INFLUENCE OF HIGH SUBSTRATE DOPING LEVELS ON THE THRESHOLD VOLTAGE AND THE MOBILITY OF DEEP-SUBMICROMETER MOSFETS

High levels of substrate doping needed in deep-submicrometer MOS devices affect device properties strongly. We present a detailed experimental study of high-doping effects on the threshold voltage, which is shown to be affected by the quantum-mechanical splitting of the energy levels in the conduction band. A simple expression to account for these effects is proposed and the consequences for device scaling and design are discussed. Furthermore, the increasing levels of substrate doping and high normal electric fields affect the channel mobility through Coulomb and surface-roughness scattering. Several empirical models for the surface mobility are compared with the characteristics of experimental devices.