Evaluation methodology for assessment of dielectric degradation and breakdown dynamics using time-dependent impedance spectroscopy (TDIS)

摘要

We propose a method to analyze the dielectric degradation and breakdown dynamics under electrical stressing on the basis of time-resolved impedance $Z(omega, t)$ spectra-time-dependent impedance spectroscopy (TDIS). Nyquist plots of $Z(omega, t)$ show unique features at soft- and hard-breakdown stages for various dielectric films (SiO2, SiN, and high-$k$) depending on the defect creation dynamics under electrical stressing. The time evolution of $Z(omega, t)$ spectra— $R(t)$ and $C(t)$ —implies the dynamics of defects (charge trapping/de-trapping features) during stressing in accordance with degradation kinetics. At the post-breakdown stage of high-$k$ dielectrics, the $Z(omega, t)$ spectra was observed to be distorted, implying the presence of different degenerated phases. This method was also applied to the evaluation of plasma-induced damage to SiN films. The TDIS method is useful for investigating the electrical nature of defects and the degradation and breakdown dynamics of dielectric films.