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

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 x 10(-2) A/cm(2)) 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 x 10(-8) A/cm(2)). 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.