Diffusion barrier integrity and electrical performance of Cu/porous dielectric damascene lines

One issue accompanying the introduction of porous dielectrics in Cu damascene interconnects is the integrity of diffusion barriers. For the first time a direct correlation is shown between the physical integrity of the barrier layer and the electrical performance of damascene lines embedded in a dielectric with a k value of 2.0. The breakdown field at 100(degree)C for lines with a porous barrier layer is considerably lower than that for lines with an efficient sealing barrier. Irreversible degradation is also observed in the leakage current of structures with a porous barrier after thermal and electrical stress. Contamination of the porous dielectric can take place already during damascene processing, so the use of a barrier layer that can efficiently seal the pores after dielectric patterning is essential for a proper functioning of future interconnects.