Metrology and analysis

Which method evaluates the quality of compound semiconductor wafers and epi layers without contact by shining laser light and measuring the spectrum and intensity distribution of the emitted light?

  1. AAFM
  2. BPhotoluminescence (PL) measurement
  3. CFour-point probe
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Answer: B. Photoluminescence (PL) measurement

Photoluminescence creates carriers with laser light above the band gap and measures the light emitted when they recombine. The emission wavelength reveals composition and band gap, and the intensity distribution reveals defects and non-uniformity, so it is widely used to evaluate epi layers for LEDs and lasers.

  • A. AFM measures surface topography.
  • B. Correct. It measures light emitted under illumination.
  • C. The four-point probe is a contact method for resistivity.
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More Metrology and analysis questions

  1. Compared with bright-field wafer inspection, which images patterns directly, what characterizes dark-field inspection, which captures only scattered light?
  2. Which instrument traces a sample surface with a fine stylus and measures step heights and surface shape from the stylus's vertical motion?
  3. What is the technique called that uses statistical models to predict film thickness or dimensions of wafers that were not actually measured, from equipment sensor data and the like?
  4. When measuring very narrow trenches or steep sidewalls with AFM, what tends to cause errors?
  5. In TEM, which technique scans a finely focused electron beam and measures the energy lost by transmitted electrons to map elements and chemical states?