The effect of Ti sputter target oxidation level on reactive High Power Impulse Magnetron Sputtering process behaviour

This paper investigates the effect of sputter target oxidation level on reactive process behaviour during High Power Impulse Magnetron Sputtering of transition metal target (Ti) in Ar/O₂ atmosphere. It was found by this study that the sputter target state depends on the history of its use in reactive HIPIMS mode. The effect appears to be pronounced strongly due to the significance of ion irradiation induced effects leading to enhanced sputter target oxidation. The target sputter cleaning times (e.g. after a reactive deposition run) are long (compared to DC sputtering) due to the same reason. The abovementioned effect has serious implications for the hysteresis behaviour and reactive deposition process window. It is shown in this paper that the hysteresis loop can be artificially suppressed or even eliminated and the reactive deposition process window can be reduced a number of times if the starting target surface is not a clean metal surface but a partially oxidised metal surface. Such target surface condition is readily obtainable for the targets that have a history of prolonged use in reactive HIPIMS mode. Processing parameters, such as pulse frequency and peak voltage pulse values are shown to have influence on the degree to what the abovementioned effects occur.