CMP and cleaning
Which correctly describes 'dishing' in CMP?
- AThe polishing pad wears down and becomes flat
- BSlurry particles stick to and remain on the wafer
- CThe center of wide wiring is over-polished relative to its surroundings, becoming dish-shaped
Show answer and explanation
Answer: C. The center of wide wiring is over-polished relative to its surroundings, becoming dish-shaped
Dishing occurs in wide metal features, where the soft metal in the center is removed more than the surrounding insulator, creating a dish-like recess. It increases wire resistance and degrades the flatness of upper layers. Over-polishing of entire areas of dense wiring is called erosion.