Precursor synthesis and chemical vapour deposition of transition metal nitrides and carbonitrides

This thesis is concerned with the chemical vapour deposition (CVD) of tungsten and zirconium nitride and carbonitride thin films. [W(µ-NtBu)(NtBu)Cl2(H2NtBu)]2, [W(NtBu)2Cl2(TMEDA)] (TMEDA = N,N,N’,N’-tetramethylethylenediamine) and [W(NtBu)2Cl2(py)2] (py = pyridine) have been investigated as potential precursors. Additionally, two novel precursors, [W(NtBu)2Cl{N(SiMe3)2}] and [W(NtBu)2(¿5-Cp’)(¿1-Cp’)] (Cp’ = methylcyclopentadienyl), have been synthesised via metathesis reactions of [W(NtBu)2Cl2(py)2] with the appropriate lithium or sodium amide salt. The attempted synthesis of [W(NtBu)2Cl{N(H)NMe2}] by lithium salt metathesis was unsuccessful due to polymerisation. Cyclopentadienyl-based precursors to zirconium carbonitride have been investigated, including [ZrCp2(NMe2)2], [ZrCp’2(NMe2)2] and four novel compounds: [ZrCp2(¿2-MeNCH2CH2NMe)], [ZrCp’2(NEt2)2], [ZrCp’{(iPrN)2CNMe2}2Cl] and [ZrCp’2{(iPrN)2CNMe2}Cl] (Cp = n5-cyclopentadienyl, Cp’ = n5- methylcyclopentadienyl). The compounds were synthesised via sodium or lithium metathesis reactions. All compounds synthesised were characterised by NMR, mass spectrometry, elemental analysis and IR, and their decomposition was investigated by thermogravimetric analysis (TGA). The molecular structures of [ZrCp’{(iPrN)2CNMe2}2Cl] and [ZrCp’2{(iPrN)2CNMe2}Cl] were determined by single crystal X-ray diffraction. Thin films of tungsten carbonitride, zirconium carbide and zirconium carbonitride were deposited by low pressure CVD (LPCVD) at 550-600 °C and 0.1 Torr using the aforementioned precursors. In addition, aerosol-assisted CVD (AACVD) of [W(µ-NtBu)(NtBu)Cl2(H2NtBu)]2 in toluene was investigated as a comparison. All films deposited via CVD were characterised using wavelength dispersive X-ray spectroscopy (WDX), glancing-angle XRD, UV/Vis spectroscopy (for reflectance and transmission measurements) and their morphology and thickness were investigated using SEM imaging. Plasma-enhanced atomic layer deposition (PEALD) using [ZrCp2(NMe2)2] and [ZrCp2(¿2-MeNCH2CH2NMe)] was studied with the view to depositing stoichiometric ZrN. It showed these precursors to be nsufficiently volatile for the ALD system as the growth rates were low. The ALD progress was analysed using in situ ellipsometry and mass spectrometry.