Effect of Laser Scanning Speed on Microstructure of Electroplated Copper Films during Laser Scanning Annealing

As an emerging heat treatment process, laser scanning annealing is efficient in increasing the grain size of copper interconnect and thus can significantly reduce interconnect resistance. Therefore, the process parameters of laser scanning, especially the scanning speed, should be optimized to achieve a better heat treatment effect. In this paper, we discussed the effects of different laser scanning speeds on the evolution of the crystal structure of electroplated copper films with the same laser power based on phase field method (PFM). Part of the conclusions of PFM were verified by EBSD images of actual electroplated copper films after laser scanning annealing. It is found that the columnar crystal growth was the most significant and the grain size was the largest when the scanning speed was close to the crystal growth rate (0.1 μm/s) in laser scanning annealing. As the scanning speed increased, the proportion of columnar crystals decreased as the proportion of equiaxed crystals increased. When the scanning speed was too high (80 μm/s), grains obtained are almost equiaxed. These conclusions are expected to provide references for the selection of scanning speed in laser scanning annealing.