Characterization, Analysis, and Modeling of Long-Term RF Reliability and Degradation of SiGe HBTs for High Power Density Applications

This paper aims at determining RF operating limits of SiGe HBTs. Long-term stress tests consisting of RF large-signal stress and periodic measurements of small-signal parameters are performed. Reliable dynamic large-signal transistor operation is demonstrated beyond conventional static safe operating limits. In addition, RF operating limits are identified and degradation of SiGe HBTs accelerated by extreme RF stress is systematically characterized, analyzed and modeled. RF-stress-caused degradation is shown to significantly affect the collector current and demonstrated to be different from electrothermal breakdown caused by DC stress. A modeling approach for estimating SiGe HBT degradation under RF large-signal operating conditions is proposed and shown to agree very well with experimental data.