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

Abstract

Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Insights into the temperature dependence of atomic layer deposition (ALD) of Pt using (methylcyclopentadienyl)trimethylplatinum, (MeCp)PtMe 3 , precursor and O 2 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 O 2 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 CH 4 (∼18%) balanced by CO 2 (∼2%). The remaining 80% of the C-atoms are combusted during the O 2 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 O 2 and hence combustion reactions (leading to CO 2 ) whereas reduced surface reactivity also limits (de-)hydrogenation reactions (leading to CH 4 ). Below 100 • C, the carbonaceous layer fully prevents O 2 dissociation and ALD of Pt cannot proceed.

Plasma‐Assisted Atomic Layer Deposition of PtOx from (MeCp)PtMe3 and O2 Plasma

“…[23] The incorporation of H 2 O in the matrix can be related to the H 2 O formed as a reaction product from the combustion of the precursor ligands, which is well known for Pt ALD. [9,24] In the work of Hämäläinen et al an O/Pt ratio between 1.09 and 1.66 has been reported. This is significantly lower than the value of 2.5 found in this work, and is most likely due to the fact that an O 2 plasma is a stronger oxidizing reactant than ozone.…”

“…This has been attributed to the formation, by the precursor ligands during the precursor pulse, of a carbonaceous layer which blocks the catalytic dissociation of O 2 . [9] The lower limit of the temperature window can be reduced significantly however, by making use of an O 2 plasma rather than O 2 gas. [7] Since reactive O radicals are supplied from the gas phase by the plasma, there is no need to first dissociate the O 2 at the surface in order to participate in surface reactions.…”

“…This means that the carbonaceous layer formed by the precursor ligands can be combusted at much lower temperatures, and as a result, Pt can be deposited at temperatures as low as RT using PA-ALD. [7,9,10] Without the need for O 2 dissociation at the surface, nucleation of the Pt film also proceeds faster in the case of PA-ALD. [11] Generally, achieving nucleation of Pt on oxide surfaces such as SiO 2 and Al 2 O 3 is challenging because of the absence of catalytically active Pt that induces O 2 dissociation during the initial cycles.…”

“…[11] Generally, achieving nucleation of Pt on oxide surfaces such as SiO 2 and Al 2 O 3 is challenging because of the absence of catalytically active Pt that induces O 2 dissociation during the initial cycles. [12] Precursor adsorption on a bare oxide substrate is not likely to be the limiting factor during nucleation, [9] however this only results in the deposition of Pt precursor fragments leading to insufficient catalytic activity for effective O 2 dissociation. Mackus et al have shown that prolonged exposure to O 2 gas facilitates the diffusion of Pt species across the oxide surface, leading to ripening of Pt islands.…”

(Invited) Catalytic Surface Reactions during Nucleation and Growth of Atomic Layer Deposition of Noble Metals: A Case Study for Platinum

“…By using mass spectrometry, Aaltonen et al established for Ru and Pt that CO 2 and H 2 O are formed during both ALD half-reactions as the main reactions products, implying that combustion-like reactions play a dominant role (13). By gas-phase infrared spectroscopy, and later also by mass-spectrometry (15,19), it was observed for Pt ALD that CH 4 is also formed during the MeCpPtMe 3 pulse (14), which revealed a concurrent reaction pathway in addition to ligand combustion. In these studies, the catalytic nature of the surface was only partly considered.…”