Abstract

A gold-free, fully Cu metallized InGaP/GaAs HBT using platinum as the diffusion barrier has been successfully fabricated. The HBT uses Pd/Ge for ntype, Pt/Ti/Pt/Cu for p+type ohmic contacts, and Ti/Pt/Cu for interconnect metals with platinum as the diffusion barrier. The Ti/Pt/Cu structure was stable up to 350 annealing as judged from the data of XRD and sheet resistance. Current accelerated stress test was conducted on the device with current density JC=140 kA/cm2 for 24 hours, the current gain showed no degradation. The devices were also thermally annealed at 250 for 24 hours and showed little changes. We have successfully demonstrated that Aufree, fully Cu metallized HBT can be achieved by using Pt as the diffusion barrier and Pd/Ge and Pt/Ti/Pt/Cu as the ohmic contacts.