Mechanisms of target poisoning during magnetron sputtering as investigated by real-time in situ analysis and collisional computer simulation

The evolution of reactive gas uptake at the target surface has been investigated by real-time in situ diagnostics during magnetron sputtering. Using a planar circular dc magnetron for reactive sputter deposition of TiN from a Ti target in an argon/nitrogen gas mixture, the target uptake of nitrogen was determined at varying gas flows of nitrogen using the N14(d,α)C12 nuclear reaction, directly demonstrating the target “poisoning” effect. The expected hysteresis behavior at increasing/decreasing nitrogen gas flow is confirmed. Within the precision of the measurement, the nitrogen content remains unaltered after switching off the magnetron, indicating the absence of a significant mobile fraction of nitrogen in the target. The maximum amount of retained nitrogen significantly exceeds one adsorbed monolayer, which is attributed to nitrogen ion implantation and recoil implantation of adsorbed nitrogen. This is quantitatively reproduced by TRIDYN collisional computer simulations.