Atomic layer deposition of $$\text {HfO}_2$$ HfO2 for integration into three-dimensional metal–insulator–metal devices

Abstract

HfO2 nanotubes have been fabricated via a template-assisted deposition process for further use in three-dimensional metal–insulator–metal (MIM) devices. HfO2 thin layers were grown by Atomic Layer Deposition (ALD) in anodic alumina membranes (AAM). The ALD was carried out using tetrakis(ethylmethylamino)hafnium and water as Hf and O sources, respectively. Long exposure durations to the precursors have been used to maximize the penetration depth of the HfO2 layer within the AAM and the effect of the process temperature was investigated. The morphology, the chemical composition, and the crystal structure were studied as a function of the deposition parameters using transmission and scanning electron microscopies, X-ray photoelectron spectroscopy, and X-ray diffraction, respectively. As expected, the HfO2 layers grown at low-temperature (T=150∘C) were amorphous, while for a higher temperature (T=250∘C), polycrystalline films were observed. The electrical characterizations have shown better insulating properties for the layers grown at low temperature. Finally, TiN/HfO2/TiN multilayers were grown in an AAM as proof-of-concept for three-dimensional MIM nanostructures.