Etching

Which metric indicates how small the variation in etch rate is across the wafer?

  1. ASelectivity
  2. BUniformity
  3. CAspect ratio
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Answer: B. Uniformity

Uniformity indicates how consistent the etch rate and profile are between, for example, the center and edge of the wafer. Poor uniformity causes under-etching in some places and over-etching in others, so it is improved by adjusting plasma distribution, gas flow, wafer temperature and more.

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More Etching questions

  1. After the etch endpoint is detected, what is it called to continue etching for a set time to ensure the film is removed across the whole wafer?
  2. 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?
  3. Which is a characteristic of downstream etching, which supplies only plasma-generated radicals to the wafer?
  4. Which are examples of profile defects seen in high-aspect-ratio etching?
  5. 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?