MECHANICAL-PROPERTIES AND MICROSTRUCTURAL CHARACTERIZATION OF AL-0.5-PERCENT CU THIN-FILMS

Using a wafer curvature technique we have studied the variation of stress with temperature in Al-0.5%Cu thin films deposited on oxidized silicon wafers. Concurrently, the microstructural changes in the films induced by the thermal cycling inherent to this technique were studied with in-situ transmission electron microscopy heating experiments. On heating an as-sputtered film a stress drop occurs, corresponding to the onset of grain growth. The in-situ TEM experiments indicate that the extent of grain growth is significantly altered by the presence of compressive stresses in film. During cooling, dislocation loops nucleate on {111} planes inclined to the film surface, although the grains size plays an important role in determine the extent to which this mechanism can account for the deformation. A native oxide can influence the stress levels in the film by pinning one end of the dislocation loops. Upon cooling below 200-degrees-C a rapid increase in stress occurs. Although this increase has been attributed to hardening due to the precipitation of excess copper, no evidence of precipitate-dislocation interactions were observed.