Compact modeling of the rf and noise behavior of multiple-gate mosfets

La reducción de la tecnología MOSFET planar ha sido la opción tecnológica dominante en las últimas décadas. Sin embargo, hemos llegado a un punto en el que los materiales y problemas en los dispositivos surgen, abriendo la puerta para estructuras alternativas de los dispositivos. Entre estas estructuras se encuentran los dispositivos DG, SGT y Triple-Gate. Estas tres estructuras están estudiadas en esta tesis, en el contexto de rducir las dimensiones de los dispositivos a tamaños tales que los mecanismos cuánticos y efectos de calan coro deben tenerse n cuenta. Estos efectos vienen con una seria de desafíos desde el pun to de vista de modelación, unos de los más grandes siendo el tiempo y los recursos comprometidos para ejecutar las simulaciones. para resolver este problema, esta tesis propone modelos comlets analíticos y compactos para cada una de las geometrías, validos desde DC hasta el modo de operación en Rf para los nodos tecnológicos futuros. Dichos modelos se han extendido para analizar el ruido de alta frecuencia en estos diapositivos

Multiphysics simulation of corona discharge induced ionic wind

Ionic wind devices or electrostatic fluid accelerators are becoming of increasing interest as tools for thermal management, in particular for semiconductor devices. In this work, we present a numerical model for predicting the performance of such devices, whose main benefit is the ability to accurately predict the amount of charge injected at the corona electrode. Our multiphysics numerical model consists of a highly nonlinear strongly coupled set of PDEs including the Navier-Stokes equations for fluid flow, Poisson's equation for electrostatic potential, charge continuity and heat transfer equations. To solve this system we employ a staggered solution algorithm that generalizes Gummel's algorithm for charge transport in semiconductors. Predictions of our simulations are validated by comparison with experimental measurements and are shown to closely match. Finally, our simulation tool is used to estimate the effectiveness of the design of an electrohydrodynamic cooling apparatus for power electronics applications.Comment: 24 pages, 17 figure

Generalized Scharfetter-Gummel schemes for electro-thermal transport in degenerate semiconductors using the Kelvin formula for the Seebeck coefficient

Many challenges faced in today's semiconductor devices are related to self-heating phenomena. The optimization of device designs can be assisted by numerical simulations using the non-isothermal drift-diffusion system, where the magnitude of the thermoelectric cross effects is controlled by the Seebeck coefficient. We show that the model equations take a remarkably simple form when assuming the so-called Kelvin formula for the Seebeck coefficient. The corresponding heat generation rate involves exactly the three classically known self-heating effects, namely Joule, recombination and Thomson-Peltier heating, without any further (transient) contributions. Moreover, the thermal driving force in the electrical current density expressions can be entirely absorbed in the diffusion coefficient via a generalized Einstein relation. The efficient numerical simulation relies on an accurate and robust discretization technique for the fluxes (finite volume Scharfetter-Gummel method), which allows to cope with the typically stiff solutions of the semiconductor device equations. We derive two non-isothermal generalizations of the Scharfetter-Gummel scheme for degenerate semiconductors (Fermi-Dirac statistics) obeying the Kelvin formula. The approaches differ in the treatment of degeneration effects: The first is based on an approximation of the discrete generalized Einstein relation implying a specifically modified thermal voltage, whereas the second scheme follows the conventionally used approach employing a modified electric field. We present a detailed analysis and comparison of both schemes, indicating a superior performance of the modified thermal voltage scheme.Comment: 26 pages, 7 figure

Simulation of hot carriers in semiconductor devices

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 109-113).by Khalid Rahmat.Ph.D

Simulation of Heterojunction Bipolar Transistors in Two Dimensions

This work describes the formulation and, development of a two-- dimensional drift-diffusion simulation program for accurate modeling of heterojunction bipolar transistors (HBT\u27s). The model described is a versatile tool for studying HBT\u27s, allowing the user to determine the terminal characteristics and physical operation of devices. Nonplanar structures can be treated, response to transient conditions can be computed, and the high frequency characteristics of transistors may be projected. The formulation of an electron energy balance equation is presented and included in the model in an attempt to more accurately compute high-field transport characteristics. The model is applied to some common design questions and experimental results are reproduced

Simulation of hot carriers in semiconductor devices

Includes bibliographical references (p. 109-113).Supported by the U.S. Navy. N00174-93-C-0035Khalid Rahmat

Generalized Scharfetter--Gummel schemes for electro-thermal transport in degenerate semiconductors using the Kelvin formula for the Seebeck coefficient

Many challenges faced in today's semiconductor devices are related to self-heating phenomena. The optimization of device designs can be assisted by numerical simulations using the non-isothermal drift-diffusion system, where the magnitude of the thermoelectric cross effects is controlled by the Seebeck coefficient. We show that the model equations take a remarkably simple form when assuming the so-called Kelvin formula for the Seebeck coefficient. The corresponding heat generation rate involves exactly the three classically known self-heating effects, namely Joule, recombination and Thomson--Peltier heating, without any further (transient) contributions. Moreover, the thermal driving force in the electrical current density expressions can be entirely absorbed in the (nonlinear) diffusion coefficient via a generalized Einstein relation. The efficient numerical simulation relies on an accurate and robust discretization technique for the fluxes (finite volume Scharfetter--Gummel method), which allows to cope with the typically stiff solutions of the semiconductor device equations. We derive two non-isothermal generalizations of the Scharfetter--Gummel scheme for degenerate semiconductors (Fermi--Dirac statistics) obeying the Kelvin formula. The approaches differ in the treatment of degeneration effects: The first is based on an approximation of the discrete generalized Einstein relation implying a specifically modified thermal voltage, whereas the second scheme follows the conventionally used approach employing a modified electric field. We present a detailed analysis and comparison of both schemes, indicating a superior performance of the modified thermal voltage scheme