In this work, the possibility of Cu electrodeposition on Ru-Ta alloy thin films is explored. Ru and Ta were sputter deposited on Si substrate with different composition verified by RBS. Four point probe, XRD, TEM and AFM were used to study the properties of Ru-Ta thin films such as sheet resistance, crystallinity, grain size, etc. Cyclic voltammetry is used to study the Cu electrodeposition characteristics on Ru-Ta after various surface pretreatments. The results provide insights on the removal of Ta oxide such that it enables better Cu nucleation and adhesion. Bimetallic corrosion of Cu on modified Ru-Ta surface was studied in CMP related chemicals. In Cu interconnect fabrication process, the making of trenches and vias on low-k dielectric films involves the application of fluorocarbon plasma etch gases. Cu microdots deposited on Ru and Ta substrate were treated by fluorocarbon plasma etch gases such as CF4, CF4+O2, CH2F2, C4F8 and SF6 and investigated by using x-ray photoelectron spectroscopy, contact angle measurement and electrochemical techniques. Micropattern corrosion screening technique was used to measure the corrosion rate of plasma treated Cu. XPS results revealed different surface chemistry on Cu after treating with plasma etching. The fluorine/carbon ratio of the etching gases results in different extent of fluorocarbon polymer residues and affects the cleaning efficiency and Cu corrosion trends.

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The effect of a magnetic field on copper electrodeposition was investigated. Copper was electrodeposited onto square copper cathodes 1 sq cm in area from an aqueous solution (0.5 M CuSO4, 0.5 M H2SO. A glass cell was placed between the pole pieces of an electromagnet, and the magnetic fields applied were in the range from 0 to 12.5 kG. The current density was in the range from 80 mA/sq cm to 880 mA/sq cm. In each of the experiments, cell current, cell voltage, and cell temperature were monitored with a microcomputer. The weight change, deposit surface and cross section morphology, and the hardness were also found. Anodes used in the experiments were studied to see the effect of various conditions on the surface finish. Copper was also electrodeposited onto copper grids in order to study how the uniformity of the deposit is affected by an applied magnetic field.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第22673号 / エネ博第405号 / 新制||エネ||77(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー応用科学専攻 / (主査)教授 平藤 哲司, 教授 馬渕 守, 教授 土井 俊哉 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第23396号 / エネ博第423号 / 新制||エネ||80(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー応用科学専攻 / (主査)教授 平藤 哲司, 教授 土井 俊哉, 准教授 三宅 正男 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DGAM

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Functional coatings produced using scalable and cost-effective processes such as electrodeposition and etching lead to the creation of random roughness at multiple length scales on the surface. The first part of thesis work aims at developing a fundamental mathematical understanding of multiscale coatings by presenting a fractal model to describe wettability on such surfaces. These surfaces are described with a fractal asperity model based on the Weierstrass-Mandelbrot function. Using this description, a model is presented to evaluate the apparent contact angle in different wetting regimes. Experimental validation of the model predictions is presented on various hydrophobic and superhydrophobic surfaces generated on several materials under different processing conditions. Superhydrophobic surfaces have myriad industrial applications, yet their practical utilization has been severely limited by their poor mechanical durability and longevity. Toward addressing this gap, the second and third parts of this thesis work present low cost, facile processes to fabricate superhydrophobic copper and zinc-based coatings via electrodeposition. Additionally, systematic studies are presented on coatings fabricated under different processing conditions to demonstrate excellent durability, mechanical and underwater stability, and corrosion resistance. The presented processes can be scaled to larger, durable coatings with controllable wettability for diverse applications. Apart from their use as superhydrophobic surfaces, the application of multiscale coatings in photo-thermal conversion systems as solar selective coatings is explored in the final part of this thesis. The effects of scale-independent fractal parameters of the coating surfaces and heat treatment are systematically explored with respect to their optical properties of absorptance, emittance, and figure of merit (FOM). / Master of Science / Coatings are extensively used through various industries and serve a range of purposes such as providing protection, changing the physical and chemical properties, decoration, and adding other new properties to the base surface. Coatings produced using scalable and cost-effective processes such as electrodeposition and etching are inherently rough and have features ranging from micro- to nano-scale, leading to their multiscale nature. The first part of thesis work aims at developing a fundamental mathematical understanding of these rough coatings by presenting a model to describe and predict the wettability on such surfaces. Wettability of a surface is its ability to maintain contact with a liquid, resulting from intermolecular interactions when the two are brought together. Wettability for a solid surface is generally quantified by the contact angle, measured through the liquid, where a liquid-vapor interface meets the solid surface. A mathematical model is presented to evaluate the apparent contact angle on such multiscale rough surfaces. Experimental validation of the model predictions is presented on various hydrophobic and superhydrophobic surfaces generated on several materials under different processing conditions. Superhydrophobic surfaces do not get wet by water and water droplet contact angle on these surfaces exceed 150°. Such surfaces have extensive industrial applications, yet their practical utilization has been severely limited by their poor mechanical durability and longevity. Toward addressing this gap, the second and third parts of this thesis work present low cost, facile processes to fabricate superhydrophobic copper and zinc-based coatings via electrodeposition. Additionally, systematic studies are presented on coatings fabricated under different processing conditions to demonstrate excellent durability, mechanical and underwater stability, and corrosion resistance. The presented processes can be scaled to larger, durable coatings with controllable wettability for diverse applications. Apart from their use as superhydrophobic surfaces, the application of multiscale coatings in photo-thermal conversion systems as solar selective coatings is explored in the final part of this iv thesis. Solar selective coatings aim to improve photo-thermal conversion efficiency by providing a high solar absorptance and low thermal emittance. Solar selective coatings ensure that maximum incoming solar radiation is absorbed into the surface and radiative losses due to emissions at high temperatures are minimized. The effects of scale-independent mathematical parameters of the coating surfaces and heat treatment are systematically explored with respect to their optical properties of absorptance, emittance, and figure of merit (FOM).

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