HfO₂ / HfO_x N_y / HfO₂ gate dielectric fabricated by in situ oxidation of plasma-enhanced atomic layer deposition HfN middle layer

By using H₂plasma as a reactant with tetrakis(dimethylamino) hafnium precursor during plasma-enhanced atomic layer deposition, we deposited the HfO_x N_y layer between HfO₂ layers. The 5 nm thick HfO₂ / HfO_x N_y / HfO₂ (HfONO) trilayer gate oxide shows reduced capacitance equivalent oxide thickness (1.25 nm) than that (1.40 nm) of the HfO₂ film with the same thickness due to the contribution of nitrogen incorporation to the high dielectric constant. The HfONO film utilizing H₂plasma shows lower values of interface trap density (Dit), trapped positive charge density (Δ N_p), and gate leakage currents than the HfO₂ layer with the same thickness while maintaining comparable hysteresis (30 mV). The results can be attributed to the presence of N-H bonds, which can reduce localized states below the conduction band and prevent the conduction-band lowering, and decrement of N-N and N-O bonds, which contribute to trap density, confirmed by the combination of X-ray photoelectron spectroscopy and near-edge X-ray absorption fine-structure analyses.