SiGe, GaAs, and InP Heterojunction Bipolar Transistors

CHAPTER EIGHT

Reliability

Heterojunction bipolar transistors have demonstrated excellent performance for high-frequency IC applications and for insertion of this technology into practical systems. The ultimate usefulness of this technology for system applications is determined by its reliability. The reliability-related parameters of interest, such as failure rates, mean time to failure (MTTF), and activation energies, are commonly determined by stressing devices and circuits under high forward biases and/or elevated temperatures. This procedure is known as high-current and high-temperature accelerated aging or life testing. The interpretation of the statistical life-test data is very important to ensure that the high-temperature and high-current stress tests induce realistic failures, which are expected under normal operating conditions. For bipolar transistors it is important to determine the actual device junction temperature or “hot spot” under biased-stress conditions. The junction temperature differential depends on the device thermal resistance, device size, and temperature.

8.1   ELECTRICAL AND THERMAL OVERSTRESS

Reliability requirements are dictated by the application. Reliability qualification work is aimed at establishing robust process and design rules for achieving high mean time between failure. General HBT reliability testing includes stabilization bake, accelerated life testing, and step-stress testing. An initial stabilization bake is performed to stabilize the ...