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.