CMP and cleaning

What is the main purpose of installing filters in the lines that supply CMP slurry to the polisher?

  1. ATo remove all abrasive particles
  2. BTo remove large agglomerated particles and the like, preventing scratches on wafers
  3. CTo warm the slurry
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Answer: B. To remove large agglomerated particles and the like, preventing scratches on wafers

Abrasive particles in slurry can agglomerate into large clumps during storage and transport, and these scratch wafers. Filters in the supply line remove such large particles and pass only abrasives of the required size.

  • A. Without abrasive particles, polishing is impossible.
  • B. Correct. They remove coarse agglomerates to prevent scratches.
  • C. Filters are not for warming the slurry.
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More CMP and cleaning questions

  1. When removing particles from a wafer surface by cleaning, how does particle size generally relate to ease of removal?
  2. As CMP continues, the polishing pad temperature rises. How does the removal rate generally change?
  3. In SC-1 (a mixture of ammonia and hydrogen peroxide), what role does the hydrogen peroxide play?
  4. Which method is commonly used to count particles on a wafer surface after cleaning?
  5. Why is it considered important to transfer wafers to cleaning right after CMP while still wet, without letting them dry?