Acceleration factors for THB induced degradation of AlGaAs/InGaAs pHEMT devices

PHEMT devices initially showing high failure rates during Temperature Humidity Bias (THB) reliability testing were investigated further using a number of temperature and humidity conditions. Ambient temperature was varied from 85 °C to 110 °C, humidity from 65% RH (Relative Humidity) to 85% RH. Failure rates were fit to a Peck acceleration model using the method of maximum likelihood. Median time to failure (MTTF) estimates were calculated at anticipated field service conditions using the experimentally determined model parameters. The MTTF is predicted to be typically less than a year for the die variant studied. Countermeasures outside the scope of this investigation have been implemented to effectively eliminate this issue allowing RFMD to supply products with suitable reliability.