Low frequency noise characteristics in HfAlOx/SiO2 n-MOSFETs

Low frequency noise (LFN) characteristics in n-MOSFETs with HfAlO x /SiO 2 gate stacks were investigated. The effects of the high-k layer and SiO 2 interface layer (IL) thicknesses on LFN were evaluated. It was found that the input-referred voltage noise power (S Vg ) of 'high-k MOSFETs' was one order of magnitude larger than that of 'SiO 2 MOSFETs' for a given surface carrier density (N s ), and was approximately proportional to N 2 s in the higher N s region. The S Vg vs. N, plots of MOSFETs with 2.9 nm of HfAlO x on SiO 2 ILs with thicknesses of 1.3 nm, 1.6 nm, and 2.3 nm could be expressed by a single empirical curve. The nature of the dependence of S Vg on N s suggests that the mobility fluctuation term in the unified model contributes to the LFN as well as the number fluctuation term, indicating that the oxide trap density N t (E) around the quasi-Fermi level is about 2×10 18 cm -3 .eV -1 near the interface. In addition, the dispersive dielectric relaxation in the high-k dielectric was examined as an extra source of LFN in high-k MOSFETs. It is likely that relaxation-induced noise (RIN) partly contributes to the LFN.