Metrology and analysis

Which technique directs X-rays at a very shallow angle and determines thin-film thickness and density from oscillations in reflectivity?

  1. ASIMS
  2. BX-ray reflectometry (XRR)
  3. CFour-point probe method
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Answer: B. X-ray reflectometry (XRR)

XRR measures reflectivity while varying the angle of X-rays incident at shallow angles. X-rays reflected from the film surface and interface interfere, making reflectivity oscillate; thickness is obtained from the period, and density from the angle at which total reflection occurs. It is used to evaluate ultrathin films a few nm thick.

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