Ionisation fractions of sputtered titanium species at target and substrate region in HiPIMS

Abstract

In this paper, the ground state number densities of titanium atom and ion, ionised density fraction and ionised flux fraction were determined in a high power impulse magnetron sputtering process. Three regions of interest within the deposition chamber were studied; the magnetised plasma region, middle region, and substrate region. Pulse length and applied power were kept constant and working pressure and duty cycle were varied. The effective branching fractions method was utilised to evaluate the number densities of sputtered species from a measured optical emission signal. A biasable quartz crystal microbalance system was used to evaluate the ionised flux fraction and deposition rate. The highest ionised density fraction of 90% was reached in the target region for 1.2% duty cycle and it was mostly independent on working pressure. Moving from the target, the ionised density fraction was observed to decrease. In the substrate region for a duty cycle below 2% and the whole studied working pressure range, the ionised density fraction always reached at least 50%.