Etching

If the oxide etch rate is 100 nm/min and the mask is consumed at 20 nm/min, what is the selectivity to the mask?

  1. A0.2
  2. B5
  3. C80
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Answer: B. 5

Selectivity = etch rate of the target film ÷ etch rate of the mask (or underlayer) = 100 ÷ 20 = 5. For example, etching 500 nm of oxide would consume 100 nm of mask.

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More Etching questions

  1. Which solution, made by buffering hydrofluoric acid with ammonium fluoride, is used for wet etching of SiO2?
  2. Why is cryogenic etching, which cools the wafer to very low temperatures, attracting attention for high-aspect-ratio processing?
  3. 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?
  4. What is an advantage of pulsed plasma, which etches while switching the RF power on and off?
  5. Which gases are commonly used for dry etching of GaN?