intergranular (principalmente contorno de grão) e intragranular (grãos) para a resistividade elétrica. A ideia principal foi coletar dados sobre sinterização assistida por campo elétrico, procurando entender o mecanismo atuando no método de sinterização, conhecido por produzir peças cerâmicas densas em temperaturas menores do que as usadas em sinterização convencional, em tempos curtos, e com inibição do crescimento de grão. Os resultados principais mostram que: 1) o nível de retração depende da frequência do campo elétrico AC, 2) quanto maior a porosidade, maior o efeito do campo elétrico, 3) quanto maior o valor da densidade de corrente, maior a densificação, até um determinado limite a partir do qual a amostra é danificada, 4) o pulso de corrente elétrica flui preferencialmente pela região intergranular, e 5) amostras submetidas a sinterização assistida por campo elétrico mostraram aumento da condutividade do contorno de grão. Um mecanismo para a sinterização assistida por campo elétrico é proposto, baseado em que 1) aquecimento Joule é o efeito principal, 2) a corrente elétrica, que surge como resultado da aplicação do campo elétrico, flui pela região intergranular, 3) o aquecimento Joule difunde as espécies químicas depletadas nas interfaces de volta aos grãos, aumentando a concentração de defeitos, levando ao aumento da condutividade do grão, e 4) o aquecimento Joule é responsável por diminuir a barreira potencial na região de carga espacial, inibindo o bloqueio dos íons de oxigênio nos contornos de grão. / Experiments on sintering ZrO2: 3 mol% Y2O3 polycrystalline ceramics (Y-TZP, hereafter 3YSZ) were carried out by three methods: heating following the room temperature-1400°C-room temperature profile (conventional sintering), heating from room temperature to 1000-1100°C under an applied AC electric field (dynamic electric field-assisted sintering), and heating to 1000-1100°C for application of an AC electric field (isothermal electric field-assisted sintering). The last method was performed under different specimen conditions (green pellets, green pellets isostatically pressed with different loads, pellets pre-sintered at 1400°C) and different experimental conditions (different frequencies of the AC electric field, DC electric fields, different limitation of the electric current densities, applying loads simultaneously to application of the electric field). All 3YSZ sintered samples, besides having their apparent densities determined, had their surfaces observed in a scanning electron microscope to evaluate average grain size and distribution of grain sizes (some, along the surface from the center to the border). Moreover, impedance spectroscopy analyses were carried out to evaluate the intergranular (mainly grain boundary) and intragranular (bulk) contributions to the electrical resistivity. The primary idea was to collect data on electric field-assisted sintering looking for understanding the mechanisms behind that sintering method, known to produce dense ceramic pieces at temperatures lower than those used in conventional sintering, in short times and inhibiting grain growth. The main results show that 1) the shrinkage level depends on the AC frequency, 2) the larger the porosity the higher the electric field effect, 3) higher current densities promotes higher densification up to a limit that could damage the sample, 4) the electric current pulse follows preferentially the intergranular instead of the bulk pathway, and 5) electric field-assisted sintered specimens show enhanced grain boundary conductivity. A mechanism for the electric field-assisted sintering is proposed based on that 1) Joule heating is the primary event, 2) the electric current, as a result of the electric field, follows the intergranular pathway, 3) Joule heating diffuses chemical species depleted at the interfaces back to the bulk, increasing the defect concentration, leading to the enhancement of the bulk conductivity, and 4) that same Joule heating is responsible for the decrease of the potential barrier at the space charge region, inhibiting the blocking of oxide ions at the grain boundaries.

No description available.

Grain boundary processes play a major role in controlling different rate processes in yttria stabilized tetragonal zirconia. The present study concentrated on rate processes in tetragonal zirconia, which were significantly influenced by the grain boundary processes. In this present study, nanocrystalline zirconia with grain size as low as 66 nm and density as high as 98.5% was processed using a two steps sintering-sinterforging process in the temperature range of 1473K to 1373K. Significant suppression of grain growth was noted in the second step of the two step process. It was observed that two step sintering-sinterforging process can reduce the processing time by an order of magnitude compared to the two step sintering process. A high grain size dependency of 3.3 indicated grain boundary controlled process dominating this technique. The dense nanocrystalline zirconia was used for microstructural and deformation characterization. An influence of electric field on grain growth behaviour was studied by annealing the specimens at 1573K for 10 hours under an applied field of 4 V/cm to 80 V/cm. It was noticed that grain growth was significantly retarded under a very weak field and the magnitude of retardation dependent on the applied voltage, an extensive grain growth was observed on the other occasion when the applied voltage crossed the threshold value of 3.5V. It was proposed that electrical boundary resistance provides minima in the grain boundary energy during annealing and that retards the grain growth. This technique presented a huge potential application in ceramic processing involving rate process. Again the grain boundary process was reported to control this phenomenon. Low temperature creep properties of nanocrystalline zirconia were investigated in great detail in the present study. Grain boundary sliding was noted as the mode of deformation at 1423 K. Study on the specimens with wide range of grain sizes (65 nm to ~0.4 µm) suggested that the deformation mechanism of the nanograin is similar to that of the submicron grain zirconia. A study on the segregation of yttrium ions to the grain boundaries showed that the segregation behaviour of nanograin and submicron grain 3YTZ was similar, which again indicated towards the possibility of nanocrystalline tetragonal zirconia to be superplastic as the scaling law was applicable from submicron to nanocrystalline 3YTZ. Grain boundary sliding is the mode of deformation of 3YTZ at high temperatures. This study aimed at understanding the influence of grain boundary sliding on rate processes at the boundary namely grain boundary diffusion. Grain boundary diffusivity of the deformed specimens was measured using secondary ion mass spectroscopy. The study revealed that the sliding process is much slower compared to the atomic jumps causing grain boundary diffusion, hence no significant influence of the grain boundary sliding on grain boundary diffusion was observed. This present study demonstrated new techniques which have a huge potential application in processing ceramics at low temperatures. This study also developed an understanding of the grain boundary processes which involved in low temperature rate processes of nanocrystalline zirconia.

In this work, ultrafine-grained (UFG) Al-5wt%Zn alloy was produced by equal channel angular extrusion (ECAE). The microstructure evolution during ECAE and the mechanical properties of the UFG Al-Zn alloy were investigated. In order to identify the effect of Zn in the Al-Zn alloy, pure aluminum (4N, 99.99%) was also studied for comparison. The grains of the Al-Zn alloy could be refined effectively by increasing the ECAE passes. However, as the ECAE passes increased, the microhardness increased initially but maintained constant after 4 ECAE passes. The dislocation density within grain interior was decreased gradually with increasing ECAE passes. After being processed to twelve ECAE passes, the UFG Al-Zn alloy exhibited 53.7% of the grain boundaries being high angle grain boundaries (HAGBs). The UFG Al-5wt%Zn alloy exhibits superior tensile strength and elongation as compared with pure aluminum fabricated by the same ECAE process. Experimental results indicated that adding Zn in aluminum alloy could provide solid-solution strengthening and considerable enhancement in tensile ductility which might be related to an improved post-uniform elongation (PUE). The strain rate sensitivity (SRS) of the UFG Al-Zn alloy also increased with increasing the ECAE passes, which might be related to the fine grain size and the contribution of grain boundary sliding. The activation volume of the UFG Al-Zn alloy was in the range of 32b3~76b3, and the pure aluminum was in the range of 57b3~122b3. Because of the small value of the activation volume, it is suggested that the controlling mechanism for dislocation glide in the UFG Al-Zn alloy might be related to the generation and absorption of dislocations in grain boundary, as well as the interaction between dislocations and solute Zn atoms in the grain boundary.

The increasing clock speed and the further reduction of the feature size in integrated circuits lead to increasing demands on the interconnecting material. Thus an increasing need for a metallization with low electrical resistance and high electromigration endurance exist. Copper can be count as a material with these properties. Since 1998 Copper interconnections are commercially manufactured for integrated circuits. Electromigration is the most lifetime limiting factor in modern integrated circuits. The main the electromigration behavior influencing parameter and especially the influence of the microstructure is unknown. In this work the influence of the grain boundaries and their properties on the electromigration is examined at sputtered (PVD) and electroplated (ECD) Copper interconnects. For this investigation microstructure mappings produced by electron backscatter diffraction (EBSD) are correlated to in-situ electromigration experiments inside the SEM to research the electromigration behavior and the diffusion paths. Microstructure analysis shows big a difference between the two investigated types of interconnects. In both a strong <111> fibre texture is observed, but the PVD Copper shows a stronger texture than the electroplated one. The texture index of the PVD interconnects is 15,9 whereas the ECD lines show an index of 3,9. The frequency densities of the grain boundary misorientation, which is important for the electromigration behavior, are very different for both films. The ECD lines show a fraction of 55% Sigma 3 twin boundaries and 40% high angle grain boundaries. In contrast the PVD interconnects show a fraction of 5% Sigma 3 twin boundaries, 75% high angle grain boundaries and 20% small angle grain boundaries. This shows that a reduction of the high angle grain boundaries is not related to a strong <111> fibre texture. With in-situ experiments correlated to microstructure analysis it is shown, that voiding at high angle grain boundaries occur in the down wind of blocking grains or sites where only Sigma 3 twin boundaries are present. Hillocks were formed at high angle grain boundaries in the upwind of blocking grains or sites where only small angle grain boundaries or Sigma 3 twin boundaries are found. By a statistical evaluation of the in-situ experiments it is shown that more than 50% of the observed electromigration damages could be ascribed clearly to a grain boundary related local mass flux divergence. At strings of high angle grain boundaries voiding at the cathode side and hillock growth at the anode side is shown. The distance between these voids and hillocks is always higher than the Blech length. As the current density increases the distance between these voids and hillocks decreases according to Blech´s law, whereby it´s valid for local divergence is shown. FIB cuts show, that hillocks on PVD lines grow non-epitaxial in contrast to hillocks on ECD lines, which show epitaxial growth. These differences of hillock´s growth may suggest different underlying growth mechanisms. Reliability testing performed on PVD Copper interconnects lead to an activation energy for electromigration of 0,77eV ± 0,07eV. The confidence interval includes reported values for surface and also grain boundary diffusion. This indicates that the electromigration in these experiments is mainly influenced by surface and grain boundary diffusion. In this work the nucleation of voids and hillocks related to the previous analysed microstructure is observed inside the SEM and correlated to high angle grain boundaries and their misorientation angle. The result of this work show that electromigration damage in Copper interconnects is mostly caused by inhomogeneities of the microstructure. In this process the high angle grain boundaries are the main diffusion path. / Mit steigender Taktrate u. weiter fortschreitender Integrationsdichte in mikroelektr. Schaltungen nehmen d. Anforderungen an d. Metallisierungsmaterial weiter zu. Es besteht d. zunehmende Forderung nach Metallisierungen mit geringem elektrischen Widerstand u. hoher Elektromigra- tionsfestigkeit. Kupfer kann als Material angesehen werden, welches d. Anforderungen erfüllt. Seit 1998 wird Kupfer als Metallisierungsmaterial in höchstintegr. Schaltun- gen eingesetzt. Die Elektromigration (EM) ist der d. Zuver- lässigkeit am meisten begrenzende Faktor in mod. mikro- elektron. Schaltungen. Die Haupteinflußgrößen auf d. Elektromigrationsverhalten u. insbes. d. Einfluß d. Gefüges ist unklar. In d. Arbeit wird an nichtpassivier- ten physikalisch (PVD) u. galvanisch (ECD) abgeschied. Kupferleitbahnen d. Einfluß d. Korngrenzen u. deren Eigenschaften auf d. Elektromigrationsverhalten untersucht. Dazu werden Gefügeanalysen mittels Kikuchi-Rückstreutechnik u. in-situ Elektromigrationsexperimente im Rasterelektron- enmikroskop gekoppelt, um d. Elektromigrationsverhalten u. d. Migrationspfade zu erforschen. Gefügeuntersuchungen zeigen, daß d. untersuchten Leitbahnen sich in ihren Gefügeeigenschaften deutl. unterscheiden. Beide Schichten zeigen e. <111> Fasertextur, wobei d. PVD-Leitbahnen e. deutl. schärfere Textur mit e. Texturfaktor von 15,9 gegenüber den ECD-Leitbahnen d. e. Texturfaktor von 3,9 aufweisen. Die Häufigkeitsverteilungen d. Korngrenz- Misorientierung, sind für d. beiden Schichten unterschiedl. Die ECD-Leitbahnen zeigen e. Anteil von 55% Sigma 3-Korngrenzen und 40% Großwinkelkorngrenzen. Die PVD- Leitbahnen hingegen weisen nur e. Anteil von 5% Sigma 3-Korngrenzen, 75% Großwinkelkorngrenzen u. 20% Kleinwin- kelkorngrenzen auf. Dadurch wird gezeigt, daß e. scharfe <111> Textur keine Reduzierung d. Großwinkelkorngrenzen zur Folge haben muß. Anhand von in-situ Experimenten gekoppelt mit Gefügeanalysen wird gezeigt, daß Porenbildung an Groß- winkelkorngrenzen hinter blockierenden Körnern oder hinter Bereichen auftritt, in d. nur Sigma 3-Korngrenzen o. Kleinwinkelkorngrenzen vorliegen. Hügelbildung tritt an Großwinkelkorngrenzen vor blockierenden Körnern o. Berei- chen auf, in denen nur Kleinwinkelkorngrenzen o. Sigma 3-Korngrenzen vorliegen. Mit e. statist. Auswertung d. in-situ Experimente wird gezeigt, daß mehr als d. Hälfte aller Elektromigrationsschädigungen bei beiden Herstellungsmethoden eindeutig auf e. korngrenzbedingte lokale Divergenz im Massenfluß zurückzuführen sind. An Ketten von Großwinkelkorngrenzen wird verdeutl., daß kathodenseitig Porenbildung und anodenseitig Hügelbildung auftritt. Der Abstand zw. Pore u. Hügel liegt hier immer oberh. d. Blechlänge. Mit zunehmender Stromdichte nimmt d. Pore-Hügel-Abstand entspr. d. Blechtheorie ab, wodurch gezeigt wird, daß d. Blechtheorie auch bei lokalen Flußdivergenzen gilt. FIB-Querschnittsanalysen zeigen, daß Hügel auf PVD-Leitbahnen nicht epitaktisch mit d. darunterliegenden Schicht verwachsen sind im Gegensatz zu Hügeln auf ECD-Leitbahnen, die teilw. e. epitaktische Verwachsung mit d. Leitbahn zeigen. Lebensdauermessungen an PVD-Leitbahnen ergeben e. Aktivierungsenergie von 0,77eV ± 0,07eV. Es ist davon auszugehen, daß das Elektromigrationsverhalten d. hier untersuchten unpassi- vierten Leitbahnen haupts. von Korngrenz- u. von Oberfläch- endiffusion beeinflußt wird. In d. Arbeit wurde zum ersten Mal an Kupferleitbahnen d. Entstehung von eit- bahnschädigungen im Zusammenhang mit dem vorher aufgenomme- nen Gefüge im Rasterelektronenmikroskop direkt beobachtet u. mit d. Korngrenzen u. d. Korngrenzwinkeln in Zusammenhang gebracht. Die Ergebnisse d. Arbeit zeigen, daß Schädigungen durch Elektromigration in Kupferleitbahnen vorw. durch Gefügeinhomogenitäten entstehen. Bei d. Prozeß sind Großwinkelkorngrenzen d. bevorzugte Diffusionspfad.