Texture Evolution of Cu Thin Films during Annealing

摘要

The microstructural evolution of pure electroplated Cu films upon annealing has been investigated using texture analysis as the main characterization tool. The study was carried out on films of 0.89, 1.81, and 3.0 μm thickness. It has been found that film thickness influences significantly both the pre-annealing and the annealing texture. The pre-annealing texture in the thinnest films is formed by a sharp <111> fiber, i.e., grains are predominantly oriented such that (111) planes are parallel to the film surface. As the film thickness increases, the volume fraction of (111) grains decreases, other components such as the <100> and the <110> fibers become apparent, and the texture becomes gradually more random. A significant fraction of twinned material (around 20%) is found in the as-deposited state in all the films investigated. Upon annealing, grain growth takes place. No significant texture changes are apparent in the thicker films (1.81 and 3.0 μm). In the thinnest films (0.89 μm), however, the intensity of the <111> fiber decreases, and the texture becomes slightly more random. No new components appear. Texture randomization is attributed to multiple twinning and growth of randomly oriented grains. These observations are not consistent with current models of microstructural evolution in thin films, which predict that strain minimization upon annealing is achieved by anomalous growth of (100) grains.