Inelastic Electron Tunneling Spectroscopy Study of MOS Diodes Based on High-$\kappa $ Gate Dielectrics

Inelastic electron tunneling spectroscopy was applied to characterize the microstructure, interface, and trap-related states in silicon MOS diodes made of high $\kappa $ gate dielectrics HfO$_{2}$, Y$_{2}$O$_{3}$, and stacked HfO$_{2}$/Y$_{2}$O$_{3}$ bilayers by molecular beam epitaxy and atomic layer deposition under various heat treatments. Reproducible vibrational modes of monoclinic HfO$_{2 }$and cubic Y$_{2}$O$_{3}$ were identified from IETS spectra. The gate bias dependence of the spectrum enables to ascribe the phonon modes adjacent to the lower or upper interface. A simple modeling was employed to analyze the trap related features in the spectra of stacked HfO$_{2}$/Y$_{2}$O$_{3}$ bilayers, and showed that most traps are located near the HfO$_{2}$/Y$_{2}$O$_{3}$ interface due to dissimilar charge distributions of two ionic oxides of different cation valences, and the interfacial strains of dissimilar structures. Work is now extended to Y-doped HfO$_{2}$ films in cubic phase with an enhanced $\kappa $ over 30.