CMP and cleaning

Why are particles, once detached, unlikely to redeposit in alkaline cleaning solutions such as SC-1?

  1. ABecause the solution is very viscous
  2. BBecause the wafer surface and particles carry charges of the same sign and repel each other
  3. CBecause the particles dissolve in the solution and disappear
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Answer: B. Because the wafer surface and particles carry charges of the same sign and repel each other

In alkaline solutions, both the silicon surface and many particle surfaces become negatively charged (negative zeta potential). Like charges repel, so particles that have left the surface are unlikely to reattach. This is one reason SC-1 is effective at removing particles.

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More CMP and cleaning questions

  1. What problems are caused by metal contamination such as iron and copper on the wafer surface?
  2. What is the main cause of fine scratches on the wafer surface in CMP?
  3. To prevent fine structures from collapsing, which method removes native oxide and the like without using liquids?
  4. Which combination correctly lists processes in which CMP is used?
  5. What is the operation called in which the surface of a CMP pad is dressed with a diamond tool to stabilize the removal rate?