Synthesis and characterization of tantalum and group 6 metal complexes containing nitrogen donor ligands as potential source compounds for thin film growth and atomic layer deposition using novel precursors

Tantalum(V) oxide films have been deposited by atomic layer deposition (ALD) using tert-butylimidotris(di-tert-butylpyrazolato)tantalum and ozone as precursors. Self-limited growth was demonstrated at a deposition temperature of 325°C. Between 300 and 450°C, the growth rate remained constant at approximately 0.30 A/cycle. At 475-500°C, the growth rate increased to 0.35-0.41 A/cycle, whereas at 250-275 °C, the growth rate decreased to 0.14-0.20 A/cycle. The films were amorphous as-deposited, and crystallized as hexagonal delta-Ta2O5 upon annealing. Atomic force microscopy revealed the film surfaces to be smooth, with rms roughnesses of 0.4-0.8 nm. Scanning electron microscopy showed smooth, pinhole-free films at all magnifications.;A series of tantalum complexes containing imido, amidinate, and either halide or dialkylamide ligands has been synthesized. All of these complexes are volatile; they sublime between 120-203°C. Several of these complexes possess high thermal stability and undergo solid-state decomposition around or above 300°C. The most promising complex of this series, tert -butylimidobis(diisopropylacetamidinato)dimethylamidotantalum, was used as an ALD precursor to Ta2O5 films, with water as the oxygen source. Self-limited growth was demonstrated at 325°C. This process exhibits an ALD window with a constant growth rate of 0.28 A/cycle between 275 and 350°C. Above and below this temperature range, increased growth rates were observed; at 375-400°C, the growth rate was 0.31 A/cycle, and at 225-250°C, the growth rate was 0.33-0.37 A/cycle. The films were amorphous as-deposited, and crystallized as hexagonal delta-Ta 2O5 upon annealing. Atomic force microscopy revealed the film surfaces to be smooth, with rms roughnesses of 0.6-0.7 nm.;A series of molybdenum(III) and tungsten(III) dimers containing four dimethylamido ligands and either two pyrazolate or an amidinate and a chloride ligand was synthesized. These dimers were studied by variable temperature NMR, due to their fluxionality on the NMR timescale. The dimers possess limited thermal stability and decompose upon attempted sublimation.