Etching

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?

  1. AFour-point probe
  2. BX-ray diffraction
  3. CLangmuir probe
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Answer: C. Langmuir probe

A Langmuir probe places a small electrode (probe) in the plasma and measures the current while sweeping the applied voltage. From the current-voltage characteristic, electron temperature, electron density, plasma potential and so on can be obtained, so it is used to evaluate the plasma state.

  • A. The four-point probe measures film or wafer resistivity.
  • B. X-ray diffraction examines crystal structure.
  • C. Correct. The plasma is evaluated from the probe's I-V characteristic.
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More Etching questions

  1. 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?
  2. 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?
  3. 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?
  4. Which research-stage etching method neutralizes plasma-generated ions before they hit the wafer, suppressing charging and UV damage?
  5. Why are coatings such as yttrium oxide (Y2O3) used on the inner walls and parts of plasma etch tools?