EFFECT OF ION AND ATOM MASSES ON THE CRYSTALLOGRAPHIC ORIENTATION OF NITRIDE FILMS PREPARED BY ION-BEAM-ASSISTED DEPOSITION

Ion-beam-assisted deposition of TiN leads to a change in crystal growth from a [111] orientation to [100] with increasing ion irradiation intensity. One of the reasons for this observation is radiation damage, which is higher for the close-packed (111) plane than it is for the open (100) plane where the ions are able to channel with much fewer atomic collisions. The magnitude of this effect is related to the mass of the ion. A comparison of TiN films deposited with nitrogen ion bombardment with those which were irradiated with argon ions shows that lower ion masses require higher irradiation intensities to achieve the same degree of preferred crystal orientation. This can be correlated with a higher degree of radiation damage and sputter etching of misaligned crystals for the heavier ions. The same relationship is observed for the mass of the metallic element in the film. Cubic TaN formed under nitrogen ion bombardment needs higher irradiation intensities than does TiN for a comparable crystal growth alignment. Radiation damage in the TaN lattice is smaller than that in the TiN lattice. Therefore, the crystal growth is less affected.