Determination of frequency and voltage dependence of electrical properties of Al/(Er_2O_3/SiO_2-Si)/Al MOS capacitor

摘要

In this study, we investigated the effects of applied voltage and frequencies on the electrical properties of Al/(Er_2O_3(150 nm)/ SiO_2(20 nm)-Si)/Al MOS capacitor. The e-beam deposited Er_2O_3/SiO_2 films were annealed at 650 °C in N_2 ambient and the crystal and phase identification of the films were confirmed by X-ray diffractometry. The capacitance-voltage (C-V) and the conductance-voltage (G/ω-V) measurements of the MOS capacitor were carried out for voltage frequencies from 50 kHz to 1 MHz at several steps. The parameters of doping concentration, diffusion potential, built-in potential, barrier height, Fermi energy level, the image force barrier lowering and the depletion layer width were calculated by C-V and G/ω-V data. While the depletion layer width decreased with increasing frequencies, the diffusion potential and the barrier height increased a little with small frequencies (200 kHz ≤ f) first, then decreased insignificantly. We also studied the frequency effects on the series resistance (R_s) and the interface state density (D_(it)) through the C-V and G/ω-V curves, and found noticeable decreases in R_s and D_(it) values with increasing frequency. The measured and calculated results reveal that both R_s and D_(it) frequency dependence have significant impacts on Er_2O_3/SiO_2-Si MOS capacitor properties. These effects are basically because of the interfacial charge behavior of thin SiO_2 layer contained in between n-Si and Er_2O_3.