Materials’ properties of low temperature deposited Cu/W and Cu/Cr multilayer thin films using high power impulse magnetron sputtering

In this study, copper/tungsten (Cu/W) and copper/chromium (Cu/Cr) multilayers were created by stacking bilayer films in a 3:1 ratio, with layer thicknesses ranging from 400 to 800 nm, deposited on Si (100) substrates using high power impulse magnetron sputtering (HiPIMS). The microstructural and surface properties of these films were examined through x-ray diffraction, atomic force microscopy, and scanning electron microscopy. Electrical properties were assessed using a four-point probe, while mechanical properties were measured via nanoindentation. Both multilayer systems showed a decrease in the hardness accompanied by an increase in the elastic modulus with each stacking bilayer. The Cu/W system experienced a gradual hardness reduction (down to 19%), compared to the Cu/Cr system, which exhibited a similar decrease (14.5%). The Cu/W and Cu/Cr multilayer film samples consistently demonstrate a softer nature compared to their bilayer counterparts due to the influence of the underlying Cu soft layers. A distinctive surface smoothness in these multilayer systems correlates with the elastic modulus in a manner unlike that with hardness. These multilayer films also demonstrated altered electrical resistivity, enhancing our understanding and capabilities in fabricating films with an increased number of layers.