Effect of Residual Stress on Lattice Parameter and Hardness of Titanium Nitride Films Deposited by Reactive HCD Ion Plating

Residual stress produced in titanium nitride films deposited onto substrates of high speed steel, SKH51, was studied by using sin2ψ method as a function of process parameters: deposition temperature, deposition time, electron beam current, substrate bias voltage, distance from an evaporation source to a substrate, tilt angle of a substrate axis, total gas pressure, and gas mixture ratio [N2]⁄[Ar+N2]. Measurements showed that compressive stress occurred in the films except one deposited without any applied bias voltage to a substrate. Applying a little bias voltage to a substrate brought about a rapid increase in the compressive stress. Higher deposition temperature and lower deposition rate reduced the compressive stress. A decrease in total gas pressure increased the compressive stress. These results suggest that kinetic energy of incident ions on a substrate affects the generation of the compressive stress. In-plane lattice parameter increased with an increase in compressive stress; this variation was in good agreement with the distance calculated on the basis of the Poisson ratio effect. Hardness of the films increased with an increase in the compressive stress. Grain size of the films was determined by the method based on “Williamson-Hall plot” which can exclude the contribution of micro strain from line broadening of X-ray diffraction. Hall-Petch relationship is established between the grain size and the hardness. It seems that mobility of adatoms is closely related to the magnitude of the residual compressive stress.