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. Temperature was varied from 85 ^oC to 110 ^oC, humidity from 65% RH to 85% RH. Failure rates were fit to a Peck acceleration model using the method of maximum likelihood.

I. Introduction

Reliability testing using accelerated temperature and humidity is normally required for semiconductor product qualification. Typical conditions are 85 °C/85% Relative Humidity (RH)¹, commonly described as THB and Highly Accelerated Stress Test (HAST)², also using 85%RH and either 110°C or 130 °C. To properly interpret product qualification data it is desirable to know the relative acceleration of the THB and HAST stress conditions. In addition a combined temperature and humidity acceleration model is needed to relate qualification data to expected product lifetimes under typical service conditions. Data for temperature and humidity acceleration of III-V compounds is somewhat limited. Ersland³ et. al. and Roesch⁴ have investigated the failure rates of pHEMT devices using THB and HAST conditions. Osenbach^{5, 6} et.al. have investigated the effects of both temperature and humidity on both lasers and photodetectors based on InGas/InP. In this study the failure rates of AlGaAs/InGaAs pHEMT devices are investigated as a function of both temperature and humidity.