基于76.2 mm圆片工艺的GaN HEMT可靠性评估

GaN HEMT on SiC substrate for microwave application with 76.2 mm wafer process are presented. Experiments were carried out to evaluate the reliability of the fabricated devices. Refractory metal was introduced in the GaN HEMT process to improve thermal stability of the Schottky barrier. The high temperature operation life test revealed that the devices exhibit no failure but degradation in saturation current after 500 hours operating under 225℃ junction temperature. Further analysis indicated that the Ohmic contact degradation resulting from electromigration is responsible for the saturation current degradation. Process improvement has been done to eliminate the electromigration. Three temperature accelerated DC life tests carried out on the improved devices showed a mean time to failure (MTTF) of 4×10^5 hours at the junction temperature of 150℃ and an active energy of 1.0 eV. A two-stage power amplifier module was developed using the fabricated GaN HEMTs. CW RF stress test carried out on the power amplifier module with 28 V operating voltage, 125℃ junction temperature and 5 dB gain compression showed less than 0.1 dB changing in output power after 1000 hours operation.