Study on vertical TDDB degradation mechanism and its relation to lateral TDDB in Cu/low-k damascene structures

We investigated the inter-level (vertical) and intra-level (lateral) Time-Dependent Dielectric Breakdown (VTDDB & LTDDB) degradation mechanisms in Cu/low-k damascene structures and the relation between the two TDDB failures. The electric-field acceleration factor of the VTDDB lifetime is smaller than that of the LTDDB lifetime at 125°C, and VTDDB has the potential to become a reliability issue for high voltage operation devices because widening a space between inter-level metals is difficult by design layout. From the temperature dependency of the VTDDB lifetime, the activation energy is larger than that of the TDDB lifetime for Cu barrier dielectric (BD) film (Cu/SiCN damascene structure). Also, the VTDDB lifetime is dependent on the pore size of the porous-SiOC between inter-level metals. Our results indicate that VTDDB is limited by the intrinsic breakdown of the inter-metal low-k dielectric (ILD) film in the Via region, not BD film breakdown. Furthermore, we found an association between a VTDDB failure mechanism and a high-temperature LTDDB failure mechanism based on the temperature and electric field characteristics.