Capacitance modeling of Short-Channel DG and GAA MOSFETs

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Based on our framework model of the electrostatics and the drain current in short-channel, nanoscale DG and GAA MOSFETs, we here present a corresponding model for the device capacitances covering all regimes of operation from subthreshold to strong inversion. In the sub-threshold regime of lightly doped devices, the electrostatics is dominated by the inter-electrode capacitive coupling. From this, analytical expressions for the charge conserving trans- and self-capacitances of the DG device can readily be derived using conformal mapping techniques for solving the 2D Laplace’s equation in the device body. A corresponding, approximate solution has been derived for the 3D GAA device. Near and above threshold, the influence of the electronic charge on the electrostatics is taken into account in a precise, self-consistent manner by combining suitable model expressions with Poisson’s equation in the device body. From this, we obtain the total, vertical electric displacement field on the source, drain and gate electrodes, from which the bias-dependent electrode charges and capacitances can be derived. In strong inversion, the electronic charge dominates the device behavior, which approaches that of long-channel devices. The model, which uses no adjustable parameters, has been verified against numerical simulations.

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Journal: TechConnect Briefs
Volume: 3, Nanotechnology 2008: Microsystems, Photonics, Sensors, Fluidics, Modeling, and Simulation – Technical Proceedings of the 2008 NSTI Nanotechnology Conference and Trade Show, Volume 3
Published: June 1, 2008
Pages: 745 - 749
Industry sector: Sensors, MEMS, Electronics
Topic: Compact Modeling
ISBN: 978-1-4200-8505-1