Dipole formation and electrical properties of high-k/SiO2 interface according to the density of SiO2 interfacial layer

Abstract

The effect of SiO₂ buffer layers with various atomic densities on the interface dipole of high-k/SiO2 is confirmed. An ultrathin SiO₂ layer is formed on Si using the plasma-enhanced chemical vapor deposition (PECVD), H2O2 oxidation and nitric acid oxidation (NAOS). The atomic density ratio between the SiO2 layer with various methods and the high-k is calculated respectively. As the oxygen density of the SiO2 increased, the amount of the dipole and the flatband voltage (VFB) shift decreased. Furthermore, leakage current density of the H2O2 (0.9 × 10−2 A/cm2) due to the formation of low-density SiO2, decreases by approximately six orders of magnitude when SiO2 buffer layer is inserted using the NAOS (5.13 × 10-8 A/cm2). Consequently, it is demonstrated that the dipoles that affects the VFB shift is formed by the diffusion of oxygen ions between the high-k and SiO2 interface, which has a significant effect of the MOS capacitor.