Copper thin films deposited under different power delivery modes and magnetron configurations: A comparative study

This study investigated the topological, structural, mechanical (hardness and Young's modulus) and tribological (critical loads and coefficient of friction) properties of copper (Cu) thin films with nanocrystalline structure, smooth and uniform surfaces and thickness of 800 nm, deposited on silicon and graphite substrates by conventional dc magnetron sputtering (dcMS) and HiPIMS operated with single ultra-short pulses (3 μs), in the absence and presence, respectively, of an additional magnetic field. Operating the HiPIMS discharge with such short pulses optimizes the deposition rate and provides a higher fraction of ionized metal flux, while the presence of the additional magnetic field facilitates the transport of charged particles towards the substrate, leading to a higher deposition rate. The density of the deposited thin films was obtained by measuring the areal atomic density using Rutherford backscattering spectrometry and the film thickness by cross-sectional scanning electron microscopy. The nanoindentation results were initially analyzed using the Oliver-Pharr method, and then, in order to correct de pile-up errors, other methods have been employed. Compared to the other samples, mainly due to the high energetic bombardment during the growing process and intense surface diffusion, the Cu thin films deposited using HiPIMS assisted by an additional magnetic field exhibit significantly smoother surfaces, higher crystallinity, denser microstructure, higher hardness and Young's modulus, and lower coefficient of friction.