The effect of Ti ion bombardment upon film samples, during deposition by the arc evaporation of Ti in pure N, was investigated. Ions with an average charge of +1.6 were accelerated by a negative substrate bias, of between 5 and 540V, which produced a steady-state substrate temperature of between 300 and 600C. It was found that the compressive intrinsic stresses in the films, as determined by using X-ray diffraction methods, changed abruptly from 1.9 to a maximum of 6.5GPa as the substrate bias was increased from 5 to 100V. The compressive stress then decreased monotonically to about 1.6GPa as the bias was increased to 540V. A broadening of the diffraction peaks revealed an associated inhomogeneous strain which was greatest for a bias of 100V. Cross-sectional transmission electron microscopy revealed a dense columnar film microstructure. Electron micro-diffraction revealed a distorted structure within the same columns, at a bias of 100V, and better-defined grains at a bias of 500V. An observed reduction in intrinsic stress with increasing Ti ion energy was additional to that normally observed in sputter-deposited TiN films, for the same energy range of mainly Ar-ion bombardment. A comparison with published work on magnetron-sputtered TiN showed that the defects which were created by Ti ions were more easily annihilated than the defects which were created by using Ar ions. The Ar atoms tended to be strongly bound to lattice defects, formed thermally stable complexes, and prevented stress relief at high substrate bias voltages; as observed in the case of arc-evaporated films. The present results were explained in terms of models for stress generation, under steady-state conditions, which involved competition between collisionally introduced point defect formation and defect annihilation during deposition.

H.Ljungcrantz, L.Hultman, J.E.Sundgren, L.Karlsson: Journal of Applied Physics, 1995, 78[2], 832-7