Etching

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?

  1. AMicrotrenching
  2. BBowing
  3. CMask recession
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Answer: A. Microtrenching

Microtrenching is the localized deeper etching at the bottom corners of trenches or holes. It is thought to be caused by ions reflected from the sidewalls concentrating at the bottom corners. Because it can punch through the underlayer, for example in gate etching, it is suppressed by tuning conditions.

  • A. Correct. The bottom corners are etched locally deeper.
  • B. Bowing is a barrel-like lateral bulge partway down the sidewall.
  • C. Mask recession is mask erosion that changes dimensions.
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More Etching questions

  1. 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?
  2. In plasma etching of high-aspect-ratio patterns, which phenomenon has electrons blocked by sidewalls so negative charge builds at the top of the pattern while positive ions are deflected at the bottom, causing profile defects and damage?
  3. Which research-stage etching method neutralizes plasma-generated ions before they hit the wafer, suppressing charging and UV damage?
  4. Why are coatings such as yttrium oxide (Y2O3) used on the inner walls and parts of plasma etch tools?
  5. In plasma etch tools, what is the main role of the focus ring surrounding the wafer edge?