On dielectric breakdown in silicon-rich silicon nitride thin films

Observations of dielectric breakdown in Si-rich silicon nitride indicate that it is initiated by threshold field trap ionization. The films exhibit the charge transport mechanism of Poole-Frenkel emission with a compositionally dependent ionization potential ranging from 0.58 to 1.22 eV. Similar to silicon oxynitride, the barrier lowering energy at the point of dielectric breakdown is correlated with within similar to 2kT of the ionization potential, thus revealing a dual role for bulk traps in the film: regulating charge transport and retarding hot electron generation. Additionally, a semiempirical expression is developed that accurately predicts the compositional dependence of the breakdown field.