HfO2/HfOxNy/HfO2 Gate Dielectric Fabricated by In Situ Oxidation of Plasma-Enhanced Atomic Layer Deposition HfN Middle Layer

Abstract

By using H-2 plasma as a reactant with tetrakis(dimethylamino)hafnium precursor during plasma-enhanced atomic layer deposition, we deposited the HfOxNy layer between HfO2 layers. The 5 nm thick HfO2/HfOxNy/HfO2 (HfONO) trilayer gate oxide shows reduced capacitance equivalent oxide thickness (congruent to 1.25 nm) than that (congruent to 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 H-2 plasma shows lower values of interface trap density (D-it), trapped positive charge density (Delta 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.