Effect of discharge power on target poisoning and coating properties in reactive magnetron sputter deposition of TiN

Reactive magnetron sputtering is a well-established technique for the deposition of high quality functional compound coatings. However, avoiding the undesired hysteresis effect that occurs when the metal target becomes covered by a compound layer at a certain reactive gas flow or partial pressure, typically referred to as target poisoning, is still an intense field of research. In the current work, the effect of the discharge power on target poisoning and coating structure and properties was assessed by determining the hysteresis and by characterizing the sputter-deposited TiNx coatings, where x <= 1. With increasing discharge power, the hysteresis was shifted to higher N-2 gas flow values. In metallic mode, the increase in discharge power enabled therefore the incorporation of high nitrogen fractions in the TiNx coatings at stable discharge conditions and high deposition rates. In poisoned mode, all coatings were stoichiometric, but the deposition rates were lower by a factor of 1/3. Regardless of the deposition mode, grain refinement and high stresses generated due to the increase in the deposition rate at elevated deposition power increased the hardness and elastic modulus of the deposited TiNx coatings. At a power density of 34 W/cm(2), the hysteresis was largely eliminated and a deposition rate of 0.15 lm/min for stoichiometric TiNx with high hardness of up to similar to 30 GPa could be achieved. The results presented in this paper demonstrate that increasing the discharge power density facilitates the deposition of stoichiometric TiN by operating in the metal/transition mode. (C) 2016 American Vacuum Society.