Etching

Which solution, made by buffering hydrofluoric acid with ammonium fluoride, is used for wet etching of SiO2?

  1. ASPM
  2. BHot phosphoric acid
  3. CBuffered hydrofluoric acid (BHF)
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Answer: C. Buffered hydrofluoric acid (BHF)

Buffered hydrofluoric acid adds ammonium fluoride to hydrofluoric acid to stabilize its pH, so the oxide etch rate changes little as the solution is consumed and resist is less likely to peel. It has been used for oxide patterning and similar steps.

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More Etching questions

  1. Why is cryogenic etching, which cools the wafer to very low temperatures, attracting attention for high-aspect-ratio processing?
  2. Because changes in the condition of an etch chamber's walls alter results, what is it called to process dummy wafers before product to stabilize the chamber?
  3. What is an advantage of pulsed plasma, which etches while switching the RF power on and off?
  4. Which gases are commonly used for dry etching of GaN?
  5. Why is it difficult to pattern copper wiring directly by dry etching?