Study on Factors in Time-Dependent Dielectric Breakdown Degradation of Cu/Low-$k$ Integration Related to Cu Chemical–Mechanical Polishing

We studied Cu/low-k integration to test the time-dependent dielectric breakdown (TDDB) reliability of Cu interconnects. We described the TDDB lifetime dependence on SiOC damage caused by sputtering and chemical–mechanical polishing (CMP) processes. The TDDB lifetime of the structure without a cap-SiO layer was three orders of magnitude shorter than that of the structure with the cap layer. However, the film properties of cap-SiO films thinner than 30 nm have a leakage path that allows TDDB degradation to occur easily. We also confirmed that narrowing of intermediate wiring levels with metal-to-metal spacing approaching 100 nm degrades TDDB performance. Moreover, we showed the possibility that chemical attack and mechanical destruction during the polishing cause degradation of TDDB. Optimizing CMP conditions and eliminating the CMP-surface leakage path likely improve line-to-line insulating reliability, such as leakage current and TDDB, because these reliabilities are dominated by the extrinsic failure mode.