CMP and cleaning
In CMP, what generally happens when pad conditioning is made more aggressive (for example, by pressing the conditioner harder)? Choose the most appropriate answer.
- AThe pad surface becomes flat (glazing) and the removal rate drops
- BThe pad stops wearing and its grooves stay deep, so the pad lasts longer
- CThe surface texture of the pad is maintained and the removal rate tends to be stable, but the pad wears faster and must be replaced more often
Show answer and explanation
Answer: C. The surface texture of the pad is maintained and the removal rate tends to be stable, but the pad wears faster and must be replaced more often
The fine asperities and pores on the polishing pad surface hold the slurry and drive polishing. Pad conditioning lightly abrades the pad surface with a diamond-grit disk to regenerate flattened asperities. More aggressive conditioning regenerates the texture well and tends to stabilize the removal rate, but it also wears the pad away faster. As the pad wears and the grooves that carry the slurry become shallow, polishing conditions change and the pad must be replaced, which stops the tool each time. Conditioning settings are therefore chosen by balancing polishing stability against consumable cost and tool uptime.
- A. Glazing occurs when conditioning is insufficient.
- B. More material is removed, so the pad wears faster and its grooves become shallower.
- C. Correct. Conditions are set by balancing polishing stability against pad life.