Yield and quality control

In the Poisson model Y = exp(−D × A), with defect density D = 0.1 /cm² and chip area A = 1 cm², approximately what is the yield?

  1. AAbout 50%
  2. BAbout 90%
  3. CAbout 99%
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Answer: B. About 90%

D × A = 0.1, so Y = exp(−0.1) ≈ 0.905, or about 90%. With the same defect density and a chip area of 5 cm², yield falls to exp(−0.5) ≈ 61%.

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More Yield and quality control questions

  1. Among defects on a wafer, what are those called that actually cause electrical failure of a chip?
  2. Which chart divides data into intervals and shows the frequencies as bars to see the shape of the distribution of variation?
  3. Which process capability index is used when the process mean is offset from the center of the specification?
  4. Which type of control automatically adjusts equipment processing conditions for the next lot or wafer based on, for example, measurement results from earlier steps?
  5. Which technique identifies possible failure modes in a product or process, evaluates their effects and severity, and takes countermeasures in advance?