Evaluation of microstructure and stress of Cu damascene interconnects using SPM

Microstructures and sub-micron scale stresses of the Cu damascene architecture were analyzed via atomic force microscopy (AFM) and scanning near-field acoustic microscopy (SNAM). SNAM images display an acoustic contrast, which is proportional to the local stress in the metal/dielectric trench regions. The architecture-induced mechanical stress and deposition-induced thermal stress affect the Cu grain microstructure, and hence affect the reliability of Cu interconnects.