Reducing Cu diffusion in SiCOH low-k films by O2 plasma treatment

This work investigates the Cu diffusion in SiCOH low dielectric constant films treated by O₂ plasma. By capacitance–voltage and current-voltage measurement, and thermal stress analysis, it is found that the O₂ plasma surface treatment of SiCOH films can lead to the decrease of flatband voltage shift ΔV_FB, the increase of activation energy E_a, and the decrease of leakage current. The small ΔV_FB and lower leakage current indicate the weak Cu diffusion. The increase of active energy means the reducing of fast Cu ions surface diffusion through the interconnected pores structure of the film. Hence, the Cu diffusion in SiCOH films can be reduced by O₂ plasma treatment. By FTIR and AFM analysis on the bonding configuration and microstructure, the reduce of Cu diffusion is related to the increase of Si-O cages and networks, which makes more open pores sealed at the surface of SiCOH films.