Yield and quality control

Which yield model accounts for defects that occur clustered unevenly on the wafer?

  1. AThe negative binomial model
  2. BOhm's law
  3. CDennard scaling
Show answer and explanation

Answer: A. The negative binomial model

The Poisson model assumes defects are distributed randomly and uniformly, but real defects tend to cluster locally. The negative binomial model includes a clustering parameter α and takes the form Y = (1 + DA/α)^(−α). The larger α is, the closer it gets to the Poisson model.

  • A. Correct. It is a yield model that accounts for clustering.
  • B. Ohm's law relates voltage, current and resistance.
  • C. Dennard scaling is a guideline for scaling.
Practice this topic Back to topic

More Yield and quality control questions

  1. What is the quantity called that, for each type of defect found by inspection, gives the fraction of chips containing that defect that actually fail electrically?
  2. Which correctly states Little's law, relating work in progress (WIP), throughput and cycle time in a factory?
  3. What is the analysis called that statistically identifies, from the manufacturing histories of many lots, the tools, chambers, materials and the like commonly used by low-yield lots?
  4. Which statistical process control technique monitors several mutually correlated characteristics together, rather than one at a time, to detect abnormal combinations?
  5. When there are several tools of the same type, what is it called to adjust and manage them so that processing results differ little between tools and chambers?