Optimal low-frequency noise criteria used as a reliability test for BJTs and experimental results

Two basic problems in the application of noise criteria to reliability testing are considered. First, the need to look at all noise mechanisms rather than noise at a specific frequency is emphasized, and noise criteria using both 1 f noise and g− r noise are established. Second, the physical mechanisms which explain the low noise level of some failed devices are discussed, and the optimal noise threshold levels are found for minimum error during reliability testing. Reliability testing results for 1000 BJTs (3DG6) show that the failure rate of devices which initially exhibit high noise is about 2–3 times higher than for devices which initially have low noise. This means that the life expectancy of BJTs with a low noise level (using optimal noise criteria) is increased by a factor of 1.5–2.5; thus, noise measurements could be a useful reliability screen classification method for BJTs.