Thermal ALD of aluminum metal at low temperature

Aluminum metal is important in semiconductor devices and as a metal itself in metallization and as an alloy in e.g. TiAl metal gates or TiAlN electrodes. Prof. Winter and his team at Wayne State have previously published new paths to thermal ALD of titanium, here they published their recent achievement for thermal ALD of aluminum!

Atomic Layer Deposition of Aluminum Metal Films Using a Thermally Stable Aluminum Hydride Reducing Agent

Kyle J Blakeney and Charles H. Winter

Chem. Mater., Just Accepted Manuscript

LINK: https://pubs.acs.org/doi/abs/10.1021/acs.chemmater.8b00445 

The thermal atomic layer deposition of aluminum metal films at temperatures as low as 100 °C is described using AlCl₃ and a new aluminum dihydride complex that is supported by a bulky amido-amine ligand. A growth rate of about 3.5 Å/cycle was observed within a 120-160 °C ALD window and self-limiting growth was established for both precursors. Resistivities as low as 3.03 Ω·cm were obtained for the aluminum metal films. Root mean square surface roughnesses were 19-23% of the film thicknesses, as determined by atomic force microscopy. Films grown on TiN substrates were crystalline by X-ray diffraction. X-ray photoelectron spectroscopy of films grown at 100 and 140 °C showed Al (> 94 at%) with C and Cl impurities below the detection limit (< 1 and 0.5 at%, respectively). Accordingly, this process affords high purity, low resistivity aluminum metal films.