CMP and cleaning

What is the state of a silicon surface whose last cleaning step was dilute hydrofluoric acid?

  1. AThe surface is hydrogen-terminated and becomes hydrophobic
  2. BThe surface is covered with metal
  3. CIt is covered with a thick oxide and becomes hydrophilic
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Answer: A. The surface is hydrogen-terminated and becomes hydrophobic

A silicon surface from which oxide has been removed with dilute HF is terminated with hydrogen atoms and becomes hydrophobic, repelling water. Such a surface temporarily resists oxidation, but particles adhere to it easily, so the time until the next step is controlled.

  • A. Correct. It becomes hydrogen-terminated and hydrophobic.
  • B. HF cleaning does not coat the surface with metal.
  • C. HF removes oxide, so it does not leave an oxide coating.
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More CMP and cleaning questions

  1. What is the main purpose of installing filters in the lines that supply CMP slurry to the polisher?
  2. When removing particles from a wafer surface by cleaning, how does particle size generally relate to ease of removal?
  3. As CMP continues, the polishing pad temperature rises. How does the removal rate generally change?
  4. In SC-1 (a mixture of ammonia and hydrogen peroxide), what role does the hydrogen peroxide play?
  5. Which method is commonly used to count particles on a wafer surface after cleaning?