The Major Effect of Trapped Charge on Dielectric Breakdown Dynamics and Lifetime Estimation

Being one of the most relevant reliability issues in electron devices, dielectric breakdown (BD) has been in the spotlight for over 50 years and the quest for a comprehensive BD model able to accurately predict the devices lifetime is still ongoing. In fact, even though many consolidated theories exist, able to equally well reproduce the BD experimental trends in accelerated conditions (i.e., thermochemical (E-model), $\sqrt E $ -model, power law (V
^N
-model), and 1/E-model), they provide very different lifetime estimations when projecting at operating conditions. However, the newly proposed Carrier Injection (CI) model reconciles the incongruities that the aforementioned theories exhibit at operating conditions within a unique picture, showing that the time-dependent dielectric breakdown (TDDB) E-field dependence may change from thermochemical to power-law, up to 1/E trend depending on the microscopic properties of key atomic species (precursors). Nevertheless, these outcomes were obtained considering that the E-field in the dielectric is only affected by the applied bias, neglecting the impact of the trapped charge at the defects and the precursors. However, the latter are well-known to significantly contribute to the local E-field within the oxide at low applied voltages (V
APP
), which marks a relevant difference between accelerated and operating conditions that must be considered for accurate TDDB lifetime estimates. In this paper, we include the influence of trapped charges in the CI model and provide a more complete description of the BD phenomenon. Results show that the effect of the trapped charge can lead to an increased reliability margin (higher TDDB lifetime) by delaying trapping into existing precursors. Also, we investigate the combined effect of trapped charge and of defect precursor sites microscopic properties on TDDB and on the leakage current through the oxide.