Structural Response of Nano-scale Damascene Copper Lines to Annealing

The high-resolution electron backscatter diffraction (EBSD) technique was applied to study microstructure and texture changes in the overburden layer as well as in upper and bottom parts of nano-scale damascene copper lines during annealing in a temperature range of 200–500°C. The microstructure in overburden layer was found to coarsen significantly at 200°C. At higher temperatures, however, it was established that the overburden layer and both parts of the lines were surprisingly stable. It was also shown that the microstructure in all studied regions was stabilized after achieving the same level of total grain-boundary area per unit volume. This observation has been interpreted as indirect evidence that grain growth behavior in the lines was governed by the pinning effect of second-phase particles entrapped during the electrodeposition process.