Target voltage measurements during DC sputtering of silver in a nitrogen/argon plasma

Abstract

During reactive sputtering, addition of the reactive gas results in a target voltage change. This effect finds its origin in the modification of the gas composition but also in the change of the target condition. In this paper, we focus on the target voltage changes during magnetron sputtering of silver in an argon/nitrogen plasma. In the first second during the nitrogen addition, we notice a decrease of the target voltage followed by an increase in target voltage. The target voltage decrease can be easily explained from the increased volume ionisation. The change of the target condition seems to be responsible for the target voltage increase. However, this effect cannot be explained from the formation of a silver nitride phase on the target surface as generally accepted during reactive sputtering of metal nitrides. Indeed, silver is a poor nitride former. To explain the target voltage increase, we have studied in this paper the influence of ion implantation of N 2 + ions on the target voltage during magnetron sputtering. The ions were implanted in situ in a silver target and the target voltage of this modified target was registered under the same conditions as during the sputtering experiments. The implantation of the N 2 + ions results in a target voltage increase. Hence, during sputtering of a silver target in an argon/nitrogen plasma, the target voltage increases by the presence of non-reacted N atoms in the target top surface layers.