Backside copper metallization of GaAs MESFETs using TaN as the diffusion barrier was studied. A thin TaN layer of 40 nm was sputtered on the GaAs substrate before copper film metallizafion. As judged from the data of X-ray diffraction (XRD), Auger electron spectroscopy (AES), and cross-sectional transmission electron microscopy (TEM), the Cu/TaN films with GaAs were very stable without interfacial interaction up to 550° C annealing. The copper metallized MESFETs were thermally stressed at 300° C. The devices showed very little change in the device characteristics (<3 %) after thermal stress, and the changes of the electrical parameters and RF characteristics of the devices after thermal stress were of the same order as those devices without Cu metallization. These results show that TaN is a good diffusion barrier for Cu in GaAs devices and the Cu/TaN films can be used for the backside copper metallization of GaAs MESFETs.
- GaAs MESFET