Tantalum-Ruthenium Diffusion Barriers for Contacts to SiC

Abstract

Tantalum-ruthenium diffusion barriers for contacts to SiC were investigated in this work. Stable specific contact resistances of (2 ± 1) x 10-5 Ω cm2 and (4 ± 2) x 10-5 Ω cm2 were measured on p-type 4H SiC for Al/Ni and Ni ohmic contacts, respectively, when they were beneath Ru-rich Ta-Ru barriers aged at 350 °C for 3000 h in air. Annealed Ni ohmic contacts on n-SiC aged at 350 °C in air for 1000 h (the longest time tested) are also very stable. Pull tests revealed greatly improved adhesion between layers in metallization stacks that contained Ta-Ru barriers in place of previously studied Ta-Ru-N barriers. A 5 nm Ta layer inserted between the Ru-rich Ta-Ru barriers and Au was found to further improve the adhesion of the metallization stacks.