Aluminum Dihydride Complexes and their Unexpected Application in Atomic Layer Deposition of Titanium Carbonitride Films

<p>Aluminum dihydride complexes containing amido-amine ligands were synthesized and evaluated as potential reducing precursors for thermal atomic layer deposition (ALD). Highly volatile monomeric complexes AlH<sub>2</sub>(tBuNCH<sub>2</sub>CH<sub>2</sub>NMe<sub>2</sub>) and AlH<sub>2</sub>(tBuNCH<sub>2</sub>CH<sub>2</sub>NC<sub>4</sub>H<sub>8</sub>) are more thermally stable than common Al hydride thin film precursors such as AlH<sub>3</sub>(NMe<sub>3</sub>). ALD film growth experiments using TiCl<sub>4</sub> and AlH<sub>2</sub>(tBuNCH<sub>2</sub>CH<sub>2</sub>NMe<sub>2</sub>) produced titanium carbonitride films with a high growth rate of 1.6-2.0 Å/cycle and resistivities around 600 μΩ·cm within a very wide ALD window of 220-400 °C. Importantly, film growth proceeded via self-limited surface reactions, which is the hallmark of an ALD process. Root mean square surface roughness was only 1.3 % of the film thickness at 300 °C by atomic force microscopy. The films were polycrystalline with low intensity, broad reflections corresponding to the cubic TiN/TiC phase according to grazing incidence X-ray diffraction. Film composition by X-ray photoelectron spectroscopy was approximately TiC<sub>0.8</sub>N<sub>0.5</sub> at 300 °C with small amounts of Al (6 at%), Cl (4 at%) and O (4 at%) impurities. Remarkably, self-limited growth and low Al content was observed in films deposited well above the solid-state thermal decomposition point of AlH<sub>2</sub>(tBuNCH<sub>2</sub>CH<sub>2</sub>NMe<sub>2</sub>), which is ca. 185 °C. Similar growth rates, resistivities, and film compositions were observed in ALD film growth trials using AlH<sub>2</sub>(tBuNCH<sub>2</sub>CH<sub>2</sub>NC<sub>4</sub>H<sub>8</sub>). </p>