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

The effect of N 2 -plasma-treated SiO 2 interfacial layer on the interfacial and electrical characteristics of HfO 2 /SiO 2 /p-Si stacks grown by atomic layer deposition (ALD) was investigated. The microstructure and interfacial chemical bonding configuration of the HfO 2 /SiO 2 /Si stacks were also examined by high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). Compared with the samples without N 2 -plasma treatment, it is found that the samples with N 2 -plasma treatment have less oxygen vacancy density for SiO 2 interfacial layer and better HfO 2 /SiO 2 interface. In agreement with XPS analyses, electrical measurements of the samples with N 2 -plasma treatment show better interfacial quality, including lower interface-state density ( D it , 9.3 × 10 11 cm −2 ·eV −1 near midgap) and lower oxide-charge density ( Q ox , 2.5 × 10 12 cm −2 ), than those of the samples without N 2 -plasma treatment. Additionally, the samples with N 2 -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 N 2 -plasma treatment have better electrical stability than the samples without N 2 -plasma treatment.