Etching

Exposing silicon to XeF2 gas and an argon ion beam simultaneously etches it far faster than the sum of either alone. What property of dry etching does this show?

  1. AEtching depends only on temperature
  2. BIons play no role in etching
  3. CThe synergy between ions and radicals (ion assistance)
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Answer: C. The synergy between ions and radicals (ion assistance)

Coburn and Winters showed that etch rates are small with XeF2 alone or argon ions alone, but increase greatly when both are applied together. This synergy, in which ion bombardment assists surface reactions and product desorption, is why reactive ion etching can be both fast and anisotropic.

  • A. It cannot be explained by temperature alone.
  • B. It shows that ions greatly accelerate the reaction.
  • C. Correct. It shows the synergy between ions and radicals.
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More Etching questions

  1. In plasma etching of high-aspect-ratio patterns, which phenomenon has electrons blocked by sidewalls so negative charge builds at the top of the pattern while positive ions are deflected at the bottom, causing profile defects and damage?
  2. Which research-stage etching method neutralizes plasma-generated ions before they hit the wafer, suppressing charging and UV damage?
  3. Why are coatings such as yttrium oxide (Y2O3) used on the inner walls and parts of plasma etch tools?
  4. In plasma etch tools, what is the main role of the focus ring surrounding the wafer edge?
  5. Which correctly describes anisotropic etching?