Correlation of low-frequency noise and emitter-base reverse-bias stress in epitaxial Si- and SiGe-base bipolar transistors

We give the first demonstration that the emitter-base reverse bias stress configuration commonly used in reliability testing causes not only current gain degradation but also significant degradation in the low-frequency noise characteristics of epitaxial Si and SiGe bipolar transistors. The time-dependent current gain degradation and corresponding evolution of random-telegraph-signal (RTS) noise is monitored as a function of emitter-base stress. Perimeter-to-area (P/A) analysis on electrically stressed transistors shows the expected increase in current gain degradation with increasing P/A ratio. However, post-stress noise degradation is shown to increase more substantially as the area of the device is increased