Low-Resistivity Ru-Ta-C Barriers for Cu Interconnects

Ru-Ta-C films deposited on silicon substrates were evaluated as barriers for copper metalization. The films were prepared by magnetron cosputtering using a Ru target and a Ta-C target. Compositions and structure of resultant films were optimally tuned by the respective deposition power of each target. The fabricated Ru-Ta-C films were characterized via four-point probe measurement, x-ray diffractometry, field-emission electron probe microanalysis, and transmission electron microscopy. Failure temperature was evaluated by the sudden rise in electrical resistivity after annealing the Cu/Ru-Ta-C/Si sandwich films, and a reference bilayer Cu/(5 nm Ru)/(5 nm Ta-C)/Si scheme. The optimal compositions were 10 nm Ru 77 Ta 15 C 7 and (5 nm Ru)/(5 nm Ta-C), both of which showed failure temperature of 650°C for 30 min and electrical resistivity less than 150 μ Ω cm. Because of their high thermal stability and low electrical resistivity, both Ru-Ta-C and Ru/Ta-C films are promising barriers for Cu metalization.