Interconnect copper metallization of InGaP HBTs using WNxas the diffusion barrier

Interconnect copper metallization of InGaP HBTs using WN x as diffusion barrier was studied. The WN x (40 nm) and Cu (200nm) films were deposited sequentially on the InGaP/GaAs HBT wafers as the interconnect metallization layers using sputtering method. The I-V curve of the HBT with Cu metallization has a higher saturation current than the HBT with Au metallization. To test the reliability of the Cu metallized HBT, it was bias with V CE =3 V, J C =125 kA/cm 2 and stressed for 15 hours. The current gain (β) of the GaAs HBT shows no degradation and is still higher than 100 after the high current density stress for 15 hours. From the electrical measurement, WN X demonstrated to be a good diffusion barrier for Cu in GaAs device and the Cu/WNx films can be used for the interconnection copper metallization for GaAs HBTs.