Underlying physics of the thermochemical E model in describing low-field time-dependent dielectric breakdown in SiO2 thin films

The underlying physics behind the success of the thermochemical E model in describing time-dependent dielectric breakdown (TDDB) in ${\mathrm{SiO}}_{\mathrm{2}}$ thin films is presented. Weak bonding states can be broken by thermal means due to the strong dipolar coupling of intrinsic defect states with the local electric field in the dielectric. This dipole-field coupling serves to lower the activation energy required for thermal bond-breakage and accelerates the dielectric degradation process. A temperature-independent field acceleration parameter γ and a field-independent activation energy $\mathrm{\Delta H}$ can result when different types of disturbed bonding states are mixed during TDDB testing of ${\mathrm{SiO}}_{\mathrm{2}}$ thin films. While γ for each defect type alone has the expected $\text{1/T}$ dependence and $\mathrm{\Delta H}$ shows a linear decrease with electric field, a nearly temperature-independent γ and a field-independent $\mathrm{\Delta H}$ can result when two or more types of disturbed bonding states are mixed. The good agreement between long-term TDDB data and the thermochemical model suggest strongly that the oxygen vacancy is an important intrinsic defect for breakdown and that field, not current, is the primary cause of TDDB under low-field conditions.