Physics-based thermal impedance models for the simulation of self-heating in semiconductor devices and circuits.

摘要

Inherent in the operation of semiconductor devices is self-heating, an increase in operating temperature due to a device's own power dissipation. The magnitude of the self-heating effect can be quantified by the value of the thermal impedance, which describes the dynamic response of the device temperature to variations in device power. The thermal impedance is determined primarily by material properties and device structure. The implication of the self-heating effect is that the change in temperature can alter the operating characteristics of a device, which in turn, can affect circuit performance.;The primary focus of this dissertation is the development of physics-based models for the thermal impedances of semiconductor devices. Models for the thermal impedances of bipolar and field-effect transistors, on both bulk and silicon-on-insulator (SUI) substrates, are presented. All of the thermal impedance models were derived from the time-dependent heat conduction equation, resulting in compact analytic expressions for the thermal impedances. The physical nature of the thermal impedance models allows them to scale with the device structure and material properties, and they successfully reproduce results from both measurements and three-dimensional finite-element simulations. A circuit model for thermal coupling between transistors in a common substrate is also presented. The coupling model was used in conjunction with the bulk bipolar thermal impedance model to extract a lumped electrothermal model for multiple-emitter bipolar transistors.;The secondary objective of this work is the provision of an approach for incorporating these models into circuit simulators. It has been shown that the thermal impedance models can be represented by thermal equivalent circuits made up of resistors and capacitors, making them suitable for efficient circuit simulation. The computer program TIPP (Thermal Impedance Pre-Processor) is introduced. TIPP was developed to provide circuit simulators with convenient algorithms for generating thermal equivalent circuits. TIPP can calculate the component values for thermal equivalent circuits from either physical models or measured data, and is easily modified to interface with different circuit simulators.