Conductive ultra-thin silver films are commonly fabricated by physical vapor deposition methods such as evaporation or sputtering. The line-of-sight geometry of these techniques impedes the conformal growth on substrates with complex morphology. In order to overcome this issue, volume deposition technologies such as chemical vapor deposition or atomic layer deposition are usually preferred. However, the silver films fabricated using these methods are generally non-electrically conductive for thicknesses below 20–50 nm due to island formation. Here, we demonstrate a novel approach for producing ultra-thin conductive silver layers on complex substrates. Relying on chemical vapor-phase deposition and plasma post-treatment, this two-step technique allows the synthesis of highly conductive and uniform silver films with a critical thickness lower than 15 nm and a sheet resistance of 1.6 Ω/□ for a 40 nm-thin film, corresponding to a resistivity of 6.4 μΩ·cm. The high infrared reflectance further demonstrates the optical quality of the films, despite a still large root-mean-square roughness of 8.9 nm. We successfully demonstrate the highly conformal deposition in lateral structures with an aspect ratio of up to 100. This two-step deposition method could be extended to other metals and open new opportunities for depositing electrically conductive films in complex 3D structures.

The control of nanometer-scale metallic silver particles morphology and their functional properties on a large scale represent a key factor for applications such as plasmonics, sensors, catalysts, or antimicrobial surfaces. The present work investigates in detail the growth of Ag nanoparticles deposited by plasma-enhanced atomic layer deposition (PE-ALD), from triethylphosphine­(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate)­silver­(I) [Ag­(fod)­(PEt3)C16H25AgF7O2P] as the Ag precursor and H2 as the reducing agent. The uniformity of the deposition in terms of nanoparticle morphology and chemical composition over a large surface area (8 in.) is analyzed using an original method. For all morphological, crystallographic, and chemical quantities, we report both the value at the center position and more originally, the gradient over a 10 cm distance on the substrate. The evolution of the gradient provides significant information on the growth mechanism. An effective growth rate of 0.020 ± 0.003 nm/cycle at 130 °C determined by energy-dispersive X-ray spectroscopy is found uniformly over the whole 8-inch area of the sample. According to X-ray diffraction and X-ray photoemission spectroscopy performed on the whole silicon wafer, the deposited material is made of polycrystalline pure metallic Ag, with a low amount of impurities emanating from the precursor, showing the completeness of the reduction reaction. Under self-limiting conditions, the effects of the chamber temperature and cycle number on the morphology of Ag nanoparticles deposited on silicon are analyzed. The results suggests that the Ag thin films mainly evolve following a material transfer. Two potential mechanisms are in competition: the migration of the particles and their further coalescence through the Volmer–Weber growth mode or a “surface Ostwald ripening”-like process. Under certain conditions, this last mechanism could explain the nonuniformity of the deposition.

Simultaneously inducing preferred crystalline orientation with a strong piezoelectric response in polycrystalline aluminum nitride (AlN) thin films by atomic layer deposition is a technical challenge due to the upscaling of the integration of piezoelectric functionalities, such as sensing and actuation, in micro-devices without any poling process. Utilizing low-temperature plasma-enhanced atomic layer deposition (PE-ALD), highly c-axis-oriented AlN films have been prepared with precise control over the relative composition, purity levels, and chemical states of constituent elements. Tailoring thermodynamic parameters, such as the growth temperature and purging time after the trimethylaluminum precursor pulsing before the N2:H2:Ar plasma reaction, provide the possibility of modulating the texture coefficient and the relative piezoelectric response. The effective transverse piezoelectric e31,f coefficient of 0.37 C/m2 was achieved on the AlN film grown at 250 °C and 30 s with the highest texture coefficient TC(002) of 2.75 along the c-axis orientation. The process proposed, at a low temperature with the highly conformal growth of aluminum nitride thin films by PE-ALD, opens up pathways to design novel piezoelectric functional materials for micro-electro-mechanic system devices with complementary metal oxide semiconductor process temperature compatibility.

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In this study, less contaminated and porous SiO2 films were grown via ALD at room temperature.