Interdiffusions and reactions in Cu/TiN/Ti/Si and Cu/TiN/Ti/SiO2/Si multilayer structures

Sputtered TiN (30-120 nm thick)/Ti (30 nm thick) films were studied as a diffusion barrier between silicon substrate and copper films. The effects of TiN thickness and the existence of a SiO2 layer between Ti and silicon substrate on the diffusion barrier property were investigated using various characterization methods. The copper diffusion barrier property of TiN/Ti was found to be affected not only by the TiN thickness, that is diffusion distance, but also by the microstructure of the TiN, which changes with the thickness of TIN film. The existence of the SiO2 layer enhanced the diffusion barrier property of TiN/Ti. This is because the SiO2 layer between Ti and Si inhibited the formation of titanium silicides, so the Ti layer was available to be used as the sacrificial diffusion barrier for copper.