Mass Spectrometry Study of the Temperature Dependence of Pt Film Growth by Atomic Layer Deposition

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Insights into the temperature dependence of atomic layer deposition (ALD) of Pt using (methylcyclopentadienyl)trimethylplatinum, (MeCp)PtMe3, precursor and O2 are presented, based on a study of reaction products by time-resolved quadrupole mass spectrometry (QMS) measurements. Above 250°C, Pt ALD proceeds through unhindered O2 dissociation at the Pt surface, inducing complete and instantaneous combustion of the precursor ligands. Quantification of the QMS data revealed that at 300°C, approximately 20% of the C-atoms react during the precursor pulse, forming mainly CH4 (∼18%) balanced by CO2 (∼2%). The remaining 80% of the C-atoms are combusted during the O2 pulse. Time-resolved data indicated that the combustion reactions compete with the hydrogenation reactions for the available surface carbon. Combustion reactions were found to be dominant, provided that a sufficient amount of chemisorbed oxygen is available. When the temperature drops below 250°C, deposition becomes hindered by the presence of a carbonaceous surface layer of partially fragmented and dehydrogenated precursor ligands, formed during the precursor pulse. The carbonaceous layer limits dissociative chemisorption of O2 and hence combustion reactions (leading to CO2) whereas reduced surface reactivity also limits (de-)hydrogenation reactions (leading to CH4). Below 100°C, the carbonaceous layer fully prevents O2 dissociation and ALD of Pt cannot proceed.