Hydrogen effects on reliability of GaAs MMICs

Investigations into unexplained RF gain changes versus time during life tests have lead to the conclusion that hydrogen gas in quantities as small as 0.5% of ambient atmosphere can cause significant performance degradation in as little as 168 h at elevated temperatures (125 degrees C). This amount of hydrogen has been readily observed in Kovar hermetic packages with 0.1 cm/sup 3/ internal volume. The apparent mechanism for this degradation is the conversion of gaseous hydrogen into atomic hydrogen in Pt metallization, with subsequent doping compensation due to the atomic hydrogen. The loss of electron carriers leads directly to lower transconductance and lower RF gain. A change in the Schottky diode characteristics is also noted. >