An accelerated on-wafer test to improve long-term reliability of a 0.25 μm PHEMT process

Performance walkout is a phenomenon observed in AlGaAs/GaAs PHEMTs (Pseudomorphic High Electron Mobility transistors) which can adversely affect the long term reliability of devices that have applications in power amplifier design [5]. Temperature-accelerated tests can help assess long term reliability [10], but due to the aggressive timelines involved in the development of a commercial process, techniques are needed to increase the speed with which reliability tests can be performed. This paper presents techniques that cut down testing time to hours and can diagnose if there is a shift in the reverse leakage of the PHEMT gate, a decrease in breakdown voltage, and a degradation in output power; all of which are factors which negatively affect long term reliability. The test was automated using Python, and involved measuring device characteristics before and after placing each device under short term RF stress. This technique was used to successfully optimize the 0.25 μm PHEMT power process at MACOM (PH6)