New strategy for the deposition of metals by CVD and ALD: mechanistic and kinetic investigation for the growth of cobalt as model system
Final Report Abstract
The project aimed at contributing to the mechanistic understanding of the growth conditions of metallic films synthesised by the previously established technique of pulsed spray evaporation chemical vapour deposition (PSE-CVD). While this process had been demonstrated earlier for the deposition of thin films of a variety of transition metals, cobalt was selected as an example to study links between the macroscopic deposition conditions and the microscopic processes involving the precursor, surface properties and the growing thin film. This choice of cobalt as an initial target was particularly interesting because of the earlier observation of carbide formation as a function of the growth conditions. To combine macroscopic and microscopic approaches, several modifications in existing setups as well as some new apparatus had to be designed and built up as a consequence of the joint studies, combining deposition and material characterisation under growth conditions. In particular, a novel deposition reactor was constructed that permits in-situ surface diagnostics while performing PSE-CVD. This reactor was directly attached to a UHV chamber with a transfer mechanism that allowed to study the film growth at any stage of the deposition without contamination. With this novel reactor established in Bremen, systematic investigations using surface analysis were conducted under growth conditions that had been identified, characterised and optimised in Bielefeld. The joint investigations addressed important features of the growth process including the influence of the nature of the metal centre, the temperature sensitivity of carbon contamination versus carbide growth, the role of ethanol, both as a solvent as well as a catalytic agent, the influence of nickel as a seed layer for different combinations of boundary conditions as well as detailed investigation of the mechanism of PSE-CVD from Co(acac)2 in ethanol. The reproducibility of the depositions – necessary also to study similar conditions in both laboratories – was not entirely satisfactory until the important role of water in the deposition became clear and was investigated in more detail.
Publications
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Design of a compact ultrahigh vacuum-compatible setup for the analysis of chemical vapor deposition processes. Review of Scientific Instruments 85, 104104 (2014)
Th. Weiss, M. Nowak, U. Mundloch, V. Zielasek, K. Kohse-Höinghaus, M. Bäumer
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Influence of Water on Chemical Vapor Deposition of Ni and Co thin films from ethanol solutions of acetylacetonate precursors. Scientific Reports volume 5, Article number: 18194, 2015
Th. Weiss, V. Zielasek, M. Bäumer
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Investigation of the growth behaviour of cobalt thin films from chemical vapour deposition, using directly coupled X-ray photoelectron spectroscopy. Zeitschrift für Physikalische Chemie, Bd. 229, H. 10-12, (2015), S. 1887–1905
P.H. Tchoua Ngamou, A. El Kasmi, Th. Weiss, H. Vieker, A. Beyer, V. Zielasek, K. Kohse-Höinghaus, M. Bäumer
