Chemical mechanism for nucleation enhancement in atomic layer deposition of Pt by surface functionalization

Atomic layer deposition (ALD) of metals on oxide substrates often yields islandlike growth, undesirable toward conductor applications. Thus, enhancement of initial nucleation of metal ALD is of great importance. One potential solution reported is to functionalize the substrate surface with small molecules, such as trimethylaluminum (TMA) and aluminum chloride (AlCl3) before metal ALD, so that nucleation delay is reduced, and the coverage and conformality are enhanced. In this study, density functional theory calculations are utilized to elucidate the chemical mechanism toward a change of the reactivity of the surface toward metal ALD upon functionalization by TMA or AlCl3. Surface adsorption of a typical Pt ALD precursor, trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe3), on an OH-terminated SiO2 surface is compared to its adsorption on AlCH3-terminated and AlCl-terminated surfaces. Considering rate-limiting steps on each surface, greater rates for adsorption of Pt are found for the organometallic-functionalized surfaces than the bare SiO2 surface, confirming the chemical enhancement effect by functionalization.