Band diagram and carrier conduction mechanisms in ZrO2 MIS structures

Energy-band diagrams and carrier-conduction mechanisms in ZrO₂ dielectrics were investigated by using X-ray photoemission spectroscopy and carrier separation measurements for ZrO₂ /Zr-silicate/Si structures. It was found that the carrier conduction mechanisms in ZrO₂ layer dominate the leakage current in the ZrO₂ /Zr-silicate/Si-stacked structure. Furthermore, it was found that the dominant electron conduction mechanism in ZrO₂ dielectrics is a Poole-Frenkel (P-F) conduction and that the dominant hole conduction mechanism in ZrO₂ dielectrics is a Fowler-Nordheim conduction. On the basis of the understanding of these carrier conduction mechanisms, it was indicated that the leakage current density in the dielectrics with the P-F conduction mechanism having the small barrier height of 0.8 eV could not be reduced below 1 A/cm² at the operation voltage of 1 V. Furthermore, we suggest that the ultrathin Zr-silicate single layer is a promising candidate gate dielectric material for advanced MISFET having 1-nm effective thickness.