Reliability

Regarding BTI degradation, part of the threshold voltage shift recovers once the stress is removed. What does this imply for evaluation?

  1. AMeasurement timing does not affect the results
  2. BResults depend on the time between removing stress and measuring, so measurements must be fast or conditions standardized
  3. CBecause it recovers, the degradation can be ignored
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Answer: B. Results depend on the time between removing stress and measuring, so measurements must be fast or conditions standardized

In BTI, stopping the stress releases some trapped charge, and the threshold voltage shift gradually recovers. A long delay between stopping stress and measuring therefore underestimates the degradation. Evaluation uses fast measurement methods and considers real circuit operation (repeated on/off switching).

  • A. Because of recovery, measurement timing affects the results.
  • B. Correct. Recovery makes measurement timing important.
  • C. Only part recovers; degradation remains.
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More Reliability questions

  1. To evaluate susceptibility to soft errors caused by cosmic-ray neutrons, which method measures quickly by applying neutrons far more intense than in the real environment?
  2. When extrapolating TDDB test results to operating voltage, there is the E model, which expresses lifetime as an exponential of field, and the 1/E model, which uses the reciprocal of field. Which statement about their difference is correct?
  3. Which correctly lists the three periods that make up the bathtub curve, showing how failure rate changes over time?
  4. Which correctly describes electromigration?
  5. Which correctly describes MTBF (mean time between failures)?