Unravelling nucleation in Pt atomic layer deposition using grazing incidence X-ray total scattering, grazing incidence small- angle X-ray scattering, and X-ray fluorescence

Atomic layer deposition (ALD) of metals is typically nucleation-controlled: initially, 3D nanoislands/nanoparticles (NPs) form. They grow and eventually coalesce to create a continuous thin film as the number of ALD cycles increases. To achieve a continuous layer at a lower thickness, which is important for applications in the semiconductor industry [1], a higher nucleation density is needed. Existing research predominantly emphasizes NP size and coverage during the later stages of nucleation. However, the current state-of-the-art lacks comprehensive insights into the initial stages of nucleation and the atomic 3D structure of NPs, thereby limiting controllability. This study aims to investigate the early stages of nucleation, within a length scale of < 10 nm, with multi-modal X-ray methods in grazing incidence geometry. X-ray total scattering, used to derive the pair distribution function (PDF) in grazing incidence geometry (GIPDF), is a recent development for studying the structure of thin films.[2] The main benefit of the total scattering method for this work is its sensitivity to the length scales manifested in the early stages of nucleation, specifically size < 4 nm. Pt NPs deposited on fused silica with conventional, thermal ALD (MeCpPtMe3-O2) at varying, relatively low loadings ( 4 nm). Simultaneously with GISAXS measurement, Pt loadings (# atoms/cm2) of the samples were extracted from the Pt fluorescence line obtained via X-ray fluorescence (XRF). Combined, these X-ray techniques advance understanding of nucleation, especially during early stages, and pave the way to better control the nucleation density. References: [1] George, S. M. et al. Chem. Rev. 110, 1, 111-131 (2009) [2] Dippel, A.-C. et al. IUCrJ, 6, 290-298 (2019) [3] de Paula, C. et al. Chem. Mater. 32, 315-325 (2020) [4] Juan Santo Domingo Peñaranda. Doctoral Thesis (2024)