Polarity dependence of the conduction mechanism in inter-level low-k dielectrics

Leakage currents of inter level carbon-doped silicon oxide low-k dielectric in copper interconnect structure are investigated over the electric field range of zero to the breakdown field at different temperatures. A remarkable bias polarity dependence of conduction current and breakdown voltage is observed in such structure. Different conduction mechanisms are found in different electric field ranges. Ohmic conduction of electron hopping dominates at the low electric field. Poole-Frenkel emission and Fowler-Nordheim tunneling occur at high field on the different bias conditions respectively. The activation energy or energy barrier belong to each conduction mechanism was estimated. These conduction phenomena were explained by the asymmetry energy band diagram and surface defects. The bias polarity dependence of breakdown voltage indicates the breakdown mechanism of inter level low-k dielectric is attribute to carrier current but not electric field as ascribed by E-model.