Yield and quality control

What is the main purpose of analyzing wafer maps, which show wafer test results as pass/fail for each chip position on the wafer?

  1. ATo set the selling price of chips
  2. BTo infer the process or equipment that caused defects from their distribution pattern
  3. CTo decide the dicing order
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Answer: B. To infer the process or equipment that caused defects from their distribution pattern

Defective chips concentrated around the wafer edge, appearing repeatedly at specific positions, or lined up in streaks — distribution patterns have characteristics that depend on the cause. Analyzing wafer maps allows the problematic process or equipment to be inferred and leads to countermeasures.

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More Yield and quality control questions

  1. With all else equal, about how many times larger does wafer area become when wafer diameter is increased from 200 mm to 300 mm?
  2. In a control chart, which is an example that should be judged abnormal even though all points are within the control limits?
  3. 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?
  4. Among defects on a wafer, what are those called that actually cause electrical failure of a chip?
  5. Which chart divides data into intervals and shows the frequencies as bars to see the shape of the distribution of variation?