Superimposed high power impulse and middle frequency magnetron sputtering: Role of pulse duration and average power of middle frequency

The low deposition rate of the high power impulse magnetron sputtering (HiPIMS) somewhat limits its commercial applications in thin film and coating industries. In this work, an effective way to improve the deposition rate of TiN film by superimposing the middle-frequency (MF) pulses during off-time of HiPIMS pulsing was discussed. Superimposition of HiPIMS and MF fabricated TiN films with relatively smooth surface. All samples were found to have a single phase TiN according to the chemical composition and crystallographic analyses. The highest film hardness of ~ 31 GPa, elastic modulus of 313 GPa, and a density of 5.35 g/cm3 were obtained in the sample grown at a MF pulse duration of 150 μs in each superimposed cycle. The higher the deposition rate was achieved with longer MF pulse duration. This superimposition technique successfully improved the power-normalized deposition rate from 4.5 to 17.2 nm/kW·min without significantly declining the mechanical properties and adhesion quality of deposited films. The role of MF pulse duration and average MF power were further studied in this work. It can be concluded that the MF pulse duration played a more significant role and showed a dominant influence on the plasma characteristics and resulting properties of deposited TiN films.