Metal diffusion barriers for porous SiO2

The diffusion characteristics of metal barrier materials in porous films having low dielectric constant are studied using the Rutherford backscattering spectrometry technique. It is shown that barrier materials such as TaN and TiN do not diffuse into the xerogel film with porosity of 70%–75% after 450 °C annealing in N2 ambient for 2 h. This result points to an interesting possibility that one may not require a dielectric liner for a porous film (to prevent the diffusion of metal barrier materials into the porous material) in the Cu porous film interconnect technology.