Atomic layer deposition (ALD) has emerged as an important technique for depositing thin films in both scientific research and industrial applications. The goal of this work is to integrate functional materials using ALD including high-κ dielectric, LaAlO₃, ferroelectric BaTiO₃, photocatalytic CoO, and room temperature ferromagnetic thin films of Co metal for spin-transfer torque random-access memory applications. The work is also to demonstrate the formation of a quasi-two-dimensional electron gas (2-DEG) at the γ-Al₂O₃/SrTiO₃ heterointerface enabling a method for all-oxide device manufacturing using ALD. High permittivity oxide thin films are needed to replace SiO₂ in complementary metal oxide semiconductor (CMOS) transistors. The replacement of SiO₂ by hafnium oxide-based high-κ materials in CMOS devices in 2007 was a revolutionary development in semiconductor front end of line. The continued device feature shrinking requires higher-κ dielectrics, compared to HfO₂-based materials. Crystalline perovskite oxides, such as SrTiO₃, LaAlO₃, and BaTiO₃, etc. have from high to very high dielectric constant and being proposed to replace HfO₂-based materials in CMOS devices if the leakage problem is resolved. The work explores the monolithic integration of crystalline perovskite oxide films with Si(001) using combined molecular beam epitaxy (MBE) and ALD techniques. Four unit cells of SrTiO₃ were grown directly on Si(001) by MBE and transferred in-situ into the ALD chamber for further depositions. The integration of oxide thin films on Si(001) using the MBE-ALD technique allows us to maintain clean oxide/Si(001) interfaces since low temperatures (180–250 °C) were maintained during the ALD deposition. The goal of my work is also to explore processes to enable area selective deposition of cobalt (II) oxide, CoO. The effectiveness of poly(trimethylsilylstyrene) in selectively inhibiting surface nucleation of CoO on SiO₂ and MgO substrates is demonstrated. Carbon-free cobalt thin films are formed by reducing CoO using Al and Sr metals to scavenge oxygen from CoO. The work explores the ability to control the structure and morphology of the resultant cobalt film by tuning the reduction conditions, allowing us to tune magnetic properties of the cobalt thin film. My work also focuses on the growth of γ-Al₂O₃ on the TiO₂-terminated SrTiO₃ substrate at temperatures higher than 300 °C. The formation of a quasi-2-DEG is found at the γ-Al₂O₃/TiO₂-terminated SrTiO₃ interface. In-situ x-ray photoelectron spectroscopy reveals the presence of Ti³⁺ feature at the heterointerface. Conductivity at the interface was found to be proportional to the amount of Ti³⁺ species. Oxide quasi-2-DEG might provide opportunities for new generations of all-oxide electronic devices using ALD.

The past decade and a half has seen the rapid emergence of a new material class known as photonic crystals (PCs), structures that exhibit 1, 2, or 3, dimensional periodicity of their dielectric constant, resulting in a modification of the dispersion characteristics from the normal w = vk relationship found in isotropic materials. Several remarkable electromagnetic phenomenon result, including the formation of photonic band gaps (PBGs), which are specific energy ranges where electromagnetic wave propagation is forbidden, and the existence of energies where the photon group velocity is slowed drastically from its normal value. The resulting modification of a materials photonic band structure allows unprecedented control of light, resulting in phenomena such as self-collimation, and spontaneous emission modification or lasing threshold reduction through either band edge effects (low group velocity) or microcavity defect incorporation. PCs for operation at visible wavelengths are difficult to form due to the need for nanoscale fabrication techniques. The research described focused on the fabrication of photonic crystal phosphors by using the infiltration and subsequent removal of self-assembled opal templates to make inverted opal-based photonic crystals. This thesis shows the advantages that atomic layer deposition (ALD) has as an important method for use in photonic crystal fabrication, and highlights the exciting results of use of ALD to fabricate luminescent ZnS:Mn and optically inactive titania inverse opals, as well as ZnS:Mntitania luminescent composite inverse opals.

No description available.

The growth of single and multilayer BN films on several substrates was investigated. A typical atomic layer deposition (ALD) process was demonstrated on Si(111) substrate with a growth rate of 1.1 Å/cycle which showed good agreement with the literature value and a near stoichiometric B/N ratio. Boron nitride films were also deposited by ALD on Cu poly crystal and Cu(111) single crystal substrates for the first time, and a growth rate of ~1ML/ALD cycle was obtained with a B/N ratio of ~2. The realization of a h-BN/Cu heterojunction was the first step towards a graphene/h-BN/Cu structure which has potential application in gateable interconnects.

<p dir="ltr">As silicon (Si) technology advances to 3 nm node and beyond, vertically stacking in 3D is considered as the primary choice to increase the density of transistors per unit area for better chip performance. Therefore, looking for new materials capable of replacing Si in back-end-of-line (BEOL) compatible monolithic 3D (M3D) integration has become one of the most important topics in the current field of electronic devices. Recent developed atomic layer deposition (ALD) deposited indium oxide (In₂O₃) field-effect transistors (FETs) have realized excellent electrical performance including field effect mobility over 100 cm²/V·s, on/off ratio up to 10¹⁷ and on-state current (I_ON) over 2.5 mA/μm in nanometer thin In₂O₃ FETs, providing promising prospect for next generation electronics. In this thesis, four main In₂O₃ related topics are discussed to examine the practicality of ALD In₂O₃ as channel material in BEOL compatible applications. First, the bias stability of planar In₂O₃ transistors and the effect of tin doping are studied. Second, gate-all-around (GAA) In₂O₃ FETs are implemented to improve I_ON up to record high 20 mA/μm, and its reliability is systematically measured and analyzed. Third, multilayer In₂O₃ FETs are constructed to investigate the possibility of vertical stacking. Last, vertical full oxide transistors with In₂O₃ gate are demonstrated to prove the feasibility of potential 3D integration.</p>

Inside your microelectronic devices there are up to a billion transistors working in flawless operation. Silicon has been the workhorse semiconductor used for the transistor; however, there must be a transition to materials other than silicon, such as germanium, with future device sizes. In addition, new dielectric oxide materials are needed. My research has examined a type of crystalline oxide, known as a perovskite, which is selected for its ability to bond chemically to Si and Ge, and eliminate the electrical defects that affect performance. Many perovskite oxides are lattice-matched to the Si (001) and Ge (001) surface spacing, enabling heteroepitaxy. To date, the majority of research on crystalline oxides integrated with semiconductors has been based on strontium titanate, SrTiO3, epitaxially grown on Si (001) by molecular beam epitaxy. Alternative low-temperature growth methods, such as atomic layer deposition (ALD), offer both practical and economic benefits for the integration of crystalline oxides on semiconductors. My initial research informed the broader community that four unit cells (~1.5 nm) of SrTiO3 are required to enable heteroepitaxy on Si. The research has also shown that heteroepitaxial layers can be monolithically integrated with Si (001) without the formation of a SiOx interlayer between the Si (001) surface and the SrTiO3 layer because ALD is performed at lower temperatures than are typical for MBE. Thus, a combined MBE-ALD growth technique creates possible advantages in device designs that require the crystalline oxide to be in contact with the Si (001) surface. In recent work, I have demonstrated a method for integrating crystalline oxides directly on Ge by ALD. Germanium is being explored as an alternative channel material due to its higher hole and electron mobilities than Si, potentially enabling device operation at higher speed. This all-chemical growth process is expected to be scalable, is inherently less costly from a manufacturing cost of ownership, and is based on current manufacturing tool infrastructure. The impact of my research will be in continued scaling of device dimensions with novel materials that will provide faster speed and lower power consumption for microelectronic devices. / text

Ultra-thin films of pure elements are important in microelectronics due to their wide range of applications. Atomic Layer Deposition (ALD) has drawn increasing attention as the thin films deposition technique for applications in microelectronics, due to its ability to deposit thin films with high conformality with atomic level control of the thickness of the film. However, due to the limited number of suitable precursor/co-reactant pairs available, only a few pure elements have been deposited successfully by ALD to date. The current study involves the synthesis and identification of potentially suitable precursor and co-reactant molecules for ALD of elemental Zn and Ge, neither of which have previously been achieved. MeZnOiPr, Zn(OiPr)2, and ZnEt2 were investigated as Zn precursors while GeCl2(Dioxane), Ge{N(SiMe3)2}2, and Ge(OCH2CH2NMe2)2 were investigated as Ge precursors. Co-reactants of interest were, 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (HBpin), PhSiH3, [H2Al(tBuNCH2CH2NMe2)] (LAlH2), BH3(NMe3), and AlH3(Quinuclidine). Ligand-exchange reactions between precursors and co-reactants were expected to produce unstable zinc or germanium hydride species, which would then reductively eliminate to produce the pure element. Solution reactivity studies were employed to identify potential precursor/co-reactant pairs. Solution reactions of Zn precursors with the selected co-reactants indicated that unstable ZnH2 is produced during the reactions, and will dissociate into its elements (Zn and H2) at room temperature. These solution reactivity studies revealed that, HBpin and LAlH2 were more reactive as co-reactants than BH3(NMe3), AlH3(Quinuclidine), and PhSiH3. Additionally, MeZnOiPr and ZnEt2 exhibited the highest reactivity as precursors, although the lower reactivity of Zn(OiPr)2 may simply be due to low solubility. Solution reactions of Ge precursors produced a polymeric mono-germanium hydride species (GeH)x, which will only dissociate into its elements upon heating at elevated temperatures. While LAlH2 indicated high reactivity with all Ge precursors, it was difficult to arrange co-reactants in order of reactivity as most reactions immediately produced insoluble (GeH)x upon mixing reagents at room temperature. Ge(OCH2CH2NMe2)2 found to be the most reactive precursor out of all Ge precursors investigated. / Thesis / Master of Science (MSc)

This research thesis covers work done on building an atomic layer deposition (ALD) reactor followed by the development and optimization of an ALD process for indium oxide thin films on crystalline silicon substrates from new precursors using this new homebuilt cost-effective tool. This work describes the design, building and testing of the ALD system using an indium triazenide precursor and water in a novel precursor combination. The reactor was built to be capable of depositing films with comparable results to commercially built systems.Indium oxide thin films were deposited as the deposition temperature was varied from 154 to 517 0C to study the effects of deposition temperature on the obtained film thicknesses and ascertain the ALD temperature window between 269-384 0C. The presence of indium oxide films was confirmed with X-ray diffraction analysis, which was also used to study their crystallinity. The films were found to have a polycrystalline structure with a cubic phase. Measurement of film thickness was performed using X-ray reflectivity which determined a growth rate of approximately 1 Å/cycle. Elemental composition was determined by X-ray photoelectron spectroscopy which confirmed contamination-free indium rich films. Scanning electron microscope imaging was used to examine the surface morphology of the films as well as thick cross-sectional thicknesses.Since indium oxide films are potentially useful in various electronic, optical, and catalytic applications, emphasis is also placed on the accurate characterization of the chemical and physical properties of the obtained thin films. Optical and electrical properties of the produced transparent conducting oxide films were measured for transparency (and optical band gap) and electrical characterization by resistivity measurements, from UV-Vis spectrophotometry and 4-point probe data respectively. A high optical transmission &gt;70 %, a wide band gap 3.99-4.24 eV, and low resistivity values ∼0.2 mΩcm, showed that In2O3 films have interesting properties for various applications confirming indium oxide a key material in transparent electronics.

Avec l’augmentation de la densité de fonctionnalités dans les différents circuits intégrés nous entourant, l’intégration 3D (empilement des puces) devient incontournable. L’un des point-clés d’une telle intégration est la métallisation des vias traversant (TSV, Through Silicon Via) reliant deux puces entre-elles : ces TSV ont des facteurs de forme de plus en plus agressifs, pouvant dépasser 20. Les dépôts des couches barrière à la diffusion du cuivre et d’accroche pour le dépôt électrolytique du cuivre étant actuellement réalisées par dépôt physique en phase vapeur, ceux-ci sont limités en termes de conformité et de facteur de forme. Le travail de cette thèse porte sur le développement du dépôt de couches atomiques (ALD, Atomic Layer Deposition) de cuivre et de nitrure de tantale afin de résoudre les problèmes énoncés lors de la métallisation de TSV. Les précurseurs de cuivre étant actuellement mal connus, différents précurseurs ont été dans un premier temps évalués, afin de sélectionner celui répondant au cahier des charges précis de notre étude. Nous nous sommes par la suite attachés à l’étudier selon deux axes : d’abord en examinant ses propriétés thermodynamiques afin de mieux appréhender les réactions de dépôt, puis lors d’élaboration de films de cuivre sur différents substrats et à différentes conditions afin d’optimiser le procédé d’élaboration de films mince de cuivre. Dans un second temps, nous nous sommes attachés à l’étude d’un précurseur de tantale pour la réalisation de couches barrière à la diffusion. Celui-ci a été étudié en ALD, afin de proposer à l’industrie microélectronique un procédé de dépôt de couches barrière et d’accroche optimisé. Pour finir, nous avons vérifié que l’ALD permet le dépôt conforme dans des TSV à haut facteur de forme, et que les films obtenus ont les propriétés correspondant au cahier des charges de l’industrie la microélectronique. / With the increasing density of features in the various integrated circuits surrounding us, 3D integration (stacking chips) becomes essential. One key point of such integration is the metallization of Through Silicon Vias (TSV) connecting two chips together: the aspect ratio of these TSV will be higher than 20 in the near future. The copper-diffusion barrier layer and seed layer for the electrodeposition of copper are currently deposited by physical vapour deposition, and this technique is limited in terms of conformality in high aspect ratio structure. This work focuses on the development of the Atomic Layer Deposition (ALD) of copper and tantalum nitride in order to propose conformal deposition method of barrier and seed layers. Copper precursors being not well known, different precursors were initially evaluated following the specifications of our study. Once the most promising precursor selected, it has been studied in two different ways. Firstly, a thermodynamic study has been carried out to understand the deposition mechanism; then copper ALD films were deposited on different substrates using different conditions to optimize the deposition. In a second step, a tantalum precursor has been studied for ALD of diffusion barrier, in order to offer the microelectronics industry a deposition method for both barrier and seed layer. Finally, we verified that ALD leads to conformal deposition on high aspect ratio TSV, and that the resulting films have properties corresponding to the specifications of the microelectronic industry.

La réduction des recombinaisons aux surfaces des cellules solaires est un enjeu fondamental pour l'industrie photovoltaïque. La passivation des défauts électriques en surface peut être obtenue par la formation de liaisons chimiques ou par l'apport de charges électriques capables de repousser un type de porteurs. Ces effets peuvent être obtenus grâce à des couches minces fonctionnalisées déposées sur les surfaces des matériaux qui constituent les cellules. Dans le cadre de cette thèse nous avons étudié la passivation de surface du silicium par des couches minces d’Al2O3 déposées par ALD. La caractérisation physique, optique, structurale et chimique des couches déposées a été réalisée. Une optimisation du procédé d’élaboration (nettoyage pré dépôt, paramètres de dépôt et de recuit) de couches d’alumine a été nécessaire pour répondre aux exigences de la réduction de recombinaisons de surface et obtenir des résultats de passivation optimisés. Enfin, différentes briques technologiques nécessaires à l’intégration de ces couches dans l’architecture d’une cellule solaire silicium ont été étudiées et développées. / The reduction of recombination at the surfaces of solar cells is a fundamental challenge for the photovoltaic industry. Passivation of surface electrical defects can be achieved by the formation of chemical bonds or by the supply of electric charges capable of repelling a type of carrier. These effects can be obtained by means of functionalized thin layers deposited on the surfaces of the materials which constitute the cells. In this thesis we studied the surface passivation of silicon by thin layers of Al2O3 deposited by ALD. The physical, optical, structural and chemical characterization of the deposited layers was carried out. An optimization of the preparation process (pre-deposition cleaning, deposition and annealing parameters) of alumina layers was necessary to meet the requirements of reduction of surface recombinations and to obtain optimized passivation results. Finally, various technological bricks necessary for the integration of these layers in the architecture of a silicon solar cell have been studied and developed.