Study of parasitic trapping in alumina used as blocking oxide for nonvolatile memories

Alumina layers deposited by Atomic Layer Deposition followed by Rapid Thermal anneal were characterized. We found that the crystallization of alumina in γ-phase occurs between 700 and 850°C. Optical band gap, stress and density were found to increase upon crystallization Hydrogen content in alumina was characterized by ToF-SIMS and infrared spectroscopy. We found that annealing ambience has a strong influence on hydrogen concentration: oxygen favors hydrogen desorption from alumina. Finally, charge trapping in alumina was characterized by C(V) measurements. A strong correlation between hydrogen concentration and trapping was established.