Impact of aspect ratio and line spacing on microstructure in damascene Cu interconnects

The present work focuses on the microstructure of annealed damascene Cu interconnects with different trench aspect ratio and line spacing. The X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) measurements are conducted on the surface of Cu interconnects after removal of the SiN layer. The experimental results show that strong {111} fibre texture exists in the Cu interconnects, and the volume fractions of both high angle grain boundaries and Σ3 twin grain boundaries are very large. With trench aspect ratio increase, the bamboo-like structure appears. The trenches reduce the proportion of high angle grain boundaries and increase the volume fraction of Σ3 twin grain boundaries, comparing with the Cu blanket film. Both trench aspect ratio and line spacing can largely affect the microstructure of damascene Cu interconnects.