Dielectric properties of thermal and plasma-assisted atomic layer deposition Al2O3 thin films

comparative electrical characterization study of aluminum oxide (Al2O3) deposited by thermal and plasma-assisted atomic layer depositions (ALDs) in a single reactor is presented. Capacitance and leakage current measurements show that the Al2O3 deposited by the plasma-assisted ALD shows excellent dielectric properties, such as better interfaces with silicon, lower oxide trap charges, higher tunnel barrier with aluminum electrode, and better dielectric permittivity (k=8.8), than the thermal ALD Al2O3. Remarkably, the plasma-assisted ALD Al2O3 films exhibit more negative fixed oxide charge density than the thermal ALD Al2O3 layers. In addition, it is shown that plasma-assisted ALD Al2O3 exhibits negligible trap-assisted (Poole–Frenkel) conduction unlike the thermal ALD Al2O3 films, resulting in higher breakdown electric fields than the thermal ALD prepared films