Influence of CMP Slurries and Post-CMP Cleaning Solutions on Cu Interconnects and TDDB Reliability

Abstract

We investigated Cu/low-k integration to test the time-dependent dielectric breakdown (TDDB) reliability of Cu interconnects. We described the relationship between TDDB lifetime and defects possibly caused by the Cu chemical-mechanical polishing (CMP) 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 (BTA). 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.