A UNIFIED MODEL FOR THE FLICKER NOISE IN METAL OXIDE-SEMICONDUCTOR FIELD-EFFECT TRANSISTORS

At present, there are two major theories to explain the physical origins of flicker (1/f) noise in metal-oxide-semiconductor (MOS) field-effect transistors. One is the number fluctuation theory based on the McWhorter's charge trapping model; the other is the bulk mobility fluctuation theory based on Hooge's hypothesis. Extensive noise data have been reported and interpreted with both models, but a discrimination or reconciliation between them has not yet been reached. We have developed, based on new experimental observations on the random telegraph noise generated by a single trap, a unified flicker noise model which incorporates both the number fluctuation and the correlated surface mobility fluctuation mechanism. The latter is attributed to the Coulombic scattering effect of the fluctuating oxide charge. The new model has a functional form resembling that of the number fluctuation theory, but at certain bias conditions it may reduce to a form compatible to Hooge's empirical expression. The model can unify the noise data reported in the literature, without making any ad hoc assumption on the noise generation mechanism, as often encountered in the bulk-mobility fluctuation models. Specifically, the model can predict the right magnitude and bias dependence of the empirical Hooge parameter. In order to demonstrate the superiority of the unified model, we have developed a circuit-simulation-oriented flicker noise model based on the new formulation and compared the simulation results with our own experimental noise data. Excellent agreement between the calculations and measurement was observed in both the linear and saturation regions for MOS transistors fabricated by different technologies. Our work shows that the flicker noise in MOS transistors can be completely explained by the trap charge fluctuation mechanism, which produces mobile carrier number fluctuation and correlated surface mobility fluctuation. © 1990 IEEE