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 hi gh currents and high temperatures produced gain degradations or failur es of transistors from three technologies. Similarly the application o f high currents and high temperatures produced changes in transistor n oise characteristics. Specifically, in all transistors stressed, the l ow-frequency noise initially decreased. It was also observed in two te chnologies that the noise eventually increased again as the stress con tinued. Electromigration induced stress is believed to play an importa nt role in these phenomena. The third technology eventually showed fai lures of the transistors due to electromigration produced open circuit s.