Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The electrochemical quartz crystal microbalance (EQCM) has been proven an effective mean of monitoring up to nano-scale mass changes related to electrode potential variations at its surface. The principles of operation are based on the converse piezoelectric response of quartz crystals to mass variations on the crystal surface. In this work, principles and operations of the EQCM and piezo-electrodes are discussed. A conductive oxide, ruthenium oxide (RuO2) is a promising material to be used as a diffusion barrier for metal interconnects. Characterization of copper underpotential deposition (UPD) on ruthenium and RuO2 electrodes by means of electrochemical methods and other spectroscopic methods is presented. Copper electrodeposition in platinum and ruthenium substrates is investigated at pH values higher than zero. In pH=5 solutions, the rise in local pH caused by the reduction of oxygen leads to the formation of a precipitate, characterized as posnjakite or basic copper sulfate by means of X-ray electron spectroscopy and X-ray diffraction. The mechanism of formation is studied by means of the EQCM, presenting this technique as a powerful in-situ sensing device.

Copper under-potential deposition (UPD) on iridium was studied due to important implications it presents to the semiconductor industry. Copper UPD allows controlled superfilling on sub-micrometer trenches; iridium has characteristics to prevent copper interconnect penetration into the surrounding dielectric. Copper UPD is not favored on iridium oxides but data shows copper over-potential deposition when lower oxidation state Ir oxide is formed. Effect of anions in solution on silver UPD at platinum (Pt) electrodes was studied with the electrochemical quartz crystal microbalance. Silver UPD forms about one monolayer in the three different electrolytes employed. When phosphoric acid is used, silver oxide growth is identified due to presence of low coverage hydrous oxide species at potentials prior to the monolayer oxide region oxide region.

The continued miniaturization of interconnects results in performance and reliability issues for integrated circuit (IC) chips. As the critical dimension of Cu interconnects approaches dimensions near the mean free path of the metal (39.9 nm at room temperature), a rise in resistivity is observed. This phenomenon, termed resistivity size effect, is the result of electron scattering at grain boundaries and surfaces. Cobalt (Co) and ruthenium (Ru) are considered promising candidates to replace Cu as an interconnect metal because these metals exhibit a lower product of mean free path times bulk resistivity when compared with Cu. Additionally, given that electron scattering from grain boundaries is a major contributor to the resistivity-size effect in nanoscale interconnects, we investigate the electrodeposition of epitaxial Co, Ru, and Cu and demonstrate the capability of electrodeposition to fabricate epitaxial, single crystal metal films. Co, Ru, and Cu have a misfit strain that is tensile, zero, and compressive with the epitaxial Ru(0001) seed layer, respectively. This allowed for the study of every kind of misfit relationship that is possible in epitaxial film growth. Ultimately, the successful electrodeposition of Co and Cu epitaxial to a single crystal, conductive seed layer suggests the plausibility of electrodeposited, single crystal interconnects in future IC chips. Co electrodeposited as an epitaxial, single crystal film onto the Ru(0001) seed layers to finite thicknesses relevant for interconnect fabrication. Electrodeposition onto polycrystalline Ru seed layers, however, resulted in the growth of a rough, polycrystalline Co film with faceted growth. Despite a large misfit strain of 7.9%, the epitaxial electrodeposition of planar Co was achieved up to a thickness 75x beyond the calculated critical thickness for defect formation before a transition to island growth was observed. Thus, the importance of a conductive, single crystal seed layer, preferably with a minimal misfit strain with the depositing layer, is demonstrated. Metallic Ru was found to electrodeposit onto Ru(0001) as a porous layer comprised of (0001) oriented Ru crystallites. The presence of a porous Ru deposit was found to be independent of the seed layer, Ru metal ion source, and deposition mode used. An optimization of the deposition electrolyte to improve Ru atomic mobility is necessary to achieve the epitaxial electrodeposition of single crystal Ru. Finally, Cu demonstrated epitaxial growth on the Ru(0001) seed layer, with an out-of-plane epitaxial orientation relationship of Cu(111) | Ru(0001). The hexagonal close packed Ru(0001) seed layer allows Cu to deposit with two equivalent in-plane orientations; thus, the electrodeposited Cu film was determined to be a bicrystal, not a single crystal. While epitaxial deposition of Cu was achieved, a seed layer that permits only one orientation of Cu is required for a significant reduction in electron grain boundary scattering, hence, resistivity.

This master’s thesis deals with the possibility of creating a compact nickel-silicide layer on austenitic substrates. The theoretical part describes a variety of surface treatments, silicide division, and basic principles of electron beam. The experimental part contains a description of used experimental methods for evaluation of samples, creation of Ni-Si coating using electroplating, and the parameters of electron beam used for melting the sample coating. The last part is devoted to structural evaluation of the sample coating and its microhardness.

En konceptlösning för ett elektrovinningssystem utvecklas baserat på Glenngårds (2019) tidigare arbete. Arbetet är genomfört så att det besvarar tre frågor om en potentiell konceptlösning. Frågeställningarna inkluderar vilka krav som behöver uppfyllas, design av en passande arkitektur och hur vissa konceptparametrar kan verifieras. Krav formuleras i huvudsak baserat på Glenngårds parametrar; säkerhet, kvalitet, användarvänlighet, enkelhet att tillverka, montera, underhålla systemet, kostnadseffektivitet och användning av standardiserade komponenter. Konceptet som genereras är baserat på att använda en elektrolytbehållare kring vilken andra system är fästa eller indränkta. Designen tillåter en grad av automatisering. En bruksprocess för konceptet beskrivs, relevanta komponenter förklaras och vidare utveckling föreslås. En lista med föreslagna tester för verifikation med hjälp av prototypen är också given. / A concept solution for an electro winning system is developed based on the previous work done by Glenngård (2019). This project is made to answer three questions about a potential concept solution, including what requirements need to be fulfilled, design of a suitable architecture and how to verify certain parameters of the concept. Requirements are formulated mainly based on Glenngård’s parameters; safety, quality requirements, ease of use, ease of manufacturing, ease of assembly, ease of maintenance, cost efficiency and use of standardized components. The concept that is generated is based on a single electrolyte container around which surrounding systems are attached or immersed. The design allows a degree of automatization. A process of use is described, relevant components are explained, and further developments are suggested. A list of suggested tests to be carried out for verification using a prototype is also provided.

Silicon carbide has many properties that make it a promising and desirable material for diverse applications. One such application for silicon carbide wafers is as a transparent cryogenic probe card. This thesis briefly describes the design of a probe card based on a silicon carbide wafer substrate. It includes a description of electroplating fundamentals and demonstrates the feasibility of electroplating copper onto a wafer for the formation of bond pads between the substrate and external PCB ring. The process for electroplating copper with good adhesion and quality based on metal alloy formation, current control, and materials selection is outlined. Results of this process are also presented. This work also demonstrates the ability to machine silicon carbide using electrical discharge machining, abrasive water jet machining, and diamond bit milling, proving diamond grinding to be the most versatile of the described methods for machining intricate patterns into the wafers.

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The optimal conditions for deposition of nickel coating and Ni-layered double hydroxide metal matrix composite coatings onto stainless steel discs in a modified all-sulfate solutions have been examined. Nickel films provide good general corrosion resistance and mechanical properties as a protective layer on many metallic substrates. In recent years, there has been interest in incorporation nano-dimensional ceramic materials, such as montemorillonite, into the metal matrices to improve upon the corrosion and mechanical properties. Layered double hydroxides have been used as corrosion enhancer in polymer coatings by increasing mechanical strength and lowering the corrosion rate but until now, have not been incorporated in a metal matrix by any means. Layered double hydroxides can be easily synthesized in a variety of elemental compositions and sizes but typically require the use of non-polar solvents to delaminate into nanodimensional colloidal suspensions. The synthesis of a Zn-Al LDH has been studied and characterized. The effects of the non-polar solvents dimethylformamide and n-butanol on the deposition and corrosion resistance of nickel coatings from a borate electrolyte bath have been studied, a nickel-LDH nanocomposite coating has been synthesized by electrochemical deposition and the corrosion resistance has been studied. Results indicate an improvement in corrosion resistance for the coatings with minimal change in the nickel matrix's internal strain and crystallite size.