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

TL;DR

This paper introduces a non-pyrophoric method for depositing metallic aluminum at low temperatures, which could improve safety and efficiency in microelectronics manufacturing.

Contribution

A new non-pyrophoric aluminum precursor is developed for low-temperature deposition of metallic aluminum.

Findings

An aluminum complex decomposes into metallic aluminum at 100 °C under vacuum, confirmed by XRD, TEM, and XPS.

A highly conductive aluminum film was deposited at room temperature after three weeks under nitrogen.

The method uses β-ketoiminate compounds to synthesize stable aluminum hydride complexes.

Abstract

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.

The development of microelectronics requires precursors that can deposit conductive features, however Al is normally deposited using pyrophoric AlH3 etherates/aminates. Here, the authors use ligands to impart stability and report an aluminium complex that can undergo conversion to Al(0) at 100 °C.

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