Titanium film deposition by high-power impulse magnetron sputtering: Influence of pulse duration

Surface modification with high-power glow discharges is a promising physical vapor deposition (PVD) technology for industrial usage. A metal ion density higher than 1018 m−3 can be obtained due to a high-power input in the plasma. In the present paper, titanium films were deposited on Si (100) substrates using high-power impulse magnetron sputtering (HIPIMS). The pulse duration was varied to investigate the deposition rate and the titanium film structure. The plasma source was an unbalanced magnetron sputtering (UBMS) discharge generation system. The deposition rate was correlated to the electrical characteristics. There was an instantaneous power threshold of approximately 36 kW to significantly increase the deposition rate by 4–5 times. The deposition rate increased linearly with respect to the average power until the average power reached 5.6 kW (about 30 W/cm2 for a total area of the target), and an 83% increase of the deposition rate from the linear relationship was observed. The increase of the deposition rate was possibly closely related to the so-called thermal spike, where the target temperature increases due to a high power input to the target. The surface morphology and the crystalline structure of the films were studied for a variety of pulse durations, and the results were compared to the case of the direct-current magnetron sputtering (dcMS) process. The titanium films at an average power of 1.2 kW and a pulse duration of 50 μs have a smaller crystalline size and a smoother surface than those at an average power of 825 W by dcMS. The crystal orientation (101) was dominated when the pulse duration was lengthened to 180 μs, although the (002) orientation was dominant in dcMS. The crystal size and the surface roughness increased significantly when the pulse duration was increased from 50 μs to 180 μs in HIPIMS. The consumed power in the plasma by HIPIMS can be an important parameter for the crystal size and the structure.