CMP and cleaning

Which abrasive particles are often used in STI CMP to achieve high polishing selectivity of oxide to silicon nitride?

  1. ACeria (cerium oxide)
  2. BIron powder
  3. CCoarse diamond grit
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Answer: A. Ceria (cerium oxide)

Ceria-based slurries, combined with additives, polish oxide quickly while polishing nitride very slowly. They are therefore used in STI CMP, where nitride serves as the stop layer, to achieve both planarity and a reliable stop.

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More CMP and cleaning questions

  1. Which cleaning method applies MHz-range ultrasound to the cleaning solution to remove tiny particles from the wafer surface?
  2. What is the main purpose of cleaning with ozone dissolved in ultrapure water (ozonated water)?
  3. What is the role of benzotriazole (BTA) and similar additives in copper CMP slurries?
  4. What is the role of the retaining ring that surrounds the wafer in a CMP polishing head?
  5. Why are particles, once detached, unlikely to redeposit in alkaline cleaning solutions such as SC-1?