Thermal Circuit for SOI MOSFET Structure Accounting for Nonisothermal Effects

Abstract

An accurate thermal circuit model for 2-D silicon-on-insulator (SOI) MOSFETs is presented to account for nonisothermal effects. The circuit model is modified from an approach developed earlier for the temperature distribution in 2-D SOI MOSFETs. A generalized approach to establishing a nonisothermal circuit and its circuit elements is presented for different SOI structures, such as multidevices on a single island and multifinger structure. The developed circuit model is verified with the finite-element method (FEM) in different SOI structures, including a structure coupled with interconnects. Heat flow to the contacts, poly gate, and buried oxide (BOX)/field oxide (FOX) is examined. Heat exchange via FOX between neighboring islands is carefully investigated, as compared to the FEM. It is shown from the developed model and FEM simulations that heat exchange via FOX between two thin islands is negligible if the distance between the islands is near or greater than the island thickness plus the BOX thickness.