A New TDDB Degradation Model Based on Cu Ion Drift in Cu Interconnect Dielectrics

A new physical model of time-dependent dielectric breakdown (TDDB) in Cu interconnect dielectrics is proposed. TDDB occurs due to the drift of Cu ions under an electric field E. An activation energy analysis of the leakage current demonstrates that these injected Cu ions affect the conduction mechanism of electrons. The dominant electron conduction mechanism changes from Poole-Frenkel electron current through the Cu barrier dielectrics to Fowler-Nordheim current due to the Cu pile-up at the cathode end. We assumed two possible types of Cu ion drift mechanism, Schottky type or Poole-Frenkel type. The field acceleration model (radicE model) of the Poole-Frenkel type fits both TDDB lifetime and activation energy very well. The TDDB lifetime is proportional to the exponential of the square root of the electric field radicE