Etching

What is a mask of nitride, carbon or similar material called, used when photoresist alone cannot survive as a mask, such as when etching deep holes?

  1. APellicle
  2. BPhase-shift mask
  3. CHard mask
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Answer: C. Hard mask

In deep etching the resist would be consumed partway through, so the resist pattern is first transferred into a nitride, oxide or amorphous carbon film, which is then used as the mask to etch the actual film. Such inorganic masks are called hard masks.

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More Etching questions

  1. Which is a characteristic of downstream etching, which supplies only plasma-generated radicals to the wafer?
  2. Which are examples of profile defects seen in high-aspect-ratio etching?
  3. 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?
  4. Which solution, made by buffering hydrofluoric acid with ammonium fluoride, is used for wet etching of SiO2?
  5. Why is cryogenic etching, which cools the wafer to very low temperatures, attracting attention for high-aspect-ratio processing?