Enhancement in electrical via-yield of porous low-k/Cu integration by reducing CMP pressure

The effects of CMP pressure on the via resistance yield of dual- and single-damascene interconnects consisting of porous low-k films have been investigated. Porous low-k films with different mechanical strengths (Young's modulus and hardness) were used. The via resistance yield was found to strongly depend on both the CMP pressure of the via-layer and mechanical strength of the via low-k film. Analysis of the results considering the mechanical and chemical aspects of the CMP process showed that using low-pressure CMP (1.5 psi) resulted in excellent electrical properties for Cu interconnects composed of the porous low-k (k=2.3) film with high mechanical strength (E=9.8GPa, H=1.2GPa).