A non-pyrophoric precursor for the low temperature deposition of metallic aluminium

The development of microelectronics prompts a search for precursors that can deposit conductive features. There is scarce research on Al as it is normally deposited using pyrophoric AlH₃ etherates/aminates. Ligands can impart increased stability while maintaining the ability to deposit target materials. Accordingly, we have engineered an aluminium complex that can undergo conversion to Al(0) at 100 °C. Our multi-step synthetic design features β-ketoiminate compounds, [Al(R-ketoiminate)₂Cl] (R = Me, Et, ⁱPr, Ph and Mes, 1-5) as starting materials to obtain aluminium hydride complexes: the polymeric amidoalane Li[AlH₂(ⁱPr-Hacnac)AlH₃]_n (6) and the imidoalane cluster [AlH₂AlH₂(N-Mes)₃(AlH₂ ּ Li(Et₂O)₂)₂] (8). Decomposition of 8 into aluminium metal is observed when heated under vacuum at 100 °C and is confirmed by XRD, TEM, XPS. Deposition of a highly conductive film of Al is achieved from 8 after three weeks under nitrogen at room temperature. This represents a route to metallic aluminium involving non-pyrophoric precursors at low temperatures.