A non-pyrophoric precursor for the low temperature deposition of metallic aluminium
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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 AlH 3 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) 2 Cl] (R = Me, Et, i Pr, Ph and Mes, 1 - 5 ) as starting materials to obtain aluminium hydride complexes: the polymeric amidoalane Li[AlH 2 ( i Pr-Hacnac)AlH 3 ] n ( 6 ) and the imidoalane cluster [AlH 2 AlH 2 (N-Mes) 3 (AlH 2 ּ Li(Et 2 O) 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.
