Browsing by Subject "Tantalum"
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Item Atomic layer deposition and properties of refractory transition metal-based copper-diffusion barriers for ULSI interconnect(2003) Lemonds, Andrew Michael; Ekerdt, John G.; White, John M.Refractory transition metals have played an important role in the manufacturing of microelectronic devices for interconnect applications including metal contacts, adhesion layers, and diffusion barriers. The diffusion barrier application has become crucial for the integration of copper as the choice conductor in ultra-large scale integrated (ULSI) circuit interconnect. The refractory metal tantalum has been used commercially in previous ULSI technology generations, and atomic layer chemical vapor deposition (ALD) processes for this metal are highly desired for its use in future generations. This dissertation presents surface chemistry and film growth investigations exploring tantalum ALD and an investigation of barrier film adhesion to relevant interconnect surfaces. In-situ surface analysis techniques including X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) were used to study the fundamental adsorption behavior of TaCl5, which was used in the first reported Ta ALD process, on a polycrystalline Ta surface. Based upon these results and those of recently published works, a TaF5/Si2H6 precursor chemistry for Ta ALD was proposed. In this method, alternating half-reactions, which, in this case, are the reaction of TaF5 with a Si2H6-treated surface (the TaF5 halfreaction) and the reaction of Si2H6 with a TaF5-treated surface (the Si2H6 halfreaction), are used sequentially and repetitively to deposit a film. The adsorption and half-reactions of these precursors in the range of 303 to 523 K on polycrystalline Ta were studied in ultra-high vacuum using XPS, TPD and secondary ion mass spectrometry. These half-reactions were subsequently used in practice to deposit thin Ta films in a specially designed, research-scale ALD reactor. This is the first non-plasma enhanced method reported to deposit Ta by ALD. Finally, the adhesion properties of similar tungsten carbide thin films to SiO2 and candidate low-permittivity dielectric substrates was characterized by the four-point bend delamination technique.Item Organometallic Chemistry Supported by the PNP Pincer Framework for Both Early and Late Transition Metals(2012-08-20) Brammell, Christina 1987-Tridentate "pincer" ligands provide a unique balance of stability and reactivity in organometallic chemistry. The development of diarylamido-based PNP pincer ligands has led to many applications in catalysis, including the potential to facilitate unique chemical transformations at transition metal centers. The main objective of this thesis was to explore transition metal chemistry supported by the PNP pincer framework for both early and late transition metals. In Chapter I, the history behind the design and synthesis of pincer complexes is described. The advantages and disadvantages of various pincer ligands are reviewed to show the reasoning behind the synthesis of the PNP pincer framework. Chapter II discusses the synthesis of novel Hf and Ta complexes involving the PNP ligand. Reactions of (PNP)HfCl3 with large alkyl Grignards led to double alkylation and triple alkylation was achieved with methyl Grignard. (PNP)HfMe3 and (PNP)Hf(CH2SiMe3)2Cl displayed remarkably irregular coordination environments about hafnium, in contrast to the approximately octahedral structure of (PNP)HfCl3. (PNP)HfMe3 was found to be thermally stable at 75 degrees C, whereas thermolysis of (PNP)Hf(CH2SiMe3)2Cl under similar conditions led to a mixture of products. The major decomposition product is believed to be a Hf alkylidene complex on the basis of in situ NMR spectroscopic observations (e.g., delta 248.2 ppm in the 13C{1H} NMR spectrum). The reaction of (PNP)TaF4 with an excess of ethyl Grignard led primarily to the double alkylation product, (PNP)Ta(CH2CH3)2F2. Repeating this reaction in the presence of excess ethyl Grignard and dioxane resulted in the formation of an ethylene complex, (PNP)Ta(=CHCH3)(C2H4). In Chapter III, a C-C reductive elimination study is described comparing two pincer ligand scaffolds: Me(PNP) ligand and TH(PNP) ligand. The tied ligand has previously been found to be more sterically demanding than the untied ligand, which has allowed for faster N-C cleavage, faster oxidative addition and a more selective alkyne dimerization catalyst. This study reveals that the tied ligand complex, TH(PNP)Rh(C6H4CF3)(Ph), undergoes slower reductive elimination of p-Ph-C6H4CF3 (< 4% after 7 h at 38 degrees C; t1/2 = 7.7 h at 64 degrees C; t1/2 = 2.13 h at 75 degrees C) than Me(PNP)Rh(C6H4CF3)(Ph) (t1/2 = 15.6 min at 38 degrees C).