Forward-bias stress effects on BJT gain and noise characteristics

The effect of large current forward-bias stress on bipolar transistor gain and noise characteristics was investigated. The combination of high currents and high temperatures produced gain degradations or failures of transistors from three technologies. Similarly the application of high currents and high temperatures produced changes in transistor noise characteristics. Specifically, in all transistors stressed, the low-frequency noise initially decreased. It was also observed in two technologies that the noise eventually increased again as the stress continued. Electromigration induced stress is believed to play an important role in these phenomena. The third technology eventually showed failures of the transistors due to electromigration produced open circuits