Modeling and parameter extraction of gate-all-around nMOS/SOI transistors in the linear region

Abstract

Analytical models valid in weak, strong and moderate inversion regions are derived for the gate-all-around (GAA) nMOS silicon-on-insulator (SOI) MOSFETs. The non-ideal GAA MOSFETs was modeled as a parallel connection of one long-double-gate and two edge-gate transistors. Using Poisson's equation which considers both the depletion charges and minority carriers, the current-voltage relationship and the expressions for the surface potential and surface electric fields were derived in the regions near and below threshold. Due to the volume inversion characteristics of the GAA device, the surface potential at threshold is no longer pinned at the classical limit (i.e., 2 φ F, where φ F is the Fermi potential) of strong inversion. By taking into account the mobility degradation factor and the parasitic series resistance effects, the expressions of threshold voltage, threshold-surface potential, and current-voltage characteristics were derived. The models allow the parameter extraction of low-field mobility μ 0, surface state density N ss, series resistance R s, and the surface scattering parameter θ from the measured static current-voltage curves in the linear region of the GAA devices. Values of the threshold voltage ( V T) for the long-double-gate transistor and ( V Te) for the edge-gate transistors were also determined by using the maximum transconductance change (TC) method. Good agreement of the ( I d- V gs) characteristics between the measurement and simulation was obtained when the extracted parameters were used in the models.