Bias-stress-induced evolution of the dielectric properties of porous-ULK/ copper advanced interconnects

The dielectric properties of porous ULK/Cu interconnects designed for sub 65nm nodes are degraded at high bias-stress. The resulting increase of dielectric constant and defect density can be estimated from the Poole-Frenkel modeling of the leakage currents above 1MV/cm. More generally, the porous SiCOH dielectric materials showing this transport mechanism appear to be inherently less reliable when their initial k value is the lowest. This trend is obviously a major issue for further downscaling developments of porous ULK/Cu interconnects.