Effect of pore sealing on the reliability of ULK/Cu interconnects

The combination of porous ultra low k dielectric and copper metallization is an attractive alternative to meet the requirements of ITRS roadmap concerning the 65 nm interconnection technology, but very little is known about the reliability of such an approach. Porous materials are usually unstable and sensitive to moisture, but pore sealing is a possible strategy to overcome these detrimental effects. In this paper, we have studied the effect of pore sealing on the electrical performance and long-term reliability of ULK/Cu interconnects. The best pore sealing efficiency is obtained for a nominal thickness of 10 nm of a SiC:H sealing layer. With these conditions, the dielectric constant of the ULK is kept at 2.2 even after integration and an electromigration activation energy of 1.2 eV is obtained. The failures mechanisms have been correlated to SEM and FIB analysis.