Flüchtige, stickstoffreiche Metallverbindungen für die chemische Gasphasenabscheidung

In der vorliegenden Arbeit werden flüchtige Metallkomplexe als potentielle Präkursorenverbindungen fur die Abscheidung von metallischen Filmen aus der Gasphase entworfen, dargestellt und charakterisiert. Diese Beschichtungverfahren, chemische Gasphasenabscheidung (CVD) und Atomlagenabscheidung (ALD)...

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Bibliographic Details
Main Author: Lange, Alexander
Contributors: Sundermeyer, Jörg (Prof. Dr.) (Thesis advisor)
Format: Doctoral Thesis
Language:German
Published: Philipps-Universität Marburg 2024
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In this Thesis volatile metal complexes were synthesised, characterised and discussed as potential precursors for thin metallic film deposition from the gas phase. These deposition techniques, chemical vapour deposition (CVD) and the atomic layer deposition (ALD), are applied in the fabrication of nanostructured semiconductors. Therefore precursor compounds are needed, which deposit their metal as pre-defined functional material on a surface through a thermally or chemically induced consecutive reaction from the gas phase. In order to meet these special requirements, potentially volatile metal complexes with nitrogen rich chelating ligands were developed. These new precursors show thermally weak N−N-bonds in the ligand and chemically vulnerable M−N-bonds. The research focus was to synthesise and characterise volatile complexes containing ruthenium and rare-earth metals combined with the chelating ligands N,N’-bis(dimethylamino)methylacetamidine H(bdma), di-tert- H(dbt) und methyl-tert-butyltriazene H(mbt), 1,5-di-tert-butyl-3-methylformazane H(dbmf), und 1,4-di-iso-propyldiazadiene iPrDAD. These compounds were tested in TGA/SDTA measurements regarding evaporability at standard pressure and thermal stability in a nitrogen atmosphere. Their qualification for ALD/CVD is screened by results of TGA/SDTA measurements. Different η6-arene-ruthenium complexes were synthesised and studied, starting from [RuII(η6-arene)Cl2]2-dimers. The new compounds were classified into Ru0 - and RuII precursors. The volatile Ru0 complexes were synthesised by a metal free reduction of ruthenium with iPrOH and NEt3 in presence of neutral chelating ligands. The products obtained by route A showed lower yields with sterically higher demanding arenes and high solubility of the starting material. The synthesis of the RuII complexes was accomplished by a N−H deprotonation of protic chelating ligands in NEt3. Here, just one chlorido ligand was substituted selectively. In a consecutive reaction, the remaining chlorido ligand was substituted by a methyl or hydrido ligand to obtain the highly volatile complexes. The conversion of [RuII(cod)Cl2]n (cod = cyclooctadien) and Li(bdma) showed an uncommon, thermally induced N-demethylation of the bdma ligand to a 1,1,3,5-tetramethylformazane coordinating in its triazadiene-bonding mode. Meanwhile, the neutral cod-ligand was isomerized and deprotonated first to a cyclooctadienyl anion (η5-cod) and finally dehydrogenated to cyclooctatrien (cot). RuII was reduced to Ru0 simultaneously. The N-demethylation of the bdma ligand could be reproduced for the arene complexes with the reducing agent iPrOH in NEt3. [Ru0(arene)(Me,NMe2TAD)] complexes were also obtained by heating [RuII(arene)(bdma)H] beyond 80 °C. Consequently, the latter are the first thermal decomposition products of the former. According to TGA/SDTA at higher temperatures the evaporation shifts into decomposition or happens simultaneously for most of the ruthenium precursors. The Sc and Y precursors containing ethyl cyclopentadienyl ligands were combined with nitrogen-rich, mono-anionic, chelating ligands and characterisised. Additionally to compounds of type [M(EtCp)2(LL)] (M = Sc, Y), EtCp ligands were successively substituted by dbt ligands up to the homoleptic complexes [M(dbt)3]. A new synthesis to H(dbmf) and Li(dbmf) with higher yields has been developed. Novel volatile homo- and heteroleptic complexes of the transition metals featuring the neutral 5-ring or anionic 6-ring structure of the dbmf ligand have been realised. Both bonding modes are combined at one metal centre in [Cu(Hdbmf)(dbmf)]. The molecular structures of neutral 5-membered ring complexes show no conjugation of the NHtBu group with the ligand backbone. Therefore, the bonding situation is closer to a diene than a formazane. The bisformazantes were obtained as tetrahedral complexes exclusively, because of the interlocking position of the tert-butyl substituents. All dbmf precursors, with exception of [Mo(Hdbmf)(CO)4], could be sublimed in the vacuum without decomposition. Addionally, volatile, dimeric zinc complexes were synthesised. The high volatility of the dbt derivate can be traced back on the easy dissociation of the dimers to monomers. Tris(hexamethyldisilazanides) of lanthanide metals ([Ln(hmds)3], Ln = Ce, Nd, Eu, Tb, Lu) react with triazanido ligands H(dbt) and H(mbt) in a protolysis reaction under release of H(hmds). Thereby, the volatile, homoleptic lanthanide precursors [Ln(dbt)3] and [Ln(mbt)2(μ-mbt)]2 (Ln = Ce, Nd, Eu, Tb, Lu) could be isolated. The monomeric dbt precursors evaporate according to TGD/SDTA, while the dimeric mbt precursors decompose beyond 220 °C. Crystal structures of the dimeric mbt precursors reveal a new bridging coordination type of triazenido ligands.