Angle-resolved investigation of ion dynamics in high power impulse magnetron sputtering deposition system

• Ion velocity distribution functions (IVDF) have been investigated in reactive HiPIMS.
• An effect of oxygen partial pressure on measured IVDF has been investigated.
• The modified Katsumata probe was used for angle- & time-resolved measurement of IVDF.
• The results revealed spatially non-homogeneous ion flux for reactive atmosphere.
• The IVDFs measured at angle 45° demonstrated significantly enhanced energy tail.

The high power impulse magnetron sputtering deposition system (HiPIMS) equipped with 5 cm in diameter titanium target has been investigated by means of time-resolved modified Katsumata probe. The probe allows for determination of the ion velocity distribution function. However, the modified Katsumata probe is unable to resolve the mass of ions. On the other hand, compact construction of modified Katsumata probe allows us to place the probe in an arbitrary position with respect to planar magnetron. The present construction of modified Katsumata probe allows reaching the acceptance angle of about 15°. The ion velocity distribution function (IVDF) in forward direction is then directly proportional to the derivative of measured ion current with respect to the retarding potential. An angle-resolved study of HiPIMS system operating in the reactive atmosphere has been carried out. The effect of oxygen partial pressure on measured IVDF at different angles within the plasma pulse has been investigated. The total pressure was held at 1 Pa together with the constant pulse-on time of 100 μs, pulse frequency of 100 Hz and mean discharge current of 500 mA for all the experiments. The results revealed inhomogeneous ion fluxes in different directions from the target especially for reactive atmosphere. The IVDFs measured at angle 45° demonstrated significantly enhanced energy tail in contrast to dc magnetron or mid-frequency pulsed-dc magnetron. Furthermore, higher oxygen partial pressure indicated broader IVDF for all the angles together with a slight shift of IVDF peak to negative values indicating the negative plasma potential.