Yield and quality control

Which statistical process control technique monitors several mutually correlated characteristics together, rather than one at a time, to detect abnormal combinations?

  1. AMultivariate control charts (such as Hotelling's T²)
  2. BCheck sheet
  3. CX̄-R charts only
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Answer: A. Multivariate control charts (such as Hotelling's T²)

Equipment sensor values and the like are often correlated, so a state can be abnormal as a combination even when each value is within limits on its own chart. Multivariate control charts using statistics such as Hotelling's T² monitor several values together while accounting for correlation and can detect such abnormalities.

  • A. Correct. It monitors several characteristics together.
  • B. A check sheet is a table for recording and tallying.
  • C. An X̄-R chart monitors a single characteristic.
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More Yield and quality control questions

  1. 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?
  2. A wafer yields 500 chips, of which 450 are good. What is the yield of this wafer?
  3. With the same defect density, what generally happens to yield when chip area is increased?
  4. In control charts (Shewhart control charts) used for process control, how are the control limits generally set?
  5. Which correctly describes the purpose of a Pareto chart used in quality control?