CMP and cleaning
In Cu interconnect CMP, why is polishing generally divided into stages?
- ABecause Cu and the barrier metal beneath it (such as TaN) need different polishing conditions, so most of the Cu is removed first and then the barrier
- BTo give the polishing tool a rest
- CTo make the Cu thicker
Show answer and explanation
Answer: A. Because Cu and the barrier metal beneath it (such as TaN) need different polishing conditions, so most of the Cu is removed first and then the barrier
In Cu interconnects, the thick Cu outside the trenches, the thin barrier metal beneath it and the insulator below are polished in sequence. To optimize removal rate and selectivity for each material, polishing is split into a stage that removes Cu quickly and a stage that removes the barrier and finishes planar, using different slurries.
- A. Correct. Polishing proceeds in stages with conditions changed for each material.
- B. It is not to rest the tool.
- C. CMP removes Cu, not adds it.