Articles you may be interested inDetermination of the nature of molecular bonding in silica from time-dependent dielectric breakdown dataThe underlying physics behind the success of the thermochemical E model in describing time-dependent dielectric breakdown ͑TDDB͒ in SiO 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 ␥ and a field-independent activation energy ⌬H can result when different types of disturbed bonding states are mixed during TDDB testing of SiO 2 thin films. While ␥ for each defect type alone has the expected 1/T dependence and ⌬H shows a linear decrease with electric field, a nearly temperature-independent ␥ and a field-independent ⌬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.

A thermochemical/molecular model is developed for breakdown in high dielectric constant materials and the model suggests that a fundamental relationship exists between dielectric breakdown strength (Ebd) and dielectric constant (k). The model indicates that Ebd should show an approximate (k)−1/2 dependence over a wide range of high dielectric constant materials. The model also predicts that the field-acceleration parameter (γ), from time-dependent dielectric breakdown (TDDB) testing, should increase with dielectric constant. TDDB and Ebd data are presented for model support. The thermochemical model suggests that the very high local electric field (Lorentz-relation/Mossotti-field) in high-k dielectrics tends to distort/weaken the polar molecular bonds making them more susceptible to bond breakage by standard Boltzmann processes and/or by hole capture and thus lowers the breakdown strength.

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