ROLE OF SUBSTRATE CURRENT IN THE RELIABILITY LIFE TESTING OF GAAS MMICS

GaAs monolithic microwave integrated circuits (MMICs) typically show a dramatic increase in circuit current when operated above 200 degrees C. This increase in current has been found to be in good agreement ;wi th a summation of the estimated substrate current flowing from the ind ividual components of these circuits through the bulk GaAs to the back metalization. Although the substrate current for these MMICs was smal l at room temperature, it can be a substantial portion of the total ci rcuit current at the high temperatures typical for accelerated life te sting. A procedure was developed to compensate for the substrate curre nt, thus allowing normal circuit operation during high temperature lif e testing.