La fabrication de guides d’ondes à partir d’un matériau composite CFRP isolant, nécessite de rendre la surface interne conductrice électriquement. Cela peut s’effectuer par métallisation, mais des verrous technologiques apparaissent en raison de la géométrie complexe associée à une surface inerte. Le CFRP est composé d’époxy dont la température de transition vitreuse est de 216 °C, ce qui limite le choix des techniques de métallisation. De plus, l’énergie de surface du polymère qui compose la surface du CFRP est plutôt faible (20-40 mJ/m2) et non polaire, ce qui conduit à une adhérence faible des revêtements métalliques. Le procédé DLI-MOCVD est utilisé pour le dépôt du revêtement métallique car il combine un contrôle rigoureux des débits de réactifs, des vitesses de croissance élevées et il est adapté pour revêtir des substrats tridimensionnels. Le choix du métal (le cuivre) est basé sur un savoir-faire antérieur de l’équipe de recherche, pour la possibilité de le déposer à une température bien inférieure à 216 °C, et bien entendu pour son excellente conductivité électrique et sa résistance au vieillissement ambient. Le film de Cu est élaboré à partir du précurseur organométallique (hfac)Cu(MHY), développé par P. Doppelt au CNRS. Ce précurseur qui se présente sous forme liquide à Tambiante, est dilué dans de l’octane anhydre pour pouvoir être injecté par le système DLI. Après avoir implémenté un réacteur dédié au travaux de la thèse, une étude de cinétique chimique du dépôt à partir du précurseur a permis de définir les conditions expérimentales optimales ; notamment la température de dépôt fixée à 195 °C. Les revêtements obtenus sont partiellement couvrants et sont conducteurs. Leur adhérence avec le substrat est nulle. Par conséquent, on sélectionne puis on teste différents prétraitements du substrat afin de modifier la morphologie et la réactivité de la surface CFRP. On montre à travers six prétraitements que la formation de rugosité de surface favorisant l'ancrage mécanique est un caractère prépondérant pour l’amélioration de l’adhérence, par rapport à la modification chimique. Les deux prétraitements les plus performants sont le traitement par voie humide CircupositTM et le traitement in situ à l’O3 A ce stade, les films sont conducteurs et adhérents mais ils ne mouillent pas intégralement la surface du composite lors du dépôt. On démontre alors que l’injection d’un précurseur de cobalt (Co2(CO)5) en alternance avec le dépôt de Cu permet d’obtenir un revêtement de cuivre métallique, pur à plus de 98 %, couvrant, conducteur et adhérent. A ce stade, le rôle du précurseur de Co n’est pas clairement établi. Néanmoins, les études préliminaires d’industrialisation du procédé consistant à améliorer les rendements et vitesses de croissance sont entreprises. Notamment, les coûts sont abaissés en remplaçant le solvant octane. Avec ce solvant, le dépôt de Cu est adhérent sans prétraitement préalable de la surface du substrat. A noter que le précurseur de Co est toujours nécessaire pour assurer une couverture complète de la surface CFRP. C’est dans ces conditions de dépôt, et après quelques ajustements paramétriques que les premiers guides d’ondes de 60 mm sont revêtus. Les résultats des tests de cyclage thermique étant positifs, la longueur des guides d’ondes à revêtir est augmentée à 300 mm, dimension minimale pour pouvoir effectuer des tests de transmission des ondes radiofréquences : la propriété finale. Cette modification géométrique requière une phase d’optimisation plus complexe afin de garantir l’uniformité en épaisseur et en propriétés électriques sur toute la longueur. Les guides d’ondes de 300 mm métallisés passent les cyclages thermiques avec succès. Les tests radiofréquences indiquent un taux de transmission des ondes < 30 dB, ce qui est tout à fait acceptable d’un point de vue applicatif. En revanche, les pertes sont importantes en comparaison avec l’existant, mais de nombreuses pistes d’améliorations sont proposées. / The manufacturing of waveguides from insulating C fibers reinforced polymer composites necessitates to render internal surfaces electrically conductive. This can be achieved by metallization but technological bottlenecks arise due to the complex geometry and the chemical inertia of the surface. The CFRP matrix is composed of RTM6 epoxy whose glass-transition temperature equals 216 °C, limiting the choice of metallization techniques. Additionally, the surface energy of the polymer (constituting the surface of the CFRP) is low (20-40 mJ/m2) and non-polar, i.e. a poor adherence is expected for metallic coatings. A DLI-MOCVD process is used to form the metallic coating because it combines a good control of reactive fluxes, high deposition rates, and because it is relevant for the coating of three-dimensional substrates. The choice of the metal (Cu) is dictated by the anterior know-how of the research group, by the possibility to deposit at a temperature well below 216 °C, and because Cu shows an excellent electrical conductivity and a good resistance to ambient ageing. The Cu film is formed from the organometallic precursor (hfac)Cu(MHY), developed par P. Doppelt at CNRS (Paris). The precursor is diluted in anhydrous octane to make it injectable by DLI. After the mounting and implementation of the DLI-MOCVD reactor dedicated to the PhD work, a study of the chemical kinetics of the deposition from this precursor helped in the definition of the optimal conditions; noticeably the deposition temperature fixed at 195 °C. The coatings are partially covering and interfacial adherence is poor, but they are conductive. Consecutively, we identify, develop and test several pretreatments in order to modify the topography and reactivity of the CFRP surface. Based on 6 recipes, we show that mechanical anchorage is preponderant over the chemical reactivity to improve the adherence. The two best pretreatments are the solution chemistry treatment CircupositTM, and the in situ treatment with O3. At this stage of the work, Cu films are conductive and adherent but they do not wet the entire composite surface, even after long deposition duration. We then demonstrate that the injection of a Co precursor (Co2(CO)5) alternating with the Cu deposition leads to the formation of a pure metallic Cu film (> 98%) which is covering, conductive and adherent. The role of the Co precursor is not yet established. Nevertheless, we start the preliminary process industrialization studies consisting in the improvement of the growth rate and the yield. Noticeably, costs are decreased by replacing the octane solvent. With it, the Cu coating is adherent without any pretreatment of the substrate surface! The Co precursor is still necessary to ensure the proper covering of the entire surface, though. In these conditions, and after adjustments of some parameters, the first 60 mmlong waveguides are coated. The thermal cycling resistance is excellent. Therefore, waveguides length is increased to 300 mm, the minimum dimension for the radiofrequency transmission tests (final property) to be correct. The increase of length causes a complex adaptation of the process in order to guarantee the deposition of a uniform coating over the length, in terms of thickness and electrical properties. Radiofrequency tests result in a stationary waves rate < 30 dB, which is acceptable at the industrial level. Yet, losses are too important in comparison with current waveguides, but many proposals are formulated to improve our solution.

Abstract The demands toward the development of simple and cost-effective fabrication methods of metallic structures with high lateral resolution on different substrates - applied in many fields of technology, such as in microelectronics, optoelectronics, micromechanics as well as in sensor and actuator applications - gave the idea to perform this research. Due to its simplicity, laser-assisted chemical liquid-phase deposition (LCLD) has been investigated and applied for the metallization of surfaces having practical importance (Si, GaAs, SiO2, Si3N4, etc.) since the beginning of the 80s. By the invention of novel substrates (polyimide, porous silicon), it was adequate to work out new precursors or just adopt old ones and optimise LCLD in order to fabricate metallic micro-patterns upon these materials for various purposes. According to the motivations mentioned above, LCLD was utilized for the fabrication of palladium (Pd) micro-patterns on polyimide (PI), polyimide/copper flexible printed circuit boards (PCBs), fused silica (SiO2) and silicon (Si). The selective metallization of porous silicon (PS) has been carried out with nickel (Ni). Depending on the types of lasers, either the focusing (Ar+ laser beam) or diaphragm projection (KrF and XeCl excimer laser pulses) method was employed. In the course of the work, various precursors of the corresponding metals have been investigated and utilized. In the beginning, the pyrolytic decomposition of palladium-amine complex ions ([Pd(NH3)4]2+) on PI by a scanned and focused Ar+ laser beam was optimised and discussed. Thick (up to several micrometers) and narrow (~ 10 μm) Pd conductor lines with electrical conductivity close to that of the bulk were obtained. In the continuation of these investigations, the precursor was developed further. [Pd(NH3)4]2+ was mixed with the solution of formaldehyde (HCOH) in order to induce the reduction of the metal complex ions. To our knowledge, we were the first - so far - who applied this solution and described the reaction. With the proper choice of the laser parameters, thin Pd films as catalyst layers for electroless copper plating were deposited utilizing Ar+ and excimer lasers as well. The chemically plated copper deposits - upon the obtained Pd film - have excellent electrical and good mechanical properties. In the second part of the thesis, three practical applications (metallization of via holes drilled in PI/Cu flexible PCBs, end-mirror fabrication on single-mode optical fibers, and carbon nanotube growth on Pd activated Si and Si/SiO2 substrates) of Pd LCLD were realized. The previously presented [Pd(NH3)4]2+ and [Pd(NH3)4]2+/HCOH precursors were employed for creating the catalyst Pd layers for the carbon nanotube chemical vapor-phase deposition and for the autocatalytic electroless chemical copper plating, respectively. Finally, a simple novel method was introduced for the area-selective metallization of PS. Since the surface of PS reduces spontaneously most metals from their aqueous solutions, it is difficult to realize localized metal deposition from liquid-phase precursors on it. We proposed the application of a stable Ni plating bath from which the metal deposits only when the PS is irradiated with photons having wavelength shorter than 689 nm, thus making possible an area-selective laser-assisted metal deposition. The deposited metal structures and patterns were analysed by field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectrometer (EDS), by the milling and imaging modes of a focused ion beam system (FIB), optical microscopy, profilometry, resistance, and by reflectance measurements.

No description available.

abstract: Neural interfacing applications have advanced in complexity, with needs for increasingly high degrees of freedom in prosthetic device control, sharper discrimination in sensory percepts in bidirectional interfaces, and more precise localization of functional connectivity in the brain. As such, there is a growing need for reliable neurophysiological recordings at a fine spatial scale matching that of cortical columnar processing. Penetrating microelectrodes provide localization sufficient to isolate action potential (AP) waveforms, but often suffer from recorded signal deterioration linked to foreign body response. Micro-Electrocorticography (μECoG) surface electrodes elicit lower foreign body response and show greater chronic stability of recorded signals, though they typically lack the signal localization necessary to isolate individual APs. This dissertation validates the recording capacity of a novel, flexible, large area μECoG array with bilayer routing in a feline implant, and explores the ability of conventional μECoG arrays to detect features of neuronal activity in a very high frequency band associated with AP waveforms. Recordings from both layers of the flexible μECoG array showed frequency features typical of cortical local field potentials (LFP) and were shown to be stable in amplitude over time. Recordings from both layers also showed consistent, frequency-dependent modulation after induction of general anesthesia, with large increases in beta and gamma band and decreases in theta band observed over three experiments. Recordings from conventional μECoG arrays over human cortex showed robust modulation in a high frequency (250-2000 Hz) band upon production of spoken words. Modulation in this band was used to predict spoken words with over 90% accuracy. Basal Ganglia neuronal AP firing was also shown to significantly correlate with various cortical μECoG recordings in this frequency band. Results indicate that μECoG surface electrodes may detect high frequency neuronal activity potentially associated with AP firing, a source of information previously unutilized by these devices. / Dissertation/Thesis / Doctoral Dissertation Biomedical Engineering 2018

This work examines the deposition of metallic and semiconductor elements onto self-assembled DNA templates for the fabrication of nanodevices. Biological molecules like DNA can self-assemble into a variety of complex 2-D and 3-D architectures without the need for expensive patterning tools. In addition, self-assembled DNA templates can be designed to controllably place functional nanomaterials with molecular precision. These characteristics make DNA an attractive template for fabricating electronic circuits from biological molecules. However, electrically conductive structures are required for electronic applications. While metallized DNA nanostructures have been demonstrated, the ability to make thin, continuous wires that are electrically conductive still represents a formidable challenge. DNA-templated wires have generally been granular in appearance with a resistivity approximately two to three orders of magnitude higher than that of the bulk material. An improved method for the metallization of DNA origami is examined in this work that addresses these challenges of size, morphology and conductivity of the metallized structure. Specifically, we demonstrated a metallization process that uses gold nanorod seeds followed by anisotropic electroless (autocatalytic) plating to provide improved morphology and greater control of the final metallized width of conducting metal lines. Importantly, growth during electroless deposition occurs preferentially in the length direction at a rate that is approximately four times the growth rate in the width direction, which enables fabrication of narrow, continuous wires. The electrical properties of 49 nanowires with widths ranging from 13 nm to 29 nm were characterized, and resistivity values as low as 8.9 x 10-7 Ω-m were measured, which represent some of the smallest nanowires and the lowest resistivity values reported in the literature. The metallization procedure developed on smaller templates was also successfully applied to metallize bigger DNA templates of tens of micrometers in length. In addition, a polymer-assisted annealing process was discovered to possibly improve the resistivity of DNA metal nanowires. Following metallization of bigger DNA origami structures, controlled placement of gold nanorods on a DNA breadboard (~100 x 100 nm2) to make rectangular, square and T-shaped metallic structures was also demonstrated. For site-specific placement of nanorods to a DNA template, we modified the surface of the gold nanorods with single-stranded DNA. The rods were then attached to DNA templates via complementary base-pairing between the DNA on the nanorods and the attachment strands engineered into the DNA "breadboard" template. Gaps between the nanorods were then filled controllably via anisotropic plating to make 10 nm diameter continuous metallic structures. Finally, controlled placement of metal (gold) - semiconductor (tellurium) materials on a single DNA origami template was demonstrated as another important step toward the fabrication of DNA-based electronic components. The combination of molecularly directed deposition and anisotropic metallization presented in this work represents important progress towards the creation of nanoelectronic devices from self-assembled biological templates.

Electromigration tests on different Cu dual-damascene interconnect tree structures consisting of various numbers of straight via-to-via lines connected at the common middle terminal have been carried out. Like Al-based interconnects, the reliability of a segment in a Cu-based interconnect tree strongly depends on the stress conditions of connected segments. The analytic model based on a nodal analysis developed for Al trees gives a conservative estimate of the lifetime of Cu-based interconnect trees. However, there are important differences in the results obtained under similar test conditions for Al-based and Cu-based interconnect trees. These differences are attributed to the variations in the architectural schemes of the two metallization systems. The absence of a conducting electromigration-resistant overlayer in Cu technology and the low critical stress for void nucleation at the Cu/inter-level diffusion barrier (i.e. Si₃N₄) interface leads to different failure modes between Cu and Al interconnects. As a result, the most highly stressed segment in a Cu-based interconnect tree is not always the least reliable. Moreover, the possibility of liner rupture at stressed dual-damascene vias leads to significant differences in tree reliabilities in Cu compared to Al. While an interconnect tree can be treated as a fundamental unit whose reliability is independent of that of other units in Al-based interconnect architectures, interconnect trees can not be treated as fundamental units for circuit-level reliability analyses for Cu-based interconnects. / Singapore-MIT Alliance (SMA)

The subject of this thesis is a new chip to substrate interconnection technique using self-aligning elastic chip sockets. This work was focused on the technology steps which are necessary to fulfill in order to realize the suggested technique. Elastic chip sockets offer a solution for several assembly and packaging challenges, such a thermo-mechanical mismatch, effortless rework, environmental compatibility, high interconnection density, high frequency signal integrity, etc. Two of the most challenging technology aspects, metallization and etching of the silicone elastomer were studied, but also, air bubble free casting of the silicone elastomer was taken into consideration. Elastic chip sockets and single elastic micro-bump contacts of different shapes and sizes were manufactured and characterized. The contact resistance measurements revealed that the elastic micro-bump contacts manufactured by using the developed methods require less than one tenth of the contact force to achieve the same low contact resistance as compared to commercial elastic interconnection structures. The analysis and measurements of the high frequency properties of the elastic micro-bump structures have shown that they can operate up to several tens of GHz without a serious degradation of the signal quality. The same methods were applied to manufacture very high density contact area array (approximately 80000 connections/cm2), which until now was achieved only using so called chip-first techniques. The low contact resistance, the absence of environmentally harmful materials, no need of soldering, easy rework as well as capability of very high interconnecting density and very high frequency compatibility, indicates a high potential of this technique for assembly and packaging. Moreover, the presented technology of the silicone elastomer micromachining (metallization and RIE in particular) can be used for manufacturing of other microstructures, like chemical or biological micro reactors. / QC 20110114

iv ABSTRACT OPTIMIZATION OF METALIZATION IN CRYSTALLINE SILICON SOLAR CELLS Demircioglu, Olgu M. Sc. Department of Micro and Nanotechnology Supervisor : Prof. Dr. Rasit Turan Co-Supervisor : Assist. Prof. Dr. H. Emrah &Uuml / nalan August 2012, 103 pages Production steps of crystalline silicon solar cells include several physical and chemical processes like etching, doping, annealing, nitride coating, metallization and firing of the metal contacts. Among these processes, the metallization plays a crucial role in the energy conversion performance of the cell. The quality of the metal layers used on the back and the front surface of the cell and the quality of the electrical contact they form with the underlying substrate have a detrimental effect on the amount of the power generated by the cell. All aspects of the metal layer, such as electrical resistivity, contact resistance, thickness, height and width of the finger layers need to be optimized very carefully for a successful solar cell operation. In this thesis, metallization steps within the crystalline silicon solar cell production were studied in the laboratories of Center for Solar Energy Research and Application (G&Uuml / NAM). Screen Printing method, which is the most common metallization technique in the industry, was used for the metal layer formation. With the exception of the initial experiments, 6

<p>The subject of this thesis is a new chip to substrate interconnection technique using self-aligning elastic chip sockets. This work was focused on the technology steps which are necessary to fulfill in order to realize the suggested technique. Elastic chip sockets offer a solution for several assembly and packaging challenges, such a thermo-mechanical mismatch, effortless rework, environmental compatibility, high interconnection density, high frequency signal integrity, etc.</p><p>Two of the most challenging technology aspects, metallization and etching of the silicone elastomer were studied, but also, air bubble free casting of the silicone elastomer was taken into consideration. Elastic chip sockets and single elastic micro-bump contacts of different shapes and sizes were manufactured and characterized.</p><p>The contact resistance measurements revealed that the elastic micro-bump contacts manufactured by using the developed methods require less than one tenth of the contact force to achieve the same low contact resistance as compared to commercial elastic interconnection structures.</p><p>The analysis and measurements of the high frequency properties of the elastic micro-bump structures have shown that they can operate up to several tens of GHz without a serious degradation of the signal quality.</p><p>The same methods were applied to manufacture very high density contact area array (approximately 80000 connections/cm2), which until now was achieved only using so called chip-first techniques.</p><p>The low contact resistance, the absence of environmentally harmful materials, no need of soldering, easy rework as well as capability of very high interconnecting density and very high frequency compatibility, indicates a high potential of this technique for assembly and packaging.</p><p>Moreover, the presented technology of the silicone elastomer micromachining (metallization and RIE in particular) can be used for manufacturing of other microstructures, like chemical or biological micro reactors.</p>

A novel UHV microcalorimeter has been used to study the interaction between calcium and three polymers: MEH-PPV, MEH-PPP and P3HT. All three polymers behave differently in their reaction kinetics with calcium. On MEH-PPV we measure 45 μJ/cm² of heat generated in excess of the heat of bulk metal growth, 120 μJ/cm² for MEH-PPP, and 100 μJ/cm² for P3HT. Comparison of the MEH-PPV and MEHPPP data indicate that the initial reaction of calcium with MEH-PPV occurs at the vinylene group. We propose, based on hypothetical models, that calcium reacts with the vinylene groups of MEH-PPV with a reaction heat of 360 kJ/mol and at a projected surface density of 1.7 sites/nm², while it reacts with the phenylene groups of MEH-PPP in a two-step process with reaction heats of 200 and 360 kJ/mol respectively, at a projected surface density of 3.5 sites/nm². Optical absorption experiments, using either a 1.85 eV diode laser or a xenon lamp coupled to a scanning monochromator, have also been performed using the same calorimeter sensor. In the case of MEH-PPV, using the laser we find an optical absorption cross-section of 3E-¹⁷ cm² per incident calcium atom at low coverages. The change in absorptance at higher coverages correlates perfectly with the population of reacted Ca atoms determined calorimetrically. The size of the absorbance cross-section, and its position just within the band gap of the polymer, are consistent with the reaction being one of polaron formation. Calcium does not appear to dope P3HT, while the photon energy range of 1.5 to 3.75 eV used in these experiments is likely too small for probing polaronic energy states in MEH-PPP.