Copper Airbridged Low Noise GaAs PHEMT with WNx as the Diffusion Barrier

The silicon nitride passivated copper-metallized airbridges had been successfully integrated on the low noise PHEMT (Pseudomorphic High Electron Mobility Transistor) using WNx as the diffusion barrier between copper and the conventional gold based electrodes. 400 Å PECVD (Plasma Enhanced Chemical Vapor Deposition) silicon nitride was used for copper airbridge passivation to avoid the copper oxidation. The 0.25×160μmcopperairbridged PHEMT device shows a transconductance of 480mS/mm and a noise figure of 0.76 dB with an associated gain of 10.4 dB at 12 GHz. The device performance is comparable to devices with goldmetallized airbridges. The performance did not degrade after annealing at 250C for 20 hours. This study shows promising results for copper metallization of GaAs devices in the future.