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Access Type
WSU Access
Date of Award
January 2023
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Chemistry
First Advisor
Charles H. Winter
Abstract
The transistor design and count can be altered to improve the performance of a microchip. Thus, developing new materials and their deposition processes is vital for better chip performance to expand the chip industry. For example, polycrystalline silicon was used as the material of choice for the gate electrode of the transistor. However, the complex architecture of modern transistors (e.g., multigate transistors) has demanded that metals replace Si to prevent reactions between Si and high-K oxides (oxides with high dielectric constant). ALD of pure metals is very useful in the semiconductor industry. Cations in the metal-organic precursors should be reduced to their metallic states to deposit the corresponding elemental metals. Depositing electropositive metals is extremely difficult due to the large negative electrochemical potential. Additionally, the lack of strong reducing agents limits such metal film depositions by ALD. SiO2 is the material generally used for the gate dielectric for MOSFET. It was replaced by high-κ oxide candidates such as HfO2 and ZrO2 due to the low dielectric constant of SiO2 and high leakage current for thin films (<13 nm). Lanthanide oxides are substitutes for SiO2. However, several issues are associated with the reported ALD studies of lanthanide oxide depositions, such as the inability to achieve a self-limited growth behavior and impurities in the films grown, requiring further exploration of suitable precursors and processes that will enable the wide use of these lanthanide oxide films in the intended applications in the microelectronics industry, etc. Volatile and thermally stable amino alkoxide aluminum hydride complexes were introduced in Chapter 2 as potential reducing agents to deposit electropositive metals. Aluminum hydrides were synthesized by treating the amino-alkoxide ligand L1H-L5H (ketone or alcohol) with AlH3(OEt2)x or AlH3(NMe3). Chapter 4 demonstrates the synthesis of a series of lanthanide complexes (Er, Yb, Y, and Lu) containing the β-heteroalkenolate ligand using the salt metathesis reactions. Complexes were analyzed by 1H, 13C, and 19F NMR spectroscopy, melting points, thermal decomposition studies, infrared spectroscopy, CHN microanalysis, TGA, sublimation, and X-ray crystallography. All complexes have sufficient volatility and thermal stability for use in ALD. Mg and Zn metal films were grown using M(tBu2DAD)2 (M= Mg, Zn) metal precursors and tBuNH2 as the co-reactant. CVD-type growth behavior was observed in both processes, and the resultant films were characterized using SEM, GI-XRD, XRF, and XPS techniques. Mg metal is deposited on air-oxidized Cu, CoOx, and Er2O3 substrates, and the oxide layer present in these substrates likely supports the nucleation process. The study discloses the first report of growing Mg metal films using a molecular precursor.
Recommended Citation
Sirikkathuge, Nilanka Weerathunga, "Synthesis And Characterization Of Main Group And Lanthanide Thin Film Growth Precursors: Deposition Of Magnesium And Zinc Metal Thin Films" (2023). Wayne State University Dissertations. 3867.
https://digitalcommons.wayne.edu/oa_dissertations/3867