Crystallization and chemical structures with annealing in Zr O₂ gate insulators studied by photoemission spectroscopy and x-ray absorption spectroscopy

We have performed photoemission spectroscopy and x-ray absorption spectroscopy (XAS) to investigate the chemical states and the crystallization from the amorphous structure by annealing of the Zr O2 gate insulators on Si. Angular-dependent core-level photoemission spectra revealed the chemical states including the interfacial layers. Annealing-temperature dependence in valence-band spectra and XAS revealed the relationship between crystallization and the changes in spectral line shapes although core-level photoemission spectra are not sensitive to the crystallization. Valence-band spectra are split into double peak structures and the line shapes of O K -edge x-ray absorption spectra become sharp by the annealing at 800°C corresponding to the crystallization temperature of amorphous Zr O2 films. It suggests that the valence-band spectra and XAS can be utilized to characterize the crystallization features in the gate insulators.