MICROSTRUCTURAL INVESTIGATIONS ON TITANIUM NITRIDE FILMS FORMED BY MEDIUM-ENERGY ION-BEAM-ASSISTED DEPOSITION

Titanium nitride was deposited in the rare gas mode of ion beam assisted deposition by evaporation of titanium in an atmosphere of backfilled nitrogen under bombardment with argon ions with current densities up to 70 muA/cm2. The ion energy was 12 keV which is in the medium to high energy range of IBAD. High ion energy, mass and fluence strongly influence morphology and topography of the resulting TiN films. Upon increasing ion irradiation intensity, the grain size increased from typically 10 nm up to 80 nm in diameter. The crystallographic orientation of the grains changed from a preferred [111] orientation which is typical for evaporated fcc material to the [100] orientation. The latter is a favourable channeling orientation and is therefore less damaged by ion bombardment. In the topography of the films a strong dependence on irradiation intensity was found. Several zones of varying roughness could be identified. Development of smooth or rough surfaces is attributed to several effects directly connected with ion bombardment, among which are adatom mobility, sputtering and ion incorporation.