Deposition rate enhancement in HiPIMS through the control of magnetic field and pulse configuration

In high power impulse magnetron sputtering (HiPIMS) process, the magnetic field and unbalance degree and pulsing configuration are key factors in controlling metal ionization rate and flux of sputtered species towards the substrate. This work reports results on the effect of pulsing configuration (pulse duration) and an auxiliary magnetic field on the deposition rate of ten technologically-relevant elemental target materials (C, Al, Ti, Mn, Ni, Cu, Zn, Mo, Ta, and W) sputtered using HiPIMS. An auxiliary magnetic field was created with a toroidal-shaped permanent magnet placed in front of a strong balanced magnetron. Deposition rates in HiPIMS assisted by this auxiliary magnetic field were compared to those obtained in direct current magnetron sputtering (dcMS) and HiPIMS without an external magnetic field, under the same experimental conditions (average power, gas pressure). It was found that in the case of HiPIMS assisted by the external magnetic field, the deposition rates were approximately 40% to 140% higher compared to HiPIMS without auxiliary magnetic field and, for some materials, even higher compared to those found in dcMS. For copper (Cu) target, total ion current, ion-to-metal flux ratio and ion energy distribution function were measured at the substrate position. Experimental results indicate that during HiPIMS operation (without external magnetic field), the ionized Cu flux fraction increases by 10 to 50% as the pulse duration decreases from 50 to 3 μs, while, in the presence of the external magnetic field, the ionized Cu flux fraction further increases, with values in the range of 40-80% higher. Beside higher deposition rates and increased metal ionization rate, the HiPIMS assisted by the external magnetic field significantly improves Cu target utilization from 20 to 32%. Therefore, deposition rate, metal ion flux towards substrate and target utilization may be optimized by using an appropriate magnetic field and pulsing design.