Reliability

For gate insulator breakdown lifetime, why must the difference between the area of test devices and the total gate area on an actual chip be considered?

  1. ABecause area does not affect lifetime
  2. BBecause larger areas always last longer
  3. CBecause breakdown starts at the weakest spot, larger areas are more likely to fail early, requiring area scaling based on the Weibull distribution
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Answer: C. Because breakdown starts at the weakest spot, larger areas are more likely to fail early, requiring area scaling based on the Weibull distribution

Breakdown is thought to occur first at the weakest spot in the film (weakest link). A larger area is more likely to contain a weak spot, so lifetime shortens. Results from small test devices are converted to the total gate area of a chip using the Weibull distribution to estimate product lifetime.

  • A. Area strongly affects lifetime.
  • B. Larger areas tend to shorten lifetime.
  • C. Correct. Larger areas fail earlier, so scaling is needed.
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