Thermomechanical behavior of different texture components in Cu thin films Original Research Article

Owing to their high elastic anisotropy and increasing practical relevance, copper thin films are of much scientific and technological interest. We have employed X-ray techniques to study the thermomechanical behavior of polycrystalline Cu films, 0.3–1 μm thick, during thermal cycling between room temperature and 600°C. The films were deposited on Si3N4 barrier layers on Si substrates and some were also passivated with Si3N4. The (111) and (100) grain orientations were found to behave very differently from each other in surprising ways: plastic relaxation is limited in (111) compared to (100) grains, particularly in unpassivated films, and stress distributions depend strongly on whether the sample is being heated or cooled. Thickness effects are confined to particular temperature regimes in (111) grains. Excellent agreement between stresses measured by X-ray and substrate curvature methods is found. An analysis of film strength at room temperature reveals that the texture components must be treated separately.