Effect of ion control strateaies on the deposition rate and properties of copper films in bipolar pulse high power impulse magnetron sputtering

Cu films were deposited on the silicon substrate at ground potential by bipolar pulse and conventional HiPIMS configurations in combination with different bias voltages. The fraction and energy of ion bombardment were tailored using different control strategies. The increasing deposition rate mechanism for bipolar pulse HiPIMS was discussed based on a phenomenological equilibrium analytical model. The morphology, structure, stress, electrical and mechanical properties of Cu films were investigated. Our results show that the positive pulse has a minor influence on the ionization rate of target materials in plasma, but it can effectively resist the ions back and drive them to arrive at the substrate during the deposition process. The deposition rate improves by similar to 55% for KP100 and KV100 samples than CHiPIMS. The positive reversed pulse in the whole pulse-off time benefits a compact microstructure, smooth surface morphology and minor residual tensile stress for Cu films due to the high energy of accelerating ions. Cu films prepared by BPH method exhibit good adhesion strength, electrical and tribological properties. When the kick voltage increases to 50 V with a constant kick pulse length, the critical load for the copper film reaches 10 N, and the COF is also the lowest. The high bias voltage causes a rising coefficient of friction, likely due to cavities on the film's surface.