The charge trapping characteristics of Si3N4 and Al2O3 layers on amorphous-indium-gallium-zinc oxide thin films for memory application

The charge trapping characteristics of 30-nm-thick Si3N4 and 3-nm-thick Al2O3 layers between amorphous In-Ga-Zn-O thin films and 100-nm-thick blocking oxides made of thermal SiO2 were examined. The Si3N4 layer showed several discrete trap levels with relatively low density, while the Al2O3 layer showed a higher trap density with continuous distribution for electron trapping. When no tunneling oxide was adopted, the trapped carriers were easily detrapped, even at room temperature. Adoption of a 6-nm-thick SiO2 tunneling layer grown by atomic layer deposition largely improved the retention of the trapped charges and retained ∼60% of the trapped charges even after 10 000 s.