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 ͑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.

Porous Low-Dielectric-Constant Material for Semiconductor Microelectronics

“…However, in real Cu damascene interconnects, the integration performance strongly dominates TDDB results. The interface of Cu/capping layer, lineedge-roughness line-to-line overlay errors, and via-to-line misalignment are the dominated TDDB failure mechanisms [61][62][63][64][65].…”

Copper Metal for Semiconductor Interconnects

“…To minimize Cu diffusion into the dielectric to avoid reliability degradation in TDDB, several process strategies have been proposed including using adequate metal barrier layers [167,168], minimizing residues after post-CMP cleaning [169], and minimizing air exposure prior to capping of the Cu [150,153]. Additionally, alternating polarity operation method instead of direct current stress could increase dielectric breakdown lifetime, resulting from recovery effect due to the backward migration of Cu ions during the reverse-bias stress [170,171].…”

Scratch formation and its mechanism in chemical mechanical planarization (CMP)

“…Defects typically formed during the CMP process include organic residues [29], water marks [30], particle adherence and impingement [31], corrosion pit, and scratches [30,31]. However, the removal of organic residues and water mark formation are trivial in oxide CMP, but other types of defects, such as scratch formation, are critical, as they affect the yield and reliability of the devices [32]. Table 2 shows the CMP process induced defects and their specific effects on the replacement metal gate (RMG) process [33].…”