Effects of thermal N2 annealing on passivation capability of sputtered Ta(-N) layers against Cu oxidation

The effects of thermal N-2 annealing on the passivation capability of sputtered Ta and Ta-nitride [Ta(-N)] layers against Cu oxidation in a 200 Angstrom Ta(-N) covered Ta(-N)/Cu/SiO2/Si structures was investigated. The N-2 annealed Ta layers revealed degradation in passivation capability, presumably due to grain growth of the Ta passivation layer. In contrast, the nitrogen-doped Ta-nitride layers showed a contrary trend. For the Ta-nitride layer with 23.5 atom % of nitrogen, passivation capability was effectively improved by N-2 annealing at 300 degrees C. For the Ta-nitride layer with 30.5 atom % of nitrogen, N-2 annealing at higher temperatures (500-700 degrees C) was necessary to improve the passivation capability. The healing of sputtering damage of Ta-nitride passivation layers by the thermal N-2 annealing was responsible, presumably, for the improvement of passivation capability.