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We investigated Cu/low-k integration to test the time-dependent dielectric breakdown ͑TDDB͒ reliability of Cu interconnects. We described the relationship between TDDB lifetime and defects possibly caused by the Cu chemical-mechanical polishing ͑CMP͒ process, such as rough copper surface corrosion, crevice corrosion, and scratches, using Cu/silicon oxycarbide interconnects. Although rough copper surface corrosion has an insignificant effect on the TDDB lifetime, crevice corrosion at the edges of wires does cause TDDB degradation. We also found that a structure's TDDB lifetime was affected by the kind of post-CMP cleaning solutions used when barrier metal slurries do not contain benzotriazole ͑BTA͒. These results indicate that two types of processes for post-CMP cleaning should be used. It is best to use solutions that do not have strong oxidized copper dissolution ability but can remove particles when a barrier metal slurry with an inhibitor other than BTA is used. Also good are solutions with a strong oxidized copper dissolution ability that have been optimized to prevent Cu corrosion when a barrier metal slurry with BTA is used. To improve TDDB reliability, care must be taken with regard to the combination of the barrier metal slurry and the post-CMP cleaning solution.

Time-dependent dielectric breakdown (TDDB) between Cu interconnects is investigated. TDDB lifetime strongly depends on the surface condition of the Cu interconnect and surrounding pTEOS. A NH3-plamsa treatment prior to cap-pSiN deposition on Cu interconnect improved the dielectric breakdown lifetime ( G~) over cap-pSiN deposition only. The plasma treatment also has the beneficial effect of suppressing wiring resistance increase during pSiN deposition. These results suggest that CuO reduction to Cu, and CUN formation at the Cu interconnect surface prevents Cu silicidation during pSiN deposition. Futhermore, SiN formation and bond termination by hydrogen radicals at the pTEOS surface diminish surface defects, such as dangling bonds. TDDB lifetime also strongly depends on the Cu CMP process, in which mechanical damage of the Si02 surface during CMP process degrades TDDB. Adoption of a mechanical damage free slurry or a post-CMP HF treatment to remove the damaged layer from the surface improves TDDB .

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.

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