Long-range Coulomb interactions in small Si devices. Part I: Performance and reliability

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Abstract
In the ever smaller silicon metal–oxide–semiconductor field-effect transistors of the present technology, electrons in the conductive channel are subject to increasingly stronger long-range Coulomb interactions with high-density electron gases present in the source, drain, and gate regions. We first discuss how two-dimensional, self-consistent full-band Monte Carlo/Poisson simulations can be tailored to reproduce correctly the semiclassical behavior of a high-density electron gas. We then employ these simulations to show that for devices with channel lengths shorter than about 40 nm and oxides thinner than about 2.5 nm, the long-range Coulomb interactions cause a significant reduction of the electron velocity, and so a degradation of the performance of the devices. In addition, the strong “thermalization” of the hot-electron energy distribution induced by Coulomb interactions has an effect on the expected reliability of the transistors.