Etching

Which correctly describes 'selectivity' in etching?

  1. AThe ratio of film thickness before and after etching
  2. BThe ratio of etch rates at the center and edge of the wafer
  3. CThe ratio of the etch rate of the target film to that of the mask or underlying film
Show answer and explanation

Answer: C. The ratio of the etch rate of the target film to that of the mask or underlying film

Selectivity is the ratio of the etch rate of the film being removed to that of films that should not be removed (the mask or underlayer). The higher the selectivity, the more the target film can be processed without removing much of the mask or underlayer. Variation in rate across the wafer is called uniformity.

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More Etching questions

  1. Which is a general characteristic of wet etching?
  2. Which correctly describes reactive ion etching (RIE)?
  3. Which method is commonly used to detect the endpoint of dry etching?
  4. What is the aspect ratio of a hole or trench formed by etching?
  5. What is the phenomenon called in which the etch rate decreases as patterns become narrower and deeper?