Metrology and analysis

When measuring very narrow trenches or steep sidewalls with AFM, what tends to cause errors?

  1. AAFM can only be used in vacuum
  2. BThe tip has a finite size and shape, so its shape gets superimposed on the measured profile
  3. CAFM cannot measure surface topography
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Answer: B. The tip has a finite size and shape, so its shape gets superimposed on the measured profile

AFM measures shape by tracing the surface with a tip, so it cannot reach the bottoms of trenches narrower than the tip, and on steep sidewalls the side of the tip makes contact first. The measured profile is therefore a convolution of the actual shape with the tip shape. Sharper tips and analysis that corrects for tip shape are used.

  • A. AFM can also be used in air.
  • B. Correct. The tip's shape is superimposed on the result.
  • C. AFM is an instrument for measuring surface topography.
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