Atomic layer deposition (ALD) processes of noble metals are gaining increasing interest for applications in catalysis and microelectronics. Platinum ALD from (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and O2 gas has been considered as a model system for noble metal ALD. However, many questions about the underlying reaction mechanisms remain. In this work, the insight into the Pt ALD reaction mechanisms is extended by considering the catalytic nature of the Pt film. It is evaluated which surface reactions are likely to take place during Pt ALD on the basis of surface science results on the interaction of the Pt surface with O2 and hydrocarbon species, combined with previously reported Pt ALD mechanistic studies. In analogy to the reactions of hydrocarbon species on catalytic Pt, it is proposed that, in addition to combustion-like reactions, dehydrogenation of precursor ligands plays a role in the mechanism. The formation of CH4 during the MeCpPtMe3 exposure pulse is explained by hydrogenation of methyl species by hydrogen atoms released from dehydrogenation reactions. The implications of the surface reactions on the self-limiting behavior, the growth rate, and the temperature dependence of the process are discussed. Moreover, this work demonstrates that surface science studies are of great use in obtaining more understanding of metal ALD processes.
Mackus, A. J. M., Leick, N., Baker, L., & Kessels, W. M. M. (2012). Catalytic combustion and dehydrogenation reactions during atomic layer deposition of platinum. Chemistry of Materials, 24(10), 1752-1761. https://doi.org/10.1021/cm203812v