Current conduction mechanisms in atomic-layer-deposited HfO2/nitrided SiO2 stacked gate on 4H silicon carbide

Abstract

In this paper, current conduction mechanisms of an atomic-layer-deposited HfO2 gate stacked on different thicknesses of thermally nitrided SiO2 based on n-type 4H SiC have been investigated and analyzed. Current-voltage and high-frequency capacitance-voltage measurements conducted at various temperatures (25−140 °C) were performed in metal-oxide-semiconductor test structures with 13 nm thick HfO2 stacked on 0-, 2-, 4-, or 6 nm thick nitrided SiO2. Various conduction mechanisms, such as Schottky emission, Fowler-Nordheim tunneling, Poole-Frenkel emission, and space-charge-limited conduction, have been systematically evaluated. The mechanisms of the current conducted through the oxides were affected by the thickness of the nitrided oxide and the electric field applied. Finally, current conduction mechanisms that contributed to hard and soft dielectric breakdown have been proposed.