ALD/ALE 2024 Session AS-TuM: Selective ALD

Tuesday, August 6, 2024 10:45 AM in Room Hall 3E

Tuesday Morning

Start	Invited?	Item
10:45 AM	Invited	AS-TuM-12 Novel Carbon-based Ligands on Planar Metal Surfaces: Self Assembled Monolayers and Applications in Atomic Layer Deposition Cathleen Crudden (Queen's University, Canada) The use of N-heterocyclic carbenes to modify homogeneous metal catalysts is widespread since the high metal–carbon bond strength renders high oxidative and chemical stability to the resulting metal complexes. The use of these carbon-based ligands to modify metal surfaces has received considerably less attention. We will describe the modification of planar metallic surfaces with carbene ligands. The nature of the surface overlayer is strongly dependent on the structure of the carbene. The ability of these carbene overlayers to bind to a range of metals and act as small molecule inhibitors for atomic layer deposition processes will be described.
11:15 AM		AS-TuM-14 Enhancing Selectivity for AS-ALD of MoO₂ through Hydrogen Treatment: Strategy of Surface Cleaning and Expanding Deactivated Areas Hae Lin Yang, Ji-Hyeon Kwon, Chang-Kyun Park (Hanyang University, Korea); Seunghwan Lee, Beomseok Kim, Changhwa Jung, Hanjin Lim (Samsung Electronics Co., Inc.); Jin-Seong Park (Hanyang University, Korea) Recently, in the field of DRAM capacitors, the demands for precisely depositing MoO₂ thin films for resolving the high leakage issue between high-k dielectric and TiN electrodes, onto TiN without additional patterning¹. To meet these demands, Area selective atomic layer deposition (AS-ALD), which allows selective deposition on certain areas without undesired deposition on adjacent areas, is essential. Also accomplish the high selectivity of high-resolution films with high spatial resolution, the introduction of inhibitors is needed especially small molecular inhibitors (SMIs). SMIs consist of inert tail portions composed of single molecules, enabling them to have small sizes suitable for narrow lines at the nanometer scale. However, SMIs typically have short tail groups that cannot undergo van der Waals interactions, and they cannot densely cover the substrate surface due to steric hindrance from adjacent adsorbed SMIs during precursor adsorption². Therefore, considerations regarding the treatment of unadsorbed areas and the removal of remaining reactive groups after SMI adsorption are necessary. To address this, we added a hydrogen treatment process during the AS-ALD process of MoO₂ using TCPS [C₆H₅SiCl₃] and DMA-TMS [(CH₃)₃SiN(CH₃)₂] as SMIs and analyzed the effects of hydrogen treatment on surface properties and selectivity using XPS, WCA, and AES mapping. Additionally, we calculated reaction energies for each adsorption step and final forms for each SMI-adhered surface using DFT and RSA simulations. TCPS, owing to its aromatic phenyl ring, covers a wider range of SiO₂ surfaces than DMA-TMS. However, only two out of three Cl ligands react, leaving about 1.4% of the remaining Cl ligands after TCPS adsorption, increasing the surface energy and acting as adsorption sites for Mo precursors. However, by adding a hydrogen treatment cycle during the process, all remaining Cl ligands were removed, resulting in a 13° increase in WCA and a dramatic increase in selectivity from 61% to 96%. Furthermore, hydrogen treatment not only removed residual impurities but also reduced exposed -OH groups on the surface by converting them to -H, as confirmed by the results of hydrogen treatment added during the DMA-TMS process. Despite the absence of impurities to be removed, the WCA increased by approximately 7° after hydrogen treatment, and the selectivity also increased from 84% to 94.5%. In this way, appropriate treatments during AS-ALD processes, though simple, can effectively increase selectivity, enabling precise selective deposition in desired areas even in complex structures. View Supplemental Document (pdf)
11:30 AM		AS-TuM-15 Contra-Selective Deposition of SiO₂ on Metals Chad Brick, Tomoyuki Ogata (Gelest, Inc) In recent years, an increasing number of area selective processes have been developed for the deposition of dielectric films on dielectric layers. However, reports of the selective deposition of dielectric films on metal regions of a substrate are comparatively rare, typically involving the deposition of high-k dielectric films with significantly different chemistry with respect to the target low-k non-growth areas such as SiO₂ or SiN. In this study, a series of heteroatom-containing silanes with inherent selectivity towards metals over SiO2 and SiN and their conversion to SiO2 via plasma-enhanced atomic layer deposition have been investigated. It will be shown that under appropriate conditions, indefinitely thick films of SiO2 can be selectively grown on metals such as copper and cobalt with pre-existing native or thermal silicon dioxide as the non-growth substrate. Mechanisms of this unusual “contra-selectivity”, with a film growing not only on a material other than itself with its unblocked self as a non-growth surface, but also continuing to grow to arbitrary thickness despite the near-identical nature of the growth and non-growth surfaces after the first few deposition cycles, will be discussed.
11:45 AM		AS-TuM-16 Photoluminescent Graphene-Lanthanide Heterostructures via Direct Laser Writing and Area-Selective Atomic-Molecular Layer Deposition Aleksei Emelianov, Kamila Mentel (University of Jyväskylä); Amr Ghazy (Aalto University); Andreas Johansson (University of Jyväskylä); Maarit Karppinen (Aalto University); Mika Pettersson (University of Jyväskylä) Area-selective atomic-molecular layer deposition (AS-ALD/MLD) is a promising “bottom-up” alternative to the current nanopatterning techniques [1,2]. It has been used on a variety of materials, including the growth of two-dimensional materials (2DM). While there are examples of AS-ALD being used on 2DM, the approach of combining it with AS-MLD is still mostly unexplored. Due to the inherent 2D nature, the surface of 2DM does not provide sufficient reactive sites for the chemisorption of ALD/MLD precursors compared with traditional microelectronics. Functionalization of certain surface areas is required to provide the selective growth of materials. Recently, we have overcome the chemical inertness of graphene to ALD precursors by local activation using direct femtosecond laser two-photon oxidation (TPO) [3] for selective ZnO deposition [4]. In this study, we guided the growth of Eu-organic thin films on top of single-layer graphene via TPO. We achieved high homogeneity and more than 90% selectivity in locally activated predefined regions for Eu films up to 15 nm. The polymer used for graphene transfer significantly affects the selectivity of the ALD/MLD process, as it might leave residues and promote unnecessary deposition in pristine graphene areas. The fabricated graphene/Eu-organic thin films exhibited high photoluminescence at 615 nm even when excited with a 532 nm laser. The films are suitable for various applications in optoelectronics, sensors, and LEDs. References: [1] G. N. Parsons, R. D. Clark, Chemistry of Materials, 32, 4920 (2020). [2] J. Multia, M. Karppinen, Advanced Materials Interfaces, 9, 2200210 (2022). [3] J. Aumanen, A. Johansson, J. Koivistoinen, P. Myllyperkiö, M. Pettersson, Nanoscale, 7, 2851 (2015). [4] K. K. Mentel, A. V. Emelianov, A. Philip, A. Johansson, M. Karppinen, M. Pettersson, Advanced Materials Interfaces, 9, 2201110 (2022). View Supplemental Document (pdf)