Nanocrystallization of amorphous-Ta40Si14N46 diffusion barrier thin films

The nanocrystallization process in thin amorphous-Ta40Si14N46 films, annealed in the range between 800 and 1000 °C for 1 h, is investigated by high-resolution transmission electron microscopy and high-angle annular dark-field and energy-dispersive x-ray analyses. At 800 °C clusters of about 2 nm in size indicate that compositional inhomogeneities have developed while the film has still remained structurally amorphous. The sample annealed at 900 °C contains a high density of nanograins of TaN measuring about 2 nm as well as amorphous structures measuring 75–100 nm having a high tantalum content. After annealing at 1000 °C, an almost entirely crystalline structure is observed with 4-nm-sized particles of cubic TaN and 15-nm-sized grains of Ta5Si3. Possible mechanisms driving these structural changes are discussed.