Defect level vs. yield and fault coverage in the presence of an unreliable BIST

Yoshiyuki Nakamura, Jacob Savir, Hideo Fujiwara

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Built-in self-test (BIST) hardware is included today in many chips. This hardware is used to test the chip's functional circuits. Since this BIST hardware is manufactured using the same technology as the functional circuits themselves, it is possible for it to be faulty. It is important, therefore, to assess the impact of this unreliable BIST on the product defect level after test. Williams and Brown's formula, relating the product defect level as a function of the manufacturing yield and fault coverage, is re-examined in this paper. In particular, special attention is given to the influence of an unreliable BIST on this relationship. We show that when the BIST hardware is used to screen the functional product, an unreliable BIST circuitry tends, in many cases, to reduce the effective fault coverage and increase the corresponding product defect level. The BIST unreliability impact is assessed for both early life phase, and product maturity phase.

Original languageEnglish (US)
Pages (from-to)1210-1216
Number of pages7
JournalIEICE Transactions on Information and Systems
Issue number6
StatePublished - Jun 2005

All Science Journal Classification (ASJC) codes

  • Software
  • Hardware and Architecture
  • Computer Vision and Pattern Recognition
  • Electrical and Electronic Engineering
  • Artificial Intelligence


  • BIST
  • Defect level
  • Fault coverage


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