Comparison of time-to-failure of GeSi and Si bipolar transistors

The effects of Ge in the epitaxial-base on the reliability of Si/Ge_xSi_1-x/Si heterojunction bipolar transistors were investigated. The ten-year time-to-failure under emitter-base junction reverse-bias stress was measured at the designed operation voltage by the current-acceleration method and compared to that of Si bipolar junction transistors with no Ge (x=0). The investigation shows that the Ge incorporated by the reduced pressure chemical vapor deposition epitaxial technology to give the ramp-type Ge profile has no adverse effects on the transistor reliability