Etching

Which metric expresses how far the sidewall of an etched hole or trench tilts from vertical?

  1. AAspect ratio
  2. BTaper angle
  3. CSelectivity
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Answer: B. Taper angle

The taper angle expresses the inclination of an etched sidewall. The closer to vertical (90°), the more anisotropic the etch. Because a slight slope can make later filling easier, it is controlled according to the application.

  • A. Aspect ratio is the ratio of depth to width.
  • B. Correct. It is the angle of the sidewall slope.
  • C. Selectivity is the ratio of etch rates, such as film to mask.
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More Etching questions

  1. What is the general effect of adding a little oxygen to fluorine-based etching gas?
  2. In a typical etching plasma, how do the numbers of ions and radicals compare?
  3. Which method inserts a small electrode into a plasma and measures the current as the voltage is varied to determine the plasma's electron temperature and density?
  4. In dry etching, what is the profile defect called in which the bottom of a trench is etched deeper near the sidewalls than in the center, creating narrow grooves?
  5. Exposing silicon to XeF2 gas and an argon ion beam simultaneously etches it far faster than the sum of either alone. What property of dry etching does this show?