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

Abstract

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.