Improving interfacial and electrical properties of HfO₂/SiO₂/p-Si stacks with N₂-plasma-treated SiO₂ interfacial layer

The effect of N₂-plasma-treated SiO₂ interfacial layer on the interfacial and electrical characteristics of HfO₂/SiO₂/p-Si stacks grown by atomic layer deposition (ALD) was investigated. The microstructure and interfacial chemical bonding configuration of the HfO₂/SiO₂/Si stacks were also examined by high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). Compared with the samples without N₂-plasma treatment, it is found that the samples with N₂-plasma treatment have less oxygen vacancy density for SiO₂ interfacial layer and better HfO₂/SiO₂ interface. In agreement with XPS analyses, electrical measurements of the samples with N₂-plasma treatment show better interfacial quality, including lower interface-state density (D _it, 9.3 × 10¹¹ cm⁻²·eV⁻¹ near midgap) and lower oxide-charge density (Q _ox, 2.5 × 10¹² cm⁻²), than those of the samples without N₂-plasma treatment. Additionally, the samples with N₂-plasma treatment have better electrical performances, including higher saturation capacitance density (1.49 μF·cm⁻²) and lower leakage current density (3.2 × 10⁻⁶ A·cm⁻² at V _g = V _fb − 1 V). Furthermore, constant voltage stress was applied on the gate electrode to investigate the reliability of these samples. It shows that the samples with N₂-plasma treatment have better electrical stability than the samples without N₂-plasma treatment.