Reliability Aspects of 0.5μm and 1.0μm Gate Low Noise GaAs FETs

Reliability of GaAs FETs is an important concern and there are many change modes that can be considered failures. Catastrophic events, which make a unit unusable and the drift of various DC and RF parameters, are examples of some fairly obvious types of failures. Other long term phenomena, while not so obvious, can also be considered potential failure mechanisms. Two phenomena in this latter category are changes in Schottky gate characteristics and intermetallic reactions that can eventually cause loss of gate control. This paper presents results in both problem areas. Specifically, an explanation and solution will be given to the potential reliability problem of electrostatic discharge created changes in Schottky gate reverse leakage currents. These changes vary in degree from just discernable creation of a resistive reverse current to catastrophic eruption of gate metal, GaAs channel and source contact metal. Secondly, a very stable Al to Au metallization system will be described that allows excellent high temperature stability and low RF resistance connections without harmful intermetallic reactions.