The passivation of MMICs by polyimide is presently being applied to commercially available L-band and C-band MMICs.  The present study evaluates polyimide passivation reliability in an L-band trans-impedance amplifier.  Transimpedence amplifiers are presently being applied in multi-gigabit per second optical fiber links since they offer the advantages of wide dynamic range and large gain, reduction of noise and lower overall power consumption (500-700 mW).  Investigation, the reliability and failure mechanism of cascode type transimpedance amplifiers was determined showing that gate leakage in the FETs of the inverting amplifier followed by gold electronomigration in the drain contacts of the output stage MESFETs is the primary failure mechanism.  This study is the first such investigation reported for MMIC circuits and shows that surface states present at the GaAs-Polyimide interface increases gate leakage in the output stage resulting in failure...
 

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