Compact Modeling of Drain Current, Charges, and Capacitances in Long-Channel Gate-All-Around Negative Capacitance MFIS Transistor

Abstract

In this paper, we present a surface potential-based explicit continuous model for a metal-ferroelectric-insulator-semiconductor (MFIS) type gate-all-around negative capacitance transistor (GAA-NCFET). Unlike previously reported models, an explicit formulation to calculate the electrical characteristics of GAA-NCFET is proposed. Our model includes the radial dependence of the electric field in the ferroelectric, ignored in the previous works and accurately captures ferroelectric material parameter variations in the nonhysteretic regime. In contrast to bulk NCFETs, GAA-NCFET characteristics show different bias dependence due to the absence of bulk charge. We also present analytical expressions for the terminal charges which are essential to obtain the trans-capacitances for transient simulations. We find that, compared with conventional MOSFETs, the gate charge saturates to a different fraction of its maximum value. Furthermore, the modeling of quantum mechanical effect and overlap capacitances in an MFIS NCFET structure is discussed. Finally, the proposed model has been implemented in Verilog-A and tested for the transient response of ring oscillator in a commercial circuit simulator.