Yield and quality control

With the same defect density, what generally happens to yield when chip area is increased?

  1. AIt decreases
  2. BIt increases
  3. CIt does not change
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Answer: A. It decreases

In the Poisson model, yield is Y = exp(−D × A) (D: defect density, A: chip area). The larger the area, the more likely a chip contains a defect, so yield falls. This is one reason chiplets, which split a large chip into several smaller ones, are attracting attention.

Chip area and yield (same defect positions) Small chips ,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,, Large chips ,,, ,,,,,,,,,,, Good: 18 / 24 (75%) Good: 1 / 4 (25%) Defect Failed chip (contains a defect)
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More Yield and quality control questions

  1. In control charts (Shewhart control charts) used for process control, how are the control limits generally set?
  2. Which correctly describes the purpose of a Pareto chart used in quality control?
  3. Which formula gives the process capability index Cp (when the process mean coincides with the center of the specification)? (σ: process standard deviation)
  4. Among the causes of yield loss, what are defects called that recur in specific patterns due to, for example, interactions between design and manufacturing processes?
  5. Which diagram organizes the relationship between a problem (effect) and the factors that influence it in a shape like a fish skeleton?