CMP and cleaning

Which correctly describes the general difference between hard and soft CMP polishing pads?

  1. ASoft pads planarize better
  2. BPad hardness does not affect polishing results
  3. CHard pads planarize well, while soft pads suit finishing with fewer scratches and defects
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Answer: C. Hard pads planarize well, while soft pads suit finishing with fewer scratches and defects

Hard pads selectively remove high points and excel at planarizing over wide areas, but they scratch more easily. Soft pads conform to the surface and cause fewer scratches and defects but also remove material from low areas, lowering their planarization ability. The two are stacked or used for different stages.

  • A. Soft pads also remove material from recesses, so they planarize less well.
  • B. Pad hardness strongly affects polishing results.
  • C. Correct. Hard pads planarize; soft pads suit finishing.
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More CMP and cleaning questions

  1. What is the state of a silicon surface whose last cleaning step was dilute hydrofluoric acid?
  2. What is the main purpose of installing filters in the lines that supply CMP slurry to the polisher?
  3. When removing particles from a wafer surface by cleaning, how does particle size generally relate to ease of removal?
  4. As CMP continues, the polishing pad temperature rises. How does the removal rate generally change?
  5. In SC-1 (a mixture of ammonia and hydrogen peroxide), what role does the hydrogen peroxide play?