Analysis of Constitution and Characteristics of Lateral Nonuniformity Effects of MOS Devices Using QM-Based Terman Method

The Terman method for extracting interface trap density D_it has been used as a direct index of the lateral nonuniformity (LNU) distribution of charges in the dielectric layer of MOS capacitors. However, as dielectric layers become thin, reaching to 2-3 nm, quantum effects should be taken into consideration. The primitive Terman method has been modified with respect to quantum mechanisms, and both theoretical simulations and experimental data were examined to check the modified method´s feasibility. The quantum-mechanism-based Terman method might obtain negative D_it if the high-frequency C-V curves are distorted by LNU charge distribution in the dielectric layer of MOS capacitors. To elucidate LNU effects, external constant voltage stress and water immersion were applied to clarify the roles of injected carriers in the LNU effects. Furthermore, the amount of effective oxide charge Q_eff has been found to be responsible to the LNU effects.