Stability of Cu/Ir/Si trilayer structure to moderate annealing

The properties and behavior of trilayer structures consisting of ultrathin iridium thin films sandwiched between Cu and Si have been examined. Iridium thin films (5 nm thick) were deposited on Si substrates using magnetron sputtering, followed by in situ deposition of Cu. The film stacks were examined both as-deposited and after annealing in vacuum over a temperature range of 300–600 °C for 1 h. X-ray diffraction indicates that there is no copper silicide formation upon annealing up to 400 °C. Cross-section HRTEM and EDS line-scans on the sample annealed at 400 °C show the out-diffusion of iridium and the onset of copper diffusion across the interface. The results indicate that iridium is moderately effective as a copper diffusion barrier so long as the processing temperatures remain relatively low.