Electrodeposition of copper using additive-containing low metal ion concentration electrolytes for EnFACE applications

In the past decade a new electrodeposition process called Electrochemical nano and micro Fabrication by flow and Chemistry (EnFACE) was developed which enabled mask-less pattern transfers onto a metallic substrate. EnFACE uses a novel acid-free, additive-free plating electrolyte containing low concentrations of metal salts (0.1 MCuSO4), as the process requires electroplating under conditions of fast kinetics and low electrolyte conductivity. However, for electronic applications,industry requires the use of additives, which improve deposit properties such as thickness uniformity, strength, ductility, and conductivity. The use of pulsed current is also known to improve deposit properties such as grain structure, mechanical strength and throwing power. Therefore, in order to use EnFACE for fabrication of industrially useful products, the effect of additives on the electrochemical behaviour and deposit properties of this process needs to be assessed. In addition, the influence of current modulation; i.e. direct current vs pulsed current, on deposit properties also warrants investigation. Potentiodynamic polarisation experiments were performed on additive-free and additive-containing EnFACE electrolyte (0.1 M CuSO₄). The additives tested were Copper Gleam A, Copper Gleam B, and chloride ions (Cl⁻). The effect of two parameters: (i) additive type and (ii) additive concentration, on cathode polarisation were studied.Copper films were electroplated on stainless steel substrates from electrolytes containing different concentrations of plating additives (0%, 17%, 33%, 50%, 100%,200% of the industry recommended additive concentration). Both direct current (DC)ABSTRACT|ii and pulsed current (PC) plating were used. The deposit was characterised using scanning electron microscope (SEM), electron back scattered diffraction (EBSD),tensile test machine (UTM), four-point probe and X-ray diffraction (XRD).Cathode polarisation occurred when the additives were used individually. Thecombination of Copper Gleam B and Cl- suggested synergistic inhibition, particularly in the diffusion-limited region. The addition of Copper Gleam A to the CopperGleam B-Cl⁻ mix increased the limiting current and suggested plating acceleration.These effects are interpreted in terms of the adsorption-desorption behavior of the additives on the cathode surface. SEM and EBSD images indicated that additives caused a concentration dependent decrease in the grain size of the deposit in both the DC and PC plated deposit. This grain refinement resulted in an increase in yield and tensile strength,but reduced the ductility and resistivity of deposits. The PC-plated copper from theEnFACE electrolytes generally possessed better mechanical properties than its DC-plated counterparts, though both plating modes created copper films that can meet industry standards. The optimum additive concentration for the EnFACE electrolyte was 50% of the recommended value when using DC plating; while the optimum was only 33% when using PC plating.In the past decade a new electrodeposition process called Electrochemical nano and micro Fabrication by flow and Chemistry (EnFACE) was developed which enabled mask-less pattern transfers onto a metallic substrate. EnFACE uses a novel acid-free, additive-free plating electrolyte containing low concentrations of metal salts (0.1 MCuSO4), as the process requires electroplating under conditions of fast kinetics and low electrolyte conductivity. However, for electronic applications,industry requires the use of additives, which improve deposit properties such as thickness uniformity, strength, ductility, and conductivity. The use of pulsed current is also known to improve deposit properties such as grain structure, mechanical strength and throwing power. Therefore, in order to use EnFACE for fabrication of industrially useful products, the effect of additives on the electrochemical behaviour and deposit properties of this process needs to be assessed. In addition, the influence of current modulation; i.e. direct current vs pulsed current, on deposit properties also warrants investigation. Potentiodynamic polarisation experiments were performed on additive-free and additive-containing EnFACE electrolyte (0.1 M CuSO₄). The additives tested were Copper Gleam A, Copper Gleam B, and chloride ions (Cl⁻). The effect of two parameters: (i) additive type and (ii) additive concentration, on cathode polarisation were studied.Copper films were electroplated on stainless steel substrates from electrolytes containing different concentrations of plating additives (0%, 17%, 33%, 50%, 100%,200% of the industry recommended additive concentration). Both direct current (DC)ABSTRACT|ii and pulsed current (PC) plating were used. The deposit was characterised using scanning electron microscope (SEM), electron back scattered diffraction (EBSD),tensile test machine (UTM), four-point probe and X-ray diffraction (XRD).Cathode polarisation occurred when the additives were used individually. Thecombination of Copper Gleam B and Cl- suggested synergistic inhibition, particularly in the diffusion-limited region. The addition of Copper Gleam A to the CopperGleam B-Cl⁻ mix increased the limiting current and suggested plating acceleration.These effects are interpreted in terms of the adsorption-desorption behavior of the additives on the cathode surface. SEM and EBSD images indicated that additives caused a concentration dependent decrease in the grain size of the deposit in both the DC and PC plated deposit. This grain refinement resulted in an increase in yield and tensile strength,but reduced the ductility and resistivity of deposits. The PC-plated copper from theEnFACE electrolytes generally possessed better mechanical properties than its DC-plated counterparts, though both plating modes created copper films that can meet industry standards. The optimum additive concentration for the EnFACE electrolyte was 50% of the recommended value when using DC plating; while the optimum was only 33% when using PC plating

Über die Entwicklung von Memsensoren

Since the postulation of the experimental realization of memristive devices in 2008, a broad variety of concepts for the fabrication of memristive devices has been pursued and the underlying switching mechanisms have been studied in detail. The unique electronic properties of memristive devices inspire applications that go beyond conventional electronics, such as using memristive devices as programmable interconnects, to realize logics for in-array-computing or in neuromorphic engineering. A particularly interesting aspect of biological neural networks is the close connection between signal detection and processing at the neuron level, which is an essential contribution to their outstanding efficiency. This work evolves around the concept of memsensors, which unify the characteristic features of memristive devices and sensor devices and as such appear as promising candidates to realize a close connection between signal detection and processing on the device level. Memsensors are a highly interdisciplinary topic, bridging research in the fields of material science and electrical engineering and relating to insights from biology and medicine through neuromorphic engineering. The major objective of this thesis is to provide tools and building blocks and showcase pathways to incorporate memristive and sensitive properties into memsensor devices. For this purpose, motivated by an experimental point of view, a nanoparticle-based memristive device with diffusive memristive switching characteristics was developed and characterised in detail and sensors relying on semiconducting metal oxide thin films and nanostructures were thoroughly studied. In addition, in terms of modelling of memsensor circuits, emerging features such as amplitude adaptation are discussed, showcasing the particular eligibility of memsensors in the context of neuromorphic engineering

Defect-Rich Size-Selected Nanoclusters and Nanocrystalline Films of Titanium (IV) Oxide and Tantalum (IV) Oxide for Efficient Photocatalyst and Electroforming-Free Memristor Applications

Transition metal oxides, TiO2 and Ta2O5, are two of the most extensively studied wide bandgap semiconductor materials (with high work functions). Due to their suitable band edge positions for hydrogen evolution and exceptional stability against photocorrosion upon optical excitation, their application in heterogeneous photocatalysis has attracted a lot of attention. These oxides are also great components in the field of electronic devices such as field effect transistors, solar cells, and more recently advanced memory devices. Here, we focus on ultrasmall nanoclusters (< 5 nm) and nanocrystalline thin films of defect-rich TiO2 and Ta2O5 and their applications as high-performance photocatalysts in photoelectrochemical water splitting reactions and as resistive switching materials in memory applications. The present work is divided into two main parts. In the first part, ultrasmall nanoclusters (below 10 nm) of defect-rich TiO2 and Ta2O5 are synthesized using a gas phase aggregation technique in a nanocluster generation source based on DC magnetron sputtering. With a careful optimization of the deposition parameters such as aggregation zone length (condensation volume), Ar gas flow rate, deposition temperature and source power, we are able to produce metal/metal oxide nanoclusters with a narrow size distribution. As most of these as-grown nanoclusters are negatively charged, it is possible to conduct size-selection according to their mass-to-charge ratio. Using a quadrupole mass filter (directly coupled to the magnetron source), we achieve precise size-selection of nanoclusters, with the size distribution reduced to below 2% mass resolution. The nearly monosized nanoclusters so produced are deposited onto appropriate substrates to serve as the photoanodes for photoelectrochemical water splitting application. We demonstrate, for the first time, that the precisely size-selected TiO2 nanoclusters can be deposited on H-terminated Si(001) in a soft-landing condition and they can be used as highperformance photocatalysts for solar harvesting, with greater enhancement in the photoconversion efficiency. Three different sizes of TiO2 nanoclusters (4, 6 and 8 nm) are synthesized with appropriate combinations of aggregation length and Ar flow rate. Despite the low amount of material loading (of ~20% of substrate coverage), these supported TiO2 nanoclusters exhibit remarkable photocatalytic activities during photoelectrochemical water splitting reaction under simulated sunlight (50 mW/cm^2). Higher photocurrent densities (up to 0.8 mA/cm^2) and photoconversion efficiencies (up to 1%) with decreasing nanocluster size (at the applied voltage of –0.22 V vs Ag/AgCl) are observed. We attribute this enhancement to the presence of surface defects, providing a large amount of active surface sites, in the amorphous TiO2 nanoclusters as-grown at room temperature. We have further shown that the incorporation of metallic nanoclusters with the semiconductor photocatalysts can enhance the photoconversion efficiency. In this work, we have co-deposited surface oxygen deficient Ta2O5 or TaOx nanoclusters along with Pt nanoclusters of similar nanocluster size (~5 nm), the latter used as a promoter. The electron-hole pairs generated in the water splitting reaction can be effectively separated and stored with the presence of Pt nanoclusters, while the increase in Pt loading as a promoter can enhance the reaction by providing a large number of electrons for H2 evolution. However, loading too much Pt nanoclusters could actually reduce the photoresponse, which is due to blocking of photosensitive TaOx surface by excess Pt nanoclusters. In both cases, the photoconversion efficiency could potentially be enhanced at least 5 times by increasing the amount of nanocluster loading from 20% coverage to a monolayer coverage (e.g., by increasing the amount of deposition time for TiO2 and TaOx nanoclusters). Even higher photoconversion efficiency can be obtained with multiple layers of nanoclusters and by employing nanoclusters with even smaller size and/or with modification by chemical functionalization. These potential improvements could dramatically increase the photoconversion efficiency, making these nanocluster samples to be among the top photoelectrochemical catalysis performers. In the second part of the present work, we employ defect-rich nanocrystalline TiOx and TaOx thin films as active materials for resistive switching for memory application. Based on resistive switching principle, memristive devices (or memristors) provide the unique capability of multistep information storage. The development of memristors has often been hailed as the next evolution in non-volatile memories, low-power remote sensing, and adaptive intelligent prototypes including neuromorphic and biological systems. One major obstacle in achieving high switching performance is the irreversible electroforming step that is required to create oxygen vacancies for resistive switching. Using magnetron sputtering film deposition technique, we have fabricated the heterojunction memristor devices based on nanocrystalline TiOx and TaOx thin films (10-60 nm thick) with a high density of built-in oxygen vacancies, sandwiched between a pair of metallic Pt electrodes (30 nm thick). To avoid the destructive electroforming process and to achieve a high switching performance in the memristor device, we carefully manipulate the chamber pressure and ambient in deposition chamber during deposition to generate the required highly oxygen deficient semiconducting films. The films, as-deposited at room temperature, exhibit a crystallite size of 4-5 nm. In the fabricated Pt/TiOx/Pt memristors, a high electric field gradient can be generated in the TiOx film at a much lower electroforming voltage of +1.5 V, due in part to the nanocrystalline nature, which causes localization of this electric field and consequently enhanced reproducibility and repeatability in the device performance. After the first switching, consecutive 250 switching cycles can be achieved with a low programing voltage of ±1.0 V, along with a high ON/OFF current ratio, and long retention (up to 10^5 s). We further improve this TiOx memristor device by totally removing the electroforming step by fabricating an electroforming-free memristive device based on a heterojunction interface of TiOx and TaOx layers. In the Pt/TiOx/TaOx/Pt architecture structure (with Pt serving as the top and bottom electrodes), a high-κ dielectric TaOx layer is used to facilitate trapping and release of the electronic carriers, while a TiOx layer provides low-bias rectification as an additional oxygen vacancy source. With the incorporation of TaOx layer, the need for the electroforming step can be eliminated. More importantly, the resistance states of the device can be tuned such that switching between the high resistance state and the low resistance state can be achieved even smaller programming voltage of +0.8 V. With the low leakage current properties of TaOx, the high endurance (10^4 repeated cycles) and high retention capabilities (up to 10^8 s) can be enhanced manifold with highly stable ON/OFF current ratio. In both memristor devices, four different junction sizes (5×5, 10×10, 20×20 and 50×50 μm^2) have been evaluated according to their ON/OFF current ratio. We observe that the smaller is the junction size is, the higher is the current ratio. For the Pt/TiOx/TaOx/Pt memristor, we have also analyzed the thickness dependent effect of the switching behavior of devices with four different TaOx layer thicknesses (10, 20, 40 and 60 nm) and a TiOx layer thickness constant at 10 nm. The device with 10 nm thick TaOx (being amorphous in nature) shows unipolar switching with two SETs and two RESETs in one sweep cycle. This is in contrast to the bipolar resistive switching found in devices with the thicker TaOx films with a SET in the positive sweep and a RESET during the negative sweep. We further demonstrate that resistive switching can also occur at very low programming voltage (~50 mV), thus qualifying it as an ultralow power consumption device (~nW). The stable non-volatile bipolar switching characteristics with high ON/OFF current ratio and low power consumption make our devices best suitable for various analog and discrete programmable electric pulses. With the simplicity in the construction, the performance achieved for our memristors represents the best reported to date. This new class of defect-rich metal oxides nanomaterials with an ultrananocrystalline nature shows solid promises for various catalytic and electronic applications and, also, the simple, scalable roomtemperature device fabrication process makes this approach easily migratable further to transparent and/or flexible devices

Defect-Rich Size-Selected Nanoclusters and Nanocrystalline Films of Titanium (IV) Oxide and Tantalum (IV) Oxide for Efficient Photocatalyst and Electroforming-Free Memristor Applications

Transition metal oxides, TiO2 and Ta2O5, are two of the most extensively studied wide bandgap semiconductor materials (with high work functions). Due to their suitable band edge positions for hydrogen evolution and exceptional stability against photocorrosion upon optical excitation, their application in heterogeneous photocatalysis has attracted a lot of attention. These oxides are also great components in the field of electronic devices such as field effect transistors, solar cells, and more recently advanced memory devices. Here, we focus on ultrasmall nanoclusters (< 5 nm) and nanocrystalline thin films of defect-rich TiO2 and Ta2O5 and their applications as high-performance photocatalysts in photoelectrochemical water splitting reactions and as resistive switching materials in memory applications. The present work is divided into two main parts. In the first part, ultrasmall nanoclusters (below 10 nm) of defect-rich TiO2 and Ta2O5 are synthesized using a gas phase aggregation technique in a nanocluster generation source based on DC magnetron sputtering. With a careful optimization of the deposition parameters such as aggregation zone length (condensation volume), Ar gas flow rate, deposition temperature and source power, we are able to produce metal/metal oxide nanoclusters with a narrow size distribution. As most of these as-grown nanoclusters are negatively charged, it is possible to conduct size-selection according to their mass-to-charge ratio. Using a quadrupole mass filter (directly coupled to the magnetron source), we achieve precise size-selection of nanoclusters, with the size distribution reduced to below 2% mass resolution. The nearly monosized nanoclusters so produced are deposited onto appropriate substrates to serve as the photoanodes for photoelectrochemical water splitting application. We demonstrate, for the first time, that the precisely size-selected TiO2 nanoclusters can be deposited on H-terminated Si(001) in a soft-landing condition and they can be used as highperformance photocatalysts for solar harvesting, with greater enhancement in the photoconversion efficiency. Three different sizes of TiO2 nanoclusters (4, 6 and 8 nm) are synthesized with appropriate combinations of aggregation length and Ar flow rate. Despite the low amount of material loading (of ~20% of substrate coverage), these supported TiO2 nanoclusters exhibit remarkable photocatalytic activities during photoelectrochemical water splitting reaction under simulated sunlight (50 mW/cm^2). Higher photocurrent densities (up to 0.8 mA/cm^2) and photoconversion efficiencies (up to 1%) with decreasing nanocluster size (at the applied voltage of –0.22 V vs Ag/AgCl) are observed. We attribute this enhancement to the presence of surface defects, providing a large amount of active surface sites, in the amorphous TiO2 nanoclusters as-grown at room temperature. We have further shown that the incorporation of metallic nanoclusters with the semiconductor photocatalysts can enhance the photoconversion efficiency. In this work, we have co-deposited surface oxygen deficient Ta2O5 or TaOx nanoclusters along with Pt nanoclusters of similar nanocluster size (~5 nm), the latter used as a promoter. The electron-hole pairs generated in the water splitting reaction can be effectively separated and stored with the presence of Pt nanoclusters, while the increase in Pt loading as a promoter can enhance the reaction by providing a large number of electrons for H2 evolution. However, loading too much Pt nanoclusters could actually reduce the photoresponse, which is due to blocking of photosensitive TaOx surface by excess Pt nanoclusters. In both cases, the photoconversion efficiency could potentially be enhanced at least 5 times by increasing the amount of nanocluster loading from 20% coverage to a monolayer coverage (e.g., by increasing the amount of deposition time for TiO2 and TaOx nanoclusters). Even higher photoconversion efficiency can be obtained with multiple layers of nanoclusters and by employing nanoclusters with even smaller size and/or with modification by chemical functionalization. These potential improvements could dramatically increase the photoconversion efficiency, making these nanocluster samples to be among the top photoelectrochemical catalysis performers. In the second part of the present work, we employ defect-rich nanocrystalline TiOx and TaOx thin films as active materials for resistive switching for memory application. Based on resistive switching principle, memristive devices (or memristors) provide the unique capability of multistep information storage. The development of memristors has often been hailed as the next evolution in non-volatile memories, low-power remote sensing, and adaptive intelligent prototypes including neuromorphic and biological systems. One major obstacle in achieving high switching performance is the irreversible electroforming step that is required to create oxygen vacancies for resistive switching. Using magnetron sputtering film deposition technique, we have fabricated the heterojunction memristor devices based on nanocrystalline TiOx and TaOx thin films (10-60 nm thick) with a high density of built-in oxygen vacancies, sandwiched between a pair of metallic Pt electrodes (30 nm thick). To avoid the destructive electroforming process and to achieve a high switching performance in the memristor device, we carefully manipulate the chamber pressure and ambient in deposition chamber during deposition to generate the required highly oxygen deficient semiconducting films. The films, as-deposited at room temperature, exhibit a crystallite size of 4-5 nm. In the fabricated Pt/TiOx/Pt memristors, a high electric field gradient can be generated in the TiOx film at a much lower electroforming voltage of +1.5 V, due in part to the nanocrystalline nature, which causes localization of this electric field and consequently enhanced reproducibility and repeatability in the device performance. After the first switching, consecutive 250 switching cycles can be achieved with a low programing voltage of ±1.0 V, along with a high ON/OFF current ratio, and long retention (up to 10^5 s). We further improve this TiOx memristor device by totally removing the electroforming step by fabricating an electroforming-free memristive device based on a heterojunction interface of TiOx and TaOx layers. In the Pt/TiOx/TaOx/Pt architecture structure (with Pt serving as the top and bottom electrodes), a high-κ dielectric TaOx layer is used to facilitate trapping and release of the electronic carriers, while a TiOx layer provides low-bias rectification as an additional oxygen vacancy source. With the incorporation of TaOx layer, the need for the electroforming step can be eliminated. More importantly, the resistance states of the device can be tuned such that switching between the high resistance state and the low resistance state can be achieved even smaller programming voltage of +0.8 V. With the low leakage current properties of TaOx, the high endurance (10^4 repeated cycles) and high retention capabilities (up to 10^8 s) can be enhanced manifold with highly stable ON/OFF current ratio. In both memristor devices, four different junction sizes (5×5, 10×10, 20×20 and 50×50 μm^2) have been evaluated according to their ON/OFF current ratio. We observe that the smaller is the junction size is, the higher is the current ratio. For the Pt/TiOx/TaOx/Pt memristor, we have also analyzed the thickness dependent effect of the switching behavior of devices with four different TaOx layer thicknesses (10, 20, 40 and 60 nm) and a TiOx layer thickness constant at 10 nm. The device with 10 nm thick TaOx (being amorphous in nature) shows unipolar switching with two SETs and two RESETs in one sweep cycle. This is in contrast to the bipolar resistive switching found in devices with the thicker TaOx films with a SET in the positive sweep and a RESET during the negative sweep. We further demonstrate that resistive switching can also occur at very low programming voltage (~50 mV), thus qualifying it as an ultralow power consumption device (~nW). The stable non-volatile bipolar switching characteristics with high ON/OFF current ratio and low power consumption make our devices best suitable for various analog and discrete programmable electric pulses. With the simplicity in the construction, the performance achieved for our memristors represents the best reported to date. This new class of defect-rich metal oxides nanomaterials with an ultrananocrystalline nature shows solid promises for various catalytic and electronic applications and, also, the simple, scalable roomtemperature device fabrication process makes this approach easily migratable further to transparent and/or flexible devices

Nanocharacterisation of zirconia based RRAM devices deposited via PLD

With CMOS technology reaching fundamental scaling limitations, innovative data storage technologies have been a topic of great academic and industrial interest. Emerging technologies, not all based in semiconductors, that exploit new variables like spin, polarisation, phase and resistance, are being investigated for their feasibility as data storage devices. One very promising technology is resistive switching random-access memory (RRAM). In RRAM devices memory operation relies on the change in resistance of a metal-insulator-metal structure, typically induced by ion migration combined with redox processes. Here, RRAM devices based on amorphous and crystalline zirconia have been prepared by means of pulsed laser deposition (PLD). The thesis starts with an overview of the commissioning of a new PLD system, with a focus on characterisation of the laser ablation plume, reduction of the density of “droplets” and development of the optimal system parameters, like temperature, oxygen pressure and laser fluence, for the preparation of zirconia based RRAM devices. For both amorphous and crystalline devices, titanium was used as an active electrode as it promotes the introduction of oxygen vacancies which are responsible for inducing resistive switching. In addition, growth of epitaxial Nb doped strontium titanate (Nb:STO) via PLD was achieved, as the high temperatures used during growth hinder the use of metallic bottom electrodes. Both types of RRAM devices have good performance figures, with ON/OFF ratios of 1000 and 10000 and endurance of more than 10000 cycles. Conduction mechanisms point to two different types of resistive switching: insulator-to-metal transition and trapping and de-trapping at the metal-oxide interfaces. Surprisingly, both conduction mechanisms were found to coexists on amorphous devices. Scanning transmission electron microscopy and electron energy loss spectroscopy were used to investigate how interfaces can influence resistive switching. Results indicate that titanium, in addition to introducing oxygen vacancies, creates an ohmic interface with zirconia which forces the resistive switching to take place on the inert metal-oxide Schottky interface, which was not described so far

Indium-Gallium-Zinc Oxide Thin-Film Transistors for Active-Matrix Flat-Panel Displays

Amorphous oxide semiconductors (AOSs) including amorphous InGaZnO (a-IGZO) areexpected to be used as the thin-film semiconducting materials for TFTs in the next-generation ultra-high definition (UHD) active-matrix flat-panel displays (AM-FPDs). a-IGZO TFTs satisfy almost all the requirements for organic light-emitting-diode displays (OLEDs), large and fast liquid crystal displays (LCDs) as well as three-dimensional (3D) displays, which cannot be satisfied using conventional amorphous silicon (a-Si) or polysilicon (poly-Si) TFTs. In particular, a-IGZO TFTs satisfy two significant requirements of the backplane technology: high field-effect mobility and large-area uniformity.In this work, a robust process for fabrication of bottom-gate and top-gate a-IGZO TFTs is presented. An analytical drain current model for a-IGZO TFTs is proposed and its validation is demonstrated through experimental results. The instability mechanisms in a-IGZO TFTs under high current stress is investigated through low-frequency noise measurements. For the first time, the effect of engineered glass surface on the performance and reliability of bottom-gate a-IGZO TFTs is reported. The effect of source and drain metal contacts on electrical properties of a-IGZO TFTs including their effective channel lengths is studied. In particular, a-IGZO TFTs with Molybdenum versus Titanium source and drain electrodes are investigated. Finally, the potential of aluminum substrates for use in flexible display applications is demonstrated by fabrication of high performance a-IGZO TFTs on aluminum substrates and investigation of their stability under high current electrical stress as well as tensile and compressive strain

Cu(Ag)-Legierungsschichten als Werkstoff für Leiterbahnen höchstintegrierter Schaltkreise: Herstellung, Gefüge, thermomechanische Eigenschaften, Elektromigrationsresistenz

Die vorliegende Arbeit verfolgt das Ziel, Cu(Ag)-Dünnschichten als potentiellen Werkstoff für Leiterbahnen in der Mikroelektronik zu untersuchen. Für die Beurteilung dieses Materialsystems wurden vier Schwerpunkte bezüglich der Schichtcharakterisierung definiert: Herstellung, Gefüge, thermomechanische Eigenschaften, Elektromigrationsresistenz. Grundlage sämtlicher Untersuchungen ist eine geeignete Probenpräparation. In Anlehnung an Technologien, die zur Zeit bei der Herstellung von reinen Cu-Leiterbahnen Anwendung finden, erfolgte die Beschichtung der Cu(Ag)-Schichten (Dicke bis 1 µm) galvanisch aus einem schwefelsauren Elektrolyten unter Additiveinsatz auf thermisch oxidierten Siliziumwafern. Hierbei war nicht nur die Abscheidung von ganzflächigen Dünnschichten, sondern auch die Beschichtung auf strukturierte Substrate von Interesse. Die erzeugten Schichtproben werden in ihren Gefügeeigenschaften, vergleichend zu reinen Kupferschichten, charakterisiert. Hierzu zählen Korngrößen und -orientierungen, thermisches Gefügeverhalten, Einbau, Verteilung und Segregation von Silber und Fremdstoffen sowie die elektrischen Eigenschaften. Von grundsätzlicher Bedeutung für das Elektromigrationsverhalten und damit für die Zuverlässigkeit und das Leistungsvermögen sind die thermomechanischen Eigenschaften. Diese werden an ausgedehnten Schichten mit der Substratkrümmungsmessung bis zu Temperaturen von 500°C beschrieben. Die Diskussion des mechanischen Schichtverhaltens umfasst sowohl thermische als auch temporale Charakteristika. Die Untersuchungen geben einen Einblick in die wirkenden Mechanismen des Stofftransports und des Spannungsabbaus. Den Abschluss der Arbeit stellen erste Experimente zum Elektromigrationsverhalten der Cu(Ag)-Dünnschichten dar. Den Kern dieser Analysen bilden Messungen an sog. Blech-Strukturen (Materialdriftexperimente). Hierbei werden geeignete Technologien für die mikrotechnologische Herstellung von derartigen Cu(Ag)-Strukturen vorgestellt. Anhand erster Messungen wird das Elektromigrationsverhalten von Cu(Ag)-Metallisierungen in seinen Grundcharakteristika beschrieben