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Access Type
WSU Access
Date of Award
January 2024
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Chemistry
First Advisor
Charles C. Winter
Abstract
ALD stands out among numerous thin film deposition techniques due to its unique ability to deposit thin films layer by layer. This uniqueness is made possible by the self-limited growth behavior of ALD precursors. The layer-by-layer deposition enables precise thickness control at the Angstrom level and ensures 100% conformal coverage even on substrates with high aspect ratio features. ALD is becoming increasingly essential in the microelectronics industry due to the complexity of fabricating substrate surfaces. However, developing new ALD precursors presents challenges due to the specific requirements of volatility, thermal stability, and reactivity. The available library of ALD precursors is currently limited, necessitating efforts to expand and innovate to meet future demands in thin film depositions. To that end, this thesis contains three main chapters on developing Er, Y, and Zn metal ALD precursors and thin film deposition of Y2O3.
Late lanthanide oxide films exhibit valuable properties such as high dielectric constant, considerable band gap energy, high refractive index, and stability at high temperatures, making them attractive for potential dielectric applications. However, existing ALD precursors for late Ln films have drawbacks, including low reactivity with water, substrate oxidation with ozone, and variable thermal stability. Winter laboratory recently developed a series of volatile and thermally stable lanthanide tris(enaminolate) complexes. The synthetic studies focused on Er and Y precursor complexes, their ALD properties, and their use in depositing Er and Y oxide films using water as the co-reactant. This new class of ALD precursors has the potential to broaden the use of lanthanide oxide compounds, including multi-component complex oxides containing rare earths. The synthesis and characterization of Er(L1)3 and Y(L1)3 complexes, emphasizes the optimization of synthetic procedures and identification of their monomeric nature in the solid state. The unexpected formation of KErL14 and [KY(L1)4(L1H)] complexes are analyzed using various techniques, and detailed reaction roadmaps are developed to enhance the synthesis of Er and Y complexes. The chapter concludes with a comprehensive understanding of the chemistry of these complexes and strategies to overcome synthesis challenges.
Additionally, the growth of Y2O3 thin films was demonstrated using Y(L1)3 precursor and water as the co-reactant via thermal ALD on Si(100) and SiO2 substrates. Self-limited growth behavior is observed at 200°C, achieving a consistent growth rate of 0.33 Å per cycle within an ALD window of 175 to 225°C. Initial film analysis is performed using XRF and SE techniques, with further characterization using GI-XRD, AFM, XPS, and SEM. The Y2O3 films exhibit polycrystalline cubic phase deposition, with smooth and continuous morphologies and nearly stoichiometric compositions. This study highlights the effectiveness of lanthanide tris(enaminolate) precursors in the deposition of late Ln2O3 thin films. Additionally, it would be interesting to use lanthanide tris(enaminolate) precursors in early Ln2O3 depositions as well.
The chemistry of Zn(I) dimers is novel and important due to the reactivity of the Zn22+ ion. Zn(I) dimers have potential applications as reducing agents in metal thin film deposition and as precursors for Zn metal thin film deposition using ALD techniques, provided their chemical and physical properties are adequately adjusted. Winter laboratory developed several Zn complexes of β-ketoiminate and β-diketiminate ligands with simple and bulky alkyl groups to enhance the volatility, but their thermal stability was insufficient for ALD applications. To address this issue, two new ligand precursors were proposed with electron-rich alkyl groups containing adjustable bulkiness aiming to produce thermally stable Zn(I) precursors.
Recommended Citation
Dharmadasa, Kura Gamage Chamod Dinudaya, "Development Of Zinc, Erbium, And Yttrium Metal Ald Precursors And Deposition Of Y2o3 Thin Films Using Thermal Ald" (2024). Wayne State University Dissertations. 4116.
https://digitalcommons.wayne.edu/oa_dissertations/4116