Influence of magnetic field configuration on plasma characteristics and thin film properties in dual magnetron reactive high power impulse magnetron sputtering discharge with Al in Ar/O2 mixture

In this work, the influences of the magnetic field configuration (mirror-field and closed-field) on plasma parameters and ion flux dynamics of dual magnetron reactive high power impulse magnetron sputtering (R-HiPIMS) with Al targets in Ar/O2 mixture were studied by time-resolved Langmuir probe and time-averaged mass spectrometer. Compared with mirror-field configuration, the electron density (ne) in the closed-field discharge is obviously higher while the plasma potential (Vp), floating potential (Vf) and effective electron temperature (Teff) were lower. Time-averaged mass spectrometer results showed that the plasma compositions in both configurations were similar. The ion energy distribution functions (IEDFs) recorded at both discharges consisted of three components: a main narrow peak at low energy followed by a broad shoulder and then a high energy tail. Compared with the closed-field discharge, the mirror-field discharge exhibited higher peak energies but lower ion fluxes. For both discharges, the ions intensity increased immediately after the start of the negative voltage pulse. The signal for the mirror-field discharge peaked exactly at the end of the pulse, whereas fluxes of the ion species in the closed-field configuration reached the highest value 10μs after the voltage pulse termination. To investigate how changes in the magnet arrangement affect the film properties, Al2O3 thin films were deposited and characterized. It is confirmed that the magnet configuration appeared to have little influence on the deposition rate. In addition, high average energy per deposited atom in the closed-field discharge resulted in a well densified and stoichiometric crystalline Al2O3 film. •Crystalline Al2O3 films by dual magnetron reactive HiPIMS•The average energy per deposited atom (〈Ed〉) correlates with the refractive index.•Mirror-field discharge exhibits higher 〈Ed〉 compared to closed-field.•Closed-field discharge exhibits higher ion flux compared to mirror-field.