In-situ study of the TDDB-induced damage mechanism in Cu/ultra-low-k interconnect structures

Display Omitted We studied the TDDB-induced damage mechanism in Cu/ULK structures in-situ.The methodology combined TEM imaging, ESI analysis and in-situ electrical testing.Three major TDDB-induced damage mechanisms were observed.The breakdown spot depends on the materials, geometry and the degradation effects.The results highlight the importance of the quality of the deposition process for the Ta-based barrier. The time-dependent dielectric breakdown (TDDB) mechanism in Cu/ultra-low-k (ULK) on-chip interconnect structures has been raising serious reliability concerns for state-of-the-art microelectronic devices in recent years. An advanced experimental methodology, which combines transmission electron microscopy (TEM) imaging and an in-situ electrical test using a Hysitron PI95 TEM holder, was used to study TDDB-induced damage mechanisms and degradation kinetics in Cu/ULK interconnect structures. In flawless Cu/ULK interconnect structures with locally very thin Ta-based barriers, slow but massive Cu migration into the SiO2 layer was observed at the bottom corner of the M1 metal after the TaN/Ta barrier had been firstly ruptured by the Ta migration, driven by the high electrical field. More importantly, it was found that both the high electric field and the massive metal migration into the SiO2 can contribute to the final breakdown of the Cu/ULK interconnect structures. The final breakdown spot could be located either at the interface of the SiCN layer and the ULK material or in the SiO2 layer, which depends on the geometry, the kind of dielectric materials (particularly ULK) and the driving force (the high electric field). The results also highlight the importance of the quality of TaN/Ta barrier deposition process, especially at the bottom corner of the M1 metal, to ensure the functionality of the TaN/Ta barriers during the product lifetimes.