Effectiveness of Ta Addition on the Performance of Ru Diffusion Barrier in Cu Metallization

Ru–Ta and Ru thin films ( in thickness) as diffusion barrier for Cu metallization on and Si substrates are studied. Experimental results show that the Ru–Ta film exhibits amorphous structure until annealing at , whereas the Ru film crystallizes in as-deposited and annealed states. Sheet resistances of and stacking layers increase after annealing at 500 and , respectively, regardless of whether the substrate is or Si. Increase in resistance is concurrent with the formation of and when Cu/barrier stacks are deposited on Si substrate. Increase in resistance for Cu/barrier stacks deposited on substrate is related to the diffusion of Cu through the crystallized barrier to the underlayers. Furthermore, current–voltage measurement also reveals that the metallization has a lower leakage current than the system. The failure mechanism and the effectiveness of Ta addition on barrier performance are discussed.