Wednesday, September 16, 2015

Surface Chemistry of Copper Metal and Copper Oxide ALD

To produce continuous non-island forming films of copper by ALD is extremely difficult. Here is a good article from Fraunhofer ENAS in Chemnitz, Germany, on the mechanism behind ALD of Copper and coper oxide using the rather well studied Cu(acac)2 precursor but not so easy process. 

Surface Chemistry of Copper Metal and Copper Oxide Atomic Layer Deposition from Copper(II) Acetylacetonate: A Combined First-Principles and Reactive Molecular Dynamics Study

(Physical Chemistry Chemical Physics) Monday September 14th 2015
Author(s): Xiao Hu, Joerg Schuster, Stefan Schulz, Thomas Gessner

Atomistic mechanisms for the atomic layer deposition using the Cu(acac)2 (acac = acetylacetonate) precursor are studied by first-principles calculations and reactive molecular dynamics simulations. The results show that Cu(acac)2 chemisorbs on the hollow site of the Cu(110) surface and decomposes easily into a Cu atom and the acac-ligands. A sequential dissociation and reduction of the Cu precursor [Cu(acac)2→Cu(acac)→Cu] is observed. Further decomposition of the acac-ligand is unfavorable on the Cu surface. Thus additional adsorption of the precursors may be blocked by adsorbed ligands. Molecular hydrogen is found to be nonreactive towards Cu(acac)2 on Cu(110), whereas individual H atoms easily lead to bond breaking in the Cu precursor upon impact, and thus release the surface ligands into the gas-phase. On the other hand, water reacts with Cu(acac)2 on a Cu2O substrate through a ligand-exchange reaction, which produces gaseous H(acac) and surface OH species. Combustion reactions with the main by-products CO2 and H2O are observed during the reaction between Cu(acac)2 and ozone on CuO surface. The reactivity of different co-reactants toward Cu(acac)2 follows the order H > O3 > H2O.

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