Dielectric degradation mechanism for copper interconnects capped with CoWP

Time-dependent dielectric breakdown (TDDB) reliability of CoWP-capped copper/SiO2 interconnect structures are observed to be better than conventional SiN-capped structures. The activation energy for TDDB (Ea) is higher for CoWP-capped structures (0.66–0.84eV) as compared to SiN-capped ones (0.47eV), and is comparable to the Ea for intrinsic breakdown of SiO2. The TDDB degradation mechanism in CoWP-capped structures is postulated to be dominated by the properties of the intrametal dielectric, as opposed to being influenced by the properties of dielectric cap and associated interfaces. The presence of the dielectric cap lowers the Ea and increases leakage by Poole–Frenkel emission.