A physically-derived large-signal nonquasi-static MOSFET model for computer aided device and circuit simulation

This thesis presents a large-signal nonquasi-static model for the transient analysis of MOSFET devices and circuits. The nonquasi-static model is based on MOSFET device physics as opposed to empirical methodologies and is valid in all three regions of device operation: weak, moderate, and strong inversion. The nonquasi-static model is implemented within a CAD software package that provides for the numerical simulation of both individual MOSFET devices and CMOS logic circuits. The CAD software calculates the transient terminal currents and voltages of individual MOSFET devices while providing voltage transfer curves and switching speeds for the CMOS logic circuits. Results are compared with those obtained from SPICE Level 3 and SPICE Level 7 (BSIM 3.1) for a wide range of device geometries and circuit loading conditions.; This work addresses many issues involved in the numerical modeling of MOSFET devices and circuits. An iterative technique is used to reduce the system of partial differential equations that describe nonquasi-static behavior to a single ordinary differential equation, which can then be solved with the trapezoidal integration method. Euler's method is used in the calculation of the output voltage of each CMOS logic circuit and a bisection root finding algorithm is used to calculate any junction voltage that appears between two devices connected in series.