EFFECT OF DEPOSITION PARAMETERS ON THE MICROSTRUCTURE OF ION-BEAM-ASSISTED DEPOSITION TIN FILMS

The structure of TiN(x) films formed by low energy ion-assisted deposition has been investigated by electron microscopy techniques. A dual ion beam system was used for the deposition with two Kaufman sources; one producing a 1 keV beam for sputtering Ti, the other a 100-400 eV argon or nitrogen ion beam. The variables of the experiment are the ion energy (100-400 eV), ion species (Ar+ or N2+), ion/atom arrival ratio, the angle of incidence of the ions with respect to the film and the partial pressure of nitrogen during deposition. The structure of the films has been examined using a 200 keV electron microscope for production of electron diffraction patterns and bright and dark field images of the films. It is found that films formed by reactive sputtering (i.e., no ion bombardment) are single phase TiN(x) which has fcc structure. The grain sizes of the microcrystals, which are randomly orientated, are 10-15 nm. Ion bombardment during deposition generally leads to strong preferential (100) orientation of the microcrystals parallel to the surface of the film and this is coupled with a reduction in the grain size of the microcrystals in the film. Grain growth also appears to take place approximately along the direction of bombarding ions. Results suggest that the degree of orientation depends on the added energy per atom during deposition, indeed there seems to be an energy 'window' within which strong, preferred orientations are observed.