Aluminum dihydride complexes and their unexpected application in atomic layer deposition of titanium carbonitride films

Abstract

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 AlH2(tBuNCH2CH2NMe2) and AlH2(tBuNCH2CH2NC4H8) are more thermally stable than common Al hydride thin film precursors such as AlH3(NMe3). ALD film growth experiments using TiCl4 and AlH2(tBuNCH2CH2NMe2) produced titanium carbonitride films with a high growth rate of 1.6-2.0 Å per 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 TiC0.8N0.5 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 AlH2(tBuNCH2CH2NMe2), which is ca. 185 °C. Similar growth rates, resistivities, and film compositions were observed in ALD film growth trials using AlH2(tBuNCH2CH2NC4H8).

Synthesis and structural characterization of arsinoamides – early transition metal (Zr and Hf) and main group metal (Al, In, Sn, and Pb) complexes

“…The Al-N (1.819(3) Å) and Al-O (1.869(3) Å) bond lengths are in line with the reported values (e.g. Al-N: 1.792(2) Å and Al-O: 1.9246(10) Å) [29][30][31]. The three-coordinated nitrogen atom adopts an almost planar arrangement considering the sum of the bond angles around the nitrogen atom (357.4°).…”

Synthesis of Doped, Ternary, and Quaternary Materials by Atomic Layer Deposition: A Review

“…In the majority of cases found in Tables –, the supercycle scheme is used to combine two separate binary ALD processes that share one element (e.g., O, N, S) into a single ternary process. Some studies implement deposition with multiconstituent precursors to introduce more than one atom into the film with a single precursor, ,,− ,,,,− and others eschew the supercycle pulsing strategy in other ways ,,,− ,− as discussed in Section ; however, these are far less common among the works shown in the tables. Regarding the use of these alternative approaches, Si-containing compounds are of particular note as SiO 2 itself is often difficult to grow on its own. ,,,,,, A number of studies have successfully deposited Si-containing materials by ALD by using precursor strategies other than supercycles.…”

A Volatile Dialane Complex from Ring Expansion of an N-Heterocyclic Carbene and Its Use in the Thermal Atomic Layer Deposition of Aluminum Metal Films

“…39 Initial attempts to deposit metallic titanium or tungsten films by ALD using this precursor were unsuccessful, instead producing titanium carbonitride and tungsten carbide films, respectively. 40,41 In view of the highly stabilizing effect of NHC ligands, we sought to explore NHC−AlH 3 adducts as reducing coreagents for thermal atomic layer deposition of metal films. No volatility data for these complexes have been reported.…”

“…We recently reported the highly volatile and thermally stable aluminum dihydride complex AlH 2 (tBuNCH 2 CH 2 NMe 2 ) and its use in the thermal ALD of aluminum metal films . Initial attempts to deposit metallic titanium or tungsten films by ALD using this precursor were unsuccessful, instead producing titanium carbonitride and tungsten carbide films, respectively. , …”