Growth and properties of Ti-Cu films with respect to plasma parameters in dual-magnetron sputtering discharges

Properties of different methods of magnetron sputtering (dc-MS, dual-MS and dual-HiPIMS) are studied and compared with respect to intermetallic Ti-Cu film formation. The quality and features of thin films are strongly influenced by the energy of incoming particles. The ion velocity distribution functions (IVDFs) were measured by time-resolved retarding field analyzer (RFA) in the substrate position. Thin films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD) and X-ray reflectometry (XR). Properties and crystallography of Ti-Cu films are discussed as a function of ion energy which is affected by the mode of sputtering. It was found that IVDFs measured in pulsed discharges exhibit double-peak distribution. The IVDFs reach the maximum at ion energies about  ~8 eV. The ion saturated current is highest in dual-HiPIMS discharge (~5 μA/cm²) and is mostly represented by Cu⁺ and Ar⁺ ions. The mode of sputtering influences chemical composition and film formation. The copper forms polycrystalline fcc-phase while much smaller Ti particles enwraps the copper crystallites or are part of a solid solution.